thesis research on Health physics (CT scan research). follow the guidelines and write the thesis.

TRENDS IN EXTERNAL RADIATION EXPOSURE AMONG THE U.S NAVY MEDICAL PERSONNEL WORKING IN NUCLEAR MEDICINE DEPARTMENTS FROM 2003 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.

## ABSTRACT

**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 1,357 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, 0.05-1.27 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 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.

## ACKNOWLEDGEMENTS

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.

## TABLE OF CONTENTS

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: Yearly 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 361 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

## LIST OF TABLES

Table 1. Annual Occupational Dose Limits 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

# CHAPTER 1. INTRODUCTION

Using a USN cohort of NM workers*, this thesis tests the that NM workers’*

CHAPTER 2. BACKGROUND

## 1.1 Ionizing radiation in medicine

## 1.2 Biological effects of ionizing radiation

## 1.3 Overview of nuclear medicine

## 1.4 Nuclear medicine imaging

1.4.1 *Nuclear cardiovascular imaging*

1.4.2 *Positron Emission Tomography*

Recently, the number of performed PET procedures increased from less than 2% to …