Thesis Doctoral Project Dissertation Proposal

Thesis / Doctoral Project / Dissertation Proposal
Student Information:
Student GUID Number:
833168318
Student Name: (As it appears on your transcript)
Abdullatif Abdullah
Address:
1850 Columbia Pike Apt 406, Arlington, Virginia, 22204
E-Mail Address:
[email protected]
Phone Number:
571-340-6065
Degree:
Masters in Health Physics
Expected Graduation Month/Year
05 / 2022
Dept./Major:
Health Physics

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 w ill
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.
III. Review of Related Literature:
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.
IV. Procedure or Method:
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.
V. Selected Bibliography:
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.
V. Use of Human Subjects:
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:
VII. Student Signature:
Abdullatif Abdullah
October, 29th 2021 Signature
Date
VIII. Faculty Approvals:
COMMITTEE ROLE:
MEMBER NAME: (typed)
SIGNATURE:
DATE:
Thesis Advisor
Matthew Williams
11/5/2021
Committee Member
Stanley Thomas Fricke
11/14/2021
Committee Member
Committee Member

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
[email protected]
SE109 Medical Dental Building
[email protected]
5
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

[email protected]
PREPARATION OF THE THESIS
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Style Manuals
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Pagination
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Fonts
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.......................................................... 2
ORDER AND CONTENT OF THE THESIS
.......................................................................................... 3
Order of the Pages
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................................... 3
Title Page
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Your Name
...............................................................................................
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The Date
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Copyright Page
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Abstract
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Table of Contents
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Page Margins
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Schema of Headings and Subheadings and Hierarchy of Font
Treatments ...................................... 5
SUBMISSION OF THE THESIS TO THE GRADUATE
SCHOOL .................................................... 6
Electronic Submission of Work
...............................................................................................
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The Main
Issues......................................................................................
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Common Mistakes to Avoid
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Using a

Template.................................................................................
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Frequently Asked Questions
...............................................................................................
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ADVICE FOR . . . .
...............................................................................................
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Advice for Long Dissertations
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Advice for LaTeX Users
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Advice for APA Users
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Advice for Multi-Article Dissertations
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. 12
Advice for Figure Titles
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Advice on Placement of Figures and Tables
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APPENDIX: SAMPLE
THESIS...................................................................................

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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
numbers, titles and dot leaders and page numbers
List of Tables (if document has tables) with Next
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 stateme nt
(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 requir ed,
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/
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
students/submission-of-thesis/
students/submission-of-dissertation-or-doctoral-project
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/yt90bx3gdcds7mwuz67yhv6k
nh4v5nm7
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/yt90bx3gdcds7mwuz67yhv6k
nh4v5nm7
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
ii
Copyright 2016 by Jaime Doe Student
All Rights Reserved
ber 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.
Your TITLE should appear
centered in ALL CAPS on as
few lines as possible. There
should be no hard return
after a colon.

iv
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
...............................................................................................
.............12
...............................................................................................
.............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

...............................................................................................
................13
...............................................................................................
................14
...............................................................................................
................18
...............................................................................................
................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.
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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.
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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 numbers must be
centered
Preparation of the ThesisStyle ManualsPaginationFontsOrder
and Content of THE ThesisOrder of the PagesTitle PageYour

NameThe DateCopyright PageAbstractTable of ContentsPage
MarginsSchema of Headings and Subheadings and Hierarchy of
Font TreatmentsSubmission of the Thesis to the Graduate
SchoolElectronic Submission of WorkThe Main IssuesCommon
Mistakes to AvoidUsing a TemplateFrequently Asked
QuestionsADVICE FOR . . . .Advice for Long
DissertationsAdvice for LaTeX UsersAdvice for APA
UsersAdvice for Multi-Article DissertationsAdvice for Figure
TitlesAdvice on Placement of Figures and Tables
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
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

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 firs t
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, medi an,
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
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.
CHAPTER 2. BACKGROUND
1.1 Ionizing radiation in medicine
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 1946, 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 popul ation
comes from diagnostic and therapeutic medical applications
(2).1.2 Biological effects of ionizing radiation
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.1.3 Overview of nuclear medicine
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 Nuclear medicine imaging
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 85% 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).1.5
Occupational exposure in nuclear medicine
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 1950s, 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.
1.6 History in radiation protection
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 Dosimetry concepts
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 betw eenthe
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 0.254 mm of LiF-700H, and element 4 is 0.381 mm of
LiF-600H (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)
CHAPTER 3. MATERIALS AND METHODS
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.2.1 Data Collection
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

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