thesis research on Health physics (CT scan research). follow the guidelines and write the thesis. It should be 50 pages excluding references, table of content and appendix.
TRENDS IN EXTERNAL RADIATION EXPOSURE AMONG THE U.S NAVY MEDICAL PERSONNEL WORKING IN NUCLEAR MEDICINE DEPARTMENTS FROM
2
003
TO
2020
A Thesis
submitted to the Faculty of the Graduate School of Arts and Sciences of Georgetown University
in partial fulfillment of the requirements for the degree of
Master of Science in Health Physics
By
TJahnensattudAennwt naarmSe. Almajed, B.S.
Washington, D.C. December 10, 2021
(
viii
)
CCooppyyrriigghhtt 2021 by Jannat Anwar S. Almajed All Rights Reserved
TRENDS IN EXTERNAL RADIATION EXPOSURE AMONG THE U.S NAVY MEDICAL PERSONNEL WORKING IN NUCLEAR MEDICINE DEPARTMENTS FROM 2003 TO 2020
SJatundneanttAnnamwear S. Almajed, B.S.
TThheessiissAAddvvisisoor rn:aLmueis Benevides, Ph.D.
Objectives: To assess trends in external occupational exposure of nuclear medicine (NM) workers from United States Navy (USN) medical centers from 2003 to 2020 and compare them with previously published data on NM workers from US civilian hospitals. Materials and methods: Analysis of the annual personal dose equivalents, deep dose equivalents Hp(10) (DDE) and shallow dose equivalents Hp(
0.07
) (skin dose) recorded using the DT-702/PD was conducted on
528
NM personnel working in USN medical centers. Also, analysis of 1,
35
7 annual shallow dose equivalents Hp(0.07) (extremity dose) recorded using DXT-RAD was conducted on
285
NM workers. The data used in the study was provided by the United States Navy Dosimetry Center (NDC). Summary statistics of the distributions of annual and cumulative DDE, skin doses and extremity doses are provided in this study. Annual doses of nuclear medicine personnel working in Navy hospitals/clinics that perform PET imaging besides general nuclear medicine studies were identified using publicly available websites’ information, analyzed and compared with those who work in nuclear medicine facilities that perform only general NM studies. Doses from the two groups were compared using a two-sample t-test with
95
% confidence interval. Results:
Median
annual doses of
0.38
mSv (IQR,
0.05
–
1.2
7
mSv; mean, 0.
82
mSv), 0.
37
mSv (IQR,
0.06
–
1.22
mSv; mean = 0.
80
mSv), and
2.89
mSv (IQR = 0.
76
–
7.86
mSv; mean =
6.65
mSv) for the DDE, skin dose and extremity dose, respectively, were observed in 2003–2020. Median cumulative
DDE, skin dose and extremity dose over 2003–2020 were
0.39
mSv (IQR = 0.05 –
3.18
mSv; mean =
2.96
mSv) and 0.39 mSv (IQR = 0.05 –
3.08
mSv; mean =
2.90
mSv), and
13
.0 mSv (IQR
=2.89 – 38.5 mSv; mean = 31.6 mSv), respectively. Median annual DDE, skin and extremity doses to workers from identified PET facilities were
0.44
mSv (IQR= 0.06 –
1.60
mSv; mean = 0.
99
mSv),
0.42
mSv (IQR = 0.06 –
1.58
mSv; mean = 0.
97
mSv) and
3.16
mSv (IQR =
0.73
–
9.51
mSv; mean =
8.74
mSv), respectively, against
0.29
mSv (IQR = 0.06 –
0.95
mSv; mean =
0.65
mSv),
0.30
mSv (IQR =0.06 – 0.95 mSv; mean = 0.
63
mSv) and
2.52
mSv (IQR =
0.76
–
6.19
mSv; mean =
4.72
mSv) to workers from non-PET facilities. The resultant p-value (p<0.05) of the two-sample t-test showed a significant difference between doses to NM workers from PET vs. non-PET facilities. Conclusions: All assessed values of the DDE, skin and extremity doses were well below the annual occupational limits established by the International Commissionon Radiological Protection. The median annual DDE to NM workers in the USN was lower than NM radiological technologists from US civilian hospitals. Our study’s mean annual skin dose was lower than NM technologists and NM physicians in Kuwait and NM technologists in Saudi Arabia. Moreover, our study’s mean annual extremity dose was half the lowest extremity exposure recorded among NM workers in Serbia. As expected, working in PET facilities was associated with increased radiation doses. This study provided new data useful for future exposure assessment in this population of radiation workers and improved radiation protection programs in medical centers.
The research and writing of this thesis is dedicated to
everyone who helped along the way. I would like to express my deepest appreciation to my thesis mentor Dr. Daphnée Villoing who helped me through all stages of planning and writing my thesis. Many thanks to my thesis advisor Dr. Luis Benevides, who made this work possible by helping in providing the data and contacting the NDC on my behalf. Thanks to Dr. Timothy Jorgensen for his continuous support and help to finish my degree. Thanks to Dr. Stanley Fricke for his advice and willingness to help every time I ask.
My completion of this degree could not have been accomplished without the support of my family. I am extremely grateful to my husband Ahmad Al Marzook for his sacrifices, love, and encouragement. Thanks to my daughter Julia for her love and patience and all the time she waited for me. Thanks to my parents, sisters, and my brother for their support and prayers.
Chapter 1: Introduction 1
Chapter 2: Background… 4
Ionizing radiation in medicine 4
Biological effects of ionizing radiation 4
Overview of nuclear medicine 6
Nuclear medicine imaging… 8
Nuclear cardiovascular imaging 8
Positron Emission Tomography 9
Occupational exposure in nuclear medicine 10
History in radiation protection 12
Dosimetry Concepts 13
Dose Units 13
External radiation dosimetry in the US-Navy…
14
Chapter 3: Materials and Methods 17
Data Collection 17
Institutional Review Board 18
Dosimetry dose readings 18
Data cleansing – Inclusion and Exclusion criteria 19
Annual dose calculation… 21
Cumulative dose calculation… 21
Categorization 21
Statistical analysis 22
Chapter 4: Results 23
Annual doses 23
Annual deep dose equivalents distribution 23
Annual skin dose equivalents distribution… 26
Annual extremity doses distribution… 29
Cumulative dose 32
Cumulative deep dose and skin dose equivalents distribution. 32
Cumulative extremity doses distribution… 32
PET and non-PET 32
PET facilities distribution… 32
Non-PET facilities distribution… 32
PET vs. non-PET 33
Chapter 5: Discussion… 37
Conclusions 42
Bibliography 44
Appendix A:
Summary statistics of the annual deep dose equivalents for 528 nuclear medicine personnel working in the United States Navy medical facilities from 2003-2020
… 59
Appendix B:
Year
ly summary statistics of the annual deep dose equivalents for 528 nuclear medicine personnel working in the United States Navy medical facilities
60
Appendix C: Summary statistics of the annual shallow dose equivalents of the skin for 528 nuclear medicine personnel working in the United States Navy medical facilities from 2003-
2020…………………………………………………………………………………………..…..66
Appendix D: Yearly summary statistics of the annual shallow dose equivalents of the skin for 528 nuclear medicine personnel working in the United States Navy medical facilities
67
Appendix E:
Summary statistics of the annual shallow dose equivalents of the extremities for 285 nuclear medicine personnel working in the United States Navy medical facilities
73
Appendix F: Yearly summary statistics of the annual shallow dose equivalents of the extremities for 285 nuclear medicine personnel working in the United States Navy medical facilities 74
Appendix G: Summary statistics of the cumulative deep dose equivalents for 528 nuclear medicine personnel working in the United States Navy medical facilities from 2003-
2020……………………………………………………………………………………………….80
Appendix H: Summary statistics of the cumulative shallow dose equivalents of the skin for 528 nuclear medicine personnel working in the United States Navy medical facilities from 2003- 2020… 81
Appendix I: Summary statistics of the cumulative shallow dose equivalents of the extremities for 285 nuclear medicine personnel working in the United States Navy medical facilities from 2003- 2020… 82
Appendix G: Summary statistics of the annual deep dose equivalents corresponding to
221
NM personnel working in USN medical facilities identified as PET facilities 83
Appendix K: Summary statistics of the shallow deep dose equivalents of the skin corresponding to 221 NM personnel working in USN medical facilities identified as PET facilities 84
Appendix L: Summary statistics of the shallow deep dose equivalents of the extremities corresponding to
163
NM personnel working in USN medical facilities identified as PET facilities 85
Appendix M: Summary statistics of the annual deep dose equivalents corresponding to 3
61
NM personnel working in USN medical facilities identified as non-PET facilities 86
Appendix N: Summary statistics of the annual shallow dose equivalents of the skin corresponding to
361
NM personnel working in USN medical facilities identified as non-PET facilities 87
Appendix O: Summary statistics of the annual shallow dose equivalents of the extremities corresponding to
176
NM personnel working in USN medical facilities identified as non-PET facilities 88
Appendix P:
Two-sample t test’s result for the mean difference of the annual deep dose equivalents between non-PET and PET facilities
89
Appendix Q:
Two-sample t test’s result for the mean difference of the annual shallow dose equivalents of the skin between non-PET and PET facilities
90
Appendix R:
Two-sample t test’s result for the mean difference of the annual shallow dose equivalents of the extremities between non-PET and PET facilities
91
Appendix S: An example of a questionnaire could be used in future studies to help provide detailed information on the number of workers, workload, and radiation safety standards in the USN medical facilities
92
LIST OF FIGURES
Figure 1: DT-702 personal dosimeter 16
Figure 2: DXT-RAD finger dosimeter 16
Figure 3: Histogram of the distribution of
1,916
annual deep dose equivalents, Hp(10), previously collected and provided by the NDC for 528 workers from NM departments of the USN medical centers between 2003 and 2020. 24
Figure 4: Box-and-whisker plot of the trends in annual deep dose equivalents, Hp(10), to workers from NM departments of the USN medical centers between 2003 and 2020… 25
Figure 5: Histogram of the distribution of 1,916 annual shallow dose equivalents, Hp(0.07), previously collected and provided by the NDC for 528 workers from NM departments of the USN medical centers between 2003 and 2020… 27
Figure 6: Box-and-whisker plot of the trends in annual skin dose equivalents, Hp(0.07), to workers from NM departments of the USN medical centers between 2003 and 2020… 28
Figure 7: Histogram of the distribution of
1,357
annual shallow dose equivalents to the extremity, Hp(0.07), previously collected and provided by the NDC for 285 workers from NM departments of the USN medical centers between 2003 and 2020… 30
Figure 8: Box-and-whisker plot of the trends in annual shallow dose equivalents to the extremity, Hp(0.07), to workers from NM departments of the USN medical centers between 2003 and 2020… 31
Figure 9: Annual exposure of the personal dose equivalents Hp(10) in mSv for the USN personnel working NM facilities performing PET/CT vs. NM facilities that do not perform PET/CT 34
Figure 10: Annual exposure of the personal dose equivalents Hp(0.07), skin doses, in mSv for the USN personnel working in NM facilities performing PET/CT vs. NM facilities that do not perform PET/CT 35
Figure 11: Annual exposure of the personal dose equivalents Hp(0.07), extremity doses, in mSv for the USN personnel working in NM facilities performing PET/CT vs. NM facilities that do not perform PET/CT… 36
52
Table 2. Categories and corresponding definitions in the first dataset provided by the Navy Dosimetry Center, for DT-702/PD data 52
Table 3. Categories and corresponding definitions in the second dataset provided by the Navy Dosimetry Center, for DXT-RAD 53
Table 4. Several annual records in 2003–2020 used the DT-702/PD 53
Table 5. A yearly number of annual records in 2003–2020, using the DXT-RAD 54
Table 6. PET versus non-PET data, using the DT-702/PD 54
Table 7. PET versus non-PET data, using the DXT-RAD 55
Table 8. The number of observations, several workers, median, mean,
Q1
,
Q3
, and
95th
percentiles, and the minimum to a maximum of various annual dose records for 2003-2020… 55
Table 9. Summary statistics of the annual dose records per year of the Hp(10). 55
Table 10. Summary statistics of the annual dose records per year of the skin dose equivalents, the Hp(0.07). 56
Table 11. Summary statistics of the annual dose records per year of the extremity dose equivalents, the Hp(0.07). 56
Table 12. The workers, median, mean, Q1, Q3, and 95th percentiles and minimum to a maximum of the cumulative deep dose equivalents, skin dose equivalents and extremity dose equivalents for 2003-2020… 57
Table 13. Summary statistics of the personal dose equivalents the Hp(10) and Hp(0.07) for the PET facilities’ skin and extremity records 57
Table 14. Summary statistics of the personal dose equivalents Hp(10) and Hp(0.07) for skin and extremity records in the non-PET facilities 58
Nuclear medicine (NM) is a specialized area of radiology that experienced significant developments in the second half of the 20th century (1). The evolution of instrumentation, a surge of new radiopharmaceuticals (2), and the advent of Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET) (3) have all contributed to the increased use of nuclear medicine worldwide and, more specifically in the United States (US) (2). The number of NM procedures performed worldwide increased from 23.5 million in 1980 (4) to 37 million in
2006
(5) and from 7 million in 1982 (6) to 17.2 million in 2006 in the United States (5). Hence, in 2006, about half of the worldwide NM procedures were performed in the United States (2). The tremendous increase in the performance of NM studies resulted in increasing the annual per-capita effective radiation dose to the US population (7), therefore increasing the occupational exposure among medical workers in NM departments (8).
Medical radiation workers are exposed to protracted low-level radiation for extended periods. In contrast to other medical radiation workers, NM technologists are in direct contact with the source of radiation by manipulating and handling radionuclides (9), which elevates their risk of certain cancers such as breast cancer and squamous cell carcinoma (SCC), and circulatory diseases such as myocardial infarction (10). Due to the possible risks from increased radiation exposure, the International Commission on Radiological Protection (ICRP) established recommendations to limit occupational doses and ensure the workers’ safety (11). It also emphasizes that the radiation exposure to the workers and patients should be kept As Low As Reasonably Achievable (ALARA) (12).
Previous studies of occupational doses to US radiologic technologists show that radiation doses have decreased since 1939 (13). Reducing these doses is likely due to improved radiation
(
10
)
safety practices (11,14). However, a recent study involving NM technologists from nine US medical institutions showed that the maximum values of the annual personal dose equivalents generally increased from 1992 to
2015
. In this study, the mean annual personal dose equivalent (2.69 mSv) was consistent with annual mean doses to NM technologists from other countries (1.5 to 3.5 mSv) and higher than the estimated annual mean effective dose to general medical workers worldwide (0.7 mSv) (15). Moreover, it was also higher than the mean annual dose to US radiologic technologists. Another recent study that examined dose trends among US radiologic technologists performing NM procedures or not over 36 years period showed that the annual dose records for US radiologic technologists performing NM procedures (median 1.2 mSv) were higher than for general radiologic workers (75th percentile= 0.40 mSv) (16). Finally, the study showed that higher doses were associated with performing more diagnostic NM procedures, specifically cardiac and PET procedures.
Variations in work practices and radiation safety techniques between institutions and countries can lead to heterogenous radiation exposure measurements among different groups of NM workers (14). For example, studies conducted in the US to examine the effect of the changes in NM practices on occupational doses included technologists from different medical institutions all over the country. Therefore, these studies are susceptible to heterogeneity and measurement biases due to the variations between NM departments regarding the radiation protection standards, the radiopharmaceuticals in use, and technology updates. The present study has the advantage of focusing specifically on exposures over time to a specific population of workers, all serving within the United States Navy (USN) — a group of NM workers subject to the same radiation safety programs and regulations. This should significantly mitigate the problem of exposure heterogeneity within the study group.
Using a USN cohort of NM workers, this thesis tests the hypothesis that NM workers’
annual personal dose equivalents in USN medical centers are lower than NM workers’ annual personal dose equivalents from civilian medical centers across the United States due to a stringent radiation protection program within the USN. Conclusions based on these results may help understand occupational exposure in nuclear medicine and improve radiation protection programs.
Radiation is energy; released from a source that travels through space in electromagnetic waves or particles. Radiation consists of ionizing radiation (IR) and non-ionizing radiation. This dissertation will focus on IR, a type of radiation with a short wavelength and enough energy to remove or relocate an electron from an atom. The whole population is naturally exposed to IR from the space, the earth, the air, and the radionuclides present in our bodies, such as Pottasium-
40. In the 1980s, eighty-two percent of the exposure to the U.S population was from natural background radiation (2).
In 1895, Wilhelm Roentgen accidentally discovered X-rays while experimenting on a cathode tube (17). Within a year of this discovery, X-rays were used in medicine for many applications, from finding a bullet in a patient’s leg to diagnosing kidney stones (17). Two years later, X-rays started to be used in military hospitals (18). At the same period of X-ray discovery, other scientists such as Pierre and Marie Curie or Henri Becquerel were studying natural radiation (17). The Curies discovered polonium and radium, first used in industrial applications (17). Later, in 19
46
, manufactured sources of gamma radiation were also available. These discoveries and the invention of technologies in the medical field resulted in a new radiation exposure source to the population (17). Nowadays, about half of the radiation exposure (48%) to the U.S population comes from diagnostic and therapeutic medical applications (2).
Widespread unregulated use of IR was observed in the early years following its discovery. The lack of understanding of radiation-related risks on health led to severe injuries. Due to the late manifestation of detrimental radiation effects, the need for radiation safety was not immediately
recognized (19). First dermatitis and skin cancers were observed one and six years after discovering X-rays, respectively (18). Most of our understanding of radiation hazards came from the study of Atomic Bomb survivors after World War II (17).
When radiation interacts with the human body, the damage occurs at the cellular level, making it hard to detect (17). Radiation can cause two biological effects: deterministic (non- stochastic) and stochastic. Deterministic effects have a threshold: the severity of the response increases with the radiation dose, and below a certain dose threshold, no biological effect can occur (19). Some examples include skin burn, radiation sickness, sterility, and acute radiation syndrome (19). These effects depend on different variables such as the dose, dose fractionation, and type of radiation (19). In contrast, stochastic effects are random, and there is no threshold dose (19). The probability of the effect is proportional to the radiation dose, but the severity is independent (19). Cancer and heritable or genetic changes are the two main types of stochastic effects (19). As far as cancer is concerned, most cancers have a 20 year latency period and can occur after many years of exposure. Due to the long latency period, it is challenging to know whether the cancer was caused by radiation exposure or other factors.
There are different types of theoretical dose-response models related to the use ofany carcinogen, including radiation (20). The first is the linear no-threshold model, which states that there is a risk at any level of radiation exposure, no matter how small (20). This model is based on biological responses at high radiation doses (20). Still, because no clinical effects are seen from radiation exposure below 0.5 Gray (Gy), it is best to be conservative and take the low doses cautiously (20). The second model is the linear threshold which consists of a known threshold below no clinical effects are seen, but at the threshold level (0.5 Gy), the effect will increase linearly (20). The third model is the linear-quadratic, used for overall human response (20). This
model states that the effect is linear at low doses, but the response becomes quadratic as the dose increases. The NRC accepts the linear no-threshold model since it is the most conservative. It likely does not underestimate the actual risk, thereby allowing maximum protection when setting risk-based dose limits.
Nuclear medicine is a multi-disciplinary modality that involves administering radiopharmaceuticals for diagnostic and therapeutic purposes. Diagnostic nuclear medicine uses radioactive tracers to measure the function of an organ (physiological) and the biochemical; images in the body; in therapeutic nuclear medicine, unsealed radioactive materials are used to treat various thyroid cancer and hyperthyroidism. In nuclear medicine, radioactive chemical elements (radionuclides) can be used without any biological vector, such as iodine-131, or labeled with drugs or particles, forming a radiopharmaceutical (21).
Radiopharmaceuticals are radionuclides bound to biological molecules, targeting specific organs or tissues (22). They can be administered to the patient by intravenous or peritumoral injection, orally, or inhalation (2). Each NM imaging study corresponds to a specific radiotracer distributed in a targeted region of interest (ROI). The radiotracer emits gamma rays with given energies that can be detected by a gamma camera positioned next to the patient.
Most NM procedures focus on diagnostic, while therapeutic procedures only account for a small percentage (2). Therapeutic NM procedures are performed with a lower frequency than diagnostic NM procedures but with higher administered activities of radiopharmaceuticals (5). For example, the administered activity of iodine-131 for thyroid uptake study (diagnostic) is 2.8- 4.4 megabecquerel (MBq) (23), but 185-555 MBq for hyperthyroidism treatment (therapy) (24). However, since 1985, therapeutic NM procedures in developed countries have almost doubled (5).
Diagnostic NM studies can provide functional and anatomical information, whereas other diagnostic studies such as radiography or Computing Tomography (CT) usually provide just anatomical information (2). Diagnostic NM procedures can be divided into two categories based on technology and instrumentation: general diagnostic nuclear medicine and positron emission tomography (PET). In general diagnostic nuclear medicine, a gamma camera is used to obtain either planar imaging (two-dimensional projection image) or single-photon emission computed tomography (SPECT) imaging. In both cases, detectors collect gamma rays emanating from the patient after administering a radiotracer. The gamma camera rotates around the patient for SPECT imaging to record photons from different angles. A three-dimensional projection image is then reconstructed. Radiotracers used for planar and SPECT imaging emit low to medium energy photons (80-200 keV)(2).
Positron emission tomography (PET) was introduced at the end of the 1970s. In the early 1980s, the clinical applications of PET emerged in the field of neurology (25). In the early 1990s, PET was implemented in cardiology clinics (25). In the late 1990s, the F-18 fluorodeoxyglucose (FDG) began to be used for the evaluation of oncology patients, leading to rapid growth in the number of performed NM studies worldwide since 2000 (25) (5). This imaging technology relies on the administration of positron-emitting radionuclides and the detection of coincidence photons (i.e., 511 keV photons simultaneously emitted in opposite directions after a positron-electron annihilation) (5). The average annual growth rate of PET studies was 80 % from 2000 to
2005
, against 9 % for non-PET NM diagnostic studies (21): the rapid growth in the PET studies was due to the introduction of the integrated PET/CT system in early 2000 and the use of F-18 FDG in oncology (25).
Hybrid imaging was introduced for both diagnostic and therapeutic applications (2). SPECT or PET imaging can be used in conjunction with conventional CT (SPECT/CT, PET/CT) (2), or more rarely, MRI (PET/MRI) (2), to obtain physiological images and to provide attenuation correction, which helps in improving the images by removing the effect of the artifact. Hybrid imaging techniques improve the accuracy of detecting and localizing disease and are increasingly used in recent years (2).
1.4.1 Nuclear cardiovascular imaging
Cardiac NM are non-invasive diagnostic procedures dedicated to assessing coronary artery disease and evaluating possible heart damage from cancer treatments such as radiotherapy and chemotherapy. NM cardiovascular studies have increased rapidly since 1979 and have become the most frequent procedure performed in nuclear medicine (1). In 2005, cardiac procedures accounted for 57% of the total completed NM studies in the US (5). The most common cardiac NM study is the myocardial perfusion stress test, which allows evaluation of the coronary arteries. Myocardial perfusion stress test performed in the US in
2014
accounted for 5.98 million studies (26).
Since the late 1960s, there have been few approved radiotracers used in nuclear cardiology (23). Nowadays, 59% of performed SPECT cardiac studies use Tc-99m Sestamibi (Tc-99m MIBI), 20% use Tc-99m Tetrofosmin, and 9% use Tl-201 Thallous Chloride (23). The amount of activity administered per procedure increased due to the reduction in the use of Tl-201 Thallous Chloride in myocardial NM studies. The typical administered amount of activity of Tl-201 Thallous Chloride before 2000 was
111
MBq and after 2000 is 148 MBq, while the administered amount of activity of Tc-99m MIBI and Tc-99m Tetrofosmin is 1110 MBq for one day protocol (23).
Furthermore, cardiac NM studies account for 8
5%
of the effective dose to the NM patient population (5).
In
2011
, a Turkish study estimated radiation doses to technologists per NM procedure (27). It showed that cardiac studies performed using Tc-99m MIBI delivered higher doses toNM technologists than whole-body bone scans, thyroid scans, and renal scans (27). The cumulative radiation exposure to technologists performing cardiac NM scans increased over time, which might be due to an increased frequency of cardiac procedures (1). Moreover, the myocardial perfusion stress test usually includes two injections, and technologists spend a longer time with the patient during injection, stress test, and camera positioning, contributing to increased occupational exposure (1).
1.4.2 Positron Emission Tomography
Positron emission tomography (PET) is a more recent NM technology. The science behind PET imaging started early in 1929 (28). Still, it was not clinically applicable until Ter-Pogossian et al. developed in 1975 a PET whole-body camera that provides high contrast images of positron- emitting organs (29). PET imaging relies on detecting photons emitted from the patient’s body after the injection of a positron-emitting radioisotope (29). When the emitted positron has lost its energy, it annihilates with an electron within the body to create two 511 keV photons (28). The PET camera is composed of scintillation crystals that absorb the photons and convert them into light photons. When two 511 keV photons are detected in coincidence (at 180° and simultaneously), the light is converted into an electrical signal (30).
Recently, the number of performed PET procedures increased from less than 2% to 15% due to several factors: the advent of the hybrid PET/CT system after 2000, an increasing number of cyclotrons for the production of short-lived positron-emitting radioisotopes (most positron
emitters have half-lives measured in minutes), and a decrease in the cost of PET cameras (2). Moreover, malignant tumors metabolize glucose faster than benign tumors, making F-18 FDG useful in oncology (28). The high demand for PET in oncology is also a leading cause of the increase in PET scans annually (31).
The annihilation photons from the radionuclides used in PET have a higher energy (511 keV) than the energy of the photons from radionuclides typically used in general NM studies. Accordingly, the annihilation photons have a greater ability to penetrate deeper tissues, which causes a higher internal organ risk to workers (31). An Australian study compared the radiation doses to technologists working in general NM with doses to those working in PET and showed that technologists rotating through PET received higher whole-body doses than those who only performed general NM procedures (31).
With ionizing radiation in medicine, medical workers are sometimes exposed. Those working in NM departments, including NM technologists, physicians, nurses, health/medical physicists, are more or less exposed to ionizing radiations depending on their occupationand workload. Occupational exposure occurs from any procedure that requires the worker to stand near a radioactive source during the shipping, preparation, or administration of the radiopharmaceutical. Furthermore, standing near the patient after the administration can also lead to radiation exposure (8). In the earliest years of nuclear medicine, scientists focused on improving the instrumentation, interpreting the medical images, and conducting clinical trials to approve new radiopharmaceuticals, with little attention to monitoring occupational exposure (8).
The US National Cancer Institute conducted a cohort study on 90,000 US radiologic technologists employed in the twentieth century (32) that showed increased risks of leukemia (33),
melanoma and non-melanoma skin cancer (34-35), and breast cancer (36), for these technologists. Another study showed a statistically significant increase in cancer mortality among British radiologists who had been working for more than 40 years in the twentieth century (37). A recent study of radiation-monitored workers employed in the nuclear industry in France, the United Kingdom, and the US showed a positive association between cumulative dose of ionizing radiation and death caused by leukemia among workers exposed to low doses of radiation (38). Compared with the nuclear industry, the medical field’s lack of historical dosimetry data made it more challenging to estimate radiation risk among those workers (39). Starting in the 19
50
s, scientists became more aware of radiation’s health hazards and gave more attention to occupational exposure. This awakening led to increasing the awareness of NM workers’ monitoring (8).
NM workers are potentially exposed to radiation internally and externally. Internal radiation exposure can occur after inhalation, ingestion, or skin contamination with radionuclides (39). Individual monitoring for internal exposure to radiation is usually achieved by body activity assessment or air sampling (39). Doses from internal exposure during routine work in the NM department are much lesser than the external exposure (39). Therefore, the dose assessment for internal exposure to NM workers is only performed when an unanticipated event has possibly internally exposed the worker. Otherwise, NM workers are externally exposed to ionizing radiations during a typical workday due to the proximity with radioactive materials during transportation, manipulation, injection, and patients’ transportation, positioning, or imaging (39). For that reason, NM workers are regularly monitored for external radiation exposure by wearing two dosimeters: a whole-body dosimeter on the chest and an extremity dosimeter on the finger.
In the 1896s, the American engineer Wolfram Fuchs established the first radiation protection recommendations: time, distance, and shielding (18). In 1925, the first meeting of the International Congress of Radiology (ICR) was held in London, and the International Commission on Radiation Units and Measurements (ICRU) was established (18). In 1928, the International X- ray and Radium Protection Committee (IXRPC) provided its first recommendation, emphasizing the importance of shielding to protect against superficial injuries and changes in the blood, and set a limit of working hours (18). In 1934, the first set of exposure limits was established for X-ray irradiation (18). This recommendation (0.2 roentgen per day) can result in an annual effective dose of about
500
mSv (18). In 1938, the same exposure limits and regulations were adopted for gamma radiation as had previously been established for X-rays (18). After world war II, in 1951, the International Commission on Radiological Protection (ICRP) was established, and this commission issued a recommendation of a maximum permissible dose of 0.5 roentgens/week and
1.5 roentgen/week for both X-ray and gamma radiation for whole-body exposure and hand exposure, respectively (18).
For the first 60 years of using ionizing radiation in industry and medicine, the main goal in radiological protection was to avoid any deterministic effects on workers (18). During this time, the ICRU started to replace roentgen ( a unit of exposure) with rem ( a unit of dose equivalence), and the limit from 1951 became 0.3 rem /week, resulting in annual occupational effective dose of
150
mSv (18). In 1954, the commission provided the first recommendation that encourages limiting the exposure from IR to the lowest possible level (18). In 1958, following the Geneva meeting, the commission published its recommendation in publication 1, including a limit of accumulated dose equivalent corresponding to an average annual occupational effective dose of
50 mSv (18). The 1954 recommendation was replaced by as low as practicable in publication 9 in the 1966’s report, and the limit of accumulated dose equivalent was replaced by an annual occupational limit of 50 mSv (18). In 1977, the ICRP established a dose limitation system and introduced the three principles of protection: justification, optimization, and the application of annual occupational dose limits (the total effective dose equivalents and the dose equivalents). In 1990, the ICRP provided more specified numerical limits to protect workers (Table 1)(11). In the United States, the Nuclear Regulatory Commission (NRC) was created by congress in 1974 to regulate the use of nuclear materials and to ensure the safe use of radioactive materials for beneficial civilian purposes while protecting the environment and people. The current Navy radiation protection standards are consistent with or more stringent than those of the NRC.
1.7.1 Dose Units
The quantities used in radiation dosimetry are divided into three categories: physical quantities, which describe the interactions between the radiation and matter (40), protection quantities, and operational quantities, both used in radiation protection dosimetry (
41
). The ICRP has supported a system for radiological protection for more than 50 years (42). In
2007
, the most recent protection quantities were recommended by the ICRP in publication
103
, which include the mean absorbed dose, the equivalent dose, HT, and the effective dose, E (42). The equivalent dose is based on the mean absorbed dose multiplied by a radiation-weighting factor, which depends on the biological effectiveness of the type of radiation (43). After applying tissue-weighting factors, the effective dose is the sum of all exposed tissues’ equivalent doses. The effective dose is used for protective dose assessment (43). It is calculated for a reference male or female but never for a specific individual.
Protection quantities are impossible to measure directly; therefore, equivalent doses and effective doses cannot be used directly in radiation monitoring but can be assessed using operational quantities (43). The ICRP and the ICRU defined operational quantities as replacing the protection quantities to ensure compliance with regulations and exposure limits to workers (44). Accordingly, many countries have used operational quantities for individual external radiation monitoring purposes (42). Although the operational quantities generally provide a conservative estimate for the protection quantities (42), the ICRU stated that they should be used as estimates for the protection quantities when doses are below dose limits (44).
Operational quantities consist of area monitoring quantities and a personal dose equivalent used for individual monitoring (42). For the present study, only the personal dose equivalent will be discussed. The personal dose equivalent, Hp (d), is a dose equivalent at an appropriate depth, d, below a specified point of the body (43). A depth of d= 10 mm is used for the deep dose equivalent (DDE-whole body), while a depth of d= 0.07 mm is used for the assessment of the shallow dose equivalent (SDE) to the skin and extremities (43). The relationship betweenthe effective dose and Hp(10) is based on a uniform whole-body irradiation (44). The deep dose equivalent Hp(10) is estimated for photons and electrons using a single detector whose output signals are proportional to the absorbed dose (44). The shallow dose equivalent Hp(0.07) is estimated using a thin detector material whose output signals are proportional to the absorbed dose to tissue and used for low-energy photons and beta particles monitoring (44).
1.7.2 External radiation dosimetry in the US-Navy
The US Navy (USN) specifies acceptable dosimetry devices for monitoring Navy radiation workers (45). All NM personnel working in the USN medical centers are required by the Navy regulations to wear personnel dosimeters (PDs). PDs are used to monitor DDE and SDE.
Simultaneously, some NM workers, such as NM technologists, must wear extremity dosimeters (45).
In 1973, the Navy introduced thermo-luminescent dosimeters (TLD) for gamma exposure monitoring. Since 2002, the Navy has been using a DT-702 manufactured by Saint Gobain (Harshaw 8840) for personnel dosimetry. It uses a high-sensitivity LiF doped with magnesium (Mg), copper (Cu), and phosphorus (P) (LiF: Mg, Cu, P) (45). The DT-702/PD is composed of a TLD card and a holder. The TLD includes four lithium fluoride (LiF) pellets of different thicknesses and compositions mounted between two Teflon sheets on an aluminum card (45).
Elements 1 and 2 are 0.381 mm thick of LiF-700H, element 3 is a thinner
0.25
4 mm of LiF-700H, and element 4 is 0.381 mm of LiF-
600
H (45) . LiF-700H can measure photon and beta radiation, while LiF-600H is useful for measuring photon, beta, and neutron radiation (45). The holder consists of filters that provide variable radiation absorption thicknesses to assess DDE and SDE (45). Element 1 is placed behind 242 mg/cm2 plastic combined with 91 mg/ cm2 copper and discriminates gamma radiation energy levels (46). Element 2 is placed behind 1,000 mg/cm2 of plastic and is used for determining the deep dose Hp(10) (46). Element 3 is covered by a 17 mg/cm2 Mylar window for shallow dose equivalent estimation (46). Element 4 is placed behind a combination of 242 mg/cm2 of plastic and 240 mg/ cm2 of Tin and used to provide neutron information as well as medium energy photon discrimination (46) (Figure 1). The NDC provides NM workers with Thermo scientific DXTRAD finger ring dosimeter for extremity monitoring. DXTRAD is a single element LiF TLD used to monitor photon and beta radiation and mounted in an adjustable ring (45) (Figure 2).
(
Figure
4:
DT-702
personal
dosimeter.
Cardholder
Filter 2:
Plastic
Filter 3:
Mylar
window
Filter 4:
Plastic and
Tin
Filter
1:
Plastic
and
Copper
LiF Card
)
Figure 5: DXT-RAD finger dosimeter.
*Image from (NAVMED P-5055, Radiation Health Protection Manual)
This study is designed to examine the changes in annual occupational exposure among a study population of NM personnel working in USN medical centers, using personal dose equivalents (deep and shallow) recorded from personnel passive dosimeters and shallow doses recorded from extremity dosimeters. A dosimetry dataset was received from the United States Navy, Naval Dosimetry Center (NDC), the centralized dosimetry processing laboratory for US Navy. NDC distributes, receives, processes, and archives exposures from the USN occupational workers deployed worldwide.
The NDC is a large-scale processor responsible for sending dosimeters to over250 locations worldwide (47) and preparing summary radiation exposure reports to the Navy and Marine Corps personnel (45). It provided two datasets that include dose records of NM personnel working in the USN medical centers over almost 20 years. The first dataset contains the radiation exposure obtained from personal dosimeters over 2002-2020. The second dataset contains radiation exposure obtained from extremity dosimeters over 2003-2020. The two datasets were provided as Microsoft Excel spreadsheets. Data used in this study are explained in Table 2-3.
Moreover, the Navy provides a 2-digit occupational code that identifies Navy employers’ occupation: the assigned code is 32 for NM occupation (45). For this study, code 32 was usedby the NDC to extract Navy personnel working in NM departments. Radiation exposure monitoring data of NM personnel working in Naval medical centers from 2003 to 2020 were included in this study. The data collection period was set to 2000-2020, corresponding to the years when the exposure to NM workers was expected to increase due to the advent of PET/CT imaging. It also matches an increased use of Tc-99m in myocardial studies, which require higher administered
activities, as previously described (Background). However, as the USN transitioned to a new dosimeter in 2002, the NDC did not provide any data collected before that year.
An institutional review board (IRB) is a group that a research center has formally designated to review and monitor research involving human subjects (48). They work to protect the rights and safety of humans who participate in the research. Georgetown University’s IRB reviewed this study’s proposal under ID: STUDY00003615 and was determined as exempt (non- human research). As defined by the US Department of Health and Human Subjects under 45 CFR 26.101(b) (48) from 45 CFR part 46 requirements, an exempt study may include existing data, but the subjects cannot be identified from the information presented in the study. To fulfill this condition, the NDC deidentified data: name, age, gender, date of birth, or any other identifiers were not used in this study.
The operational quantities Hp(d) (mSv) have been used in the applicable regulations of many countries for individual external monitoring to ensure workers’ compliance with radiation safety (49). Collected dosimetry information for external radiation monitoring to radiation workers generally includes two dose quantities: Hp(10) and Hp(0.07), which are obtained from personal and extremity monitoring devices, respectively (15). The USN requires NM workers to wear the dosimeter at the waist/chest level for photon and beta radiation monitoring and a DXT-RAD finger ring dosimeter for extremity monitoring (45).
NM personnel working in Naval medical centers have been routinely monitored using TLD dosimeters since 1973 (45). Since 2002, the NDC has issued a personnel monitor (DT-702/PD) quarterly (95 days maximum) to monitor their radiation workers (45). Still, they monitored
monthly (35 days maximum) any NM technologist and other NM worker expected to receive an annual effective dose equivalent of 5 mSv (45).
The Navy does not keep the exact job title of their workers in records. In nuclear medicine, NM workers can be either technologists, nurses, physicians, or health/medical physicists, and this distinction could not be made in our data. No further investigation could be conducted to obtain this information for the sake of anonymity. Therefore, the monitoring time of the dose records varied based on the variation in the occupations in the NM department. Although, in the data, we observed monitoring times that exceeded 95 days in 360 records corresponding to 154 individuals working in 12 USN medical centers. Dosimetry data corresponding to extended periods of 95+ days was considered acceptable in this study; they were not excluded and believed to have no detrimental effect on our study.
The lower limit of detection (LLD) of the dosimeter DT-702/PD is 0.03 mSv for DDE and SDE for photon and beta monitoring and 0.05 mSv for DDE for neutron monitoring (50). As confirmed by NDC workers, the US Navy keeps all the recorded doses, including the doses below the LLD levels, for use in retrospective studies. Therefore, annual dose equivalents below and above the LLD level were included in the data analysis in this study.
The NDC provided whole-body exposure (deep dose equivalent, DDE) and skin exposure (shallow dose equivalent, SDE) data for 528 individuals working in NM departments of 16 Naval medical centers over 2002-2020: these data were recorded using the DT-702/PD. Besides, the NDC provided extremity exposure (SDE) data for 305 individuals working in NM departments of 15 Naval medical centers over 2003-2020: these data were recorded using DXT-RAD finger rings.
Henceforth, the SDE from personal dosimeters will be referred to as “skin dose,” and the SDE from extremity dosimeters as “extremity dose.”
Records
before 2002 were excluded from this study because of a dosimetry technology transition and change in the Lower Limit of Detection in the Navy. NDC provided the data with a unique anonymized individual code to link each individual’s data. These unique individual codes ensured anonymity of the individual workers. The data included from NDC included the issue date and the collection date of the dosimeters, which was used to convert period doses to annual doses, as explained in the next paragraph.
The initial dataset received from NDC included 7,641 records of each DDE and skin dose and 4,789 records of extremity doses. Duplicates were first identified in Excel using the following variables: unique code, issue date, and collection date. After the data cleansing, 7,578 records remained for DDE and skin doses and 4,747 for extremity doses. Overlaps between years were then tracked to avoid overestimating, and doses were recalculated by calendar year. For example, if the issue date was at the end of 2003 and the dosimeter was collected early in
2004
, the total monitoring duration for this dosimeter was calculated by subtracting the issue date from the collection date. Then, the total number of days with a dose was derived for each calendar year. An average daily dose was then calculated by dividing the recorded dose by the total monitoring duration and eventually multiplied by the total number of days of that calendar year. 1,201 and 830 records were found to overlap between two years in the data from DT-702/PD and DXT-RAD dosimeters, respectively, which led to as many more new records in the datasets of these respective dosimeters. A total of 161 records of extremity doses from 20 individuals were excluded for not being linked to any individual from the whole-body data.
The unique code and the issue year converted period doses to annual doses. All the available DDE values for each worker and each year were summed to obtain annual doses. The same step was taken to calculate annual skin and extremity doses. Doses provided in Roentgen equivalent man (rem) by the US Navy were converted into millisieverts (mSv). Yearly numbers of annual records are provided in Table 4-5.
The cumulative personal dose equivalents were calculated by summing the annual records for each individual over the period a worker was exposed to radiation in USN NM departments. Five hundred twenty-eight cumulative doses of each DDE and skin records and 285 cumulative doses of extremity records were included in the analysis.
The NDC provided the mailing address associated with each issued dosimeter, including the Navy medical center name, city, state, and zip codes. Data from DT-702/PD records corresponded to 16 locations, while data from DXT-RAD records corresponded to 15 sites. These addresses were used to discriminate PET and non-PET facilities, using publicly available Navy hospitals/clinics’ websites. Our research was focused on NM and PET features in the presentations of radiology departments. If the website mentioned both NM and PET, we categorized the facility as a PET facility; otherwise, it was categorized as a non-PET facility. More detailed information is provided in Tables 6-7. For 140 dose records corresponding to 78 individuals, all from 2003, dose data were excluded from our PET vs. non PET analysis due to the absence of a mailing address.
The statistical software STATA version 16 was used to analyze the data. The distributions of annual and cumulative dose records of NM personnel working in Naval medical centers from 2003-2020 were described using summary statistics (e.g., 25th, 50th, 75th, and 95th percentiles) and graphical methods (e.g., histograms and box-and-whisker plots). Owing to the large observation number within the PET and non-PET facilities, a parametric test was conducted without the necessity to perform a normality test. The F-ratio test for the equality of the variances was served with a
95%
confidence interval (CI). It showed significant differences between the variances of the two groups: annual exposure of the personnel working in the USN NM facilities perform PET/CT vs. the annual exposure of personnel working in the USN NM facilities that do not perform PET/CT of all variables DDE, skin doses and extremity doses (p= < 0.05). Therefore, the DDE, skin doses, and extremity doses were statistically analyzed between both groups using the two-sample t-test, assuming unequal variance. For all statistical tests, p< 0.05 was considered statistically significant. The null hypothesis (i.e., the hypothesis to be tested) was no difference in the annual radiation exposure of personnel working in the USN NM facilities performing PET/CT vs. the annual exposure of personnel working in the USN NM facilities that do not perform PET/CT. The alternate hypothesis was a difference in the annual radiation exposure of personnel working in the USN NM facilities performing PET/CT vs. the annual exposure of personnel working in the USN NM facilities not performing PET/CT. (Rejection of the null hypothesis implies that the alternative hypothesis is correct).
Summary statistics of annual dose records to NM workers from medical centers of the US Navy between 2003 and 2020 are presented in Table 8. A total of 1,916 and 1,357 annual dose records were obtained from 2003 to 2020 using the DT-702/PD and the DXT-RAD, respectively (Table 4-5). The numbers of annual records varied over time, with average values of 106 (37 –
159
) and 75 (35 – 103) for DT-702/PD and DXT-RAD, respectively. The average number of annual records per NM worker were 3.63 and 4.76 for DT-702/PD and DXT-RAD, respectively.
3.1.1 Annual deep dose equivalents distribution
A total of 1,916 annual deep dose equivalents (Hp(10)) – recorded between 2003 and 2020 for 528 individuals – were included in the analysis. These annual Hp(10) varied from 0.00 mSv to
7.18
mSv, with a median value of 0.38 mSv (interquartile range [IQR], 0.05-1.27 mSv; mean,
0.82
mSv). Seventeen percent of the annual Hp(10) were below the LLD of the DT-702/PD but were included in the analysis. More than 95% of the annual Hp(10) received by NM workers in our cohort were below three mSv [95.3% (1827 of 1916])(Figure 3). Median annual Hp(10) remained relatively constant from 2003 to 2020 (range,
0.12
-0.82 mSv) (Table 9). The distribution of the maximum value of annual Hp(10) fluctuated over time (range, 1.87-7.18 mSv), with the highest value observed in 2015 (Figure 4). No correlation was found between the number of individuals monitored each year and the maximum value.
Figure 3: Histogram of the distribution of 1,916 annual deep dose equivalents, Hp(10), previously collected and provided by the NDC for 528 workers from NM departments of the USN medical centers between 2003 and 2020.
Figure 4: Box-and-whisker plot of the trends in annual deep dose equivalents, Hp(10), to workers from NM departments of the USN medical centers between 2003 and 2020.
*The upper and lower whiskers represent the maximum and minimum values.
3.1.2 Annual skin dose equivalents distribution
A total of 1,916 annual skin dose equivalents (Hp(0.07)) recorded between 2003 and 2020 for 528 individuals were also included in the analysis. These annual Hp(0.07) varied from 0.00 mSv to
7.12
mSv, with a median value of
0.37
mSv (IQR =0.06 – 1.22 mSv; mean =
0.80
mSv). Sixteen percent of the annual Hp(0.07) were below the LLD of the DT-702/PD but were included in the analysis. More than 95% of the annual Hp(0.07) received by NM workers in our cohort were below three mSv [95.6% (1831 of 1916)] (Figure 5). Median annual Hp(0.07) remained relatively constant from 2003 to 2020 (range, 0.12-0.81 mSv) (Table 10). The distribution of the maximum value of annual Hp(0.07) fluctuated over time (range, 1.96-7.12 mSv), with the highest value observed in 2015 (Figure 6). No correlation was found between the number of individuals monitored each year and the maximum value.
Figure 5: Histogram of the distribution of 1,916 annual shallow dose equivalents, Hp(0.07), previously collected and provided by the NDC for 528 workers from NM departments of the US-Navy between 2003 and 2020.
Figure 6: Box-and-whisker plot of the trends in annual skin dose equivalents, Hp(0.07), to workers from NM departments of the USN medical centers between 2003 and 2020.
*The upper and lower whiskers represent the maximum and minimum values.
3.1.3 Annual extremity doses distribution
A total of 1,357 annual extremity dose equivalents (Hp(0.07)) recorded between 2003 and 2020 for 285 individuals were included in the analysis. These annual Hp(0.07) varied from 0.00 mSv to
121
mSv, with a median value of 2.89 mSv (IQR = 0.76 – 7.86 mSv; mean = 6.65 mSv). Almost eighty-two percent of the annual Hp(0.07) received by NM workers in our cohort were below ten mSv [81.7% (1109 of 1357)] (Figure 7). Median annual Hp(0.07) remained relatively constant from 2003 to 2020 (range,
1.34
-5.26 mSv) (Table 11). The distribution of the maximum value of annual Hp(0.07) doubled in 2005 (120 mSv), then fluctuated in 2006 – 2014, and decreased again after 2015 to reach a minimum value of 12.7 mSv in 2020 (Figure 8). No correlation was found between the number of individuals monitored each year and the maximum value for the annual extremity doses.
Figure 7: Histogram of the distribution of 1,357 annual shallow dose equivalents to the extremity, Hp(0.07), previously collected and provided by the NDC for 285 workers from NM departments of the USN medical centers between 2003 and 2020
Figure 8: Box-and-whisker plot of the trends in annual shallow dose equivalents to the extremity, Hp(0.07), to workers from NM departments of the USN medical centers between 2003 and 2020.
*The upper and lower whiskers represent the maximum and minimum values.
3.2 Cumulative doses
3.2.1 Cumulative deep dose and skin dose equivalents distribution
For the 528 individuals monitored with the DT-702/PD, the cumulative deep dose equivalents (DDE) and cumulative skin dose equivalents ranged from 0.00 to 46.6 mSv and 0.00 to 44.3 mSv, respectively. Cumulative DDE and skin doses had median values of 0.39 mSv (IQR
= 0.05 – 3.18 mSv; mean = 2.96 mSv) and 0.39 mSv (IQR = 0.05 – 3.08 mSv; mean = 2.90 mSv), respectively (Table 12 a-b).
3.2.2 Cumulative extremity dose equivalents distribution
For the 285 individuals monitored with the DXT-RAD, the cumulative extremity dose equivalents ranged from 0.11 to 529 mSv and had a median value of
13.0
mSv (IQR= 2.89 – 38.5 mSv; mean = 31.6 mSv) (Table 12c).
3.3 PET and non-PET dose
3.3.1 PET facilities distribution
The analysis of the two facilities with a PET department included 221 individual and
787
annual dose records of both values the DDE and the skin dose equivalents, respectively, and 163 individual and 600 annual dose record of the extremity dose equivalents. DDE, skin dose equivalents and extremity dose equivalents had median values of 0.44 mSv (IQR= 0.06 – 1.60 mSv; mean =
0.99
mSv), 0.42 mSv (IQR = 0.06 – 1.58 mSv; mean =
0.97
mSv) and 3.16 mSv (IQR = 0.73 – 9.51 mSv; mean = 8.74 mSv), respectively (Table 13).
3.3.2 Non-PET facilities distribution
The analysis of the 14 and 13 facilities corresponding to the data from DT-702/PD and DXT-RAD dosimeters, respectively, were collected on 361 individuals, corresponding to
1,207
annual dose records of each the DDE and the skin dose equivalents, and 176 individuals, corresponding to
800
annual dose records of the extremity dose equivalents. DDE, skin dose equivalents and extremity dose equivalents had median values of 0.29 mSv (IQR = 0.06 – 0.95 mSv; mean = 0.65 mSv), 0.30 mSv (IQR= 0.06 – 0.95 mSv; mean =
0.63
mSv) and 2.52 mSv
(IQR = 0.76 – 6.19 mSv; mean = 4.72 mSv), respectively (Table 14).
3.3.3 PET vs non-PET
An independent two samples t-test was conducted to compare the annual radiation exposure of personnel working in the USN NM facilities perform PET/CT (group 1) (N=787 and N=600) vs. the annual exposure of personnel working in the USN NM facilities that do not perform PET/CT (group 2) (N= 1,207 and N= 800) for the data recorded using the DT-702/PD and the DXT-RAD, respectively.
The result showed that there is significant difference ( p= <0.001 ) in the annual DDE for group 1 with higher mean (M= 0.99 , SD=
1.24
) than group 2 (M=0.65, SD=
0.85
). The magnitude of the differences in the mean (mean difference= –
0.34
, 95% CI : – 0.44 to –
0.24
) was significant. Also, it showed that there is significant difference ( p= <0.001 ) in the annual skin doses for group 1 with higher mean (M= 0.97 , SD= 1.2 ) than group 2 (M=0.63, SD= 0.82). The magnitude of the differences in the mean (mean difference= - 0.34, 95% CI : - 0.44 to - 0.24) was significant. Moreover, the test’s result showed that there is significant difference ( p= <0.001 ) in the annual extremity doses for group 1 with higher mean (M= 8.74 , SD= 14.7 ) than group 2 (M=4.72, SD= 6.38). The magnitude of the differences in the mean (mean difference= - 4.02, 95% CI : - 5.28 to
– 2.76) was significant Figure 9, 10, and 11.
Figure 9: Annual exposure of the personal dose equivalents Hp(10) in mSv for the USN personnel working in NM facilities performing PET/CT vs. NM facilities that do not perform PET/CT.
*The upper and lower whiskers represent the maximum and minimum values.
Figure 10: Annual exposure of the personal dose equivalents Hp(0.07), skin doses, in mSv for the USN personnel working NM facilities performing PET/CT vs. NM facilities that do not perform PET/CT.
*The upper and lower whiskers represent the maximum and minimum values.
Figure 11: Annual exposure of the personal dose equivalents Hp(0.07), extremity doses, in mSv for the USN personnel working in NM facilities performing PET/CT vs. NM facilities that do not perform PET/CT.
*The upper and lower whiskers represent the maximum and minimum values.
In our record of 528 and 285 USN NM workers assessed using the DT-702/PD and the DXT-RAD from 2003-2020, respectively, we observed a median annual radiation dose of 0.38 mSv (IQR, 0.05-1.27 mSv; mean, 0.82 mSv), 0.37 mSv (IQR, 0.06 – 1.22 mSv; mean = 0.80 mSv),
and 2.89 mSv (IQR = 0.76 – 7.86 mSv; mean = 6.65 mSv) for the DDE, skin doses and extremity doses, respectively. More than 95% of the annual DDE and skin doses were below three mSv: this is less than the average annual exposure from natural background radiation in the US. Almost 82% of the annual extremity doses were less than ten mSv. These values are significantly below the annual occupational limit of 50 mSv for the effective dose equivalent and 500 mSv for the dose equivalent to the skin and extremities established by the ICRP and recommended by the NRC. These DDE, skin doses, and extremity doses spread over a wide range, which could be related to the variability of NM workers’ occupations and tasks within NM departments.
Our study focuses on analyzing the data for the period when the occupational exposure of NM workers was expected to increase due to increased use of Tc-99m in myocardial studies, for instance, and decreased use of Tl-201 thallous chloride. This period also corresponded to the advent of PET/CT imaging, possibly leading to increased radiation exposure to the workers. However, the median value of annual personal dose equivalents (Hp(10)) appeared to be lower in our study (0.38 mSv in 2003 – 2020) than the median dose value for NM technologists working at civilian U.S. hospitals (
2.07
mSv in 1979 – 2015) (15). Moreover, our result of the median annual DDE was lower than that of a recent study, including data from NM technologists working in civilian U.S. hospitals in 1980-2015 (1.2 mSv) (16). We computed summary statistics for easier comparison with other studies when excluding any annual dose below 0.03 mSv—the abovementioned studies recorded as minimal any annual dose below the LLD. After exclusion,
our dataset’s median annual DDE was higher than without exclusion, with 0.62 mSv against 0.38 mSv, but still about half the median dose values from studies performed on workers from civilian hospitals. This result supports the hypothesis that the annual exposure to NM workers in the Navy is lower than to NM workers from civilian hospitals. These lower radiation doses to US Navy workers might be due to stringent radiation protection programs within the Navy. However, this dose difference could also be linked to a variation in workload between civilian and Navy hospitals. Our mean value of annual DDE was slightly lower than that of a cohort of 588 NM technologists from Saudi Arabia, monitored between 2015 and
2019
, with 0.82 mSv against 1.22 mSv, respectively (51). Moreover, our mean annual DDE matched the estimated average annual effective dose to NM workers monitored worldwide in 1990-19
94
(
0.79
mSv). However, it was slightly higher than the estimated mean annual effective dose to general medical workers worldwide in 2000-2002 (0.70 mSv) (52).
To our knowledge, no published data reports annual occupational exposure to the skin and extremities for U.S. NM workers. Therefore, we only could compare skin doses from the present study with published skin doses from other countries. The mean annual skin dose in our study (0.80 mSv) was lower than the mean skin doses in Kuwait for NM technologists (0.94 mSv in
2009
) and NM physicians (
0.96
mSv in 2009) (53). Moreover, it was lower than the mean annual skin dose reported for 588 NM technologists in Saudi Arabia (
1.23
mSv) in 2015-2019 (51).
On the other hand, the operational quantity for extremity doses was compared with the reported values in a study that evaluated the extremity exposure among NM workers in Serbia, using DXT-RAD finger ring (
2010
-2014) (54). The lowest mean annual value was recorded among radiographers in 2014 (12 mSv), thus almost twice the average annual value recorded in our study (6.65 mSv). It is recommended to wear ring dosimeters where the highest exposure is expected.
However, no information was provided on how workers wore their dosimeters in the present study, nor whether these recommendations were followed.
Because no information was available to identify NM facilities performing PET/CT in addition to general NM studies, we used the mailing addresses provided by the NDC and publicly available information from the Navy hospitals’ website to discriminate dose records for workers performing PET/CT procedures. Our results matched those from a recent study that showed an association of higher doses for NM technologists regularly performing PET/CT in the U.S. (16). The statistical analysis of doses to workers from facilities mentioning PET/CT on their website, compared with doses to workers from non-PET facilities, showed a statistically significant difference of mean annual dose between the two groups. However, in the absence of verified information on the regular performance of PET/CT procedures for each worker in our cohort, and due to the absence of a time specification on the implementation of PET in each facility, this result should be taken with caution when interpreting these results.
A major strength of this study is the consistency in the dosimeter type and the calibration method – using a single radiation protection program –, which prevents uncertainties related to variation in dosimetry practices. Moreover, previous studies conducted on occupational radiation exposure only included NM technologists. In contrast, the present study involves all possible workers from NM departments exposed to radiation, including NM technologists, physicians, nurses, and health/medical physicists: this means a more exhaustive evaluation of occupational exposure in NM departments. Lastly, our study is the first to report dose equivalents to the skin and extremities among NM workers in the US, and this type of data is now available for comparison with future studies.
A major limitation of this study is the absence of work history, such as the frequency of performed diagnostic and therapeutic procedures, the radionuclides in use, and the radiation safety procedures. The lack of such information limited our analysis of the dose results and trends. The absence of information on each worker’s occupation or job title was a major inconvenience, making it very complex to separate dose analysis based on the occupation.
A second limitation is an assumption that doses recorded by the dosimeters reflect doses received by the workers. Based on the documentation obtained from the Navy’s radiation health protection program, the DT-702/PD dosimeter should be worn at the chest level to detect the exposure received by the body at the point where the highest exposure could occur (45). Some uncertainty arises from the obligation level each worker has toward these regulations. In addition, the data obtained from the NDC were doses per issued dosimeter. Due to overlap between years of some issued dosimeters, we recalculated doses by year, resulting in an over-or underestimation of some doses. The last limitation of our study is a common issue in radiation dosimetry: occupational exposure is assessed based on the personal dose equivalents, measured using personal dosimeters. These operational quantities are surrogates for the effective dose, which cannot be directly measured. However, report 160 from the European Commission of radiation protection on technical recommendations for monitoring individuals occupationally exposed to external radiation stated that the operational quantity Hp(10) generally overestimates the effective dose (55). Therefore, comparisons between personal dose equivalents and effective doses should be taken with caution.
Overall, a prospective study on the same group of workers or a simple survey could help
get the missing information in this study and better link the dose trends with the occupation, the workload, radiation safety program, and the performance of specific procedures such as
myocardial studies or PET/CT. A questionnaire has been drafted, and the dose analysis in the present study and could be used in future studies. It is provided as an Appendix.
CHAPTER 6. CONCLUSIONS
Nuclear medicine workers are exposed to protracted low-level radiation for extended periods, elevating their risk of breast cancer, SCC, and circulatory disease. Due to the possible risks from increased radiation exposure, the ICRP established recommendations to limit occupational doses and emphasized the ALARA principle. Previous studies conducted in the US to assess the trends of occupational exposure among NM workers included technologists from different medical institutions, which makes these studies susceptible to heterogeneity and measurement biases due to variations in work practices and radiation safety techniques between institutions. Although previous studies of occupational doses among the US radiologic technologists show that doses have decreased since 1939, which is likely due to improved radiation safety practices, a recent study of occupational doses among NM technologists in the US medical institutions showed that the maximum values of the annual personal dose equivalents among those workers generally increased from 1992 to 2015. Therefore, the present study was conducted to mitigate the problem of exposure heterogeneity within the study group and to test the hypothesis that NM workers’ annual personal dose equivalents in USN medical centers are lower than the annual personal dose equivalents of NM workers from civilian medical centers across the United States due to a stringent radiation protection program within the USN.
Our study showed that the annual DDE, skin, and extremity doses of 528 and 285 NM
personnel working at the USN medical facilities and assessed using the DT-702/PD and the DXT- RAD from 2003-2020, respectively, were well below the annual occupational limits established by the ICRP (50 mSv for the total effective dose equivalents, and 500 mSv for the dose equivalents to the skin and extremities). The median annual DDE to NM workers in the USN is lower than NM workers from US civilian hospitals, supporting our hypothesis. Also, the mean value of annual
DDE was slightly lower than that for NM technologists from Saudi Arabia (2015-2019). Our study’s mean annual skin dose was lower than the average for NM technologists andNM physicians in Kuwait and lower than for NM technologists in Saudi Arabia. The mean of annual DDE in the present study matched the estimated average annual effective dose to NM workers monitored worldwide (1990-1994), but slightly higher than the estimated mean annual effective dose to general medical workers worldwide (2000-2002).
Moreover, our study’s mean annual extremity dose was half the lowest extremity exposure recorded among NM workers in Serbia. As expected, our mean annual exposure among workers in PET facilities was significantly higher than for non-PET facilities. The present study provided new data for future radiation monitoring among those workers and should help improve radiation protection programs in medical centers. We recommend a prospective data collection or a survey to provide detailed information on the USN workload and radiation protection programs for future studies.
1. Van Dyke, Miriam E., et al. “Historical Patterns in the Types of Procedures Performed and Radiation Safety Practices Used in Nuclear Medicine From 1945–2009.” Health Physics, vol. 111, no. 1, July
2016
, pp. 37–46. DOI.org (Crossref), doi:1
0.10
97/HP.0000000000000519.
2. National Council on Radiation Protection and Measurements, editor. Medical Radiation Exposure of Patients in the United States: Recommendations of the National Council on Radiation Protection and Measurements. National Council on Radiation Protection report no. 184. Bethesda, Md: National Council on Radiation Protection and Measurements, 2019.
3. Slomka, Piotr J., et al. “Advances in SPECT and PET Hardware.” Progress in Cardiovascular Diseases, vol. 57, no. 6, May 2015, pp. 566–78. DOI.org (Crossref), doi:
10.1
016/j.pcad.2015.02.002.
4. United Nations Committee on the Effects of Atomic Radiation. Sources, Effects and Risks of Ionizing Radiation. UNSCEAR 1988 Report to the General Assembly, with Annexes. New York, NY: United Nations, 1988.
5. National Council on Radiation Protection and Measurements. Ionizing radiation exposure of the population of the United States. National Council on Radiation Protection report no.
160. Bethesda, Md: National Council on Radiation Protection and Measurements, 2009.
6. National Council on Radiation Protection and Measurements. Exposure of the U.S. Population from Diagnostic Medical Radiation. National Council on Radiation Protection report no.
100
. Bethesda, Md: National Council on Radiation Protection and Measurements, 1989.
7. Mettler, Fred A., et al. “Radiologic and Nuclear Medicine Studies in the United States and Worldwide: Frequency, Radiation Dose, and Comparison with Other Radiation Sources— 1950–2007.” Radiology, no. 2, Radiological Society of North America (RSNA), Nov. 2009, pp. 520–31. Crossref, doi:10.
114
8/radiol.2532082010.
8. Drozdovitch, Vladimir, et al. “Nuclear Medicine Practices in the 1950s through the Mid-
1970s and Occupational Radiation Doses to Technologists from Diagnostic Radioisotope Procedures:” Health Physics, vol.
107
, no. 4, Oct. 2014, pp. 300–10. DOI.org (Crossref), doi:10.1097/HP.0000000000000107.
9. Bernier, Marie Odile, et al. “Work History and Radioprotection Practices in Relation to Cancer Incidence and Mortality in US Radiologic Technologists Performing Nuclear Medicine Procedures.” Occupational and Environmental Medicine, no. 8, BMJ, May
2018
, pp. 533–61. Crossref, doi:10.1136/oemed-
2017
-104559.
10. Kitahara, Cari M., et al. “Cancer and Circulatory Disease Risks in US Radiologic
Technologists Associated with Performing Procedures Involving Radionuclides.” Occupational and Environmental Medicine, no. 11, BMJ, July 2015, pp. 770–76. Crossref, doi:10.1136/oemed-2015-102834.
11. International Commission on Radiological Protection: 1990 Recommendations of the International Commission on Radiological Protection. ICRP Publication 60. Oxford, Pergamon Press, 1991, pp 50–54.
12. International Commission on Radiological Protection: General principles for the protection of workers. ICRP Publication 75. Oxford, Pergamon Press, 1997, pp 1–7.
13. Simon, Steven L., et al. “Estimating Historical Radiation Doses to a Cohort of U.S. Radiologic Technologists.” Radiation Research, vol. 166, no. 1, July 2006, pp. 174–92. DOI.org (Crossref), doi:10.1667/RR3433.1.
14. United Nations Scientific Committee on the Effects of Atomic Radiation. Sources and Effects of Ionizing Radiation. UNSCEAR
2008
Report to the General Assembly, with Scientific Annexes. Vol 1. Sources annexes. New York, NY: United Nations, 2010.
15. Villoing, Daphnée, et al. “A U.S. Multicenter Study of Recorded Occupational Radiation Badge Doses in Nuclear Medicine.” Radiology, vol. 287, no. 2, May 2018, pp. 676–82. DOI.org (Crossref), doi:10.1148/radiol.2018171138.
16. Villoing, Daphnée, et al. Trends in Occupational Radiation Doses for U.S. Radiologic Technologists Performing General Radiologic and Nuclear Medicine Procedures, 1980– 2015. no. 0, 2021, p. 8.
17. Donya, Mohamed, et al. “Radiation in Medicine: Origins, Risks and Aspirations.” Global Cardiology Science and Practice, vol. 2014, no. 4, Dec. 2014, p. 57. DOI.org (Crossref), https://doi.org/1
0.53
39/gcsp.201
4.57
.
18. International Commission on Radiological Protection: The History of ICRP and the Evolution of its Policies. ICRP Publication 109. Oxford, Pergamon Press, 2008, pp 1–37.
19. Choudhary, Sofiya. “Deterministic and Stochastic Effects of Radiation.” Cancer Therapy & Oncology International Journal, vol. 12, no. 2, Oct. 2018. DOI.org (Crossref), https://doi.org/10.19080/CTOIJ.2018.12.555834.
20. Bolus, Norman E. “Basic Review of Radiation Biology and Terminology.” Journal of Nuclear Medicine Technology, vol. 45, no. 4, 2017, pp. 259–264., https://doi.org/10.2967/jnmt.
117
.195230.
21. National Research Council (U.S.), et al. Advancing Nuclear Medicine through Innovation.
National Academies Press, 2007. Open WorldCat,
http://public.ebookcentral.proquest.com/choice/publicfullrecord.aspx?p=3378270.
22. IAEA. (2016, April 13). Diagnostic radiopharmaceuticals. IAEA. https://
www.iaea.org/topics/diagnostic-radiopharmaceuticals.
23. Drozdovitch, Vladimir, Aaron B. Brill, Ronald J. Callahan, et al. “Use of Radiopharmaceuticals in Diagnostic Nuclear Medicine in the United States: 1960–2010.” Health Physics, vol. 108, no. 5, May 2015, pp. 520–37. DOI.org (Crossref), doi:10.1097/HP.0000000000000261.
24. Kuanrakcharoen, Pichit. Radioiodine (I-131) Dose for the Treatment of Hyperthyroidism in Rajavithi Hospital. 2016, p. 7.
25. Coleman, R. Edward, et al. “Concurrent PET/CT with an Integrated Imaging System: Intersociety Dialogue from the Joint Working Group of the American College of Radiology, the Society of Nuclear Medicine, and the Society of Computed Body Tomography and Magnetic Resonance.” Journal of the American College of Radiology, vol. 2, no. 7, July 2005, pp. 568–84. DOI.org (Crossref), doi:10.1016/j.jacr.2005.03.014.
26. IMV. Benchmark Report, Nuclear Medicine. Des Plaines, Ill: IMV Medical Information Division, 2015.
27. Bayram, T., et al. “Radiation Dose to Technologists per Nuclear Medicine Examination and Estimation of
Annual Dose
.” Journal of Nuclear Medicine Technology, vol. 39, no. 1, Mar. 2011, pp. 55–59. DOI.org (Crossref), doi:10.2967/jnmt.11
0.08
0358.
28. Rich DA. A brief history of positron emission tomography. J Nucl Med Technol. 1997 Mar;25(1):4-11. PMID: 9239597.
29. Ter-Pogossian, Michel M., et al. “A Positron-Emission Transaxial Tomograph for Nuclear Imaging (PETT).” Radiology, vol. 114, no. 1, Jan. 1975, pp. 89–98. DOI.org (Crossref), doi:10.1148/114.1.89.
30. Valk, Peter E., editor. Positron Emission Tomography: Basic Science and Clinical Practice.
Springer, 2003.
31. Roberts, Fiona O., et al. “Radiation Dose to PET Technologists and Strategies to Lower Occupational Exposure.” JOURNAL OF NUCLEAR MEDICINE TECHNOLOGY, vol. 33, no. 1, 2005, p. 4.
32. Sigurdson, Alice J., et al. “Cancer Incidence in the U.S. Radiologic Technologists Health Study, 1983-1998.” Cancer, vol. 97, no. 12, June 2003, pp. 3080–89. DOI.org (Crossref), doi:10.1002/cncr.11444.
33. Linet, M. S. “Incidence of Haematopoietic Malignancies in US Radiologic Technologists.” Occupational and Environmental Medicine, vol. 62, no. 12, Dec. 2005, pp. 861–67. DOI.org (Crossref), doi:10.1136/oem.2005.020826.
34. Freedman, D. Michal, et al. “Risk of Melanoma among Radiologic Technologists in the United States.” International Journal of Cancer, vol. 103, no. 4, Feb. 2003, pp. 556–62. DOI.org (Crossref), doi:10.1002/ijc.10854.
35. Yoshinaga, Shinji, et al. “Nonmelanoma Skin Cancer in Relation to Ionizing Radiation Exposure among U.S. Radiologic Technologists.” International Journal of Cancer, vol.
115
, no. 5, July 2005, pp. 828–34. DOI.org (Crossref), doi:10.1002/ijc.20939.
36. Doody, Michele Morin, et al. “Breast Cancer Incidence in U.S. Radiologic Technologists.” Cancer, vol. 106, no. 12, June 2006, pp. 2707–15. DOI.org (Crossref), doi:10.1002/cncr.21876.
37. Berrington, A., et al. “100 Years of
Obs
ervation on British Radiologists: Mortality from Cancer and Other Causes 1897–1997.” The British Journal of Radiology, vol. 74, no. 882, June 2001, pp. 507–19. DOI.org (Crossref), doi:10.1259/bjr.74.882.740507.
38. Leuraud, Klervi, et al. “Ionising Radiation and Risk of Death from Leukaemia and Lymphoma in Radiation-Monitored
Workers
(INWORKS): An International Cohort Study.” The Lancet Haematology, vol. 2, no. 7, July 2015, pp. e276–81. DOI.org (Crossref), doi:10.1016/S2352-3026(15)00094-0.
39. Covens, P., et al. “Personal Dose Monitoring in Hospitals: Global Assessment, Critical Applications and Future Needs.” Radiation Protection Dosimetry, vol. 124, no. 3, Aug. 2007, pp. 250–59. DOI.org (Crossref), doi:10.1093/rpd/ncm418.
40. International Commission on Radiation Units And Measurements: 1998 Fundamental Quantities and Units for Ionizing Radiation. ICRU report 60. International Commission on Radiation Units and Measurements, Bethesda, MD.
41. International Commission on Radiation Units And Measurements : 1993 Quantities and Units in Radiation Protection Dosimetry. ICRU Report 51. International Commission on Radiation Units and Measurements, Bethesda, MD.
42. International Commission on Radiological Protection: 2010 Conversion Coefficients for Radiological Protection Quantities for External Radiation Exposures. ICRP Publication 116, Oxford, Pergamon Press. Ann. ICRP 40(2–5).
43. International Commission on Radiological Protection: 2007 Recommendations of the International Commission on Radiological Protection. ICRP Publication 103. Oxford, Pergamon Press, 2007. Ann. ICRP 37 (2–4).
44. European Commission. Directorate-General for Energy and Transport. Technical Recommendations for Monitoring Individuals Occupationally Exposed to External Radiation. Publications Office, 2009. DOI.org (CSL JSON), https://data.europa.eu/doi/10.2768/19817.
45. Navy Bureau of Medicine and Surgery. NAVMED P-5055. Radiation Health Protection Manual.; Washington DC, 2011.
46. Moscovitch, M. “Personnel Dosimetry Using LIF:Mg,Cu,P.” Radiation Protection Dosimetry, vol. 85, no. 1, 1999, pp. 49–56., https://doi.org/10.1093/oxfordjournals.rpd.a032904.
47. R. Cassata, J., et al. “A New Paradigm in Personal Dosimetry Using LiF:Mg,Cu,P.” Radiation Protection Dosimetry, vol. 101, no. 1, Aug. 2002, pp. 27–42. DOI.org (Crossref), doi:10.1093/oxfordjournals.rpd.a005983.
48. Center for Drug Evaluation and Research. “(IRBs) and Protection of Human Subjects.” U.S. Food and Drug Administration, FDA,
www.fda.gov/about-fda/center-drug-evaluation-and-
research-cder/institutional-review-boards-irbs-and-protection-human-subjects-clinical- trials.
49. Petoussi-Henss, N et al. “ICRP Publication 116. Conversion coefficients for radiological protection quantities for external radiation exposures.” Annals of the ICRP vol. 40,2-5 (2010): 1-257. doi:10.1016/j.icrp.201
1.10
.001.
50. Romanyukha, Alex et al. “Effect of background radiation on the lower limit of detection for extended dosemeter issue periods.” Radiation protection dosimetry vol. 131,2 (2008): 180- 7. doi:10.1093/rpd/ncn137.
51. Alashban, Yazeed, and Nasser Shubayr. “Occupational Dose Assessment for Nuclear Medicine and Radiotherapy Technologists in Saudi Arabia.” Radiation Protection Dosimetry, vol. 195, no. 1, 2021, pp. 50–55., https://doi.org/10.1093/rpd/ncab
112
.
52. United Nations Scientific Committee on the Effects of Atomic Radiation. Sources, Effects and Risks of Ionizing Radiation. UNSCEAR 2000 Report to the General Assembly, with Annexes. New York, NY: United Nations, 2000.
53. Al-Abdulsalam, A., and A. Brindhaban. “Occupational Radiation Exposure among the Staff of Departments of Nuclear Medicine and Diagnostic Radiology in Kuwait.” Medical Principles and Practice, vol. 23, no. 2,
2013
, pp. 129–
133
., https://doi.org/10.1159/000357123.
54. Kaljevic, Jelica, et al. “Hand Dose Evaluation of Occupationally Exposed Staff in Nuclear Medicine.” Radiation Protection Dosimetry, vol. 170, no. 1-4, 2015, pp. 292–296., https://doi.org/10.1093/rpd/ncv500.
55. European Commission on Radiation Protection, Technical Recommendations for Monitoring Individuals Occupationally Exposed to External Radiation, Directorate-General for Energy and Transport 2009, no 160.
Table 1. Annual Occupational Dose Limits
|
Measurement Type |
(a) ICRP- Dose Limit (mSv) |
(b) NRC- Dose Limits (mSv) |
||
|
Total effective dose equivalent |
20* |
50 |
||
|
Lens equivalent dose |
20** |
150 | ||
|
Extremity equivalent dose |
500 | |||
|
Shallow dose (Dose equivalent to the skin) |
*Effective dose of 20 mSv/ year, averaged over five years with no single year exceeding 50 mSv
** This annual limit was lowered by ICRP in April 2011 from 150 mSv to 20 mSv, with the further provision that the dose should not exceed 50 mSv in any single year.
(
Source: Reference 11.
)
Table 2. Categories and corresponding definitions in the first dataset provided by the Navy Dosimetry Center, for DT-702/PD data.
|
Column |
Definition |
||
|
SDE_RPT |
Shallow Dose Equivalent : the external exposure to the skin. The dose is equivalent at a tissue depth of 0.007 centimeters (cm) over an area of 10 cm2. |
||
|
PDE_RPT |
Photon Dose Equivalent or what is referred to in the text as Deep Dose Equivalent (DDE): the photon external whole-body exposure equivalent at a depth of 1 cm. |
||
|
IndCode |
Individual Code: anonymized codes assigned by the NDC to help identify each’s data. |
||
|
Issue_Date |
Date the dosimeter was issued to an individual. (Year Month Date) |
||
|
Collect_Date |
Date the dosimeter was collected from an individual. (Year Month Date) |
||
|
CommAddr |
Command Address : mailing address associated with the issued dosimeter. ( Name, City, State, Zip-Code) |
Table 3. Categories and corresponding definitions in the second dataset provided by the Navy Dosimetry Center for DXT-RAD.
|
EDE_RPT |
Extremity Dose Equivalent: the extremity exposure measured using extremity dosimeter at tissue depth of 0.007 cm. |
|||
|
See Table 2. |
||||
|
Occ_Code |
||||
Table 4. Several annual records in 2003–2020 used the DT-702/PD.
Year
Number
of
annual records
2003
152
2004
143
2005
159
2006
133
2007
112
2008
99
2009
92
2010
91
2011
80
2012
103
2013
111
2014
127
2015
117
2016
107
2017
115
2018
97
2019
41
2020
37
Table 5. A yearly number of annual records in 2003–2020, using the DXT-RAD.
|
Year |
Number of annual records |
||||
|
82 |
|||||
|
100 |
|||||
|
76 |
|||||
|
67 |
|||||
|
63 |
|||||
|
46 |
|||||
|
61 |
|||||
|
2012 |
|||||
|
95 |
|||||
|
94 |
|||||
|
35 |
Table 6. PET versus non-PET data, using the DT-702/PD.
|
PET |
Non-PET |
|||
|
Number of facilities |
2 | 14 | ||
|
Number of individuals |
221 | 361 | ||
|
Number of annual records |
787 |
1,207 |
Table 7. PET versus non-PET data, using the DXT-RAD.
| 13 | |
| 163 | 176 |
|
600 |
800 |
Table 8. The number of observations, several workers, median, mean, Q1, Q3, and 95th percentiles, and the minimum to a maximum of various annual dose records for 2003-2020.
|
An |
nual Dose Recor |
ds (mSv) |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
# of |
Median |
Mean |
Q1 | Q3 | 95th |
Minimum |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Annual Dose Records |
Workers |
Percentile |
to Maximum |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Deep Dose
Equivalents |
1,916 |
528 |
0.38 |
0.82 |
0.05 | 1.27 |
2.94 |
0.00-7.18 |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Skin Dose Equivalents |
0.37 | 0.80 | 0.06 | 1.22 |
2.86 |
0.00- 7.12 |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Extremity Dose Equivalents |
1,357 |
285 |
2.89 | 6.65 | 0.76 | 7.86 |
26.5 |
0.00-121 |
Table 9. Summary statistics of the annual dose records per year of the Hp(10).
Annual Dose Records (mSv)
Median
Mean
Q1
Q3
2003
0.35
0.60
0.06
0.87
3.46
2004
1.42
4.64
2005
0.61
1.43
5.51
2006
0.28
0.07
1.41
6.44
2007
0.35
0.95
0.04
6.50
2008
0.26
0.83
0.04
1.34
4.64
2009
0.20
0.84
0.06
1.23
4.80
2010
0.12
0.78
0.02
0.88
6.05
2011
0.59
0.96
0.09
1.46
4.36
2012
0.55
0.91
0.05
1.53
5.01
2013
0.48
0.07
1.32
3.27
2014
0.72
0.04
1.33
3.87
2015
0.28
0.05
1.35
7.18
2016
0.45
0.72
0.04
1.20
3.68
2017
0.77
0.05
1.30
6.26
2018
0.18
0.51
0.05
0.82
2.88
2019
0.43
0.77
0.07
1.51
2.87
2020
0.26
0.05
0.90
1.87
Table 10. Summary statistics of the annual dose records per year of the skin dose equivalents, the Hp(0.07).
|
2003 |
3.65 |
||||||||
|
2004 |
0.81 |
1.00 |
|||||||
|
2005 |
5.36 |
||||||||
|
2006 |
0.25 |
6.11 |
|||||||
|
2007 |
1.24 |
6.47 |
|||||||
|
2008 |
5.00 |
||||||||
|
2009 |
0.22 |
1.2 |
4.73 |
||||||
|
2010 |
0.12 |
0.86 |
5.86 |
||||||
|
2011 |
0.56 |
0.92 |
0.08 |
1.40 |
4.38 |
||||
|
2012 |
0.58 |
0.89 |
1.52 |
4.89 |
|||||
|
2013 |
3.12 |
||||||||
|
2014 |
0.31 |
3.84 |
|||||||
|
2015 |
0.30 |
1.50 |
7.12 |
||||||
|
2016 |
0.44 |
1.15 |
3.57 |
||||||
|
2017 |
0.73 |
6.12 |
|||||||
|
2018 |
0.49 |
2.70 |
|||||||
|
2019 |
0.42 |
0.75 |
1.36 |
2.77 |
|||||
|
2020 |
0.24 |
0.54 |
1.96 |
Table 11. Summary statistics of the annual dose records per year of the extremity dose equivalents, the Hp(0.07).
|
3.15 |
7.24 |
1.44 |
9.91 |
48.3 |
|
| 4.57 | 10.1 |
2.15 |
11.3 |
68.8 |
|
|
11.5 |
1.31 |
12.9 |
121 |
||
|
4.45 |
9.28 |
92.3 |
|||
|
5.26 |
11.0 |
1.45 |
114 | ||
|
3.73 |
7.31 |
1.10 |
8.05 |
48.7 |
|
4.07 |
8.08 |
10.0 |
63.6 |
||
|
3.23 |
7.88 |
53.8 |
|||
|
2.71 |
5.06 |
1.21 |
7.71 |
34.8 |
|
|
3.95 |
7.59 |
0.93 |
12.3 |
42.4 |
|
|
2.35 |
6.02 |
8.94 |
36.6 |
||
| 1.34 |
5.07 |
0.23 |
5.65 |
59.8 |
|
| 2.07 |
4.69 |
6.84 |
38.3 |
||
|
2.13 |
3.78 |
5.32 |
27.1 |
||
|
1.56 |
3.41 |
0.50 |
4.33 |
20.1 |
|
|
3.04 |
0.39 |
4.31 |
21.3 |
||
|
4.12 |
1.03 |
6.24 |
15.4 |
||
|
1.49 |
2.62 |
0.74 |
3.51 |
12.7 |
Table 12. The workers, median, mean, Q1, Q3, and 95th percentiles and minimum to a maximum of the cumulative deep dose equivalents, skin dose equivalents, and extremity dose equivalents for 2003-2020.
|
Cumulative Dose Records (mSv) |
|||||
|
# of workers |
Minimum
to Maximum |
||||
|
a- Deep Dose Equivalents |
2.96 | 3.18 |
14.22 |
0.00 – 46.6 |
|
|
b- Skin Dose Equivalents |
2.90 | 3.08 |
14.39 |
0.00 – 44.3 |
|
|
c- Extremity Dose Equivalents |
13.0 |
31.64 |
38.51 |
134.10 |
0.11 – 529 |
Table 13. Table 13. Summary statistics of the personal dose equivalents the Hp(10) and Hp(0.07) for the PET facilities’ skin and extremity records.
|
PET Facilities (mSv) |
|||
| 1.60 |
3.47 |
||
| 0.97 | 1.58 |
3.40 |
|
| 3.16 | 8.74 | 9.51 |
37.2 |
Table 14. Summary statistics of the personal dose equivalents Hp(10) and Hp(0.07) for skin and extremity records in the non-PET facilities.
|
Non-PET Facilities (mSv) |
|||
| 0.65 |
2.38 |
6.13 |
|
| 0.63 |
2.27 |
6.18 |
|
| 2.52 | 4.72 | 6.19 |
16.5 |
APPENDIX A
Summary statistics of the annual deep dose equivalents for 528 nuclear medicine personnel working in the United States Navy medical facilities from 2003-2020
|
Percentiles |
Smallest |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
1% |
0 |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 5% |
.0053735 |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
10% |
.0149745 |
Obs | 1,916 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
25% |
.0548624 |
Sum of Wgt. |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
50% |
.3754083 |
.8160365 |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
75% |
1.267237 |
Largest |
6.259352 |
Std. Dev. |
1.053848 |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
90% |
2.271212 |
6.439745 |
Variance |
1.110597 |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 95% |
2.940099 |
6.49072 |
Skewness |
1.939169 |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
99% |
4.558464 |
7.176692 |
Kurtosis |
7.569551 |
Yearly summary statistics of the annual deep dose equivalents for 528 nuclear medicine personnel working in the United States Navy medical facilities
2003
|
.0158069 |
|||||
|
.0193887 |
.0017403 |
152 |
|||
|
.0558003 |
.0032977 |
||||
|
.3533911 |
.5954048 |
||||
|
.8666915 |
Largest
2.556723 |
.6878873 |
|||
|
1.557385 |
2.65008 |
.4731889 |
|||
|
2.237326 |
2.751594 |
1.587392 |
|||
|
3.45546 |
5.384345 |
2004
|
.0012822 |
|||||||||
|
.0106438 |
|||||||||
|
.0308526 |
.003324 |
143 |
|||||||
|
.1048888 |
.004826 |
||||||||
|
.8155563 |
.9941114 |
||||||||
|
1.423938 |
Largest
3.386387 |
.9653986 |
|||||||
|
2.361793 |
3.416775 |
.9319945 |
|||||||
|
2.84205 |
3.93676 |
1.14879 |
|||||||
|
4.63605 |
4.045049 |
2005
Percentiles
Smallest
1%
.0012822
0
5%
.0106438
.0012822
10%
.0308526
.003324
Obs
143
25%
.1048888
.004826
Sum of Wgt.
143
50%
.8155563
Mean
.9941114
75%
1.423938
Largest
3.386387
Std. Dev.
.9653986
90%
2.361793
3.416775
Variance
.9319945
95%
2.84205
3.93676
Skewness
1.14879
99%
3.93676
4.63605
Kurtosis
4.045049
2006
|
.004466 |
.0036347 |
||||
|
.0203855 |
|||||
|
.0342862 |
.0070844 |
133 | |||
|
.0680952 |
.0101563 |
||||
|
.2762672 |
.9519001 |
||||
|
1.412995 |
Largest
4.144266 |
1.274838 |
|||
|
3.029637 |
4.187002 |
1.625213 |
|||
|
3.806939 |
4.257892 |
1.655794 |
|||
|
5.352752 |
2007
|
.0061564 |
.0049375 |
||||
|
.013367 |
|||||
|
.0194603 |
.0074532 |
112 | |||
|
.0374651 |
.0085283 |
||||
|
.3508754 |
.9498236 |
||||
|
1.233454 |
Largest
5.223693 |
1.387288 |
|||
|
2.606879 |
5.88709 |
1.924567 |
|||
|
4.051319 |
6.130999 |
2.145686 |
|||
|
7.557846 |
2008
|
.0080472 |
99 | |||||
|
.0398241 |
||||||
|
.261023 |
.8314757 |
|||||
|
1.341586 |
Largest
3.732991 |
1.147634 |
||||
|
2.900131 |
3.970333 |
1.317064 |
||||
|
3.636149 |
4.168913 |
1.592871 |
||||
|
4.635402 |
4.595665 |
2009
|
.0001528 |
|||||||
|
.0046363 |
.0006318 |
||||||
|
.0317041 |
.0006845 |
92 | |||||
|
.0611961 |
.0007781 |
||||||
|
.1988361 |
.8411406 |
||||||
|
1.234413 |
Largest
3.45946 |
1.135638 |
|||||
|
2.563417 |
3.898583 |
1.289673 |
|||||
|
3.302218 |
1.644283 |
||||||
|
4.799671 |
5.069683 |
2010
|
.0003796 |
|||||
|
.0070811 |
.001003 |
||||
|
.009816 |
.0027117 |
91 | |||
|
.0240745 |
.0050217 |
||||
|
.1151427 |
.7796714 |
||||
|
.8781401 |
Largest
3.858491 |
1.317878 |
|||
|
2.486832 |
5.077831 |
1.736803 |
|||
|
3.747566 |
5.798368 |
2.240975 |
|||
|
6.049545 |
7.76719 |
2011
|
.0053148 |
.0020422 |
||||||
|
.0129835 |
.0030358 |
80 | |||||
|
.0885018 |
.0037949 |
||||||
|
.5875151 |
.955201 |
||||||
|
1.456991 |
Largest
3.442358 |
1.047137 |
|||||
|
2.545557 |
3.555289 |
1.096496 |
|||||
|
3.369639 |
4.103434 |
1.395265 |
|||||
|
4.355334 |
4.438917 |
2012
|
.0008358 |
||||||||
|
.0053168 |
||||||||
|
.0122175 |
.0010657 |
103 | ||||||
|
.0506676 |
.0015669 |
|||||||
|
.5462941 |
.910614 |
|||||||
|
1.528687 |
Largest
3.092861 |
1.021356 |
||||||
|
2.121116 |
3.320576 |
1.043167 |
||||||
|
2.716112 |
4.436441 |
1.449513 |
||||||
|
5.005732 |
5.332718 |
2013
|
.0032804 |
||||
|
.0140443 |
111 | |||
|
.0713282 |
.000541 |
|||
|
.4788338 |
.7891131 |
|||
|
1.321705 |
Largest
2.980606 |
.8829734 |
||
|
2.038877 |
2.986499 |
.779642 |
||
|
2.931366 |
3.244384 |
1.20218 |
||
|
3.274509 |
3.521907 |
2014
|
.0041658 |
|||||
|
.0140761 |
.0002244 |
127 |
|||
|
.0422195 |
.000234 |
||||
|
.3374017 |
.7205666 |
||||
|
1.334441 |
Largest
2.930588 |
.8674197 |
|||
|
1.917927 |
2.990605 |
.7524169 |
|||
|
2.398999 |
3.498989 |
1.380122 |
|||
|
3.872853 |
4.334483 |
2015
|
.0009826 |
|||||
|
.0050809 |
|||||
|
.011369 |
.0017945 |
117 | |||
|
.0514741 |
.0040815 |
||||
|
.2835386 |
.8453923 |
||||
|
1.346161 |
Largest
3.547054 |
1.19854 |
|||
|
2.487023 |
4.048561 |
1.436498 |
|||
|
2.715241 |
5.767288 |
2.382416 |
|||
|
10.58892 |
2016
|
.0007151 |
|||||
|
.0044666 |
.0003958 |
107 | |||
|
.0369615 |
.0004923 |
||||
|
.452927 |
.7210969 |
||||
|
1.195336 |
Largest
2.894889 |
.8832121 |
|||
|
1.925686 |
2.97426 |
.7800637 |
|||
|
2.841493 |
3.399453 |
1.445903 |
|||
|
3.678466 |
4.389815 |
2017
|
.0020566 |
.0007266 |
||||||
|
.0047266 |
|||||||
|
.0094334 |
.002233 |
115 | |||||
|
.0459444 |
.003271 |
||||||
|
.2865726 |
.7652477 |
||||||
|
1.296422 |
Largest
3.422184 |
1.047726 |
|||||
|
2.182504 |
3.560056 |
1.097731 |
|||||
|
2.765138 |
3.959037 |
2.150577 |
|||||
|
9.124552 |
2018
|
.0000456 |
||||||
|
.0004132 |
.0001181 |
|||||
|
.0088668 |
.0001385 |
97 | ||||
|
.0500798 |
.0002033 |
|||||
|
.1790895 |
.5077409 |
|||||
|
.8227307 |
Largest
1.950156 |
.6401801 |
||||
|
1.560979 |
2.171966 |
.4098306 |
||||
|
1.887049 |
2.355326 |
1.512951 |
||||
|
2.877304 |
4.711528 |
2019
|
.0079081 |
||||
|
.0134662 |
.0097465 |
|||
|
.0211412 |
41 | |||
|
.0714212 |
.0137174 |
|||
|
.4256934 |
.7709586 |
|||
|
1.510869 |
Largest
2.18502 |
.8307606 |
||
|
2.078768 |
2.313535 |
.6901632 |
||
|
2.337713 |
.9017106 |
|||
|
2.870684 |
2.520716 |
2020
|
.0010885 |
||||||||
|
.0066906 |
||||||||
|
.0240003 |
.0081717 |
37 | ||||||
|
.0511697 |
||||||||
|
.2559418 |
.5342347 |
|||||||
|
.8983554 |
Largest |
1.521588 |
.5847211 |
|||||
|
1.551218 |
.3418987 |
|||||||
|
1.698638 |
.9076189 |
|||||||
|
1.870278 |
2.378766 |
APPENDIX C
Summary statistics of the annual shallow dose equivalents of the skin for 528 nuclear medicine personnel working in the United States Navy medical facilities from 2003-2020
|
.0070037 |
|||||
|
.0182813 |
|||||
|
.0556798 |
|||||
|
.3725173 |
.7994701 |
||||
|
1.215276 |
Largest |
6.119405 |
1.026777 |
||
|
2.210767 |
6.181241 |
1.05427 |
|||
|
2.864718 |
6.473961 |
1.968534 |
|||
|
4.635141 |
7.118781 |
7.846537 |
Yearly summary statistics of the annual shallow dose equivalents of the skin for 528 nuclear medicine personnel working in the United States Navy medical facilities
2003
|
.0084649 |
|||
|
.0232357 |
.0034345 |
||
|
.0619117 |
.0035827 |
||
|
.3734783 |
.6024175 |
||
|
.8353235 |
Largest
2.54432 |
.6952061 |
|
|
1.607193 |
2.594654 |
.4833115 |
|
|
2.239701 |
2.84054 |
1.656896 |
|
|
3.64907 |
5.817352 |
2004
|
.0180982 |
|||
|
.0352173 |
|||
|
.1165865 |
.0004867 |
||
|
.8086973 |
1.001939 |
||
|
1.433539 |
Largest |
3.395016 |
.9594585 |
|
2.380001 |
3.553425 |
.9205606 |
|
|
2.818681 |
3.887628 |
1.125757 |
|
|
4.004581 |
2005
|
.0003918 |
|||
|
.0075263 |
|||
|
.026471 |
.0004055 |
159 | |
|
.0558806 |
.0019618 |
||
|
.5540211 |
.9012122 |
||
|
1.335968 |
Largest
4.501707 |
1.115336 |
|
|
2.477835 |
4.719437 |
1.243974 |
|
|
3.467109 |
4.925521 |
1.738235 |
|
|
5.361388 |
5.993091 |
2006
|
.0038637 |
.0000145 |
||
|
.0186963 |
|||
|
.0384645 |
.0046722 |
||
|
.0704271 |
.0118052 |
||
|
.251845 |
.8992895 |
||
|
1.267874 |
Largest
4.028935 |
1.205549 |
|
|
2.887704 |
4.130642 |
1.453349 |
|
|
3.45397 |
4.13113 |
1.69271 |
|
|
6.117428 |
5.526514 |
2007
|
.0045778 |
.000824 |
||
|
.0098852 |
|||
|
.0218932 |
.0059951 |
||
|
.0369207 |
.0072682 |
||
|
.3476557 |
.9470057 |
||
|
1.244687 |
Largest |
5.136432 |
1.386328 |
|
2.608834 |
6.098285 |
1.921905 |
|
|
3.781629 |
2.166295 |
||
|
7.734419 |
2008
|
.0081023 |
.000813 |
|
|
.0152435 |
.0048934 |
|
|
.0398511 |
.0052773 |
|
|
.2818285 |
.8394228 |
|
|
1.329703 |
Largest
3.590305 |
1.167257 |
|
2.842191 |
3.867624 |
1.362488 |
|
3.585802 |
4.691899 |
1.686533 |
|
5.007534 |
5.143531 |
2009
|
.0024876 |
||
|
.0318315 |
||
|
.0592 |
.0020215 |
|
|
.2181594 |
.8260686 |
|
|
1.19651 |
Largest
3.39449 |
1.120429 |
|
2.543737 |
3.792108 |
1.255362 |
|
3.215777 |
4.587036 |
1.656993 |
|
4.728184 |
5.130683 |
2010
|
.0010832 |
||
|
.0129185 |
.000339 |
|
|
.0209081 |
.000655 |
|
|
.1152964 |
.7778495 |
|
|
.8557506 |
Largest
4.029578 |
1.308913 |
|
2.380189 |
5.08658 |
1.713252 |
|
3.853779 |
5.661973 |
2.188447 |
|
5.85675 |
7.424417 |
2011
|
.006398 |
.0016755 |
|
|
.0105388 |
.0033417 |
|
|
.0819527 |
.0050043 |
|
|
.5637543 |
.9188706 |
|
|
1.399775 |
Largest
3.246475 |
1.015724 |
|
2.454417 |
3.396849 |
1.031694 |
|
3.12352 |
4.110482 |
1.460607 |
|
4.384409 |
4.76502 |
2012
|
.0008805 |
|||
|
.0103226 |
|||
|
.0153127 |
.0027984 |
||
|
.0469969 |
.005133 |
||
|
.5842557 |
.8881484 |
||
|
1.518886 |
Largest
3.005121 |
1.001568 |
|
|
2.067253 |
3.184366 |
1.003139 |
|
|
2.620567 |
4.789417 |
1.564144 |
|
|
4.886204 |
6.014499 |
2013
|
.0036849 |
|||
|
.0163677 |
.0015644 |
||
|
.0766911 |
.0015753 |
||
|
.4301052 |
.7664876 |
||
|
1.241447 |
Largest
2.896818 |
.844135 |
|
|
2.01359 |
2.957707 |
.7125639 |
|
|
2.76489 |
2.986268 |
1.17474 |
|
|
3.119043 |
3.423309 |
2014
|
.0003335 |
|||
|
.0111018 |
|||
|
.0200854 |
.0003343 |
||
|
.0565306 |
.00072 |
||
|
.3108966 |
.7162428 |
||
|
1.331176 |
Largest 2.864718 |
.8510828 |
|
|
1.876407 |
2.91954 |
.7243419 |
|
|
2.480283 |
3.45275 |
1.362852 |
|
|
3.840094 |
4.31162 |
2015
|
.0056502 |
||||
|
.0143271 |
||||
|
.0594046 |
.0032522 |
|||
|
.3000902 |
.8405839 |
|||
|
1.49064 |
Largest
3.366111 |
1.158529 |
||
|
2.349617 |
3.762578 |
1.342189 |
||
|
2.660555 |
5.842677 |
2.46023 |
||
|
11.57388 |
2016
|
.000943 |
.0005591 |
||
|
.0043598 |
|||
|
.0104486 |
.0012348 |
||
|
.0362867 |
.001927 |
||
|
.4361207 |
.717801 |
||
|
1.150011 |
Largest
2.811715 |
.8608956 |
|
|
2.037004 |
2.833677 |
.7411413 |
|
|
2.727755 |
3.376464 |
1.404647 |
|
|
3.571377 |
4.272691 |
2017
|
.0065132 |
|||
|
.0132471 |
.0042236 |
||
|
.0455055 |
.0057532 |
||
|
.2939483 |
.7275742 |
||
|
1.200172 |
Largest
3.24128 |
1.004895 |
|
|
1.952452 |
3.502958 |
1.009813 |
|
|
2.699834 |
3.965399 |
2.28546 |
|
|
9.97769 |
(
72
)
2018
|
.0002111 |
||
|
.00628 |
5.68e-06 |
|
|
.0478902 |
.0000862 |
|
|
.1792101 |
.4868667 |
|
|
.7786379 |
Largest
1.795226 |
.6123164 |
|
1.571636 |
2.047335 |
.3749314 |
|
1.752032 |
2.441648 |
1.528986 |
|
2.699398 |
4.777551 |
2019
|
.0028523 |
|||
|
.0113948 |
.0110024 |
||
|
.0343229 |
|||
|
.0699882 |
.0257073 |
||
|
.420664 |
.7523692 |
||
|
1.356327 |
Largest
2.082096 |
.8038705 |
|
|
2.04069 |
2.245001 |
.6462078 |
|
|
2.266349 |
.9159093 |
||
|
2.774321 |
2.541419 |
2020
|
.000199 |
|||
|
.0041498 |
|||
|
.0242334 |
.0130043 |
||
|
.0651802 |
|||
|
.2393117 |
.5449339 |
||
|
.9173883 |
Largest |
1.578964 |
.6009547 |
|
1.619356 |
.3611466 |
||
|
1.745904 |
.9475189 |
||
|
1.961328 |
2.48645 |
APPENDIX E
Summary statistics of the annual shallow dose equivalents of the extremities for 285 nuclear medicine personnel working in the United States Navy medical facilities
|
.0217029 |
.0022509 |
|||||||
|
.1368456 |
.0030824 |
|||||||
|
.2482247 |
.0039535 |
1,357 | ||||||
|
.7627603 |
.0039845 |
|||||||
|
2.88947 |
6.646006 |
|||||||
|
7.857769 |
Largest |
77.51325 |
11.12562 |
|||||
|
15.82636 |
92.3313 |
123.7794 |
||||||
|
26.47331 |
114.2635 |
4.206948 |
||||||
|
59.76435 |
120.6773 |
28.40237 |
(
73
)
Yearly summary statistics of the annual shallow dose equivalents of the extremities for 285 nuclear medicine personnel working in the United States Navy medical facilities
2003
|
.1100384 |
|||||
|
.3955024 |
.2269577 |
||||
|
.547952 |
.3153768 |
82 | |||
|
1.443871 |
.3639799 |
||||
|
3.151708 |
7.236618 |
||||
|
9.913731 |
Largest
30.2099 |
9.158629 |
|||
|
18.51997 |
30.57057 |
83.88048 |
|||
|
29.75217 |
31.43298 |
2.117284 |
|||
|
48.31822 |
7.800717 |
2004
|
.1592758 |
.1457507 |
||
|
.3156808 |
.1728009 |
||
|
.7206655 |
.1781174 |
100 | |
|
2.150729 |
.2141979 |
||
|
4.572249 |
10.05775 |
||
|
11.26102 |
Largest
52.39859 |
14.58192 |
|
|
23.38075 |
60.15455 |
212.6323 |
|
|
49.70239 |
64.61112 |
2.492539 |
|
|
66.71343 |
68.81573 |
8.726595 |
2005
|
.0411071 |
||
|
.1988184 |
.0841144 |
|
|
.3893005 |
.1151264 |
|
|
1.308954 |
.1585269 |
|
|
3.566083 |
11.52021 |
|
|
12.86205 |
Largest
63.17491 |
19.31912 |
|
30.22922 |
70.35617 |
373.2283 |
|
60.81975 |
74.73264 |
3.127999 |
|
14.27773 |
2006
|
.0633888 |
|||
|
.2682183 |
.1158227 |
||
|
.4955065 |
.1946463 |
76 | |
|
1.423433 |
|||
|
4.453853 |
9.275897 |
||
|
10.07067 |
Largest |
33.65672 |
14.96471 |
|
24.68233 |
35.90947 |
223.9426 |
|
|
74.88283 |
3.611937 |
||
|
18.24488 |
2007
|
.0979249 |
|||
|
.3140229 |
.1758117 |
||
|
.4655808 |
.2421001 |
67 | |
|
1.445213 |
|||
|
5.258824 |
11.02538 |
||
|
11.53873 |
Largest |
36.24613 |
18.22 |
|
26.59136 |
43.48446 |
331.9683 |
|
|
3.65816 |
|||
|
18.92618 |
2008
|
.0404472 |
|||
|
.1100654 |
.075621 |
||
|
.1668186 |
.0995994 |
63 | |
|
1.096516 |
|||
|
3.728353 |
7.314512 |
||
|
8.045874 |
Largest |
31.75814 |
10.00344 |
|
17.47653 |
32.47658 |
100.0689 |
|
|
40.23872 |
2.328275 |
||
|
48.65779 |
8.404312 |
2009
|
.0149458 |
|||
|
.2620834 |
.091006 |
||
|
.5227313 |
50 | ||
|
.8151155 |
.327626 |
||
|
4.074058 |
8.077372 |
||
|
9.955929 |
Largest
26.61095 |
12.48456 |
|
|
20.92142 |
27.81606 |
155.8641 |
|
|
53.52279 |
2.937633 |
||
|
63.55399 |
12.15962 |
2010
|
.2067398 |
|||
|
.2430426 |
.209037 |
||
|
.3298148 |
46 | ||
|
.8380799 |
.271205 |
||
|
3.228703 |
7.881159 |
||
|
6.465068 |
Largest
30.45856 |
12.79693 |
|
|
28.44971 |
40.62265 |
163.7614 |
|
|
50.89484 |
2.422633 |
||
|
53.8362 |
8.085803 |
2011
|
.0565581 |
|||
|
.1538275 |
.1202071 |
||
|
.3509958 |
.1516559 |
61 | |
|
1.209168 |
|||
|
2.745102 |
5.060928 |
||
|
7.709274 |
Largest |
14.66929 |
5.981541 |
|
10.47628 |
17.68077 |
35.77883 |
|
|
20.64693 |
2.530651 |
||
|
34.77391 |
11.77437 |
2012
|
.0140712 |
|||
|
.1567765 |
.1003516 |
||
|
.3125843 |
.1214804 |
||
|
.9313893 |
.1472311 |
||
|
3.952852 |
7.587485 |
||
|
12.33601 |
Largest
29.93611 |
9.411401 |
|
|
19.17125 |
30.04114 |
88.57448 |
|
|
28.86268 |
42.21157 |
1.807286 |
|
|
42.42496 |
6.235459 |
2013
|
.0446474 |
|||||
|
.1099062 |
.0456403 |
||||
|
.1542054 |
.0667088 |
95 | |||
|
.3843837 |
.1017152 |
||||
|
2.347798 |
6.024351 |
||||
|
8.939804 |
Largest
24.71736 |
8.073399 |
|||
|
16.54802 |
32.49219 |
65.17977 |
|||
|
21.61152 |
34.88761 |
1.860972 |
|||
|
36.60241 |
6.328581 |
2014
|
.0078511 |
|||
|
.0721064 |
.0268371 |
||
|
.1169482 |
.0601499 |
||
|
.2289982 |
.0614876 |
||
|
1.376333 |
5.065321 |
||
|
5.654953 |
Largest
28.87495 |
9.347452 |
|
|
11.97626 |
33.22704 |
87.37487 |
|
|
25.31287 |
40.4018 |
3.461458 |
|
|
17.12187 |
2015
|
.083957 |
|||
|
.1347093 |
.1053502 |
||
|
.1680737 |
.1099917 |
94 | |
|
.4778297 |
.1179634 |
||
|
2.066357 |
4.687912 |
||
|
6.83713 |
Largest
21.58343 |
6.455334 |
|
|
10.69378 |
23.77067 |
41.67134 |
|
|
18.08842 |
27.04418 |
2.578411 |
|
|
38.25689 |
11.37067 |
2016
|
.0127261 |
||
|
.1215181 |
.0170917 |
|
|
.1840531 |
.0242604 |
|
|
.6108225 |
.0443757 |
|
|
2.127224 |
3.779112 |
|
|
5.322699 |
Largest
14.35394 |
4.794174 |
|
9.018718 |
19.57408 |
22.98411 |
|
13.89317 |
19.86312 |
2.329099 |
|
27.05575 |
9.515051 |
2017
|
.1135154 |
.016183 |
||
|
.1908533 |
|||
|
.2781078 |
.1318665 |
||
|
.5008725 |
.1502714 |
||
|
1.563737 |
3.4084 |
||
|
4.332285 |
Largest
16.53289 |
4.401668 |
|
|
9.935368 |
16.76095 |
19.37468 |
|
|
13.77273 |
18.6359 |
1.963701 |
|
|
20.04729 |
6.465768 |
(
78
)
2018
|
.0079435 |
||
|
.1510461 |
||
|
.3947382 |
||
|
1.419367 |
3.04302 |
|
|
4.308156 |
Largest
11.63484 |
3.76643 |
|
8.480438 |
12.56597 |
14.18599 |
|
10.68836 |
12.67641 |
2.19236 |
|
21.30811 |
9.132303 |
2019
|
.0119237 |
|||
|
.0159467 |
|||
|
.1066185 |
.0572418 |
||
|
1.025548 |
|||
|
3.116429 |
4.137128 |
||
|
6.238679 |
Largest |
10.62188 |
3.869094 |
|
11.3914 |
14.96989 |
||
|
11.95496 |
1.052625 |
||
|
15.37549 |
3.551712 |
2020
|
.0879792 |
||||
|
.1268238 |
||||
|
.2356016 |
.1519402 |
35 | ||
|
.7384854 |
||||
|
1.487486 |
2.616966 |
|||
|
3.513096 |
Largest |
6.481418 |
3.101258 |
|
|
9.822086 |
9.6178 |
|||
|
10.20442 |
1.816878 |
|||
|
12.65337 |
5.564647 |
APPENDIX G
Summary statistics of the cumulative deep dose equivalents for 528 nuclear medicine personnel working in the United States Navy medical facilities from 2003-2020
|
.0105749 |
||||
|
.0202651 |
528 | |||
|
.0510137 |
||||
|
.385507 |
2.961223 |
|||
|
3.177992 |
Largest
35.69023 |
5.967875 |
||
|
10.05622 |
43.95685 |
35.61553 |
||
|
14.21984 |
44.11264 |
3.719745 |
||
|
29.33472 |
46.6182 |
20.76875 |
(
80
)
Summary statistics of the cumulative shallow dose equivalents of the skin for 528 nuclear medicine personnel working in the United States Navy medical facilities from 2003-2020
|
.0135532 |
||
|
.0207912 |
||
|
.0511209 |
||
|
.3863496 |
2.901108 |
|
|
3.082477 |
Largest
34.54876 |
5.82575 |
|
9.535597 |
43.16834 |
33.93936 |
|
14.38533 |
43.27398 |
3.697068 |
|
28.47435 |
44.32508 |
20.42743 |
Summary statistics of the cumulative shallow dose equivalents of the extremities for 285 nuclear medicine personnel working in the United States Navy medical facilities from 2003-2020
|
.1052364 |
|||
|
.3404641 |
|||
|
.6788423 |
285 | ||
|
2.889666 |
|||
|
12.99507 |
31.64432 |
||
|
38.50785 |
Largest
193.6166 |
56.06953 |
|
|
82.82853 |
202.7736 |
3143.792 |
|
|
134.0991 |
487.4695 |
5.003586 |
|
|
528.6354 |
38.91941 |
Summary statistics of the annual deep dose equivalents corresponding to 221 NM personnel working in USN medical facilities identified as PET facilities
| 787 | |||
|
.0552446 |
|||
|
.4414652 |
.9909822 |
||
|
1.602285 |
Largest 6.259352 |
1.237229 |
|
|
2.805705 |
1.530736 |
||
|
3.471585 |
1.651442 |
||
|
5.253173 |
5.913189 |
Summary statistics of the shallow deep dose equivalents of the skin corresponding to 221 NM personnel working in USN medical facilities identified as PET facilities
|
.0052731 |
||
|
.4244372 |
.974075 |
|
|
1.576345 |
Largest 6.117428 |
1.211676 |
|
2.699954 |
1.468158 |
|
|
1.670658 |
||
|
6.043804 |
Summary statistics of the shallow deep dose equivalents of the extremities corresponding to 163 NM personnel working in USN medical facilities identified as PET facilities
|
.0129868 |
||
|
.1224643 |
||
|
.2322271 |
600 | |
|
.7295181 |
||
|
3.155826 |
8.740191 |
|
|
9.51468 |
Largest 77.51325 |
14.68307 |
|
23.83935 |
215.5926 |
|
|
37.1934 |
3.420971 |
|
|
72.5444 |
18.26929 |
Summary statistics of the annual deep dose equivalents corresponding to 361 NM personnel working in USN medical facilities identified as non-PET facilities
|
.0004604 |
||||
|
.0201419 |
1,207 | |||
|
.0552063 |
||||
|
.6492319 |
||||
|
.9536016 |
Largest 5.005732 |
.8499088 |
||
|
1.742694 |
5.507882 |
.722345 |
||
|
2.381172 |
2.186277 |
|||
|
9.328157 |
Summary statistics of the annual shallow dose equivalents of the skin corresponding to 361 NM personnel working in USN medical facilities identified as non-PET facilities
|
.0101224 |
||
|
.0212507 |
||
|
.0556345 |
||
|
.2956524 |
.6339584 |
|
|
.9462707 |
Largest 4.789417 |
.8202126 |
|
1.702806 |
.6727487 |
|
|
2.210261 |
||
|
9.792458 |
Summary statistics of the annual shallow dose equivalents of the extremities corresponding to 176 NM personnel working in USN medical facilities identified as non-PET facilities
|
.0336422 |
||
|
.1502192 |
||
|
.2597432 |
800 | |
|
.7570839 |
||
|
2.518783 |
4.718144 |
|
|
6.193541 |
Largest 40.23872 |
6.379942 |
|
11.98545 |
40.70366 |
|
|
16.49016 |
3.081133 |
|
|
31.26666 |
16.93102 |
Two-sample t test’s result for the mean difference of the annual deep dose equivalents between non-PET and PET facilities
Two-sample t test’s result for the mean difference of the annual shallow dose equivalents of the skin between non-PET and PET facilities
Two-sample t test’s result for the mean difference of the annual shallow dose equivalents of the extremities between non-PET and PET facilities
An example of a questionnaire could be used in future studies to help provide detailed information on the number of workers, workload, and radiation safety standards in the USN medical facilities.
Section One: General
This section will include general information on your nuclear medicine (NM) department.
Q1. Is your NM department located in the United States?
YES NO
Q2. How many NM technologists, physicians, nurses, and health/ medical physicists worked in your department in the following years?
Year
# of
NM Technologist
# of NM Physicians
# of Nurses
# of Health/Medical Physicist
Section Two: Diagnostic (non-PET)
This section will focus on your department’s nuclear medicine (NM) diagnostic procedures. PET
procedures are not included.
Q1. Overall, how many diagnostic NM procedures were performed in your department in the following years?
|
# of diagnostic NM procedures |
Q2. On average, how many diagnostic NM procedures are performed per week in your department?
Answer:
Q3. How many were cardiac NM procedures performed in your department in the following years?
|
# of cardiac NM procedures |
Q4. Do you use Tc-99m to perform cardiovascular studies? If yes, in which year did you start using Tc-99m in your department?
YES NO Year :
Q5. Do you use Tl-201 to perform cardiovascular studies? If yes, in which year did you start using Tl-201 in your department?
(
:
)YES NO Year
Q6. Do you have CZT cameras for cardiac imaging?
YES NO
Section Three: Therapy
This section will focus on therapeutic nuclear medicine (NM) procedures performed in your
department. Please skip this section if your department does not perform therapeutic NM
procedures.
Q1. Overall, how many therapeutic NM procedures were performed in your department in the following years?
|
# of therapeutic NM procedures |
2016
2017
2018
2019
2020
Q2. On average, how many therapeutic NM procedures are performed per month in your department?
Answer:
Q3. Who is responsible for the preparation of radiopharmaceuticals for therapy?
NM Technologist
NM Physician
Other ………………
Q11. Who is responsible for the administration of radiopharmaceuticals for therapy?
NM Technologist
NM Physician
Other ………………
Section Four: PET
This section will focus on PET procedures. If your department does not perform PET procedures,
please skip this section.
Q1. When did you start performing PET or PET/CT procedures in your department?
Year:
Q2. Do you use a PET/CT camera?
YES NO
Q3. How many PET and PET/CT procedures did you perform in your NM department in the following years?
|
# of PET or PET/CT Procedures |
Q4. Does your department require NM technologists to rotate between general NM and PET?
YES NO
Q5. Do you have Intego or any other PET infusion system?
YES NO
Q6. On average, how many PET procedures are performed per week in your department? Answer:
Section Five: Radiation Protection
This section will focus on radiation safety practices in your department.
Q1. How many body dosimeters are NM technologists required to wear in your department?
One Two
Q2. Where do NM workers usually wear the body dosimeter in your department?
Chest Level Other
Q3. Are NM physicians required to wear a body dosimeter?
YES NO
Q4. Are NM technologists required to wear a ring dosimeter?
YES NO
Q5. Are NM physicians required to wear a ring dosimeter?
YES NO
Q6. Are NM technologists required to wear a lead apron?
YES NO
Q7. Are NM technologists required to use a syringe shield during the manipulation of the radiopharmaceuticals?
YES NO
Q8. Are NM technologists required to use a syringe shield during the injection of the radiopharmaceuticals?
YES NO
Q9. Do you receive single doses of radiopharmaceuticals from radiopharmacy?
YES NO
Q10. How often are NM technologists, NM physicians, nurses, and health/medical physicists monitored in your department? (Please, use a ✓ to assign your answer in table #6).
|
Title of the workers in the NM department |
Monthly |
Quarterly |
|
NM Technologists |
||
|
NM Physicians |
||
|
NM Nurses |
||
|
Medical/Health physicists |
GEORGETOWN UNIVERSITY GRADUATE SCHOOL
GUIDELINES FOR DISSERTATION, DOCTORAL PROJECT
AND THESIS WRITERS
The Graduate School of Arts and Sciences
3520 Prospect St NW, Car Barn Suite 140
gradstudentservices@georgetown.edu
PREPARATION OF THE THESIS ……………………………………………………………………………………………. 2
Style Manuals ………………………………………………………………………………………………………………………… 2
Pagination ……………………………………………………………………………………………………………………………… 2
Fonts ……………………………………………………………………………………………………………………………………… 2
ORDER AND CONTENT OF THE THESIS ……………………………………………………………………………… 3
Order of the Pages …………………………………………………………………………………………………………………. 3
Title Page ………………………………………………………………………………………………………………………………. 3
Your Name …………………………………………………………………………………………………………………………….. 3
The Date ………………………………………………………………………………………………………………………………… 4
Copyright Page ………………………………………………………………………………………………………………………. 4
Abstract …………………………………………………………………………………………………………………………………. 4
Table of Contents …………………………………………………………………………………………………………………… 4
Page Margins …………………………………………………………………………………………………………………………. 5
Schema of Headings and Subheadings and Hierarchy of Font Treatments ……………………………….. 5
SUBMISSION OF THE THESIS TO THE GRADUATE SCHOOL ……………………………………………. 6
Electronic Submission of Work ………………………………………………………………………………………………. 6
The Main Issues……………………………………………………………………………………………………………………… 7
Common Mistakes to Avoid ……………………………………………………………………………………………………. 9
Using a Template………………………………………………………………………………………………………………….. 11
Frequently Asked Questions …………………………………………………………………………………………………. 11
…………………………………………………………………………………………………………………. 12
Advice for Long Dissertations ……………………………………………………………………………………………….. 12
Advice for LaTeX Users ……………………………………………………………………………………………………….. 12
Advice for APA Users …………………………………………………………………………………………………………… 12
Advice for Multi-Article Dissertations …………………………………………………………………………………… 12
Advice for Figure Titles ………………………………………………………………………………………………………… 13
Advice on Placement of Figures and Tables …………………………………………………………………………… 14
APPENDIX: SAMPLE THESIS………………………………………………………………………………………………….. i
2
INTRODUCTION
The thesis you are writing is a significant step in the pursuit of your graduate degree. A well-
written and well-formatted work will reflect favorably upon you, your department, and
Georgetown University. When completed, your thesis will be a lasting contribution to your field
of knowledge. Therefore, your thesis must follow a format and style that are acceptable, readily
understandable, and consistent with your field of knowledge. This document will use the term
‘thesis’ to refer to all three types of scholarly work.
PREPARATION OF THE THESIS
Style Manuals
Every thesis must follow a style manual or style sheet that has been approved by your Thesis
Advisor or by your department or program. Some examples include:
• A Manual for Writers of Term Papers, Theses, and Dissertations by Kate Turabian
• The Chicago Manual of Style · MLA Style Manual
• Publication Manual of the American Psychological Association
The Lauinger Library website has information on these on the Citation Guides tab on
https://www.library.georgetown.edu/citations
Pagination
The pagination must meet the following guidelines:
• Title page — No page number
• The pages that follow — Copyright page, Abstract, Table of Contents, etc. — are
numbered with lower-case Roman numerals: ii, iii, etc.
• All page numbers, including lower-case Roman numerals, at the bottom center of the
page
• The remainder of the thesis, beginning with the Introduction or Chapter One, must be
numbered consecutively using Arabic numerals (1, 2, etc.)
• Pages in each section must be numbered consecutively from beginning to end. The lower
case Roman numerals and the Arabic numerals form two separate numeric series, the
former beginning with ii, and the latter with 1.
• Blank pages are not permitted.
• The page number for any page printed in horizontal or “landscape” mode must still
appear at the bottom of the page when the page is held vertically.
Fonts
The fonts used in the thesis must meet the following guidelines:
• Times New Roman 12 point or Arial 10 point.
• Italics may not be used in the Table of Contents unless it is used for a foreign word.
• The font size requirement applies to all prefatory material (title page, Acknowledgments,
Table of Contents, , etc.), the body of the text, page numbers, all footnotes or endnotes, and all
concluding material (Appendices and Bibliography). Some charts, graphs, or tables may contain
type that is one point smaller.
3
ORDER AND CONTENT OF THE THESIS
Order of the Pages
Page Page Numbering
Title Page Not numbered (but counts as i)
Copyright Page ii (Roman numeral)
Abstract (not required for theses) Next consecutive Roman numeral(s)
Acknowledgments, Dedication (if used) Next consecutive Roman numeral(s)
Table of Contents with dot leaders and page Next consecutive Roman numeral(s)
numbers
List of Figures (if document has figures) with Next consecutive Roman numeral(s)
numbers, titles and dot leaders and page numbers
List of Tables (if document has tables) with Next consecutive Roman numeral(s)
numbers, titles and dot leaders and page numbers
Text, beginning with the Introduction Arabic numerals ( 1, 2, 3, 4, etc.) for the
remainder of the work
Appendices (if used) Next consecutive Arabic numeral(s)
Bibliography Next consecutive Arabic numeral(s)
Specially bound or packaged Addenda Not numbered, but included in the Table of
Contents (e.g. maps or digital media)
Title Page
The title page should include the title, the submission statement (A Thesis or A Dissertation…),
the degree, the name of your department or program, your name, highest previous degree, the
location (“Washington, D.C.”), and the date. The title page is not numbered. An example title
page appears in the Appendix. Note that department is not necessary on Public Policy theses
because the program is included in the degree.
Your Name
The format of your name must appear as it appears on your transcript in MyAccess on the title
page, copyright page and abstract page. The name must match exactly in each location.
On the title page of your thesis, your name should be followed by the SINGLE highest degree
you have previously received, not a list of all the degrees you have received. You should list
only the initials of the degree itself, for example: B.A., B.S., M.S., M.A., J.D., Ed.M., etc. Do
not list the majors, concentrations, specialties, or the institution where the prior degree was
earned. Following are two examples of the correct format for your name on the thesis title page:
Jamie Doe Smith, M.S. John D. Smith, Jr., B.A.
4
The Date
At the bottom of the title page of your thesis, underneath “Washington, D.C.,” type the date you
defended your thesis or dissertation. If no defense was required, you should insert the date your
advisor signed the cover sheet to approve the thesis. DO NOT allow MSWord to add a
superscript st, nd or th to the date. Samples of date notation can be found in the Appendix below.
Copyright Page
You possess the copyright to your thesis from the time you record it in some tangible form. If
you claim copyright, either informally or through a formal application, the appropriate notice
should be printed on its own numbered page immediately following the title page of the thesis.
For example:
Copyright 2020 by Jamie Doe Student
All Rights Reserved
Abstract
The purpose of the abstract is to provide a brief summary of the contents of the thesis. The
abstract, must be written in English. The maximum permissible length of the abstract is 350
words (2,450 characters). The abstract is optional for a Master’s thesis.
See the Appendix at the end of this document for an example of how your Abstract page should
be formatted. The abstract should start with the title of the thesis (in ALL CAPS, centered),
followed by your name and highest degree (centered), followed by the word “Advisor:” and the
name and highest degree of your Thesis Advisor (centered). The word ABSTRACT appears
(centered, in caps), followed by the text of the abstract itself
Table of Contents
• Each chapter or section heading in the body of text, appendices and bibliography or
references section must be shown with corresponding page numbers for each item.
• The numbering of chapters or sections in the Table of Contents—whether written out as
words, or shown as Roman or Arabic numerals—must be shown in the same way in the
text.
• The items must appear in plain typeface without stylistic treatments such as bold,
underlining, italicization, size variations, etc.
• You must list all main section or chapter headings, and may choose to include
subheadings as well. If you choose to include subheadings, you must show all instances
of a given level, for example first-level but not second-level subheadings or first-level
AND second-level subheadings, for all chapters that have subheadings at that level.
• Headings and subheadings must appear in the Table of Contents word-for-word as
they appear in the body of text including capitalization.
• Note: Do not use MS Word’s built-in Table of Contents formatting options, but rather
use Custom Table of Contents.
• Page numbers must also be right-aligned along the right margin. Instructions on how to
do this in MS Word appear on page 9.
• Page numbers in the Table of Contents must be the page numbers where the item
actually appears in the text.
5
Page Margins
Page margins must be 1” on all sides.
Considerations for Formatting Subheadings in the Text
• Subheadings at a given level must be formatted in the same way throughout the
document. A common schema has first-level subheadings centered in ALL CAPS,
second-level subheadings in bolded mixed case at the left margin, and third-level
subheadings in un-bolded mixed case at the left margin.
• The formatting reviewer will assume that the formatting of the first section or chapter
will be the formatting for the entire document. Pay close attention to the Introduction to
make sure that its formatting schema matches that of the rest of the document.
• Make sure that each section or chapter has the SAME formatting schema.
• Subheadings must not be left orphaned at the bottom of a page with no text below them.
• Spacing must be consistent between paragraphs, above and below subheadings, above
and below figures and tables. The top line of a page should not be blank.
Schema of Headings and Subheadings and Hierarchy of Font Treatments
The formatting of each level of subheading must be the same through all chapters or sections of
the document. An example schema, excluding consideration of numbering, would be:
Chapter or section heading ALL CAPS, bold,
centered
First-level subheading Mixed Case, bold, at the left
margin
Second-level subheading Mixed Case, plain text, at the left margin
Third-level subheading Mixed Case, italics, at the left margin
Examples of this schema would look like:
ASSOCIATIONAL FREEDOM AND EQUAL ACCESS
(Chapter/Section Heading)
Introduction
(First-level subheading)
The Value of Associations
(Second-level subheading)
Associational Freedom and the Right to Exclude
(Third-level subheading)
Your document need not have all these levels. The point is that all chapters or sections with
multiple levels of subheading must follow the same schema—which can mirror this schema or
can be a schema of your own choosing.
The level of headings and subheadings that appear in the Table of Contents must be the same for
all sections/chapters.
The schema of the first section will be assumed to be the schema for the whole document.
6
SUBMISSION OF THE THESIS TO THE GRADUATE SCHOOL
Electronic Submission of Work
The Graduate School requires electronic submission of all theses via the ProQuest website.
Please refer to the Graduate School websites for information on the submission process:
https://grad.georgetown.edu/info-for/current-students/submission-of-thesis/
https://grad.georgetown.edu/info-for/current-students/submission-of-dissertation-or-doctoral-
project
There is no cost associated with publishing your work. There is a cost if you elect certain
publishing or copyright options in ProQuest or order copies of your thesis from ProQuest. Refer
to the Lauinger Library website for more information.
Review of the Thesis by the Graduate School
The Graduate School reviews all theses submitted to ProQuest. We ensure that the works are
formatted according to Graduate School standards and are ready for publication. The care you
take to prepare your work according to these guidelines generally determines the amount of time
we will need to review your thesis, and the number and nature of any changes you may be
required to make.
Formatting of the Introduction will be assumed to be the formatting for each section or chapter of
the entire document. Pay close attention to the Introduction to make sure that its formatting
schema matches that of the rest of the document
https://grad.georgetown.edu/info-for/current-students/submission-of-thesis/
https://grad.georgetown.edu/info-for/current-students/submission-of-dissertation-or-doctoral-project
https://grad.georgetown.edu/info-for/current-students/submission-of-dissertation-or-doctoral-project
7
FORMATTING GUIDANCE
The Main Issues
Initial Section
• There must be no page number on the title page
• Pages prior to the Introduction must use Roman numerals rather than Arabic numerals
• Sections prior to the Introduction DO NOT appear in the Table of Contents
Table of Contents
• Do not use MS Word’s built-in Table of Contents formatting options. Use Custom Table
of Contents instead.
• All Table of Contents items should appear in plain typeface and not include stylistic
treatment such as bold, color, underlining, italicization or size variations.
• With the exception of the most commonly recognized abbreviations and acronyms, like
HIV, abbreviations and acronyms must be written out in words in all headings and
subheadings.
• DO NOT include the items that have Roman numeral page numbers, including the
Abstract, Acknowledgements, Table of Contents and List of Figures.
• If a given level of subheading appears in the Table of Contents, all subheadings at the
same level (and all higher levels) must appear for EACH section or chapter.
• Page numbers in the Table of Contents must be the page where the item actually appears
in the text. Check all page numbers before uploading.
• The page number for the first page of the Introduction or Chapter One must be 1.
• Page numbers for each item must appear with dot leaders, . . . ., and be right-justified on
the right margin.
• If any items wrap to a second line, add a hard return before a word in the first line so that
the second line does not begin with dot leaders ……..
• In all headings and subheadings, major words should be capitalized.
• Items in the Table of Contents must match the corresponding items in the text word-for-
word–and in terms of capitalization and punctuation.
• Appendices (if the document has one or more) and the Bibliography or References
section must appear in the Table of Contents.
List of Figures / List of Tables
• If the document has five or more figures or tables, it requires a List of Figures and List of
Tables.
• The word Figure or Table, the number and the title presented in mixed case. The words
through the first period are considered the title and ONLY they appear here. Do not show
the entire title and caption.
• Items in the List of Figures and List of Tables must match those items in the text word-
for-word–and in terms of capitalization and punctuation.
• To the greatest extent possible, abbreviations should be written out in words.
• Page numbers for figures or titles must be right-justified with dot leaders.
• If any items wrap to a second line, add a hard return before a word in the first line so that
the second line does not begin with dot leaders ……..
8
• The List of Figures and List of Tables must be separate lists. If they are short enough to
fit on one page, the two separate lists can appear on a single page. Otherwise, the List of
Figures must appear on its own page with the List of Tables on the next page.
• Page numbers listed in the List of Figures and List of Tables must reflect the page where
the figures and tables appear in the text. Check all page numbers before uploading.
Text
• The organizing schema for all headings and subheadings and their formatting must be
consistent both within and across chapters
• Headings, subheadings, figure titles and table titles must appear in the text word-for-word
as they appear in the Table of Contents/List of Figures/List of Tables.
• All headings at a given level must be formatted in the same way, in terms of
capitalization, bolding, italics, punctuation, spacing, etc., throughout the document.
• Where the page is presented in landscape orientation rather than portrait, the page number
must appear on the left side of the page turned 90 degrees so that it would be readable if
the page appeared in a book with the page number at the bottom of the page.
• All figures and tables in the text require numbers and titles.
• Figure and table numbers and titles must appear without italics and in bold face.
Additional caption text should not be bolded.
• Figure and tables numbers and titles must be the same size as the font in the body of the
document.
• Table titles must appear ABOVE the table.
• Figure titles must appear BELOW the figure.
• Figures and tables MUST fit within the regular 1-inch page margins.
• Figures must be centered along with their titles (and captions).
• Tables must appear on a single page wherever possible.
• When a table goes onto a second page, the column headers must be added to the top of
the second page. Above the table, add a notation of Table # (Cont.) Do not include the
table title.
• The text in figures and tables must be large enough as to be legible, with text no more
than 1 point smaller than the main text.
• Subheadings must not be orphaned at the bottom of a page. Move them to the top of the
following page.
• Be sure that the heading or text for each page–first page of a chapter possibly aside–
appear at the top line of the page
9
Common Mistakes to Avoid
Mistake: Your name used in the document does not match your transcript. The name that
appears on your signed cover sheet must be your name as it appears on your transcript in
MyAccess. The same format of your name must be used on your thesis. If you have recently had
a name change, take steps to update it with the Registrar’s Office using the form at
https://georgetown.app.box.com/s/yt90bx3gdcds7mwuz67yhv6knh4v5nm7
Mistake: Formatting such as bold, color, italics, underlining and size variations appears in
the Table of Contents. The words in the Table of Contents must appear in plain typeface.
Mistake: Headings in the document do not match the headings in the Table of Contents. All
of the headings in your Table of Contents must appear word-for-word the same as the headings
used in your document. For example, if the title of your third chapter appears in the document as
“Chapter Three: Writing a Thesis at Georgetown University,” the heading in your table of
contents cannot be “Chapter 3: Writing a Paper at GU.” They must match exactly. The same rule
applies for the titles of figures and tables and the respective items listed in your List of Figures,
List of Tables.
Mistake: Page numbers shown in the Table of Contents do not match the location in the
text. If a subheading is listed as appearing on page 10 in the Table of Contents, it must appear on
page 10 in the text, not page 11. This holds true for figures and tables as well.
Mistake: Page numbers do not appear right-justified at the right margin in the Table of
Contents, List of Figures and List of Tables. Due to modern proportional fonts, it is not
possible to just type periods and have the justification come out right. In MSWord, the Tabs
dialog box allows you set a right tab at the right margin and then choose the style of dot leader.
1) Highlight the items–the words and the page numbers–in the table/list and open the
Tabs menu, Home->Paragraph->Tabs is in the bottom left of the dialog box.
2) For Tab stop location, enter the location of the right margin most likely 6.5.
a) For Alignment, select Right
b) For Leader, choose 2 ……
c) Returning to your document, place your cursor at the end of the words for the table/list
entry before the page number and hit Tab. The page number should jump to the right
margin with a series of dot leaders
Mistake: Sections with Roman numeral page numbers (like the Abstract and
Acknowledgements) appear in the Table of Contents. The Introduction or first chapter should
be the first item in the Table of Contents. Other pages prior to the introduction or first chapter are
not be included in the Table of Contents.
Mistake: The document is missing a List of Figures and List of Tables. A thesis with five or
more tables must include a List of Figures and List of Tables formatted like Tables of Contents
on the page after the Tables of Contents.
https://georgetown.app.box.com/s/yt90bx3gdcds7mwuz67yhv6knh4v5nm7
10
Mistake: Entries wrap to a second line that begins ……… at the left margin in the Table of
Contents, List of Figures or List of Tables. To avoid this, add a hard return at about 80% of the
first line on the subheading or figure/table title.
Mistake: Figures and tables have no titles. ALL figures and tables require titles whether or not
there is a List of Figure and List of Table. Figure titles, must appear BELOW the figure. Table
titles must appear ABOVE the table. Examples of properly formatted figure and table titles:
Figure 1. Map of sectarian neighborhoods in Belfast, 1982.
Table 1. Monthly output of widgets by company, 2010-2015.
Mistake: Figures titles appear within the figure box. Crop the title from the top of the figure
box or go back to Excel and remove the title from within the figure box. Re-type the title as a
properly numbered and formatted figure title below the figure box.
Mistake: Tables appear on more than one page. Look for extra white space in the table that
can be removed or columns that can be narrowed so that the table fits on one page. When a
second page is necessary, the second page should be identified as such for instance as Table 3.
(Cont.)
Mistake: Sections of the document (title page, table of contents, list of figures, list of tables,
appendix, and bibliography) are not in the correct order. The Graduate School requires the
sections of your document follow a specific order. The template provided by the Graduate
School (available on our forms website at: https://grad.georgetown.edu/academics/dissertation-
thesis-information#. You can also refer to page 3 of the “Guidelines for Thesis Writers”
document to see the correct order.
Mistake: A subheading appears alone at the bottom of a page. Move the subheading to the
top of the following page.
Mistake: Appendix figures and tables are missing from the List of Figures and List of
Tables. Number Appendix items as Figure A.1, A.2, Table A.1, A.2, etc., add descriptive titles
and include them in the List of Figures and List of Tables.
Mistake: Incomplete upload to the ProQuest site after making edits. Do not email the
revised document. Be sure to click the “confirm” button after you upload your revised document
to the ProQuest website. Students sometimes overlook this step and upload a revised draft
without officially submitting it. The Graduate School will not see your submission on the
ProQuest site until it is officially submitted. At one point, you will see:
“Your revisions have been made, but still need to be submitted to your graduate school for
review.”
“I’m done – submit my changes.”
On that page, click “I’m done – submit my changes.”, but continue to the next screen where you will see a
Submit Revisions button. Click the Submit Revisions button to ensure that Graduate School staff receive
the submission.
Mistake: Page numbers not aligned at the bottom of the document after conversion to PDF.
Note that the PDF converter on the ProQuest site should not be used.
https://www.etdadmin.com/cgi-bin/student/revpayment?siteId=163;revId=465605
https://www.etdadmin.com/cgi-bin/student/revpayment?siteId=163;revId=465605
11
Mistake: Edits not submitted by the deadline. You must submit the edits and the document
accepted by the Graduate School by deadline posted online. If edits that are not completed on
time, your graduation will be delayed until the next available graduation date.
Using a Template
The Graduate School provides three different templates to help format your thesis. They are
available at: http://grad.georgetown.edu/academics/dissertation-thesis-information/
• MS-Word on a PC
• Word for Mac
• LaTeX markup language
Note that use of these templates is not a guarantee of a smooth review process. The PC and
Mac templates are unlocked and can be edited by you. The LaTeX template requires additional
steps to remove the Roman numeral items from the Table of Contents. The Graduate School
cannot provide technical support related to the use of these templates. Use of the template is not
required; you may format the work on your own based on these guidelines.
Frequently Asked Questions
What style guide should I use? This is a question for your academic department (advisor and/or
thesis committee members).
Does the Graduate School have a template I can use to format my work? Templates are
linked from the Graduate School forms website on:
http://grad.georgetown.edu/academics/dissertation-thesis-information/
How soon will my thesis be reviewed after I submit it to the Graduate School? The Graduate
School works to review all works submitted within three business days. We receive an
automated system email when a PDF is uploaded or updated. There is no need to notify the
Graduate School that you have uploaded a new version.
Are the edits identified by the Graduate School required? Yes.
What is the deadline for submitting my edits? In August, the deadline to submit any required
edits is the final working day of the month. There are different deadlines for May and December
graduates (see https://grad.georgetown.edu/academics/dissertation-thesis-information/submit-
dissertation/#).
How can I order bound copies of my thesis? You can order bound copies of your work via the
ProQuest website.
What publishing option should I choose? Lauinger Library has produced a set of videos that
lay out the options you can select on the ProQuest site,
https://www.library.georgetown.edu/scholarly-communication/etds-videos.
https://www.library.georgetown.edu/scholarly-communication/etds-videos
12
ADVICE FOR . . . .
Advice for Long Dissertations
Dissertations are written over the course of months a chapter at a time. We often see that the
structure and formatting within each chapter is consistent, but they are not consistent across
chapters. The Introduction and Conclusion are often written last–with a different structure.
When reviewing a document, we take the organizational structure and formatting of subheadings
of the first section as the pattern for the whole document and identify edits in the subsequent
sections by comparing them to the standard of the first section. (See the Schema of Headings and
Subheadings and Hierarchy of Font Treatments section on page 5.) As a result, it is especially
important that the Introduction use the formatting scheme that you will use for the entire
document.
Advice for LaTeX Users
The complexity of the LaTeX template can give the impression that there is no need to pay
attention to formatting. Unfortunately, there are several things that it does not take into account.
The template does not control for capitalization in headings and subheadings. Even though items
in the Table of Contents, headings and subheadings appear in SMALL CAPS, capitalization of the
words still matters. All subheadings at each level and across chapters must be capitalized in the
same way.
Figure numbers and titles must be placed UNDER the figures. Table numbers and titles must be
placed ABOVE the tables.
Advice for APA Users
The APA Style Guide uses un-numbered subheadings. This can make is seem like it imposes
little structure. In fact, the five levels of subheadings are very specifically prescribed. Whether
your thesis has two levels of subheadings, three or five, each level must adhere to the schema.
Level Number and Format
1 Centered, Boldface, Title Case Heading
2 At the Left Margin, Boldface, Title Case Heading with a hard return at the end
3 At the Left Margin, Boldface Italics, Title Case Heading with a hard return at the end
4 Indented, Boldface Title Case Heading Ending with a Period. The text continues on the
same line as the subheading.
5 Indented, Boldface Italics, Title Case Heading Ending With a Period. The text
continues on the same line as the subheading.
Advice for Multi-Article Dissertations
Dissertations in the sciences are often a collection of journal articles–often ones submitted to
different publications each with their own formatting requirements. A dissertation is a unitary
academic work with a single abstract at the beginning of the document and consistent formatting
of headings and subheadings throughout the document.
13
Advice for Figure Titles
Figure 1. Simple Histogram of Proficiency.
Figure 1. Simple Histogram of Proficiency.
Figure titles must be bolded
All figures and tables
need numbers whether
or not you have a List of
Figures and List of
bl
WRONG
RIGHT
14
Advice on Placement of Figures and Tables
WRONG: Extends beyond the right margin
WRONG: Extends beyond both margins
At left margin: GOOD
Centered: ALSO GOOD
Pa
ge
M
ar
gi
n
APPENDIX: SAMPLE THESIS
STARTLING BRILLIANCE: DIAMONDS MAY BE FOREVER BUT WHAT IS THEIR
AFFECT ON MARRIAGE RATES?
A Thesis
submitted to the Faculty of the
Graduate School of Arts and Sciences
of Georgetown University
in partial fulfillment of the requirements for the
degree of
Master of Arts
in
Asian Studies
By
Jamie Doe Student, B.A.
Washington, DC
October 7, 2019
The LOCATION
AND DATE should
appear at the bottom
margin
ALL TEXT
must be
the
same
size
No page number
ii
Copyright 2016 by Jaime Doe Student
All Rights Reserved
Page number is ii
iii
STARTLING BRILLIANCE: DIAMONDS MAY BE FOREVER BUT WHAT IS THEIR
AFFECT ON MARRIAGE RATES?
Jamie Doe Student, M.A.
Thesis Advisor: Name O. Professor, Ph.D.
ABSTRACT
The text of the abstract begins here and continues, double-spaced. There should be spaces
between the last line of the title, your name, your advisor’s name, the word Abstract and the top
line of the abstract. Overall limit of 350 words of text (2,450 characters) must be strictly
observed for abstracts of doctoral projects, due to space limitations for publication in
Dissertation Abstracts International; this limit does not include the title, your name, your Thesis
Advisor’s name, or the word “ABSTRACT.” For Master’s theses, the abstract is not required
but is useful for people to get a sense of the content of your thesis.
Page number is iii
Your TITLE should appear
centered in ALL CAPS on as
few lines as possible. There
should be no hard return
after a colon.
i
v
The research and writing of this thesis
is dedicated to everyone who helped along the way.
Many thanks,
Jamie Doe Student
v
TABLE OF CONTENTS
Chapter 1. Introduction …………………………………………………………………………………………………. 1
Chapter 2. Literature Review ………………………………………………………………………………………….. 6
Chapter 3. Material and Methods ……………………………………………………………………………………. 8
Chapter 4. Data ………………………………………………………………………………………………………….. 11
Chapter 5. Results ………………………………………………………………………………………………………. 16
Chapter 6. Policy Discussion ………………………………………………………………………………………. 20
Chapter 7. Conclusion ………………………………………………………………………………………………….. 27
Appendix: Supplementary Tables ………………………………………………………………………………….. 30
References ………………………………………………………………………………………………………………….. 32
The format of the Table of
Contents, List of Figures and
List of Tables heading must
be the same whether in ALL
CAPS or Mixed Case.
If you use Arabic or Roman
numerals here, the same
number style must appear in
the text.
vi
LIST OF FIGURES
Figure 1. Title for Figure 1 ………………………………………………………………………………………………..4
Figure 2. Title for Figure 2. ……………………………………………………………………………………………..11
Figure 3. Title for Figure 3 ………………………………………………………………………………………………12
Figure 4. Title for Figure 4 ………………………………………………………………………………………………14
Note:
If a figure or table title, or an item in the Table of Contents wraps to a second line, the second
line CANNOT begin with a series of dots, called dot leaders.
Figure 3. Diagram of the changes in the lifecycle of a diamond mined in South Africa’s mines
……………………………………………………………………………………………………………………………………..12
The solution is to add a hard return before a word toward the end of the line so that at least one
word appears on the second line, as
Figure 3. Diagram of the changes in the lifecycle of a diamond mined in South Africa’s
mines …………………………………………………………………………………………………………………………….12
vii
LIST OF TABLES
Table 1. Title for Table 1 …………………………………………………………………………………………………12
Table 2. Title for Table 2 …………………………………………………………………………………………………13
Table 3. Title for Table 3 …………………………………………………………………………………………………14
Table 4. Title for Table 4 …………………………………………………………………………………………………18
Table 5. Title for Table 5 …………………………………………………………………………………………………19
Table A1. Title for Table A1 ……………………………………………………………………………………………30
Table A2. Title of Tables A2 ……………………………………………………………………………………………31
Tables (and figures) that
appear in an appendix
should be included in the
List of Table or Figures.
CHAPTER 1. INTRODUCTION
You have now begun to type the body of text for your manuscript, as is shown here in the
Appendix of the Guidelines for Doctoral Project, Dissertation and Thesis Writers. Georgetown
University and the Graduate School of Arts and Sciences will be pleased to add the faculty-
approved final copy of your dissertation, doctoral project or thesis to our collection in the
University Library. Your work will be an addition to your field of knowledge and to the world of
research. Congratulations and best wishes as you make the final changes in the content of your
work, and the final adjustments to the formatting.
Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque
laudantium, totam rem aperiam, eaque ipsa quae ab illo inventore veritatis et quasi architecto
beatae vitae dicta sunt explicabo. Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut
odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt.
Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit, sed
quia non numquam eius modi tempora incidunt ut labore et dolore magnam aliquam quaerat
voluptatem. Ut enim ad minima veniam, quis nostrum exercitationem ullam corporis suscipit
laboriosam, nisi ut aliquid ex ea commodi consequatur? Quis autem vel eum iure reprehenderit
qui in ea voluptate velit esse quam nihil molestiae consequatur, vel illum qui dolorem eum fugiat
quo voluptas nulla pariatur
Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque
laudantium, totam rem aperiam, eaque ipsa quae ab illo inventore veritatis et quasi architecto
beatae vitae dicta sunt explicabo. Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut
1
Page number is 1.
Page numbers must be
centered
Style Manuals
Pagination
Fonts
Order of the Pages
Title Page
Your Name
The Date
Copyright Page
Abstract
Table of Contents
Page Margins
Schema of Headings and Subheadings and Hierarchy of Font Treatments
Electronic Submission of Work
The Main Issues
Common Mistakes to Avoid
Using a Template
Frequently Asked Questions
ADVICE FOR . . . .
Advice for Long Dissertations
Advice for LaTeX Users
Advice for APA Users
Advice for Multi-Article Dissertations
Advice for Figure Titles
Advice on Placement of Figures and Tables
Estimation of Peak Skin Dose and Its Relation to the Size Specific Dose Estimate
Abdullatif Abdullah
1
, *, Matthew Williams
2
, *
1
3
700 O St NW, Washington, DC, 20057
23800 Reservoir Rd NW, Washington, DC, 20007
Received December 10, 2021, amended month date year, accepted month date year
Abstract:
The research aims to test the concept that the size specific dose estimete (SSDE) has a significantly higher linear relationship with the peak skin dose (PSD). To determine the connection between the two measurements, a NEMA phantom and ACR phantom were provided with a peak skin dose measured using the external dosimeters (Nanodots) to measure the level of delivered radiation. For the experiment’s success, different measuring techniques and methods were utilized in the research. Nanodots dosimeters which use optically stimulated luminescence (OSL) technology, were used to determine peak skin dose. The findings revealed a somewhat favorable connection in both PA and lateral regions, suggesting that the PSD and SSDE may be related. Posterior and Lateral angles have some potential since, in most projections, the greater the PSD, the higher the SSDE. The measured PSD and SSDE revealed that a physicist can predict the PSD within 80% of the actual dose estimates with considerable some uncertainties.
1
2
3
Introduction
The Federal Drug Administration (FDA) states that the Peak Skin Dose is the highest radiation dose accruing actually at a single site on a patient’s skin (1). Knowing the appropriate highest dosage is vital so that no harm is caused to the patient. The United States has regulated that the fluoroscopic system provides a display of the irradiation time, dose rate at the interventional reference point during irradiation, and the cumulative dose for the procedure upon completion of irradiation (2). In preparation for actual patients, technologists and physicists would revert to the manufactured dose estimation which is called the Computed Tomography Dose Index (CTDI). The CTDI is generally utilized for quality control including the radiation output of CT machines (2). Specifically, the volume CTDI is shown on the control center of all CT machines and is promptly accessible to the administrator. In any case, the CT Dose Index (CTDIvol) was originally designed as an index of dose associated with various CT diagnostic procedures, not as a direct dosimetry method for individual patient dose assessments (3).
Moreover, CTDIvol is reported in two units: a 16-cm phantom for head exams or 32-cm phantom or body exams. The relationship between the CTDIvol and skin dose entrance depends on various factors, one of which is the patient size (5). CTDIvol is displayed on the console of CT scanners, and it gives genuine estimates of the dose being delivered to a phantom,
which can over or under estimate dose to an actual patient. For instance, report 204 was generated to help better estimate the dose to a patient based on the patient size and shape that differs from size and shape of phantoms used to generate CTDIvol (4).
CTDIvol is a measurement taking with an ion chamber inserted into a phantom but not laying on outside of a phantom at the point of skin entrance. Specifically, estimating Peak Skin Dose is ideal since it is a surely known dosimetric amount that directly identifies with radiation-incited skin injures. For example, radiation directly damages the skin as well as its deep tissue cells, causing dryness, loss of elasticity, pigmentation, soft tissue fibrosis, capillary dilatation, and radiation dermatitis in irradiated areas. Therefore, there is a threshold range for transient erythema and temporary epilation is 2-5 Gray (Gy) peak skin dose, prolonged erythema and permanent partial epilation have threshold ranges of 5-10 Gy peak skin dose and severe skin injury is associated with larger values of peak skin dose (5).
Besides, estimates of PSD values, utilizing appropriate phantoms can be made across all types of CT units and scan protocols accessible in clinics (6). This is significant for comparing doses for a similar CT examination in different facilities, which can change fundamentally. More recently, modifications to the original CTDI concept have attempted to convert it into to patient dosimetry method, but have mixed results in terms of accuracy (7).
Nonetheless, CTDI-based dosimetry is the current worldwide standard for estimation of patient dose in CT (8). Therefore, CTDIvol is often used to enable medical physicists to compare the dose output between different CT scanners (8). Also, since CTDIvol estimates the patient’s radiation exposure from the CT procedure, the exposures are the same regardless of
patient size, but the size of the patients is a factor in the overall patient’s absorbed dose (SSDE) (4). The size-specific dose estimate (SSDE) is measured in mGy, and it is a method of estimating CT radiation dose that takes a patient’s size into account (4).
From a radiation protection point of view, determining the maximum dose delivered to the skin would allow deriving quantities that can be compared with dose reference levels set by national and international standards. The most important outcome from a radiation safety perspective is evaluating if a radiation injury had occurred quickly (10). In this research, the peak skin dose delivered to a patient was estimated experimentally by measuring the dose delivered to the surface of a NEMA phantom and an ACR phantom using external dosimeters (11). These dosimeters provided PSD values for a given protocol and its related CTDIvol. From this, a relationship was evaluated between both quantities. The aim of this project was to test the hypothesis that the size-specific dose estimate (SSDE) has a sufficiently strong linear relationship with PSD to allow direct calculation of the PSD directly from the SSDE. Comment by ,Abdullatif abdullah: Prof. Jorgensen note “What are you saying here? Do you mean that dose rate is the most important parameter determining skin injury? Or do you mean that shorter latency means higher doses? I don’t understand why this sentence is stuck in here.”
MATERIALS AND METHODS
The measurements were performed with a Siemens 64 slices, Biograph mCT. A comparison was made between the CTDIvol value displayed on the CT console and the measured CTDIvol value using the AAPM protocol. For every examined scanner, the CTDIvol was obtained from scans in an axial mode for head scans and helical mode of the routine pelvis, cervical spine, abdomen, and thoracic scans using the scan parameters. The corresponding CTDIvol displayed on the console was recorded as shown in Table 1.
Peak Skin Dose was estimated by using Nanodots dosimeters (12) (International Specialty Products, Inc., Wayne, NJ, USA) which have optically stimulated luminescence (OSL) technology which is a single point radiation monitoring dosimeter. It is a useful tool in measuring the patient dose, and it is an ideal solution in multiple settings, including diagnostic radiology, nuclear medicine, interventional procedures and radiation oncology (12).
Nanodots dosimeters also have minimal angular or energy dependencies with appropriate calibration which can be used to measure skin dose at a point of interest. Moreover, LANDAUER provides a set of calibration dosimeters exposed at a beam quality of 80 kVp on a PMMA phantom at normal incidence for conventional (non-mammography) diagnostic radiology applications (12). For radiation oncology applications, LANDAUER provides a set of screened, unexposed calibration dosimeters that can be irradiated using a radiation therapy beam quality. Another way for calibration is to request a dosimeter set exposed to a 662 keV beam quality (Cs-137) (12).
The Nanodot dosimeters were placed on three different locations (Anterior-Posterior, Lateral (LAT) and Posterior-Anterior) as shown in figure 1, and the dose to the skin was measured at these locations.
1
2
3
CT TABLE
Figure1. (a) a set-up used for the Peak Skin Dose measurements with placing the Nanodots on the three locations (Anterior, Posterior and lateral) with using the NEMA phantom. The cylindrical phantom was placed in the center of the CT scan. (b) The Peak Skin Dose measurements with using the ACR phantom which was placed in the center of the CT scan. Comment by ,Abdullatif abdullah: I will change this figure once I am back on campus. I will place both phantoms we used in the center of the scanner and upload the pictures here instead.
Experimental set-up and procedure:
The CTDIvol displayed by the scanner was validated to the true CTDIvol following the ACR testing guidelines (13). A correction factor was used to correct the inaccuracies in the displayed value. This correction was applied to the DLP displayed by the scanner.
Peak skin dose and its relation were measured by the 2 phantoms, and the phantoms were aligned at the isocenter of the scanner and a single axial CT scan was made. After placing the Nanodot dosimeters on the AP, LAT and PA locations, the phantoms were scanned over the scan length for a fixed value of the tube current. The measurement was repeated several times using various scanning techniques (with varying energy, current) as shown in table 1. Size conversion factors used were based on the dimension of the phantom being scanned. These K-factors with the CTDIvol produced the size-specific dose estimates (SSDEs), and since the CT dose index was provided at the CT scanner too, the size-specific dose estimate for the phantoms was calculated. Also testing if the correlation between the size-specific dose estimate and the measurement of the peak skin dose match was done, and since such a relationship exists, finding that factor was achieved.
RESULTS
To determine the connection between the Peak Skin Dose and Size Specific Dose Estimates, a comparison was done using the NEMA phantom and ACR phantom with a peak skin dose measured using the Nanodots. After testing if the correlation between the size-specific dose estimate and the measurement of the peak skin dose, the SSDE was calculated using the corresponding k-factor based on the AP and lateral dimension from AAPM Report 204. The Size Specific Dose estimate values as shown in table 1, are based on the CTDIvol value which was displayed on the console. (effective diameter = ), the effective diameter represented the diameter of the phantom at a given location along the z-axis of the phantom (4). The anterior (AP) in the NEMA phantom was 22.37 cm whereas the lateral (LAT) in the same phantom was 29.27 cm. The effective diameter for the NAMA phantom was 26 cm.
(SSDE = CTDIvol x K factor), this formula was used to solve for the Size Specific Dose Estimates. Report 204, has tables with different conversion factors based on the use of the NEMA phantom. Table 1D in the report, provided conversion factors as a function of the
Tables 1 illustrates the difference kilovoltage peaks, milliampere-seconds, CTDIvol in mGy, the Peak Skin Dose of all the Nanodot dosimeters that were used in the specific locations and the measured size specific dose estimate.
effective diameter. The data on the report are used when the CTDIvol is known. In this study, the conversion factor for 26 cm effective diameter NEMA phantom in all the projections besides head was 1.43. For head scans, different protocol was used which was similar to the protocol used with the ACR phantom. The effective diameter for the ACR phantom was 19 cm. The AAPM Report 204 stated that the conversion
factor based on the use of the ACR phantom with 19 cm effective diameter was 0.90. The SSDE was calculated and measured in mGy as shown in table 1.
Table 1 includes a comparison between the peak skin dose that was measured by the Nanodots in the three locations. The measured PSD values varied between
0.13
and
70.77
mGy. The highest PSD was measured using the ACR phantom with head projection at the anterior location and the lowest was Peak Skin Dose was measured at the anterior location of the NEMA phantom with abdomen projection.
|
NEMA Phantom |
Scans: |
kVp |
mAs |
CTDIvol (mGy) |
PSD in Dosimeter A, (mGy) |
PSD in Dosimeter Lat, (mGy) |
PSD in Dosimeter P, (mGy) |
SSDE (mGy) |
||||
|
ABD |
120 |
155 |
8.76 |
0.13 |
0.19 |
0.39 |
12.53 |
|||||
|
Head |
916 |
158 |
0.68 |
1.09 |
2.62 |
142.2 |
||||||
|
Thoracic |
100 |
125 |
5.56 |
9.52 |
9.64 |
11.69 |
7.95 |
|||||
|
Pelvis |
113 |
8.78 |
9.88 |
10.80 |
12.55 |
|||||||
|
C-Spine |
535 |
23.86 |
27.33 |
30.05 |
32.27 |
34.12 |
||||||
|
ACR Phantom |
46 |
2.06 |
6.21 |
5. 50 |
4.88 |
1.85 |
||||||
| 50 |
3.81 |
7.50 |
5.97 |
7.12 |
3.43 |
|||||||
|
99 |
3.77 |
27.83 |
6.17 |
5.94 |
3.39 |
|||||||
|
408 |
18.23 |
36.86 |
27.16 |
30.54 |
16.41 |
|||||||
|
856 |
87.69 |
70.77 |
62.76 |
56.43 |
78.92 |
Figure 2: The graph illustrates the relationship between Peak Skin Dose in AP location and the Size Specific Dose Estimates in AP location in the NEMA phantom and the ACR phantom.
Figure 2, illustrates the measured PSD in AP location against the SSDE in AP location with using 2 different phantoms (NEMA phantom and ACR phantom). For both phantoms, there was a linear relationship between the size specific dose estimates and the peak skin dose. In this study, the R-squared value was 0.75 which indicate that 75% of the variance of the dependent variable being studied is explained by the variance of the independent variable (14). Therefore, the relationship between the PSD in AP location and the SSDE in AP location has a positive correlation.
Figure 3: The graph demonstrates the relationship between Peak Skin Dose in PA location and the Size Specific Dose Estimates in PA location in the NEMA phantom and the ACR phantom.
The third figure demonstrates the measured PSD in PA location against the SSDE in PA location. For both phantoms, there was linear relationship between the size specific dose estimates and the peak skin dose. In this graph, the R-squared value was 0.85. Therefore, the relationship between the PSD in PA location and the SSDE has a positive relationship and high correlation.
Figure 4: The graph illustrates the relationship between Peak Skin Dose in Lateral location and the Size Specific Dose Estimates in Lateral location in the NEMA phantom and the ACR phantom.
Figure 4, illustrates the measured PSD in the lateral location against the SSDE in Lateral location. For both phantoms, there was linear relationship between the
size specific dose estimates and the peak skin dose. In this graph the R-squared value was 0.78 which indicated that there was a positive linear relationship between the PSD in lateral location and the SSDE in lateral location.
In all the plots, linear relationship between the PSD and SSDE was found, and the linear fitting equation was calculated. Peak Skin Dose can be predicted in the anterior location with knowing the CTDIvol which is shown on the console. (SSDE = 0.8373 x (PSD) – 2.3412), this was the fitting equation for the AP location graph (1st graph).
(SSDE = 0.6833 x (PSD) + 4.9856), this was the linear fitting equation for the posterior location graph (2nd graph) which indicates that PSD can be measured with knowing the SSDE value.
(SSDE = 0.9384 x (PSD) – 3.084), this was the linear fitting equation for the lateral location graph (3rd graph).
The three equations have a high positive relationship, so predicting the value of SSDE or PSD will be possible but not 100% accurate. With using these data and fitting equations, a physicist can estimate the PSD, but with some limitations.
The physicist would be within 80% the true dose estimates and a large error would be there as well. The regression was almost 80% in the three locations, so roughly 80% of the data points will fall close to the linear line.
DISCUSSION
The regression of the Peak Skin Dose was different in the AP and LAT locations comparison with the lateral location which is because the thickness of the phantom. Considering that examination is performed in the lateral location of the body which has the highest x-ray attenuation, thus requiring higher beam energy to penetrate. With increasing the patient average diameter, the peak skin dose was higher. According to the data that was measured, the measured PSD was higher in all the lateral location than the AP and PA locations. The bigger the phantom (more tissue to penetrate), the more dose was required to attenuate and reached the dosimeter.
In the is study the AP, PA and lateral dimensions of the phantom were used to measure the SSDE which is a factor that is used to estimate the absorbed dose. This could’ve been an error in measuring the peak skin dose since the SSDE was not measured at that time. Also, there was a linear relationship between the PSD and the SSDE because the Size Specific Dose Estimates dictate the patient’s dose and this could be one of the reasons that the linear relationship occurred. Also, there could be better modifications to the K-factors in order to dictate the patient’s more accurately.
When calculating how much radiation dose a patient is actually receiving, it’s best to consider their actual size. CTDIvol and DLP are common methods to estimate a patient’s radiation dose from a CT procedure. The dose is the same regardless of patient size, but the size of the patients is a factor in the overall patient’s absorbed dose. Therefore, SSDE measured in mGy, would allow the physicists to use the patient’s size as a factor in order to estimate the radiation dose. In the other hand the PSD is the maximum absorbed dose in mGy to the most heavily exposed region of the skin in specific location. In this study, the measured values of the PSD and SSDE had a linear relationship in most projections (C-spine, thoracic and pelvis). The higher the PSD was, the higher the SSDE which was due to the measured CTDIvol which displayed in the console (the higher the CTDIvol was, the higher SSDE was calculated).
There is a difference between the CTDIvol that was shown on the console and the actual CTDIvol. The CTDIvol or its derivative the DLP, as seen on consoles and outputted, do not represent the actual absorbed or effective dose for the patient. They should be taken as an index of radiation output by the system for comparison purposes. In this study, it is not possible to compare the true CTDIvol to the displayed because the phantoms that were used were not CTDI phantoms, so it is not possible to place a CTDI probe.
However, nowadays many modifications to original CTDI concept have attempted to make it more accurate patient dosimetry method, with mixed results. Body CTDIvol reported by the CT scanner, or measured on a CT scanner, is a dose index that results from air kerma measurements at two locations, to a very cylinder of plastic phantom with a density of 1.19 g/cm3 (15).
CTDIvol is primary affected by kVp and mAs, so parameters which were used in most of the previous researches such as (Auto-kVp and dose reduction initiative parameters) were not used in this research because in a normal system as the tube rotate around the phantom, the thickness of the phantom varies, LAT location usually requires more dose so more kVp and mAs than AP location, so the kVp and mAs values will fluctuate which will lead to change the CTDIvol as well. Therefore, fixed kVp and mAs values were used in order to have a continuous CTDIvol for the entire process, and for a different phantom a different parameter was used in different exam so an abdomen phantom had different parameter than the one for the cervical spine.
According to the measured data, some scan projections such as abdomen had high PSD and high SSDE due to the high measured CTDIvol and DLP caused out wire and low regression. Taking out the abdomen PSD and SSDE from the graphs make the regression higher (more positive) which means correlation could exist. Therefore, some projections such as an abdomen and head might make the data points and graphs not clear and hard to be read.
When graphing the measured PSD and SSDE in each phantom separately, a higher regression (more positive correlation) was found (close to 90%) in all the three locations. This means that the closer the patient to become cylindrical, the better relationship between PSD and SSDE will be and more accurate doses will be measured. It fails at very large effective circumferences with perfectly cylindrical patients.
In this study, only two phantoms were used (NEMA and ACR phantoms) with specific thicknesses, so other phantoms such as anthropomorphic phantoms and fake human phantoms with different thickness styles could be used to get better data and correlation.
In this study, only 9 measurements were taken in the three different location due to the limitation of the Nanodots. More measurements could have been taken and a better data points would have been measured. With more data testing that the SSDE has a sufficiently strong linear relationship with PSD could be proven.
CONCLUSION
In this study a measured value of the dose was delivered to two different phantoms (NEMA and ACR phantoms) during a CT examination. The Peak Skin Dose values were calibrated and reported by LANDAUER labs. The Size Specific Dose estimates was calculated using the CTDIvol that was shown in the console and the corresponding k-factor based on the AP and lateral dimension from AAPM Report 204. The results showed there was a positive linear relationship in AP, PA and lateral locations, and there was a sufficiently strong linear relationship between the PSD and SSDE. The higher the PSD was, the higher the SSDE was in almost all the projections. The measured PSD and SSDE showed that a physicist can estimate the PSD within 80% the true dose estimates with a small error. The R-squared value was around 0.80 in all the locations which indicated that there was a positive linear relationship.
REFERENCES
Center for Devices and Radiological Health. (n.d.). Radiation Dose Quality Assurance: Questions and Answers. U.S. Food and Drug Administration. Retrieved November 19, 2021, from https://www.fda.gov/radiation-emitting-products/initiative-reduce-unnecessary-radiation-exposure-medical-imaging/radiation-dose-quality- assurance-questions-and-answers.
De las Heras, H., Minniti, R., Wilson, S., Mitchell, C., Skopec, M., Brunner, C. C., & Chakrabarti, K. (2013). Experimental estimates of peak skin dose and its relationship to the CT dose index using the CTDI head phantom. Radiation protection dosimetry, 157(4), 536-542.
Jones, A. K., Kisiel, M. E., Rong, X. J., & Tam, A. L. (2021). Validation of a method for estimating peak skin dose from CT‐guided procedures. Journal of applied clinical medical physics.
Publications. AAPM Publications – AAPM Reports. (2021). Retrieved 17 December 2021, from https://www.aapm.org/pubs/reports/rpt_204
Stephen Balter et al., “Fluoroscopically Guided Interventional Procedures: A Review of Radiation Effects on Patients’ Skin and Hair,” Radiology Vol. 254, No. 2, pp. 326-341, February 2010.
Tack, D., & Gevenois, P. A. (2018). Radiation dose from adult and pediatric Multidetector computed tomography. Springer Science & Business Media.
McCollough, C. H., Leng, S., Yu, L., Cody, D. D., Boone, J. M. and McNitt-Gray, M. F. CT dose index and patient dose: they are not the same thing. Radiology 259(2), 311 – 316 (2011).
Bauhs, J. A., Vrieze, T. J., Primak, A. N., Bruesewitz, M. R. and McCollough, C. H. CT dosimetry: Comparison of measurement techniques and devices. Radiographics 28, 245 – 253 (2008).
Nationals Council on Radiation Protection and measurements. NCRP Report No. 160: Ionizing radiation exposure of the population of the United States (2009).
Beganovic, A., Sefic-Pasic, I., Skopljak-Beganovic, A., Kristic, S., Sunjic, S., Mekic, A., Gazdic-Santic, M., Drljevic, A. and Samek, D. Doses to skin during dynamic perfusion computed tomography of the liver. Radiat. Prot. Dosim. 153(1), 106–111 (2013).
NanoDot™. LANDAUER. (n.d.). Retrieved November 19, 2021, from https://www.landauer.com/product/nanodot.
ACR–sar–SPR practice parameter for the performance of … (n.d.). Retrieved November 19, 2021, from https://www.acr.org/-/media/ACR/Files/Practice-Parameters/CT-Entero .
Frost, J. (2021). How To Interpret R-squared in Regression Analysis. Retrieved 1 December 2021, from
Morgan, M. (2021). Size specific dose estimate | Radiology Reference Article | Radiopaedia.org. Retrieved 1 December 2021, from
https://radiopaedia.org/articles/size-specific-dose-estimate?lang=us
McCollough, C., Leng, S., Yu, L., Cody, D., Boone, J., & McNitt-Gray, M. (2011). CT Dose Index and Patient Dose: They AreNotthe Same Thing. Radiology, 259(2), 311-316. doi: 10.1148/radiol.11101800
NEMA phantom 12.53 7.95 12.55 34.119999999999997 1.85 3.43 3.39 16.41 78.92 0.39 11.69 12.55 32.270000000000003 4.88 7.12 5.94 30.54 56.43 ACR phantom 1.85 3.43 3.39 16.41 78.92 4.88 7.12 5.94 30.54 56.43
Peak Skin Dose (mGy)
Size Specific Dose Estimates (mGy)
NEMA phantom 12.53 7.95 12.55 34.119999999999997 1.85 3.43 3.39 16.41 78.92 0.13 9.52 9.8800000000000008 27.33 ACR phantom 12.53 7.95 12.55 34.119999999999997 1.85 3.43 3.39 16.41 78.92 6.21 7.5 27.83 36.86 70.77
Peak Skin Dose (mGy)
Size Specific Dose Estimates (mGy)
NEMA phantom 12.53 7.95 12.55 34.119999999999997 1.85 3.43 3.39 16.41 78.92 0.19 9.64 10.8 30.05 ACR phantpm 12.53 7.95 12.55 34.119999999999997 1.85 3.43 3.39 16.41 78.92 5.5 5.97 6.17 27.16 62.76
Peak Skin Dose (mGy)
Size Specific Dose Estimates (mGy)
|
Thesis / Doctoral Project / Dissertation Proposal |
Student Information:
Student GUID Number:
8
3
3
1
68318
Student Name: (As it appears on your transcript)
Abdullatif Abdullah
Address:
1850 Columbia Pike Apt 406, Arlington, Virginia,
2
2204
E-Mail Address:
aa2388@georgetown.edu
Phone Number:
571-340-6065
Degree:
Masters in
Health Physics
Expected Graduation Month/Year
05 / 2022
Dept./Major:
I. Title:
Estimation of Peak Skin Dose and Its Relation to the Size Specific Dose Estimate
II. Problem or Hypothesis:
The CT Dose Index (CTDIvol) was originally designed as an index of dose associated with various CT diagnostic procedures not as a direct dosimetry method for individual patient dose assessments. There is no current method for calculating peak skin dose (PSD) using the key metrics provided from the radiation dose structure report of a CT scanner. Every CT study is required to output the kVp and mAs that were used, the dose length product and CT dose index volume which will all be shown on the CT console, but there is no direct method to go straight to the PSD. This project will test the hypothesis that the SSDE has a sufficiently strong linear relationship with PSD to allow direct calculation of the PSD directly from the SSDE.
The highest radiation dose accruing at a single site on a patient’s skin is referred to as the peak skin dose (PSD) which is related to the Computed Tomography dose index (CTDIvol) that is displayed on the console of CT scanners. However, the CT Dose Index was originally designed as an index not as a direct dosimetry method for patient dose assessment. More recently, modifications to original CTDI concept have attempted to convert it into to patient dosimetry method, but have with mixed results in terms of accuracy. Nonetheless, CTDI-based dosimetry is the current worldwide standard for estimation of patient dose in CT. Therefore, CTDIvol is often used to enable medical physicists to compare the dose output between different CT scanners.
Fearon, Thomas (2011) explained that current estimation of radiation dose from CT scans on patients has relied on the measurement of Computed Tomography Dose Index (CTDI) in standard cylindrical phantoms, and calculations based on mathematical representations of “standard man.” The purpose of this study was to investigate the feasibility of adapting a radiation treatment planning system (RTPS) to provide patient-specific CT dosimetry. A radiation treatment planning system was modified to calculate patient-specific CT dose distributions, which can be represented by dose at specific points within an organ of interest, as well as organ dose-volume (after image segmentation) for a GE Light Speed Ultra Plus CT scanner. Digital representations of the phantoms (virtual phantom) were acquired with the GE CT scanner in axial mode. Thermoluminescent dosimeter (TLDs) measurements in pediatric anthropomorphic phantoms were utilized to validate the dose at specific points within organs of interest relative to RTPS calculations and Monte Carlo simulations of the same virtual phantoms. Congruence of the calculated and measured point doses for the same physical anthropomorphic phantom geometry was used to verify the feasibility of the method. The advantage of the RTPS is the significant reduction in computation time, yielding dose estimates within 10%–20% of measured values.
De las Heras (2013) elaborated on the concept of CT scanners and their critical implementation in diagnostic imaging. His method was based on estimating the peak skin dose delivered by CT scanners by measuring the PSD values related to the volume CT dose index (CTDIvol), a parameter that is displayed on the console of modern CT scanners. He obtained the PSD measurement estimates in CT units by placing radio-chromic film on the surface of a CTDI head phantom, and different x-ray tube currents were then used to irradiate the phantom. The PSD and the CTDIvol were independently measured and later related to the CTDIvol value that was displayed on the console. They found that there was a relationship between the measured PSD and the associated CTDIvol displayed on the console, and the measured PSD values varied among all scanners when the routine head scan parameters were used. This work showed the widely used CTDIvol could be used to accurately estimate an actual radiation dose delivered to the skin of a patient. Also, the method and the analysis provided valuable information to patients, radiological technologists, medical physicists, and physicians to relate the displayed CTDIvol to an actual measured dose delivered to the skin of a patient.
Jones, A. Kyle (2021) recently developed a new method to estimate the peak skin dose from CTDIvol. The objective of this study was to validate the methodology during CT-guided ablation procedures. Radio-chromic film was calibrated and used to measure PSD as well. Real patients, rather than phantoms, were used in the study. CTDIvol stratified by axial and helical scanning was used to calculate an estimate of PSD, and both calculated PSD and total CTDIvol were compared to measured PSD. The calculated PSD were significantly different from the measured PSD, but the measured PSD were not significantly different from total CTDIvol which prove that the CTDI can help in measuring the patient dose. Considering that CTDIvol was reported on the console of all CT scanners, is not stratified by axial and helical scanning modes, and is immediately available to the operator during CT-guided interventional procedures.
Each of the methodologies mentioned above represents a reasonably accurate approach for computing the patient dose from CT procedures. Reassuringly, estimation of the dose to either phantoms or actual patients yielded comparable doses. However, all the methodologies used to obtaine the PSD measurement were based on the same experimental approach. They estimated in CT units by placing a radio-chromic film on the surface of a CTDI phantom. This research project will use a completely different approach — it will make patient dose estimates by means of Nanodots dosimeters. Nanodots have optically stimulated luminescence (OSL) technology which is a single point radiation monitoring dosimeter. It is a useful tool in measuring the patient dose, and it is an ideal solution in multiple settings, including diagnostic radiology, nuclear medicine, interventional procedures and radiation oncology. These dosimeters have the technical advantage that they can be placed anywhere on the body or phantom and the nondestructive readout supports reanalysis and electronic data archiving.
The CTDIvol displayed by the scanner will be validated to the true CTDIvol following the ACR testing guidelines. A correction factor will be used to correct any inaccuracies in the displayed value. This correction will also be applied to the DLP displayed by the scanner.
Peak skin dose and its relation will be measured by various phantoms such as NEMA phantoms, 16 cm CTDI and 32 cm CTDI phantoms. The phantoms will be aligned at the isocenter of the scanner with the chamber in the center hole of the phantom. The longitudinal axis of the chamber and cylindrical phantom will be aligned parallel to the longitudinal axis of the CT gantry. With using those different phantoms, the dosimeter will be placed serially in center hole ad peripheral hole. Those measurements are combined to produce the weighted CTDI, so a 100-mm-long cylindrical (pencil) chamber, approximately 9 mm in diameter, inserted into either the center or a peripheral hole of a phantom as shown in figure 1, and with the pencil chamber located at the center (in the z-dimension) of the phantom and also at the center of the CT gantry, a single axial CT scan is made. An ionization chamber can only produce an accurate dose estimate if its entire sensitive volume is irradiated by the x-ray beam. Therefore, for the partially irradiated 100-mm CT pencil chamber, the nominal beam width which is the total collimated x-ray beam width as indicated on the CT console, is used to correct the chamber reading for the partial volume exposure. The 100-mm chamber length is useful for x-ray beams of thin slices such as 5 mm to thicker beam collimations such as 40 mm. The correction for partial volume is essential and is calculated using the correction for partial volume is essential and is calculated using which B can be either the total collimated beam width, in mm, for a single axial scan or the width of an individual CT detector (T) number of active detectors (n)
Then the CTDI will be calculated as CTDI100 = (1/3) x CTDIcenter + (2/3) x CTDIperiphery. Combining the center and peripheral measurements using a 1/3 and 2/3 weighting scheme provides a good estimate of the average dose to the phantom at the central CT slice along z, giving rise to the weighted CTDI, CTDIw. The CTDI100, which is the amount of radiation delivered to one slice of the body over a long CT scan and it is also known as CTDI weighted. The scanner scans the entire volume in a helical trajectory. Thus, there isn’t really a true ‘slice’, as the z-position of the scanner is different at each angle. Also, the spacing between successive revolutions of the CT tube represents the pitch of the scan. In fact, the wider the helix, the less dose the patient will receive because the same portion of tissue is being irradiated at fewer angles, so the larger the pitch the lower the dose. Therefore, CTDIvol represent the dose for a specific scan protocol which considers gaps and overlaps between the radiation dose profile from consecutive rotations of the x-ray source and it can be calculated; CTDIvol = (1/pitch) x CTDIw. The CTDIw represents the average radiation dose over the x and y direction whereas CTDIvol represents the average radiation dose over the x, y and z directions.
Nanodot dosimeters will be placed on the LAT and AP locations as shown in figure 2, the dose to the skin will be measured at these locations. Then, the phantoms will be scanned over the scan length for a fixed value of the tube current. The measurement will be repeated several times using various scanning techniques (with varying energy, current). Size conversion factors used will be based on the dimension of the phantom being scanned used. These K-factors with the CTDIvol can produce size specific dose estimates (SSDEs), and since the CT dose index will be provided at the CT scanner too, the size specific dose estimate for the phantoms will be calculated. Also testing if the correlation between the size specific dose estimate and the measurement of the peak skin dose match will be done, and if such a relationship exists, trying to find that factor will be the aim.
Finally, in null hypothesis significance testing, the p-value is the probability of obtaining test results at least as extreme as the results observed under the assumption that the null hypothesis is correct. Since reporting the p-values of statistical tests is common practice in academic publication of many quantitative fields, then calculating the p-value will be done and looking for very small p-value will be the hope. Because small p-value (p-value <0.05) means that such an extreme observed outcome would be very unlikely under the null hypothesis and regression analyses and correlation coefficients are statically significant.
Phantom
Phantom
Figure1: a 100-mm-long cylindrical (pencil) chamber, approximately 9 mm in diameter, inserted into either the center or a peripheral hole of a phantom.
1
CT TABLE
3
2
Figure2: a phantom in the middle of the CT scan and 1 is the AP location, 2 is the LAT location and 3 is the PA location.
|
Andersson, J., Bednarek, D. R., Bolch, W., Boltz, T., Bosmans, H., Gislason-Lee, A. J., … & Zamora, D. (2021). Estimation of patient skin dose in fluoroscopy: summary of a joint report by AAPM TG357 and EFOMP. Medical physics (Lancaster). da Silva, E. H., Baffa, O., Elias, J., & Buls, N. (2021). Conversion factor for size specific dose estimation of head CT scans based on age, for individuals from 0 up to 18 years old. Physics in Medicine & Biology, 66(8), 085011. Fleury, A. S., Durand, R. E., Cahill, A. M., Zhu, X., Meyers, K. E., & Otero, H. J. (2021). Validation of computed tomography angiography as a complementary test in the assessment of renal artery stenosis: a comparison with digital subtraction angiography. Pediatric Radiology, 1-14. Greffier, J., Hamard, A., Berny, L., Snene, F., Perolat, R., Larbi, A., … & Beregi, J. P. (2021). A retrospective comparison of organ dose and effective dose in percutaneous vertebroplasty performed under CT guidance or using a fixed C-arm with a flat-panel detector. Physica Medica, 88, 235-241. Jauhari, A., Anam, C., Ali, M. H., Rae, W. I. D., Akbari, S., & Meilinda, T. (2021). The effect on CT size-specific dose estimates of mis-positioning patientsfrom the iso-centre. European Journal of Molecular & Clinical Medicine, 8(3), 155-164. Jones, A. K., Kisiel, M. E., Rong, X. J., & Tam, A. L. (2021). Validation of a method for estimating peak skin dose from CT‐guided procedures. Journal of applied clinical medical physics. Loose, R. W., Vano, E., Mildenberger, P., Tsapaki, V., Caramella, D., Sjöberg, J., … & Damilakis, J. (2021). Radiation dose management systems—requirements and recommendations for users from the ESR EuroSafe Imaging initiative. European Radiology, 31(4), 2106-2114. Mohamed, A. I. A. (2021). Estimation of Effective Dose for Pediatric Patients During Computed Tomography Examinations (Doctoral dissertation, Sudan University of Science and Technology). Okamoto, H., Kito, S., Tohyama, N., Yonai, S., Kawamorita, R., Nakamura, M., … & Shioyama, Y. (2021). Radiation protection in radiological imaging: a survey of imaging modalities used in Japanese institutions for verifying applicator placements in high-dose-rate brachytherapy. Journal of Radiation Research, 62(1), 58-66. Saeed, M. K. (2021). Comparison of estimated and calculated fetal radiation dose for a pregnant woman who underwent computed tomography and conventional X-ray examinations based on a phantom study. Radiological Physics and Technology, 14(1), 25-33. Steuwe, A., Weber, M., Bethge, O. T., Rademacher, C., Boschheidgen, M., Sawicki, L. M., … & Aissa, J. (2021). Influence of a novel deep-learning based reconstruction software on the objective and subjective image quality in low-dose abdominal computed tomography. The British Journal of Radiology, 94(1117), 20200677. Sundell, V. M., Kortesniemi, M., Siiskonen, T., Kosunen, A., Rosendahl, S., & Büermann, L. (2021). Patient-Specific Dose Estimates In Dynamic Computed Tomography Myocardial Perfusion Examination. Radiation Protection Dosimetry, 193(1), 24-36. Tabari, A., Li, X., Yang, K., Liu, B., Gee, M. S., & Westra, S. J. (2021). Patient-level dose monitoring in computed tomography: tracking cumulative dose from multiple multi-sequence exams with tube current modulation in children. Pediatric Radiology, 1-9. Thierry-Chef, I., Ferro, G., Le Cornet, L., Dabin, J., Istad, T. S., Jahnen, A., … & Simon, S. L. (2021). Dose estimation for the european epidemiological study on pediatric computed tomography (EPI-CT). Radiation Research, 196(1), 74-99. De las Heras, H., Minniti, R., Wilson, S., Mitchell, C., Skopec, M., Brunner, C. C., & Chakrabarti, K. (2013). Experimental estimates of peak skin dose and its relationship to the CT dose index using the CTDI head phantom. Radiation protection dosimetry, 157(4), 536-542. |
Does your research involve the use of human subjects? No
|
Yes |_| |
No |
If yes, you must obtain approval from the appropriate University Institutional Review Board before your proposal can be submitted to the Graduate School. Submit a copy of the IRB Approval Memo for your research along with this form.
|
IRB Number: |
|
Abdullatif Abdullah October, 29th 2021
| COMMITTEE ROLE: |
MEMBER NAME: (typed) |
SIGNATURE: |
DATE: |
|
Thesis Advisor |
Matthew Williams |
11/5/2021 |
|
|
Committee Member |
Stanley Thomas Fricke |
11/14/2021 |
|
|
Committee Member |
|||
|
Director
of Graduate Studies |
Completed form should be returned to:
BGE students should return the form to:
Graduate School of Arts & Sciences
Biomedical Graduate Education Office
Car Barn 207, 3520 Prospect Street, NW
gradstudentservices@georgetown.edu
SE109 Medical Dental Building
bgestudentservices@georgetown.edu
5
