The National Academies Press: Tracking Radiation Exposure From Medical Diagnostic Procedures: Workshop Report

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Tracking Radiation Exposure from Medical Diagnostic

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Tracking Radiation Exposure from Medical Diagnostic Procedures: Workshop Report
TRACKING RADIATION
EXPOSURE FROM
MEDICAL DIAGNOSTIC
PROCEDURES
WO R K SH O P R E PO RT
Committee on Tracking Radiation Doses from

Medical Diagnostic Procedures
Nuclear and Radiation Studies Board
Division on Earth and Life Studies
Copyright National Academy of Sciences. All rights reserved.

THE NATIONAL ACADEMIES PRESS 500 Fifth Street, N.W. Washington, DC 20001
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the report were chosen for their special competences and with regard for appropri-
ate balance.
This study was supported by the following government agencies:
Contract No. 200-2005-13434, TO 26 Centers for Disease Control and Prevention

Contract No. HHSF2232008100201, TO 19/HHSF22301017T Food and Drug
Administration
Contract No. IOMHP060002-01-00 Department of Health and Human Services
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that provided support for the project.
International Standard Book Number-13: 978-0-309-25766-4

International Standard Book Number-10: 0-309-25766-2
Cover: Image titled “Drop in the Bucket,” courtesy of Dr. Aaron Sodickson (Brigham
and Women’s Hospital). Drops signify the exposure of patients who undergo medi-
cal imaging exams that utilize ionizing radiation; exposure may vary by amount and
frequency. The workshop explores how tracking radiation exposure from medical
diagnostic procedures can improve health care.
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COMMITTEE ON TRACKING RADIATION DOSES

FROM MEDICAL DIAGNOSTIC PROCEDURES
BARBARA J. MCNEIL (Chair), Harvard Medical School, Boston,

Massachusetts
HEDVIG HRICAK (Vice Chair), Memorial Sloan-Kettering Cancer
Center, New York
AMY BERRINGTON DE GONZÁLEZ, National Cancer Institute,
Bethesda, MD
WALTER HUDA, Medical University of South Carolina, Charleston
FRED A. METTLER, JR., New Mexico VA Healthcare System,
Albuquerque
RICHARD L. MORIN, Mayo Clinic, Florida, Jacksonville
Staff
OURANIA KOSTI, Study Director, Nuclear and Radiation Studies Board
TONI GREENLEAF, Administrative and Financial Associate
SHAUNTEÉ WHETSTONE, Senior Program Assistant
JAMES YATES, JR., Office Assistant

NUCLEAR AND RADIATION STUDIES BOARD
JAY DAVIS (Chair), Hertz Foundation, Livermore, California

BARBARA J. MCNEIL (Vice Chair), Harvard Medical School, Boston,
Massachusetts
JOONHONG AHN, University of California, Berkeley
JOHN S. APPLEGATE, Indiana University, Bloomington
MICHAEL L. CORRADINI, University of Wisconsin, Madison
PATRICIA J. CULLIGAN, Columbia University, New York
ROBERT C. DYNES, University of California, San Diego
JOE GRAY, Oregon Health and Science University, Portland
DAVID G. HOEL, Medical University of South Carolina, Charleston
HEDVIG HRICAK, Memorial Sloan-Kettering Cancer Center, New York
THOMAS H. ISAACS, Stanford University, Palo Alto, California
ANNIE B. KERSTING, Glenn T. Seaborg Institute, Lawrence Livermore
National Laboratory, Livermore, California
MARTHA S. LINET, National Institutes of Health, Bethesda, Maryland
FRED A. METTLER, JR., New Mexico VA Health Care System,
Albuquerque
BORIS F. MYASOEDOV, Russian Academy of Sciences, Moscow
RICHARD J. VETTER, Mayo Clinic, Rochester, Minnesota
RAYMOND G. WYMER, Oak Ridge National Laboratory, Oak Ridge,
Tennessee (retired)
Staff
KEVIN D. CROWLEY, Senior Board Director
JENNIFER A. HEIMBERG, Senior Program Officer
OURANIA KOSTI, Program Officer
TONI GREENLEAF, Administrative and Financial Associate
LAURA D. LLANOS, Administrative and Financial Associate
SHAUNTEÉ WHETSTONE, Senior Program Assistant
ERIN WINGO, Senior Program Assistant
JAMES YATES, JR., Office Assistant
vi

Reviewers
T
his report has been reviewed in draft form by individuals chosen
for their diverse perspectives and technical expertise, in accordance
with procedures approved by the Report Review Committee of the
National Research Council. The purpose of this independent review is to
provide candid and critical comments that will assist the National Research
Council in making its published report as sound as possible and will ensure
that this report meets institutional standards for objectivity, evidence, and
responsiveness to the study charge. The review comments and draft manu-
script remain confidential to protect the integrity of the deliberative process.
We thank the following individuals for their participation in the review of
this report:
• David Brenner, Columbia University

• James Brink, Yale University
• Cynthia McCollough, Mayo Clinic
• Orhan Suleiman, U.S. Food and Drug Administration
Although the reviewers listed above provided many constructive com-

ments and suggestions, they were not asked to endorse the contents of this
report, nor did they see the final draft of the report before its release. The
review of this report was overseen by Theodore Phillips, Professor Emeri-
tus, University of California, San Francisco. Appointed by the National
Research Council, Dr. Phillips was responsible for making certain that an
vii

viii REVIEWERS
independent examination of this report was carried out in accordance with

institutional procedures and that all review comments were considered care-
fully. Responsibility for the final content of this report rests entirely with
the authorizing committee and the institution.

Contents
OVERVIEW 1
1 INTRODUCTION 3
2 BACKGROUND 5
2.1 Trends in Diagnostic Imaging, 5
2.2 Potential Health Risks from Diagnostic Imaging, 7
2.3 Appropriateness of Diagnostic Imaging, 10
2.4 Reduction in Radiation Doses, 11
2.5 Recent Progress in Radiation Safety in Medicine, 13
3 WORKSHOP SUMMARY 17
3.1 Opening Comments, 17
3.2 Population Utilization of Imaging, 20
3.3 National and International Efforts in Dose Tracking, 27
3.4 From Dose Indices to Dose Estimates, 30
3.5 From Dose to Risk Estimates, 33
3.6 Why Track Doses?, 38
3.7 Lessons Learned from Pediatrics, 49
3.8 Some Possible Next Steps Suggested at the Workshop, 51
APPENDIXES
A Project Statement of Task 59
B Workshop Agenda 61
C Committee and Staff Biographical Sketches 65
D Workshop Speakers Biographical Sketches 71
ix


Overview
T
his report provides a summary of the presentations and discussions
that took place during the December 8-9, 2011, workshop titled
“Tracking Radiation Exposures from Medical Diagnostic Proce-
dures.” The workshop was organized by the Nuclear and Radiation Studies
Board of the National Academy of Sciences and sponsored by the Cen-
ters for Disease Control and Prevention (CDC), the U.S. Food and Drug
Administration (FDA), and the U.S. Department of Health and Human
Services. This workshop report was authored by a six-member committee
of experts appointed by the National Academy of Sciences. To respond to
its statement of task (see Appendix A), the workshop committee brought
together public health regulators, physicians, manufacturers, researchers,
and patients to explore “why,” “what,” and “how” to track exposure from
medical diagnostic procedures and possible next steps. The committee is
responsible for the overall quality and accuracy of the report as a record
of what transpired at the workshop, but the points discussed do not repre-
sent a consensus of the workshop participants or the authoring committee;
instead, they represent views expressed by individual participants during
the workshop.
The growing use of medical diagnostic procedures is correlated with
tremendous and undeniable benefits in the care of most patients. However,
it is accompanied by growing concerns about the risks associated with
diagnostic computed tomography (CT) and other procedures that utilize
ionizing radiation. A number of initiatives in radiation safety in medicine
have taken place in the United States and internationally, each serving dif-

2 TRACKING RADIATION EXPOSURE
ferent purposes. Their ultimate goals are to provide higher quality clinical
management of the patient and to ensure that reasonable steps are taken
to keep the exposures as low as possible without compromising diagnostic
efficacy.
Workshop participants discussed four goals of tracking radiation expo-
sure from medical diagnostic procedures: justification, optimization, indi-
vidual risk assessment, and research purposes. Many workshop participants
emphasized that a primary motivator for tracking exposures was to imple-
ment and maintain dose reduction strategies through optimization and
justification with the ultimate goal of improving care. These participants
reiterated that such strategies ought to be adopted by all facilities that per-
form diagnostic imaging, including hospitals and imaging centers, as well as
free-standing private physician, dental, and chiropractor practices. Several
workshop participants also noted that although it would be desirable to
have a national registry that tracks radiation exposures from medical diag-
nostic procedures, such a national effort is not likely to be implemented in
the near future for many reasons including the following: lack of sharing of
medical information across different health care facilities, lack of a unique
patient identifier and integrated medical records, non-automated dose infor-
mation collection processes, and data protection and patient privacy issues.
It is hoped that this workshop report will be a valuable testimony to the
questions other groups will have to face, and the consensus they will have
to achieve, if radiation exposure tracking is to become a reality institution-
ally or nationally in the future.

Introduction
T
his report provides a summary of the presentations and discussions
that took place during the December 8-9, 2011, workshop titled
“Tracking Radiation Exposures from Medical Diagnostic Proce-
dures.” The workshop was organized by the Nuclear and Radiation Stud-
ies Board of the National Academy of Sciences and was sponsored by the
Centers for Disease Control and Prevention (CDC), the U.S. Food and Drug
Administration (FDA), and the U.S. Department of Health and Human Ser-
vices. To respond to its statement of task (see Appendix A), the workshop
committee brought together public health regulators, physicians, manufac-
turers, researchers, and patients to explore “why,” “what,” and “how” to
track exposure from medical diagnostic procedures and possible next steps.
This six-member committee of experts appointed by the National Academy
of Sciences prepared the workshop agenda (see Appendix B) and produced
this workshop report. (Biographical sketches of the committee members
are provided in Appendix C.) The committee met twice over the course of
the study: in August 2011 to plan the workshop and in December 2011 to
hold the workshop and finalize the workshop report.
This report does not contain findings, conclusions, or recommenda-
tions, and it does not represent a consensus of the workshop committee
members or workshop participants. Although the workshop committee
is responsible for the content of this report, any views contained in the
report are not necessarily those of the committee or the National Academy
of Sciences.

The report is organized into three chapters:
• Chapter 1 (this chapter) provides an introduction to the workshop.

• Chapter 2 contains background information intended to provide
the context for this study to the reader.
• Chapter 3 provides the workshop summary.

Background
T
his chapter contains background factual information, much of which
was distilled from remarks made by workshop committee members
and workshop presenters.
2.1 TRENDS IN DIAGNOSTIC IMAGING

Dr. Hedvig Hricak, workshop committee vice-chair and chairman,
Department of Radiology, Memorial Sloan-Kettering Cancer Center,
explained the workshop’s scope and discussed the current advances and
trends in diagnostic imaging.
Advances in medical imaging in the past few decades using procedures
such as computed tomography (CT), fluoroscopy, and nuclear medicine
imaging exams have dramatically improved health care. Tissues deep within
the body can be easily accessed using these procedures, permitting radiolo-
gists to make diagnoses that previously would have necessitated exploratory
surgery (Wittenberg et al., 1978). Other direct benefits of modern imaging
procedures include more effective surgical treatment (Godoy et al., 2011),
potentially shorter hospital stays (Batlle et al., 2010), safer discharge of
patients (Litt et al., 2012), better diagnosis and treatment of cancer (Wagner
and Conti, 1991), more efficient treatment after injury (Philipp et al., 2003),
better treatment of stroke and cardiac conditions (Saini and Butcher, 2009;
Winchester et al., 2010), and rapid diagnosis of life-threatening vascular
conditions (Furukawa et al., 2009). Today in the United States, medical

imaging occurs in hospitals and imaging centers, as well as free-standing

private physician, dental, and chiropractor practices.
A report released in early 2009 by the National Council on Radiation
Protection and Measurements (NCRP)1 titled Ionizing Radiation Exposure
of the Population of the United States indicated that in 2006 Americans
were exposed to more than six times as much ionizing radiation from medi-
cal diagnostic procedures than in 1980 (NCRP, 2009). The average effective
radiation dose2 to which the U.S. population is now exposed is estimated
to be 3 mSv,3 which is comparable to the annual exposure from natural
background radiation which has remained unchanged for the past 20 years.
The most significant changes in medical diagnostic imaging were attrib-
uted to rapid increases in usage of higher-dose procedures particularly CT
and nuclear medicine (especially nuclear cardiology [Mettler, 2009]). Close
to 82 million CT exams are now performed annually in the United States
(IMV, 2011), up from 46 million in 2000 and 13 million in 1990 (Brenner
and Hall, 2007). Cardiac diagnostic nuclear procedures increased from 1
percent of the total number of diagnostic nuclear medicine examinations
performed in 1973 to 57 percent in 2005 (Mettler et al., 2009).
Many factors have been suggested as explanations for the sharp
increase in CT use (Baker et al., 2008; Iglehart, 2009), such as advances in
CT technology that have increased ease of use for physicians and comfort
for patients during testing; increased CT scanner availability; favorable
financial reimbursements for imaging procedures; and shifts in the practice
of medicine including more time constraints and promotion of defensive
medicine. Newer radiographic imaging modalities such as positron-emis-
sion tomography/CT (PET/CT), single-photon emission CT (SPECT/CT),
and potentially CT for screening of high-risk asymptomatic patients (for
example, smokers screened for early lung cancer detection) are likely to
further increase the population’s exposure (Brenner and Hricak, 2010).
1 The NCRP is a congressionally chartered organization that formulates and disseminates
information and research data related to radiation exposure and protection.

2 Effective dose is a dose parameter used to normalize partial-body radiation exposures
relative to whole-body exposures to facilitate radiation protection activities (ICRP, 1991).

Effective dose can also be used to enable comparison of risks between procedures that utilize
ionizing radiation. The International Commission on Radiological Protection (ICRP) does not
recommend use of effective dose for estimating population or individual risks. Effective dose
is expressed in sieverts (Sv).
3 The exposures of particular individuals could be higher or lower than these reported aver-
ages depending on how many medical imaging procedures that use ionizing radiation they
undergo. As discussed in Section 2.2, a number of individuals undergo multiple imaging exams
in their lifetime. Others may not undergo any. Therefore, their exposure would be higher or
lower than the estimated average.

BACKGROUND 7
2.2 POTENTIAL HEALTH RISKS FROM DIAGNOSTIC IMAGING

Although the growing use of medical diagnostic procedures is corre-
lated with tremendous and undeniable benefits in care of most patients, it
comes with growing concerns about risks associated with the use of ionizing
radiation. A 2001 article in USA Today generated visibility and publicity
and became a critical component in changing the prioritization of image
quality alone to image quality balanced with radiation dose in both adults
and children (Sternberg, 2001). Dr. David Brenner (Columbia University)
noted that ionizing radiation is an initiator and promoter of carcinogenesis.
In the absence of sufficient empirical knowledge regarding radiation effects
at low doses4 typically encountered in medical diagnostic procedures, it
is assumed that the probabilistic (stochastic) risk of cancer proceeds in a
linear fashion at lower doses without a threshold. Scientific groups such
as the International Commission on Radiological Protection (ICRP), the
United Nations Scientific Committee on the Effects of Atomic Radiation
(UNSCEAR), NCRP, and the National Research Council Committee on
the Biological Effects of Ionizing Radiation (BEIR), repeatedly review and
endorse the use of the linear-no-threshold (LNT) model for assessing risk
(NCRP, 1993; ICRP, 2005; NRC, 2006; UNSCEAR 2008). The LNT model
is often considered to be conservative and gives emphasis to public health
and is currently used to set radiation protection standards and operating
policies, such as the “as low as reasonably achievable” (ALARA) policy.
There is large scientific debate, however, on the nature of the shape of the
dose-response curve for radiation-induced cancers at low doses.
Assuming a linear relationship between dose and cancer risk at low
doses, a potential small increase in the chance of developing cancer is the
main health effect of concern associated with the use of medical diagnostic
procedures. The level of risk depends on the type of imaging procedure.
For example, the typical radiation exposure from a CT examination is
~100 times larger than that from an x-ray examination.5 The theoretical
individual risk of fatal cancer from a single CT for a dose of 10 mSv is
estimated to be around 1 in 2000 (Mettler et al., 2000).6 For comparison,
the natural occurrence of fatal cancer in the U.S. population is about 1 in 5.
When a diagnostic procedure is medically justified (e.g., in a symptom-
4 There is near-universal agreement that epidemiologic studies have demonstrated that radia-
tion doses above 100 mSv are associated with increased risk of developing cancer. However,
scientific debate on the potential cancer risks exists at low doses (< 100 mSv).
5 The average effective dose for a typical chest CT exam is 7 mSv and for a chest x-ray 0.1
mSv; an x-ray of the shoulder is around 0.01 mSv; the average effective dose for most nuclear
medicine procedures varies between 0.3 and 20 mSv (Mettler et al., 2008).
6 See also: http://www.fda.gov/radiationemittingproducts/radiationemittingproductsand
procedures/medicalimaging/medicalx-rays/ucm115329.htm.

atic patient), it is apparent that the likely benefit to the patient is greater
than the risk, although the imaging exam should be optimized to the low-
est dose that provides acceptable diagnostic information (ICRP, 2008).
Special care is needed, however, for evaluating nonsymptomatic screening
protocols, such as for CT lung screening, where the estimated annual risk
from low-dose protocols is ~1.8 percent (upper limit is 5 percent) (Brenner,
2004) and the estimated benefit (measured as reduction in mortality from
lung cancer) among current or former heavy smokers is ~20 percent (NLST
Research Team et al., 2011). Because large numbers of individuals receive
radiation doses from medical imaging, whether for screening or diagnostic
purposes, the possibility exists that even small potential risks per individual
attributed to these exams could translate into many cases of cancer.
Not surprisingly, because CT is used to not only diagnose disease but
also follow the course of therapy and complications, a number of individu-
als have multiple CT scans in their lifetime. Wiest et al. (2002) reported
that in 2001 approximately 30 percent of their patients had more than three
CT exams in their medical histories, 7 percent had more than five, and 4
percent had more than nine. The percentages of repeated exams were higher
in a more recent study at one institution (33 percent of patients had 5 or
more lifetime CT exams and 5 percent had between 22 and 132) (Sodickson
et al., 2009). The patients who underwent large amounts of recurrent imag-
ing in the study generally had substantial underlying disease such as cancer
diagnosis (Sodickson et al., 2009). Irrespective of the presence or severity
of underlying disease, multiple CT scans of a patient can result in absorbed
doses that have been empirically shown to increase the risk of cancer. This
may be one of the reasons why for tracking radiation exposure from medi-
cal diagnostic procedures, CT scanning has received the majority of interest.
In contrast to the stochastic effects following radiation (e.g., develop-
ment of cancer and some cardiovascular diseases), accidental exposure
to very high levels of radiation can cause acute effects such as skin red-
dening, skin necrosis, hair loss, and severe tissue damage. These acute
effects are known as “deterministic” or “non- stochastic” radiation effects.
The problem of skin reactions following fluoroscopy were reported and
summarized by Shope (1996). Recently, several unfortunate and highly
publicized radiation overexposure events have been reported, especially
involving CT exams. In 2009 officials of the Cedars-Sinai Medical Center
in California notified the Food and Drug Administration (FDA) of acci-
dental overexposure of about 200 patients undergoing brain-perfusion CT
examination, resulting in hair loss and skin redness. The FDA identified
additional patients who received overexposures at other hospitals7 and
has subsequently issued advisory warnings to initiate preventive actions
7 See: http://www.fda.gov/MedicalDevices/Safety/AlertsandNotices/ucm185898.htm.

BACKGROUND 9
(Kuehn, 2010). These events have heightened the awareness of radiation

dose among radiologists, technologists, patient populations, regulators, and
international agencies.
Assuming compliance from both the medical provider and patient,
confirming and reporting the visible events of direct radiation injury may
be a relatively straightforward task. However, measuring the potential long-
term risks associated with low-level radiation doses from medical diagnostic
procedures is challenging and therefore the risks have not been fully quanti-
fied. This is because the number of excess cancer cases expected to result
from exposure to ionizing radiation from medical diagnostic procedures
is low and difficult to differentiate from background cancer rates, which
normally affect 42 out of every 100 persons.8 Studies to assess these small
risks would require very large numbers of individuals and long follow-up
periods (Land, 1980). Because any radiation-induced cancer would not
appear for years, it would be difficult, if not impossible, to relate it to past
imaging procedures. Results from large-scale epidemiologic studies assess-
ing the risks of medical diagnostic procedures that utilize ionizing radiation
are not available yet. However, a number of epidemiologic studies of risks
associated with CT exams are underway (see Section 3.5.1). CT exams are
likely the high-dose medical diagnostic imaging exams associated with the
easiest exposures and dose parameters to collect both in terms of equipment
output and in terms of estimation of actual patient doses.
An alternative to directly examining cancer occurrence or death from
cancer in the exposed populations is use of risk projection models. Such
models use population dose estimates and existing risk coefficients to
extrapolate the effects of medical diagnostic procedures. Typically popula-
tion risk estimates are derived from the atomic-bombing survivors cohort
in Hiroshima and Nagasaki; today, this cohort is widely considered the
“gold standard” in the assessment of radiation-induced cancer risks at low
doses.9 Medically exposed cohorts are also used to provide risk estimates
for risk projection studies.
The risks determined from projection models represent theoretical risks
rather than empirical observed risks and rely upon the assumption of a
linear relationship between radiation dose and risk at low doses. A study
with frequency data from Medicare claims and data from the IMV Medical
Information Division estimated that 29,000 future cancers could be related
to CT scan use in the United States in 2007 (Berrington de González et al.,
8 See: http://www.cancer.org/Cancer/CancerBasics/lifetime-probability-of-developing-or-
dying-from-cancer.
9 The effective dose from a typical CT exam is estimated to be about 8 mSv. This dose is
comparable to the lowest doses of 5 to 20 mSv received by some of the Japanese atomic-
bombing survivors.

2009). Fifty-seven million CT scans were used for the calculation of the
potential future cancers. A second study showed that the lifetime cancer
risk estimates for standard cardiac scans varied widely depending on age
and gender, from 1 in about 3,000 for an 80-year-old man to 1 in about
140 for a 20-year-old woman (Einstein et al., 2007).
The risk estimates in the projection models used in the above-mentioned
studies deal with particularly challenging problems related to uncertainty
from various sources, in terms of both the dose for a given examination and
the cancer risk per unit dose in the estimations. Moreover, the magnitude
of cumulative individual doses from single or multiple procedures has not
been fully characterized because of limited medical recording and the lack
of sharing of medical information across different health care facilities.
2.3 APPROPRIATENESS OF DIAGNOSTIC IMAGING

The appropriateness of diagnostic imaging in terms of justification and
optimization were discussed by Dr. Donald (Don) Miller, acting chief, Diag-
nostic Devices Branch, Division of Mammography Quality and Radiation
Programs, Center for Devices and Radiological Health, FDA, and other
workshop participants.
There are two ways to reduce doses from diagnostic imaging: (1) do
imaging only when justified and appropriate and (2) for any given examina-
tion, use dose reducing approaches consistent with acceptable image quality
and diagnostic performance.
Although based on limited data, one in four procedures is believed to
be unjustified and therefore associated with unnecessary potential radia-
tion risk. Examples include unnecessary CT scanning of the chest both
with and without contrast or multi-phase scanning for patients undergoing
abdominal and pelvic CTs (Guite et al., 2011). It is estimated that each
year approximately 75,000 patients across the country have unnecessary
pre- and post-contrast chest CT scans (Bogdanich and McGinty, 2011). A
straw poll among pediatric radiologists indicated that about 30 percent of
CT examinations in children were unnecessary or could have been replaced
by imaging exams not using ionizing radiation such as ultrasound-based
imaging modalities (Berdon and Slovis, 2002). Although the outcome of
the straw poll does not constitute scientific evidence, it is an indicator that
the issue of unnecessary exams is recognized by the medical community.
Lack of training regarding clinical decisions is one cause of the use
of inappropriate examinations. In addition, ordering physicians may be
unaware that recommended criteria can guide them in particular clinical
decisions. Various professional organizations (e.g., the American College
of Radiology [ACR]) have produced evidence-based guidelines, but several
studies suggest that these guidelines have not been widely adopted by the

BACKGROUND 11
medical community. In a retrospective study of 200 trauma patients, for

whom imaging decisions were made without the use of formal decision
rules, 169 of 200 patients underwent one or more CT scans, resulting in
an overall total of 660 CT scans. The authors found that application of the
ACR appropriateness criteria could have prevented 44 percent of those CT
scans from being ordered (Hadley et al., 2006). Other studies have found
that similar percentages (20-40 percent) of CT scans could be avoided by
following decision guidelines (Garcia Pena et al., 2004; Kuppermann et
al., 2009; Holmes et al., 2009; Stein et al., 2009). A pilot study showed
that two out of three nuclear cardiology scans performed were appropriate
according to the American College of Cardiology criteria, while the remain-
der were either inappropriate or of uncertain appropriateness (Hendel,
2009).
A successful approach to increasing the use of decision guidelines has
been to incorporate them into computerized imaging order entry systems
(Sistrom et al., 2009). However, even when decision guidelines are readily
accessible, a variety of factors may contribute to the ordering of unjustified
CT scans such as emergency department patient throughput, fear of liability
for a missed diagnosis, lack of information from other sources, and patient
and physician self-referrals (Dunnick et al., 2005).
2.4 REDUCTION IN RADIATION DOSES

Reducing the dose per exam is the second way to reduce unnecessary
exposure to radiation from medical diagnostic procedures, and this is dis-
cussed in the context of optimization10 and the need to create reference
values based on best practices (ICRP, 2008). Interest in this area has arisen
because wide variations have been observed among radiation doses associ-
ated with particular imaging exams both within and across medical centers.
Again, there is a specific interest in CT scanning, because of its amenability
to significant dose reductions (or increases) by the ease of manipulation of
technical factors during protocol adjustments.
One study in four San Francisco Bay Area institutions showed that
radiation doses varied significantly among different types of CT studies
performed on adult patients. A mean 13-fold variation between the highest
and lowest doses for routine head CT exams and multiphase abdomen and
pelvis CT exams was reported (Smith-Bindman et al., 2009). The authors
state that this observed variation cannot be entirely explained by differ-
ences in patient size (which were not accounted for in the analysis) or the
specifics of the clinical question that was being addressed. Large variability
10 Radiation dose is optimized when imaging is performed with as low as possible amount
of radiation required to provide adequate image quality for diagnosis or intervention.

in doses was also observed in a recent multicenter study in France that

included children aged 0-5 years undergoing at least one CT scan between
2000 and 2006 (Bernier et al., 2012). In regard to nuclear medicine, a
survey of 13 pediatric hospitals in North America identified a broad range
of administered doses from institution to institution; these administered
doses would directly lead to variability in radiation-absorbed doses to the
pediatric patients (Treves et al., 2008).
Optimization of the techniques is viewed as a joint responsibility and
effort of the radiology facilities and equipment designers. For example,
manufacturers of CT scanners and fluoroscopy equipment have made many
successful attempts to reduce the doses associated with particular exam
types. These reductions have been accomplished through technological
advances in equipment design, implementation of features such as auto-
matic exposure control, and efforts to educate physicians and technologists
and create awareness of potential adverse radiation effects. A comprehen-
sive review of dose reduction efforts in nuclear medicine is presented else-
where (Hricak et al., 2011).
One of the earliest success stories of procedure optimization was an
effort to improve technical aspects of mammography, which culminated in
the passage of the Mammography Quality Standards Act in 1992 (Spelic et
al., 2007). This legislation set national standards for high-quality mammog-
raphy, including standards for mammographic x-ray equipment, patient
dose, and image quality and ensured that facilities in the United States
would meet those standards.
Radiologists attempt to reduce dose through use of optimized protocols
in accordance with national and international guidelines (ICRP 2000a,b,
2007a; McCollough, 2011). However, the information available to them
is frequently inadequate. For example, on the technical side, although new
CT and fluoroscopic devices include displays of dose metrics, some lack
other safeguards, such as default parameter settings that optimize radiation
dose or alerts when the radiation dose in a given exam exceeds a particular
reference level or range. Even when these safeguards are in place, users may
not have received adequate training in the proper use of these features and
the importance of optimizing radiation dose. Additionally, training often
takes place in the hospital or imaging center with all the concomitant dis-
tractions and without a verification of acquisition of knowledge at the end
of the training sessions (Slovis, 2002) or quality assurance practices within
the imaging facility.
On the dose side, Lee and colleagues (2004) performed a survey to
determine the awareness of emergency department physicians and radiolo-
gists of the radiation exposure from the CT scans that they order. About
75 percent of the entire group significantly underestimated the radiation
dose from a CT scan, and 53 percent of radiologists and 91 percent of

BACKGROUND 13
emergency department physicians did not believe that CT scans increase

the lifetime risk of cancer. The risks and benefits of imaging procedures are
rarely communicated to patients (Lee et al., 2004) and are not recorded
in the patient’s medical record. In addition, many medical imaging devices
that communicate with radiology information systems do not forward data
on radiation dose despite recommendations to the contrary from the ACR
(Amis et al., 2007).
2.5 RECENT PROGRESS IN RADIATION SAFETY IN MEDICINE

A number of initiatives in radiation safety in medicine have taken place
in the United States and internationally and were discussed by the work-
shop invited speakers. Each of these initiatives serves different purposes.
The ultimate goal is to provide better quality clinical management of the
patient and to reduce dose by adhering to the ALARA principle, without
compromising diagnostic efficacy (ICRP, 2007b).
2.5.1 Image Gently and Step Lightly Campaigns

The Alliance for Radiation Safety in Pediatric Imaging11 launched the
Image Gently (in 2008) and Step Lightly (in 2009) campaigns aiming to
reduce unnecessary exposure to radiation during pediatric imaging and
interventional radiology, respectively. The campaigns’ goal is to promote
the special precautions required for children who undergo medical imag-
ing that utilizes ionizing radiation (Sidhu et al., 2009; Goske et al., 2010).
Through separate education material directed to patients, the health care
team (radiologists, technologists, and pediatricians), physicists, and the
news media, the Image Gently campaign has successfully disseminated its
message by partnering with prominent medical organizations and agencies.
2.5.2 Image Wisely Campaign

In 2010, the ACR and the Radiological Society of North America
(RSNA), together with the American Association of Physicists in Medi-
cine and the American Society of Radiologic Technologists, established
the Image Wisely campaign for minimizing radiation exposure in adults.
The campaign resembles but does not exactly mirror the Image Gently
campaign. The mission of the Image Wisely campaign is to raise aware-
ness of opportunities to eliminate unnecessary imaging examinations and
11 The Alliance for Radiation Safety in Pediatric Imaging is an organization of more than
60 national and international professional societies and agencies with the goal of promoting
radiation safety for children.

to optimize the amount of radiation used in imaging examinations to only

what is necessary to acquire appropriate medical images. Image Wisely
has developed a web site with selected and logically indexed educational
material for imaging professionals, referring practitioners, and the public
and has partnered with imaging equipment vendors through the creation of
vendor-specific web pages to provide the most current information on dose
reduction techniques available on specific equipment. Participants in the
program are asked to demonstrate their commitment to the Image Wisely
principles by taking a pledge, pursuing accreditation, and participating in
national dose index registries (Brink and Amis, 2010).
2.5.3 ACR’s Dose Index Registry

The ACR launched the Dose Index Registry in May 2011 to address
the lack of a substantial database for determining the average dose indices
for a CT exam in the United States. Once these are determined, the data
can be used to establish national benchmarks and practice patterns in dose
indices and provide feedback to the participating facilities as to where they
stand compared to those benchmarks and how far they are from achiev-
ing optimal practices. The Dose Index Registry collects and compares CT
dose index information from facilities across the country and internation-
ally. Information is collected using automated standardized techniques and
includes exposure parameters (kVp, mAs) and dose indices (CT index vol-
ume [CTDIvol],12 dose length product [DLP]13). Currently the Dose Index
Registry does not collect information on dose estimates because they are
not available.
2.5.4 IAEA Smart Card

In 2006 the International Atomic Energy Agency (IAEA) initiated an
ambitious program named Smart Card with the purpose of tracking the
radiological procedures of individual patients and radiation dose. The pro-
gram, launched in 2009, will be implemented in some countries in three to
five years. Until the program was launched, the only way to track a patient’s
lifetime (cumulative) exposures was by manual search of physical or elec-
tronic records in a hospital or hospitals or reliance on the patient’s memory.
The Smart Card program emphasizes the need for a more systematic track-
ing method resulting from the substantial increase in the use of high-dose
radiation exams (Rehani and Frush, 2011). The major goals of tracking are
12 CTDI describes the amount of radiation that machines emit during one scan; that is, CTDI
is not the amount of radiation that enters the body.

13 DLP combines all the scans from an examination into one value.

BACKGROUND 15
stated in the recent Joint Position Statement on patient exposure tracking14

and include: supporting accountability for patient safety, justification, and
optimization; providing information for assessment of radiation risks; and
establishing a tool for use in research and epidemiology.
The original name of the Smart Card program tended to give the
impression that the card would contain the patient’s estimated dose data;
thus, the name Smart Card/SmartRadTrack was subsequently adopted to
place the emphasis on tracking. The estimated patient doses are not avail-
able on the card. Instead, like an ATM card or a credit card, the card simply
provides the methodology (digital signature) to access dose information,
which is available online. The IAEA Smart Card/SmartRadTrack is con-
sidered to be an improvement over a more basic tracking approach such
as a vaccination card, which stays in the possession of the patient. Such a
method would rely fully upon compliance and maintenance by the patient
and may not have an impact on the quality of radiation dose management.
2.5.5 National Institutes of Health Clinical Center Initiative

The National Institutes of Health (NIH) Clinical Center has mandated
that imaging equipment manufacturers provide for electronic reporting
of patients’ radiation exposures from their equipment in this setting. The
information on radiation exposure reports will be logged into the patient’s
electronic medical record (EMR). Exposures from CT and PET/CT will be
the first to be recorded using this system, because CT and PET/CT scan-
ners already output this information (Neumann and Bluemke, 2010). The
goal of this policy within the NIH Clinical Center is to achieve an accurate
assessment of whether low-dose radiation exposure from medical imaging
exams increases the patient’s risk of developing cancer. It is understood
that steps taken within a single institution will not be sufficient to allow a
precise population-based assessment of cancer risk from lose-dose radiation
and that tracking of medical imaging doses from a truly large number of
individuals in the United States will ultimately be necessary. This initiative
is, however, necessary to begin building a prototypical data set (Neumann
and Bluemke, 2010).
Besides building a database for population-based risk assessment, the
NIH Clinical Center will require that vendors ensure that radiation expo-
14 The joint statement was endorsed by the World Health Organization, FDA, the European
Society of Radiology, the International Organization for Medical Physics, the International
Society of Radiographers and Radiological Technologists, and the Board of Directors of the
Conference of Radiation Control Program Directors. See: https://rpop.iaea.org/RPOP/RPoP/
Content/Documents/Whitepapers/iaea-smart-card-position-statement.pdf.

sure can be tracked by patients via personal electronic health record plat-
forms such as Google Health and Microsoft HealthVault.
2.5.6 California Legislation

California became the first state in the United States to regulate CT
scans.15 The law dictates that facilities with CT systems capable of cal-
culating and displaying radiation dose index document the dose index of
each CT exam within the patient’s radiology exam report. (The deadline
for meeting the requirement is July 2012.) The law also requires that a
medical physicist verify annually the dose index for each protocol and that
any reported errors are communicated to patients and physicians. (The law
does not set a limit as to what the dose indices should be.) For the purposes
of this bill, the radiation dose that should be recorded is defined as any
metrics such as CTDIvol and DLP or a dose unit as recommended by the
American Association of Physicists in Medicine (AAPM).16 This legislation
was enacted in response to multiple events where patients were exposed to
excessive radiation by diagnostic CT scanners, with the intent to prevent
such events.17
15 Florida, New York, and Texas are also considering similar legislation (Schmidt, 2012).
16 AAPM is a member society concerned with the topics of medical physics, radiation oncol-
ogy, and imaging physics with a primary goal of identifying and implementing improvements
in patient safety for the medical use of radiation in imaging and radiation therapy.
17 See: http://www.leginfo.ca.gov/pub/09-10/bill/sen/sb_1201 1250/sb_1237_bill_20100929_
chaptered.html.

Workshop Summary
F
or increased readability, the chapter is organized by theme rather than
chronologically based on the workshop agenda (see Appendix B). An
integrated summary of the presentations and discussions are reported
in this chapter. This summary should not be construed as reflecting consen-
sus or endorsement by the workshop committee members (see Appendix C
for committee roster), the invited workshop presenters (see Appendix D)
and other participants, or the National Academy of Sciences.
3.1 OPENING COMMENTS

The organizing committee invited two speakers to provide opening
remarks to help establish the context for the workshop discussions: Charles
Miller (chief, Radiation Studies Branch, Division of Environmental Hazards
and Health Effects, National Center for Environmental Health, CDC) and
Donald (Don) Miller (acting chief, Diagnostic Devices Branch, Division of
Mammography Quality and Radiation Programs, Center for Devices and
Radiological Health, FDA). Both the CDC and FDA have been active in
the discussions of tracking radiation exposures from medical diagnostic
procedures.
The CDC initiated studies in 2004 on the feasibility of a tracking sys-
tem for medical diagnostic procedures involving ionizing radiation (CDC
2004a,b, 2006). The specific question explored was: “How could the pro-
cedure code in patient medical records be used to derive a radiation dose?”
17

This effort culminated in a 2006 CDC workshop that concluded that it

would be extremely difficult to monitor actual doses received by patients.
The FDA recently published the Initiative to Reduce Unnecessary Radi-
ation Exposure from Medical Imaging (http://www.fda.gov/downloads/
Radiation-EmittingProducts/RadiationSafety/RadiationDoseReduction/
UCM200087.pdf), aiming to promote safe use of medical imaging devices,
support informed clinical decision making, and increase patient awareness.
Charles Miller proposed that the workshop participants consider the
following question: Is now the appropriate time to reconsider the impact
of radiation doses from medical procedures? Specifically:
1. Can we measure and record real doses that patients receive?

2. Can we track individual doses, and should we?
3. How can we potentially use such data to inform decisions by
patients and health care providers without interfering in the use of
potentially life-saving medical procedures?
He emphasized that information about patient doses from medical

diagnostic procedures today is based on estimates and not actual measure-
ments. He provided an overview of the efforts that have been initiated
during the past five years to raise awareness about radiation exposure
in the United States, which include the Image Gently and Image Wisely
campaigns. Without endorsing them, he mentioned the many web-based
applications that encourage patients to keep records of their imaging exams
and share the information with their doctor. Patients can easily enter the
type of imaging they received, their age when they had the procedure and,
assuming some standard effective dose for a procedure (e.g., 8 mSv for an
abdominal CT exam) the applications calculate the induced risk.
Don Miller stated that any discussion on “whether,” “what,” and
“how” to track exposure regarding CT, fluoroscopy, radiography, and
nuclear medicine should be initiated with a clear understanding of the
tracking’s purpose. Table 3.1 (adapted from Don Miller’s presentation)
summarizes the information that in his view needs or does not need to be
tracked to achieve the goal(s) of a tracking system. The four goals discussed
were:
• Justification
• Optimization
• Individual risk assessment
• Research purposes
As an example, Don Miller explained that if the purpose of tracking

is to help the physician, dentist, or other health care provider to decide

WORKSHOP SUMMARY 19
TABLE 3.1 Reason to Track Radiation Exposure from Medical

Diagnostic Procedures and Information Needed to Achieve the Goal
Purpose PHI Facility Identifiersa Dose Datab
Justification Yes Yes No
Optimization No Yes Yes
Risk Assessment Yes No Yes
Research Yes Yes Yes
PHI=Personal Health Information
aFacility identifiers may include name, location, and type of facility (e.g., hospital or indepen-
dent imaging center).

bDose data may include dose indices and dose estimates. In this content, the term does not
refer to information on frequency and type of imaging exam or body part irradiated, which
would be needed for all tracking purposes.
SOURCE: Presentation by Don Miller (acting chief, Diagnostic Devices Branch, Division of
Mammography Quality and Radiation Programs, Center for Devices and Radiological Health,
FDA).
whether an imaging exam is necessary (justification), the registry should

contain information that can answer the following questions: Are there
previous exams that could answer the clinical question? What were the find-
ings? Where are the images? Having this information in a registry (which
would likely be an electronic medical record rather than a “dose registry”)
could avoid repetition of an exam that has already taken place. In such a
case, the registry/record must contain personal health information (PHI, to
identify the individual patient) and facility identifiers (to be able to retrieve
the results and images of the past imaging exam) but not dose data, in order
to serve the purpose of justification as described. In a later presentation (see
Section 3.6.1), justification was also discussed in terms of “known clinical
benefit” of an exam; in that case, tracking dose data through clinical trials
that would provide the answers regarding the clinical benefits of the exams
ordered may be necessary.
In contrast, to optimize radiation delivery from medical imaging and
establish reference levels, a registry would need to contain facility informa-
tion and dose information for examinations from a number of patients but
would not need patient-specific information (i.e., PHI). A registry that fits
this purpose is the ACR Dose Index Registry discussed in Sections 2.5.3
and 3.2.4. Information needed to achieve the goals of risk assessment and
research was also described.

3.2 POPULATION UTILIZATION OF IMAGING

Several workshop participants affirmed that comprehensive and detailed
data concerning diagnostic imaging utilization and associated radiation
doses would help to evaluate whether concern over the dramatic increase in
the population’s exposure to radiation is warranted. Dr. Mythreyi Chatfield
(director of data registries, American College of Radiology) separated the
issue of the measurement of population utilization of medical diagnostic
procedures into two challenges: a) counting the number of imaging pro-
cedures performed on the population and b) grouping these procedures
into meaningful categories that represent a single imaging procedure with
comparable radiation dose levels across patients and facilities.
A number of data sources that cover patient populations in the United
States are available, and several were discussed during the workshop. Dr.
Chatfield categorized the sources of existing information on population
utilization of imaging as surveys of patients or providers, administrative
claims, and registries. However, the information from these sources exists
only fragmentally and not in the detail required for assessment of the asso-
ciated risks and benefits.
3.2.1 FDA Surveys

David Spelic, physicist with the FDA, provided an overview of the
FDA’s past and present efforts to characterize U.S. population doses from
diagnostic x-ray imaging. The predominant means by which FDA has gath-
ered such data is by nationwide surveys. Covering a period of roughly five
decades, these surveys document the state of practice for a broad scope of
diagnostic x-ray procedures, capturing indicators of patient dose, image
quality, and an array of related technical parameters that characterize sur-
veyed exams.
The U.S. Public Health Service (USPHS) conducted the first national,
large-scale surveys, the X-ray Exposure Studies (XES), in 1964 and 1970.
These surveys captured comprehensive data regarding the state of practice
in diagnostic radiography. Dr. Spelic said that each survey consisted of two
components: a household interview of selected members of the U.S. popula-
tion and the capture of technical information from clinical sites regarding
x-ray equipment and radiologic practices for selected exams. Data regard-
ing x-ray exam history were collected for 31,289 persons representing
9,653 households in 1964 and 67,000 persons or 22,500 households in
1970. Major outcomes from these surveys included publications providing
comprehensive statistical summaries of findings as well as detailed dosim-
etry for the exams covered by the surveys (USPHS, 1966, 1969, 1973).
Their scope was large and included dental, medical x-ray, fluoroscopy,

WORKSHOP SUMMARY 21
and x-ray therapy. Film packs were sent to clinical sites to capture beam
size and dosimetry (USPHS, 1973); separate film packs were used for each
modality. Because dosimetry was an important endpoint for these surveys,
the Bureau of Radiological Health developed models to compute patient
exposure based on reported x-ray technique, collimation, and film packet
measurement. Doses were computed using phantoms; exposure ratios and
scatter were measured for dose calculations.
Dr. Spelic then discussed the Breast Exposure Nationwide Trends
(BENT) project that begun in the late 1970s. It was a joint effort by the
FDA and the National Cancer Institute (NCI) to study the current practice
of mammography with the aid of state radiological programs. Among
the survey findings was a broad variability of patient exposures ranging
from 2.2 mGy to 140.0 mGy. Direct exposure film provided the highest
exposures, while screen film the lowest. The Dental Exposure Normaliza-
tion Technique (DENT) program followed a similar pattern to the BENT
program.
The Radiation Experience Data (RED) study was conducted in 1980 by
the FDA’s Center for Devices and Radiological Health (CDRH) to estimate
numbers and types of diagnostic imaging procedures performed in hospitals
in the United States; no dosimetry data were collected. Data were collected
on all types of imaging procedures including CT, ultrasound, and nuclear
medicine from 81 sites, which is a small population compared to the XES
surveys. Among the findings was that 130.2 million x-ray procedures were
performed annually in short-stay hospitals, a 59 percent increase from the
number of procedures performed in 1970 (81.7 million). There were 2.2 mil-
lion CT exams performed, and 73 percent of these exams were of the head.1
Dr. Spelic also discussed the current FDA program. The Nationwide
Evaluation of X-ray Trends (NEXT) program was conceived in the early
1970s to address the lack of a program to collect comprehensive popula-
tion exposure data representing the state of practice in diagnostic x-ray
imaging. A committee of federal and state radiation control representatives
was formed to develop such a program, and within a few years NEXT
was annually collecting data on 12 commonly performed diagnostic x-ray
exams. State radiation control personnel conducted site visits to randomly
identify clinical facilities and captured data regarding patient exposure,
clinical technique factors, and exam workloads. By the early 1980s, NEXT
abandoned the annual collection of data for multiple exams in favor of
focusing on a single procedure. The surveys became more comprehensive,
and patient-equivalent phantoms were developed to invoke radiation out-
put representative of a typical patient. Film processing quality and the
integrity of the darkroom were evaluated.
1 Primarily because at that point body CT exams were in their infancy.

TABLE 3.2 Summary of NEXT Surveys and Survey Years

Examination Survey Years
Chest radiography 1984, 1986, 1994, 2001
Mammography 1985, 1988, 1992
Abdomen and lumbo-sacral (LS) spine radiography 1987, 1989, 1995, 2002
Fluoroscopy 1991, 1996, 2003, 2008
Computed tomography 1990, 2000, 2005
Dental radiography 1993, 1999, 2013
Pediatric chest 1998
SOURCE: Presentation by David Spelic, FDA.
Surveys now routinely collect data regarding patient exposure, indi-

cators of image quality, facility exam/procedure workloads, and staffing
levels, as well as features of quality-control and quality-assurance practices,
Dr. Spelic said. Surveys of particular exams are repeated periodically to
capture trends in the state of practice. Statistical summaries of past NEXT
surveys are available from the Conference of Radiation Control Program
Directors.2 Approximately 40-43 states participate in each survey. A sum-
mary of the NEXT surveys and survey years is presented in Table 3.2.
The 2005 NEXT CT survey is an excellent example of the mutual
benefits gained from collaboration with representatives from the manufac-
turing sector, Dr. Spelic said. Representatives from the National Electrical
Manufacturers’ Association (NEMA) supported the survey planning efforts
with insight into the state-of-art CT technology. CDRH also has active
representation on a number of International Electrotechnical Commission
(IEC) committees, with standards activities directed at various sectors of
diagnostic imaging from CT to digital-based imaging. He said that the wide
acceptance of such standards by the international community underscores
the need for continued presence at the federal agency level. NEXT supports
these efforts with population data for exam frequencies, patient exposure,
image quality indicators, and trends in the practice. Finally, IAEA has
recognized the NEXT chest and abdomen/spine phantoms and associated
protocols as scientifically established methodologies for conducting dosim-
etry for these exams.
Dr. Spelic identified several challenges that NEXT faces, including lim-
ited human and financial resources.3 Moreover, the technology is changing
faster than the ability to develop, execute, and publish surveys. NEXT aims
to continue to complement and coordinate with newer efforts to capture
2 See:http://www.crcpd.org.
3 For example, an analysis of CT survey data from 2005 has not been completed because
of insufficient resources.

WORKSHOP SUMMARY 23
complex data via dose registries and to focus on surveys of exams and
modalities that are presently outside the scope of current efforts to auto-
mate dose data collection.
3.2.2 IMV Surveys

IMV is a market research and database provider that uses a variety of
survey methods to track diagnostic medical procedures, including those that
expose patients to radiation. Although IMV covers a large number of imag-
ing facilities, it does not provide a detailed categorization of procedures.
Instead it provides estimates of the number of procedures overall or of the
numbers by broad categories such as CT or MRI.
Mr. Shah (general manager, IMV) and Ms. Prochaska (vice president,
IMV) provided an overview of the data collected by IMV and perspectives
on large-scale data collection.
IMV classifies its studies into two categories: census databases and mar-
ket reports. Census databases cover about 65 percent of the universe and
include both hospitals and independent imaging centers. Time required for
data collection depends on the modality. For example, it may take one year
to complete the data collection process for PET, whose universe is about
2,000 sites, while it might take two years for CT, whose universe is 8,000
sites. Collection costs increase significantly after about 30-40 percent of the
sample has been interviewed. Because the census database information is
quite detailed and covers a large population, it can be segmented and drilled
down depending on the question to be answered. For instance, by facility
type or geography, summary information can be obtained on:
• Availability of services (i.e., CT, PET, nuclear medicine)

• Adoption of new technology
• Number and/or age of systems in use
A powerful tool that IMV uses to achieve its satisfactory participa-

tion rates for the census databases (and a motivator for facilities) is that
it donates a free benchmark report to participating institutions (price of
report: $750), which contains information that they can use to compare
their status and performance to the national average. Variables of interest
to institutions may include number of clinical patient studies, variation of
patient studies per site, productivity, radiopharmaceutical utilization and
budgets, and inpatient versus outpatient composition.
In contrast, IMV’s market reports cover approximately 300-400 sites
(participation rates >10 percent), interviews are conducted by telephone
and online, and collection of information takes about 8-12 weeks.
Mr. Shah explained that recent changes in the health care environment

have increased the workload of potential respondents who now have less
time to participate in surveys. Additional challenges include an increasing
number of providers to survey; a larger number of entities who survey the
health care community (for example many manufacturers now survey their
customers); facilities that do not allow their employees to participate in
surveys; and the almost inevitable routing of calls to voice mail. Regardless
of survey method, a trade-off exists between the level of detail requested
and the response rate achieved.
Workshop committee member Fred Mettler (New Mexico VA Health
Care System) acknowledged IMV’s great contribution as a source of infor-
mation on the utilization of medical diagnostic procedures for the NCRP
report 160 (NCRP, 2009).
3.2.3 Medicare Administrative Claims

Although there was no workshop presentation dedicated to admin-
istrative claims as a source of information about population utilization
of medical imaging, Dr. Chatfield briefly discussed this source. She said
that detailed data on counts of procedures by current procedural termi-
nology (CPT) code (or equivalent) for large populations have historically
been available from administrative claims such as Medicare claims. She
explained that CPT codes offer an advantage over the broad categories
often used in surveys but still may not be granular enough to capture the
full range of appropriate variation in radiation doses, protocols used to
image patients for a broad range of indications, or amongst practices. Infor-
mation is automatically collected using claim submissions from Medicare
beneficiaries and is publicly available. However, it is limited to patients aged
65 or over who use this social insurance program. When available, data
from private payers only cover each plan’s participants.
3.2.4 ACR Dose Index Registry

The Dose Index Registry could serve as a source for both procedure
counts and dose index measurements. Workshop committee member Rich-
ard (Rick) Morin (chair, ACR Dose Index Registry) provided an overview
of the registry (see Section 2.5.3 for additional information).
By sending information to the Dose Index Registry, facilities can opti-
mize protocols, implement standards, and contribute to the development
of reference levels with the ultimate goal to improve imaging performance
over time. Using a report (currently generated semi-annually) with descrip-
tive statistics (mean, median, 25th and 75th percentiles) of the reported
dose indices of participating facilities broken down by location, region, and
type, the sample facilities can compare where they rank in these categories

WORKSHOP SUMMARY 25
and against the Dose Index Registry. The indices are expected to become
less variable and more aligned with the benchmarks. Dr. Morin suggested
that each facility should task a qualified “safety committee” with reviewing
the report and evaluating whether the facility’s dose indices are too high or
too low compared to the ACR benchmarks. The committee could be com-
prised of diagnostic radiologists, physicists, technologists, and diagnostic
imaging experts. Participation of imaging experts was deemed essential by
many workshop participants who stressed that monitoring the dose indices
detached from image quality does not provide the required overall quality
assurance.
It is not surprising that “when somebody is watching, behavior
changes,” Dr. Morin said. Using the Advanced Cardiovascular Imaging
Consortium in Michigan as an example, he stated that voluntary, collab-
orative quality improvement programs have proven to be successful in the
past. The consortium achieved a marked reduction in estimated radiation
doses following implementation of a radiation dose-reduction program,
with no impairment of image quality. The one-year program used educa-
tional intervention to disseminate to participating sites the best-practice
recommendations for radiation dose reduction followed by a two-month
monitoring stage (Raff et al., 2009).
At the time the workshop took place, about 300 facilities were in the
process of participating in the ACR Dose Index Registry and more than
100 had initiated data submission.4 These facilities are of different types
(academic, community hospital, multi-specialty clinic, freestanding center)
and are distributed around the country. Data from more than 350,000 CT
exams were recorded.
Drs. Morin and Chatfield described several challenges associated with
the Dose Index Registry, which reflect general outstanding issues in the
radiology community. For example, in the early pilot phase of the registry,
naming conventions were largely inconsistent. Even if they used the same
machine, different facilities may have named the procedure referred to as
“CT head” differently. The issue also existed within a facility if differ-
ent machines or different software were used. Now all exam names are
standardized and mapped to RadLex5 terms. As a result, procedures can
be grouped into standard categories. However, even though the names are
standardized, the protocols between facilities may differ. Therefore, what
4 The number of institutions participating in the ACR Dose Index Registry increased to 400
between the times the workshop took place and the report was completed (communication
with Rick Morin, chair, ACR Dose Index Registry).
5 RadLex is the lexicon for uniform indexing of radiology terminology implemented by the
Radiological Society of North America (RSNA).

is really needed is a standard name for acquisition protocol, Dr. Chatfield

said.
The second challenge relates to the variability in dose indices due to
patient size. This issue was discussed many times throughout the workshop
(see, in particular, Section 3.4) and highlighted by Dr. James Brink, profes-
sor and Chair of the Department of Diagnostic Radiology at Yale University
School of Medicine. Dr. Brink, together with colleagues, recently published
findings that, for body CT examinations performed with automatic expo-
sure control, the radiation used to examine a 100-kg patient is approxi-
mately three times that for a 60-kg patient and results in organ doses that
are generally twice as high as those in a 60-kg patient (Israel et al., 2010).
The ACR Dose Index Registry currently does not cover all imaging
modalities. It includes only CT but plans to also include computed radiog-
raphy and digital radiography and fluoroscopy within the next year or two.
Despite rapid growth, the registry currently includes only a small fraction
of the CT facilities in the country. Participation is voluntary and therefore
unlikely to be nationwide any time soon, Dr. Chatfield said. The fee to
participate is modest ($500 one-time registration and additional charges
scaled to the size of the practice) but may prevent participation by some
facilities. Data transmission to the registry is completely automated, with
high accuracy and minimal effort by the facilities, but some facilities may
still hesitate to participate because of a reluctance to undertake a new and
“unknown” effort. The registry uses industry standard practices for data
protection and signed Business Associate Agreements (BAAs)6 to protect
patient privacy. Facility information is shared only with the facility, and
facility permission is sought before the facility’s name is included on the
list of participants.
Dr. Chatfield addressed the question of whether the Dose Index Reg-
istry could be potentially used for population exposure monitoring. She
responded that before that could happen there must be expert consensus
and AAPM guidance on how to measure organ doses. If a system is imple-
mented without expert consensus or without having adequate scientific
justification for its value, then facilities will be reluctant to participate in
the registry. This would hinder the main goal of developing better diagnos-
tic reference levels for dose indices and would deprive facilities of a much
needed tool for protocol review and radiation dose optimization. Because
patient data are currently anonymized, multiple exams on the same patient
cannot be identified, and patients cannot be followed as they move from
facility to facility.
6 ABAA is a standard contract for the purpose of providing services involving the use of
protected health information.

WORKSHOP SUMMARY 27
3.3 NATIONAL AND INTERNATIONAL

EFFORTS IN DOSE TRACKING
Many workshop participants emphasized that there is momentum for
archiving of radiation exposure but multiple substantial barriers remain.
These barriers include the questions of how to translate the various dose
indices into a single quantity, whether the dose should be organ dose or
effective dose, how to automate the collection process, how to account for
individual variation in patient size, shape, and age, how to manage patient
privacy and security issues, and how to control the multiple disparate pur-
poses for which the data might be used.
3.3.1 Veterans Health Administration (VHA)

The Veterans Health Administration (VHA) health system is the larg-
est integrated health system in the United States, treating a specific patient
population and only few young patients. VHA has developed an open
source electronic medical records system, which facilitates communica-
tion of the medical history of the patient, including access to the patient’s
imaging exams. VA practitioners are protected from personal malpractice
liability and their salary is not dependant on procedure volume. Despite
the absence of these potential motivational parameters,7 diagnostic imaging
and especially body CT usage in the VA is increasing at a rate similar to
the private sector, noted Charles Anderson, chief consultant for diagnostic
services at VHA. Many of these CT exams are performed as part of cancer
screening, diagnosis, treatment, and surveillance protocols.
In light of recent FDA notices regarding potential CT overexposures,
the VHA surveyed all its hospitals for dose parameters associated with
brain perfusion studies and found that none had exceeded the threshold
for deterministic effects.
VA has taken several steps to minimize the radiation dose received by
patients, including the requirement for a national dose registry, although
it is not clear whether funds will be available to develop the software, Dr.
Anderson said. The plan is to send Digital Imaging and Communications
in Medicine (DICOM)8 dose structured reports from CT scanners and fluo-
roscopes to the VA image storage system (VistA Imaging). From there, dose
parameters (volume CTDI and DLP for CT, cumulative air kerma and dose
area product for fluoroscopy) will be extracted and placed in the procedure
7 These parameters have been discussed as few of the many reasons of increased diagnostic
imaging utilization (Baker et al., 2008).

8 DICOM is an information technology standard designed to automatically capture and
electronically report machine settings from various imaging procedures. DICOM is managed
by the Medical Imaging and Technology Alliance, a division of NEMA.

file of the VA radiology information system. The dose parameters from 150
VA hospitals will be transmitted to a national data warehouse.9 The sum of
doses will be displayed at order entry and may be released to the patient as
a dose summary, although there are outstanding issues with acquisition of
historical data and data from exams performed outside the VA hospitals.
There are no plans to calculate organ-based doses.
Dr. Anderson described further efforts within the VA to minimize the
radiation dose received by patients. A protocol optimization guide was
written to reduce CT dose while maintaining image quality. The protocol
explains the factors that control radiation dose, states the diagnostic refer-
ence levels, and provides alerts and notifications. After testing the guide
at several facilities, the VA has made protocol optimization mandatory.
The VA is considering having privileges for physicians who operate fluoro-
scopes. An on-line course and test was posted on the employee education
website, and successful completion of the test can be tracked. For fluoros-
copy, peak skin dose in excess of 3 Gy must be documented in the record,
while peak skin dose in excess of 5 Gy must be reported to the radiation
safety officer (RSO).10 Cumulative dose in excess of 15 Gy, or permanent
patient injury, is a sentinel event.
Moreover, CT patients are given an educational brochure, which
explains that there is small increase in cancer risk associated with the pro-
cedure. Consent is obtained for fluoroscopic studies that might exceed 3
Gy peak skin dose as well as CT studies that might exceed 3 Gy CTDIvol to
advise patients of the deterministic complications of epilation or erythema
in advance; however, in practice, “in the case of CT we do not ever expect
this threshold to be met,” Dr. Anderson said.
3.3.2 International Atomic Energy Agency (IAEA)

Dr. Madan Rehani (radiation safety specialist at the International
Atomic Energy Agency (IAEA) in Vienna, Austria) provided a summary
of the IAEA’s Smart Card/SmartRadTrack program (presented in Section
2.5.4) and highlighted the unresolved issues that include using a patient
identifier and incorporating nuclear medicine exams and studies that are
performed on equipment that is not electronically connected to a central
dose recording system. He noted that the world is moving in the direction
of dose tracking. The revised International Basic Safety Standards and
9 A place for data both internal and external to an organization to be stored together for
analytical and informational processing regardless of the platform or application.

10 Dr. Anderson clarified that VHA has not specified how to account for the cumulative
effect of multiple procedures; the handbook states that studies done on the same day should
be summed (personal communication with Ourania Kosti, May 3, 2012).

WORKSHOP SUMMARY 29
European Basic Safety Standards, aiming to establish basic requirements

for the health protection of the public and patients from ionizing radia-
tion, indicate that the referring physician is required to take into account
previous radiological examinations; however, there is no explicit mention
of dose tracking.
Advances in many practical issues such as movement toward electronic
medical records, provision of dose indices by modern equipment, improve-
ment in understanding the most relevant dose quantities, communication of
doses to picture archiving and communication system (PACS), and transfer
of patient files from one part of the country to another via inter-PACS
links have improved both the public acceptance of medical recording and
the technical possibility of systematically collecting radiation dose data.
The crucial point is the necessity for a permanent patient identifier, which
constitutes the major problem in countries where there are no permanent
identification numbers for the patient population, Dr. Rehani said.
Dr. Rehani noted that patient exposure tracking is now a reality in
some countries. Countries like Estonia and Malta can achieve nationwide
coverage using these systems, whereas Sweden, Finland, and Denmark,
which have nationwide PACS plans, are among the countries that can track
radiological examinations performed within a county, covering few dozens
of hospitals.
To indicate that a smart card type of tracking method has the potential
to become a reality, Dr. Rehani discussed the recently proposed, Euro-
pean Commission directive on patients’ rights to cross-border health care
that would entitle patients to obtain health care in any European Union
Member State other than own and to have the associated health care costs
reimbursed by their national health system. This directive is a step toward
the cooperation of the national health systems of different countries with
the ultimate goal of improving patients’ cross-border care. The directive
also supports the implementation of a smart card system to hold medical
information including radiation exposure. Efforts are under way to sign a
Memorandum of Understanding between the United States and the Euro-
pean Union on the interoperability of health data exchange. International
systems, particularly those outside Europe, require political consensus and
interface.
Dr. Rehani noted that in 2010, IAEA conducted a survey to assess the
current status of patient dose tracking in the world. The survey covered 76
countries including Brazil, China, India, Indonesia, and the United States.
Eight countries were actively considering patient exposure tracking systems,
and three were considering tracking systems for exposure but not dose. Sev-
enty-four percent were aware of IAEA’s Smart Card/SmartRadTrack pro-
gram (see Section 2.5.4 for a description), and all but one were interested in
joining and promoting the program in their country. Assuming practicalities

were attended to, 29 percent responded that a radiation exposure tracking

program would be extremely useful, 60 percent responded very useful, and
11 percent moderately useful; no country responded that such a program
would be mildly useful or not useful at all. All of the countries that had
immediate plans to track radiation exposures included quality assurance
and quality improvement as a goal of the planned program. Other goals
included policy development, licensing/certification, regulation, and deci-
sion support for ordering exams.
Because a key issue with the implementation of the Smart Card/
SmartRadTrack program is the existence and use of a unique permanent
identification number, IAEA conducted a survey of 36 countries to deter-
mine if such a number is widely in place. The survey showed that 81 percent
of the respondent countries have a unique permanent identification number
in place and is valid for life, but only 44 percent of those countries use this
number for medical care purposes. Most countries indicated that “lack of
technology” was the primary reason for not using the permanent identifi-
catin number; only 8 percent indicated a concern for the confidentiality of
the patient. Although the United States was not included in this survey, Dr.
Rehani mentioned the many privacy issues in the United States as a barrier
to implementing such a program.
Dr. Rehani described a third IAEA survey that captured responses from
622 referring physicians from 28 countries. Eighty-three percent of the
physicians responded that knowing their patient had undergone 10 or more
CT scans in the near past would affect their decision to order the next CT
scan; 8 percent of the respondents were not sure that this knowledge would
affect their decision. Twenty-one percent of the physicians responded that
they rarely come across situations where clinical indications are enough to
prescribe a CT scan irrespective of previous history of CT scans. To the
question “How often in your clinical practice do you think knowing the
history of CT scans will help you take a better decision,” 24 percent of
the physicians responded “always”, and 48 percent “mostly”. Sixty-two
percent of the physicians agreed that having in place a system that provides
quick information about a patient’s dose history would be helpful; 30 per-
cent responded that it might be helpful. The IAEA survey results described
by Dr. Rehani were not published at the time this workshop report was
being prepared.
3.4 FROM DOSE INDICES TO DOSE ESTIMATES

Dr. Walter Huda (professor of radiology at the Medical University
of South Carolina and workshop committee member) and Dr. Michael
McNitt-Gray (associate professor of radiology, University of California,

WORKSHOP SUMMARY 31
Los Angeles) were invited to discuss the current status of estimating patient
doses from dose indices and to provide their perspectives on what to track.
Because it is not possible to directly measure absorption of radiation
in body tissues, patient dose is calculated from measurements of the energy
that is incident on the patient. If these measurements are directly used to
reflect patient dose, then they may lead to misleading information, both
experts emphasized. This is because the absorbed dose to the patient is
affected by factors related to the radiation source as well as the patient
(size, morphology, composition, and anatomic region), which can vary
widely across patient populations (McCollough et al., 2011).
3.4.1 Radiation Metrics in Medical Imaging

The two experts explained that the CT dose index (CTDIvol) was devel-
oped to provide a standardized method to compare radiation output levels
between different CT scanners using a reference phantom. Dose Length
Product (DLP), which is the product of CTDIvol (mGy) and scan length
(cm), is related to the total ionizing energy imparted to the reference phan-
tom. Both CTDIvol and DLP are sensitive to changes in scan parameters
such as tube voltage and current, but they do not account for the physical
characteristics of the patient undergoing the CT examination. CTDIvol is
determined for either a 16 cm “head” or 32 cm “body” acrylic phantom.
The (air) kerma area product [KAP] in radiography and fluoroscopy, and
the administered activity [MBq] in nuclear medicine, are corresponding
measures of the “amount of radiation” used to perform these respective
radiological exams. These system measures can be used to quantify sys-
tem performance, quality control, and establish routine clinical protocols.
Moreover, these are the key inputs into all methods that have been devel-
oped to estimate patient doses.
In CT, given a constant scanner output (i.e., CTDIvol and DLP), Dr.
Huda estimated that reducing patient weight from 70 to 50 kg might
increase doses (and risks) by 20 to 25 percent, whereas increasing the
patient weight to 120 kg might reduce doses (and risks) by 30 to 35 per-
cent. Whether such dose adjustments were justified and required, however,
will always depend on the specific context and the reason that any specific
dose (and risk) estimate is being obtained. Inherent in current models of
radiation dose are the many uncertainties and assumptions one must make
to arrive at a patient’s estimated dose. On that, Fred Mettler commented
that any attempt to improve dosimetric precision must account for current
risk uncertainties.11
11 For more information, see Martin, 2007.

3.4.2 Organ and Effective doses

Dr. McNitt-Gray focused his presentation on organ dose as a dose
metric that reflects the absorbed dose to the patient and that attempts to
account for both patient- and source-related factors. He said that if organ
doses could be estimated reasonably accurately and robustly, then they
would provide an extremely useful basis for estimating and tracking patient
dose. Doses to specific organs could be tracked over time and could be
combined (added or by other math operation) in a much more meaningful
way than we are currently able to do (e.g., combining radiation dose indices
such as CTDIvol and/or administered activity). This could be done for very
different procedures or multimodality procedures such as PET-CT.
Organ absorbed dose conversion factors can be estimated by using
either clinically validated anthropomorphic phantoms with internal dosim-
eters or Monte Carlo computer programs. Obtaining organ dose estimates
in a robust fashion is not easy to do on a routine basis. However, each of
the modalities (radiography/fluoroscopy, nuclear medicine, and CT) has
methods that are being developed to obtain reasonable organ dose esti-
mates. Dr. McNitt-Gray pointed out that it will take some effort to fully
develop these methods and implement them into clinical practice to track
patient dose in a routine fashion. To do so requires cooperation between
equipment manufacturers, standards organizations (e.g., DICOM), profes-
sional organizations (e.g., AAPM, SNM), possibly some software develop-
ing companies (to develop databases), and finally users and patients.
Dr. Huda stated that if the goal is to estimate risk at a particular part
of the patient, then organ dose may be the dose metric of interest, and he
described one of the methods available in the literature to calculate embryo
dose estimates following a CT of the mother (Huda et al., 2010). He noted,
however, that most often the physician and patient are interested in know-
ing the dose that the patient received (which means in all exposed organs
and tissues combined and not in one organ alone). For this purpose, in his
view, the realistic way to present information on the dose distributions that
occur in all radiological examinations is to use effective dose. Use of the
effective dose also permits the radiation dose of diverse diagnostic proce-
dures to be quantified and thereby made understandable to medical imaging
practitioners, as well as the general population, he explained. Because the
effective dose is directly related to the stochastic risk associated with a given
diagnostic procedure, it also permits determination of the risk associated
with a procedure.
However, Dr. Huda noted that the effective dose is not a radiation risk
parameter per se, and, although possible, obtaining radiation risks must
be performed with great care. More specifically, when converting effective
doses into radiation risks, the following factors must be taken into account:

WORKSHOP SUMMARY 33
the exposed patient region, the size of the exposed individual, and the
patient demographics such as age and gender (Huda and He, 2011).
Dr. Brink was invited to provide a physician’s perspective on the suit-
able dose metric for tracking purposes. He argued that effective dose is an
imperfect metric for this purpose, even though it has been used as the driver
for risk estimation from medical imaging for many years. Many medical
imaging decisions would benefit from a focus on organ dose rather than
effective dose, he said.
For example, a study conducted to evaluate the relative radiation risk
of CT versus nuclear medicine evaluation for suspected parathyroid ade-
noma showed effective doses that were nearly equivalent between the two
tests. However, analysis of mean organ dose and risk showed that the thy-
roid was the most radiosensitive organ affected by the CT scan, while the
colon was the most radio sensitive organ affected by the nuclear medicine
study (Mahajan et al., 2011). When analyzed by age and gender, it became
apparent that women under the age of 30 have a relatively high risk of
thyroid cancer from the CT scan as compared to the risk of colon cancer
from the nuclear medicine exam. Over age 30, the risk of colon cancer from
the nuclear medicine exam was significantly greater than the risk of thyroid
cancer from the CT scan, in both men and women.
3.5 FROM DOSE TO RISK ESTIMATES

Dr. David Brenner (professor of radiation biophysics, Columbia Uni-
versity) discussed a number of issues regarding cancer risks from low-dose
radiation exposure, and Dr. Kiyohiko Mabuchi (senior scientist, National
Cancer Institute [NCI]) summarized the current evidence regarding non-
cancer risks in the low-dose range. Dr. Amy Berrington de González (senior
investigator, NCI and workshop committee member) described a risk cal-
culator for projecting potential cancer risks from low-dose radiation expo-
sures that has been developed at NCI.
3.5.1 Cancer Risks

Dr. Brenner explained that to evaluate the potential risks we first need
to understand the range of doses received from radiological examinations,
and for this purpose a distinction must be made between lower dose radio-
logical exams (e.g. conventional plain film, mammography, dental) and
higher dose exams (CT, PET, fluoroscopy). He explained that most of the
population dose and potential risk currently in the United States come from
the higher dose exams. Taking into account a) inter- and intra-institutional
variability, b) machine variability, c) age variability, d) scans done with and

without contrast, and e) multiple scans, the key organ doses of relevance
for CT are 5-100 mSv for a single series of CTs, and 5-250 mSv lifetime.
For organ doses corresponding to higher dose exams, some current
knowledge comes from direct evidence in other exposed populations, Dr.
Brenner said. From the atomic-bombing survivor data, there is some evi-
dence of a small but statistically significant increase in cancer risk in the
5-125 mSv range (and higher) for cancer mortality (Preston et al., 2003)
and in the 5-150 mSv range (and higher) for cancer incidence (Preston et
al., 2007). Other supportive evidence of a statistically significant increase
in cancer risk at the lower end of these dose ranges come from studies of
childhood cancers after in utero exposure (mean dose ~6 mGy) (Doll and
Wakeford, 1997) and of 400,000 nuclear workers (mean dose ~19 mGy)
(Cardis et al., 2007), although the results of the nuclear worker studies are
still under evaluation.12
According to Dr. Brenner, the challenge is to predict the biological
impact of exposure to doses less than 1 mGy. For the region below which
epidemiologic evidence is robust, the assumption of linearity is used. One
of the issues associated with extrapolating data from the atomic-bombing
survivors to medical diagnostic patients is that one involves whole body
exposure while the other exposures to only certain organs. However, evi-
dence exists that within the limits of an epidemiologic study, organ-specific
dose-dependent risks are roughly independent of whether the exposure is
whole body or partial body. Another issue with extrapolations is that the
exposures from the atomic bomb were acute while the exposures in medi-
cal diagnostic procedures are fractionated. However, current knowledge
is that the effects of fractionation are not as big as initially thought, and
therefore the dose and dose-rate effectiveness factor (DDREF) that is used
to extrapolate risk per unit dose from high doses of acute exposure to risk
per unit dose at low doses and low dose rate is now considered to be 1.5-
2.0 (NRC, 2006; ICRP, 2007b).13 In Dr. Brenner’s view, one can state with
relative confidence that the risks associated with exposure to radiation from
medical diagnostic procedures are considered to be small but non-zero; but,
the uncertainties may be three-fold in either direction, thus potentially lead-
ing to over- or under-estimation of the risk.
The cancer risks are age-dependent with those exposed in childhood
12 A major problem of the nuclear workers’ study, known as the 15-country study, is the
fact that the results were driven by the contribution of only one country, Canada (Ashmore et
al., 2010). The Canadian Nuclear Safety Commission (CNSC) requested a reexamination of
the Canadian portion of the data for their quality and validity. The resulting report confirmed
that there is no increased cancer risk among the Canadian nuclear power plant workers for
the time period examined (CNSC, 2011).
13 For example, a DDREF of 1.5 to 2.0 suggests that the risk associated with an acute dose
of 100 mSv is equivalent to a protracted dose of 150 to 200 mSv.

WORKSHOP SUMMARY 35
being at greatest risk. Furthermore, in the past, pediatric patients received

higher doses from CT scans because imaging parameters were not adjusted
for patient size (Brenner et al., 2001; Paterson et al., 2001). However, there
is increasing understanding that earlier estimates of the dependence of risk
on age at exposure probably underestimated radiation risks in middle age.
Recent studies suggested that for radiation exposure in middle age, most
radiation-induced cancer risks do not, as often assumed, decrease with
increasing age at exposure (Shuryak et al., 2010). This observation suggests
that promotional processes in radiation carcinogenesis become increasingly
important as the age at exposure increases, Dr. Brenner said. Because most
CT scans are given in middle age, exposures to patients of all ages are of
concern (Shuryak et al., 2010).
Hedvig Hricak, vice-chair of the workshop committee, asked whether
special care should be given to cancer survivors who, because of their pos-
sible inherent predisposition to DNA damage, may be more sensitive to
radiation. David Brenner and John Boice (Vanderbilt University/ Interna-
tional Epidemiology Institute) agreed that this may be true, but the direct
evidence is currently limited (Broeks et al., 2007; Bernstein et al., 2010;
Figueiredo et al., 2011).
Dr. Brink commented on the recent findings that reduced life expec-
tancy further reduces the risk of ionizing radiation in individuals with co-
morbid conditions (Brenner et al., 2011).
Dr. Brenner explained that to date no studies have directly evaluated
whether the risk of cancer increases after CT scans. However, several epi-
demiologic studies of cohorts of patients who had pediatric CT exams are
under way.
UK14 ~200,000 children

Ontario15 ~275,000 children
Israel16 ~80,000 children
14 Studycohort includes individuals under 22 years of age at first CT who received CT scans
during 1985-2002 in the United Kingdom. Information on the types and dates of CT scans
was collected from the radiology departments in approximately 100 hospitals, and patients
were linked with the national health service central registry to obtain cancer registrations and
death information. At the time this workshop report was published, results from the study
had been submitted for publication.
15 Study cohort includes individuals under 18 years of age who received CT scans during
1985-2005 in Ontario. Information is collected from the Ontario health insurance plan and
Hospital for Sick Children.
16 Study cohort includes individuals under 18 years who received CT scans during 1985-
2005. Information is collected from Maccabi Health Care and a large pediatric medical center
in Israel.

Australia17 ~150,000 children

France18 ~25,000 children
Sweden19 ~35,000 individuals
Dr. Brenner noted that the studies are large, but the expected numbers
of cancer cases are still relatively small because the follow-up will only be
through childhood and early adulthood. Therefore, power may be sufficient
to identify an increased risk of cancers that occur earlier in life such as
leukemia, thyroid, and brain cancers. Larger and longer studies are needed
to assess most of the possible risk, especially of those adulthood cancers
with longer latency periods. After the individual studies are completed, a
planned pooled analysis will be performed to increase statistical power. In a
later discussion, Dr. Brenner expressed that he does not think that over the
next few years there will be dramatic increases in knowledge regarding the
cancer risks from low-dose radiation exposures or more precise estimates
of the potential risks, even after the results from the epidemiologic studies
of pediatric CT scans become available.
3.5.2 Risk Calculator for Research Purposes

Amy Berrington de González, together with her colleagues at NCI,
developed the NCI Radiation Risk Assessment Tool (RadRAT), an interac-
tive computer software that uses risk projection models to estimate cumu-
lative lifetime cancer risks related to any low-dose radiation exposure (not
exclusively from medical diagnostic procedures). The tool was developed
for research purposes and not for patient purposes, Dr. Berrington de
González emphasized. One of the main reasons the program is not suitable
for patient risk assessment is that it requires organ-specific radiation doses
rather than effective doses. She mentioned that several simpler risk assess-
ment tools are available online that can be used by patients. These usually
just require the user to input the type of exposure (e.g., head CT scan) and
age at exposure.
The NCI risk calculator can take into account multiple exposures over
time, organ doses for multiple doses, whether the exposure was acute or
protracted, and also type of radiation. A total of 18 cancer sites are covered
in the calculator. The underlying risk models for 11 sites were based on the
National Academy of Sciences BEIR VII report (NRC, 2006), developed
17 Study cohort includes individuals under 19 years who received CT scans during 1985-
2005. Information is collected from Medicare-funded services.
18 Study cohort includes children under 5 years who received CT scans during 2000-2006.
Information is collected from several centers in France, covering almost all regions.
19 Study cohort includes children and adults who received CT scans at the Department of
Neuroradiology, Karolinksa University Hospital, Stockholm.

WORKSHOP SUMMARY 37
primarily from studies on the Japanese atomic-bombing survivors, although

some medical exposure studies were included. Seven additional models were
added for sites that are particularly important for radiation exposure from
medical diagnostic procedures, such as the brain, and that were not covered
in the BEIR VII report.
Dr. Berrington de González said that the key aspect of the NCI risk
calculator is that it incorporates Monte Carlo simulation methods to quan-
tify the impact of uncertainties in the assumptions and data. This includes
subjective uncertainties, for example how to transfer data from the Japa-
nese atomic-bombing survivor cohort to the populations of interest and the
magnitude of the dose response at low doses, as well as statistical uncer-
tainties in the model parameters. Importantly, the risk calculator provides
an estimated uncertainty interval for the lifetime risk estimate. The NCI
investigators are currently working on making the program publicly avail-
able in 2012 by developing a web-based version.
3.5.3 Non-Cancer Effects

Although risk of developing cancer is the primary concern follow-
ing exposure to low radiation doses, non-cancer diseases may also be
associated with exposure from medical imaging procedures. According to
Dr. Mabuchi, the key questions to be addressed in estimating the risk of
non-cancer disease relate to identification of the diseases of concern, dose
response, and the magnitude of risk at low diagnostic doses. As with cancer
risk estimates, the long-term follow-up study of the atomic-bombing survi-
vors is a unique opportunity to study these questions.
For the atomic-bombing cohort, mortality data have provided evidence
of causal associations for radiation and several disease categories, includ-
ing circulatory disease (heart disease and stroke), digestive system disease,
and respiratory system disease. The relative risks associated with radiation
for these diseases are relatively low compared to the radiation-related can-
cer risk, but the absolute risk as measured by excess numbers of deaths,
especially from circulatory disease, is substantial because these diseases are
more common.
Dr. Mabuchi said that the latest data indicate a significant linear dose
response for heart disease at dose levels higher than 0.5 Gy, while the
stroke data suggest a possible non-linearity. The dose response for heart
disease in the range of 0-0.5 Gy is not statistically significant, but excess
relative risk per Gy at doses below 0.5 Gy are comparable to those derived
from high doses (Shimizu et al., 2010). The dose response for circulatory
disease has also been investigated in numerous other populations with
occupational and medical exposures at medium or low dose levels. The
circulatory disease risk estimates vary significantly among different studies,

but recent meta-analysis by the Health Protection Agency has shown that
the heterogeneity is diminished (but not eliminated) if allowance is made
for confounding by endpoints and dose fractionation effects. A significantly
elevated overall excess relative risk of 0.09 per Gy was estimated in that
meta-analysis.
Regarding the age and time patterns of the radiation-related non-cancer
diseases risk, the atomic-bombing survivor data suggest that the non-cancer
patterns are similar to those for radiation-related risk of solid cancer,
with age at exposure or attained age modifying the temporal pattern and
risk persisting throughout the lifespan. However, the patterns cannot be
characterized with precision because of the low radiation-related risk for
non-cancer and the high and varying baselines rate over the long follow-
up time. The excess digestive disease risk observed may be unique to this
population, likely involving an interaction of radiation with hepatitis C
virus infections, and may not be directly extrapolated to other populations
(Sharp, 2003). Reasons for the increased respiratory disease risk need to
be clarified. Among other non-cancer conditions, cataract needs special
attention because of the latest evidence of an increased risk of not only
posterior lenticular opacity (known to be radiogenic) but also more com-
mon types of cataract at dose levels much lower than until now considered
to be a threshold.
3.6 WHY TRACK DOSES?

The reasons for tracking dose (used generically to imply exposure or
dose index) were discussed during the workshop, mainly in terms of jus-
tification, protocol optimization, individual risk assessment, and research
purposes.
3.6.1 Justification
Many workshop participants suggested that the greatest change in
reducing radiation exposure may come from ensuring that the exams
ordered are clinically justified. This could be achieved by informing the
physician on whether the exam he/she is about to order has been performed
previously or elsewhere and can be used for current clinical decisions (see
discussion on justification in Section 3.1) and by providing the physician
that orders the exam with evidence-based decision support systems that
could inform his/her decision at the point of care.
The benefits versus risks associated with medical imaging procedures
are more often discussed with emphasis on the fact that the risks are often
unknown. Dr. Michael Lauer (director, Division of Cardiovascular Sci-
ences, National Heart, Lung, and Blood Institute [NHLBI]) stated that the

WORKSHOP SUMMARY 39
clinical benefits of imaging procedures currently are also not always clear.
Collecting good quality data through randomized clinical trials that involve
tracking patient exposures and doses would help to inform the decision
support systems and justify (or not) a procedure based on whether it would
improve overall health. These systems may lead to a cultural shift, he said,
such that fewer imaging tests are performed and only when supported by
evidence from high-quality randomized trials or as part of ongoing trials.
Dr. Lauer provided two scenarios that lead to increased imaging today
with no apparent improvement in health. First, as imaging techniques
become more sensitive, cardiologists and other physicians are diagnosing
diseases that they previously could not and the threshold of defining disease
is getting lower. That gives the impression to the clinicians but also to the
patients and the public that the prevalence of disease, or the prevalence of
severe disease is increasing. As “awareness” of a disease increases, more
testing is performed to detect it.
Second, with intense and improved imaging, clinicians now diagnose
early disease or less severe forms of disease with the assumption that this
translates to improved patient outcome. Patients probably respond well
when treated for their mild disease, giving the impression and statistical
artifact that the imaging saved their lives, which, in turn, leads to more
imaging. In reality, little was done to improve health.
In Dr. Lauer’s view, only by taking a step back and insisting on large-
scale high-quality randomized clinical trials can the true value of new imag-
ing tests be determined. He noted that these randomized trials could answer
many critical clinical questions within a relatively short time, but should
continue indefinitely to enable long-term follow-up. Because uncertainties
regarding the magnitude of harm will possibly continue, an accurate under-
standing of the magnitude of benefit is a moral imperative, and Dr. Lauer
suggested national discussions for randomized clinical trials.
A successful story and relevant example is the NCI-funded National
Lung Screening Trial, which showed that helical-CT can be life-saving for
early detection of lung cancer among heavy smokers (Aberle et al., 2011).
However, not all trials have the expected outcome; for example, a recent
trial of myocardial perfusion imaging in patients with diabetes showed no
improvement in the outcome despite an accurate prediction of the events
(Young et al., 2009). At the time of this writing, the NHLBI is funding a
large-scale trial of CT angiography in patients with suspected coronary
disease.20
20 See: https://www.promisetrial.org/.

3.6.2 Protocol Optimization, Standardization, and Quality Assurance

Many workshop participants highlighted the need to optimize tech-
niques and standardize practices and processes among medical institutions
in an effort to reduce doses.21
Many of the parameters related to an imaging exam are under the
control of the radiologist or technologist and ideally would be tailored to
the particular exam and individual. One point made by many workshop
participants was that programs such as the ACR’s Dose Index Registry
are needed to educate the medical community about the benchmark dose
indices and provide appropriate uniformity by reducing the variability
among and within facilities. Efforts like the ACR Dose Index Registry can
help to inform understanding of how much doses can be lowered without
compromising the image quality. Although lowering the doses could lead
to lowering the potential associated risks, it was many times stated that the
focus should be on dose optimization.
Don Miller commented that one needs to know what the source of
the dose variability is before trying to reduce it. For example, variability
sourcing from the patient characteristics, purpose of the imaging, and com-
plexity of the procedure is expected and justified. Some variability in dose
comes from the fact that not all facilities have the same opportunities to
update their older scanners. For example, major hospitals represented at
the workshop are bound to be among the most compliant with regard to
dose optimization efforts compared to the typical community hospital that
lacks the funds, or to non-hospital settings.
Interventional CT
Dr. Thornton (vice chair for quality, safety, and performance improve-
ment, Department of Radiology, Memorial Sloan-Kettering Cancer Center
[MSKCC]) emphasized during his presentation that comparable efforts are
needed for interventional CT use, which has several unique characteristics.
Instead of scanning through entire body cavities, the interventionalist typi-
cally limits the scan range to the anatomic territory, determined from prior
diagnostic imaging, where the target lesion is located. This ability to limit
the scan range is one component of the interventionalist’s dose reduction
efforts. The work of a CT-guided procedure entails repetitive scanning of
21 The Working Group on Standardization of CT Nomenclature and Protocols of the

American Association of Physicists in Medicine (AAPM) is charged with publishing a set
of “reasonable” scan protocols for frequently performed CT examinations (such as brain
perfusion imaging), providing recommendations on notification and alert values, as well as
providing education on equipment terminology (see: http://aapm.org/pubs/CTProtocols/ for
more information).

WORKSHOP SUMMARY 41
the target anatomic territory in order to plan the needle trajectory from
the skin surface, to display the course of the needle as it is introduced and
iteratively corrected, to document arrival at the target, to record the result
of interventions (biopsy, ablation, drain insertion) at the target, and finally
to document the anatomic outcomes following intervention. Thus, at vari-
ous points during a CT-guided procedure, “noisier” lower dose images may
be adequate to accomplish the task of image guidance; in other instances,
the intent of imaging may require higher dose images similar in quality to
CT scans used for diagnostic purposes.
In this context, management of radiation dose during CT-guided proce-
dures is a dynamic, real-time process that requires the interest and knowl-
edge of both the radiologic technologist and physician, Dr. Thornton said.
Important issues for tracking the radiation dose related to CT-guided inter-
vention include reporting a summary exam dose metric (currently, DLP is
clinically available in real time) and its components (i.e., contributions from
helical scans, CT-fluoroscopy—and increasingly in multi-modality environ-
ments, any additional components attributable to traditional fluoroscopy
and PET imaging).
Uniformity in the terminology may be essential to the ability to orga-
nize and retrieve information, and unless the information is stored using
standard terms in a structured format, it will not be possible to evaluate
the progress. Some workshop participants suggested that using RadLex is
a suitable way to unify language in radiology.
The Role of the Manufacturers

Representatives from four CT vendors were invited to participate in
a panel discussion on the role of manufacturers in dose tracking and
dose reduction efforts: Kenneth Denison (GE Healthcare), Katharine Grant
(Siemens), Richard (Rich) Mather (Toshiba), and Dominic Siewko (Philips
Healthcare). It was noted that vendors face tremendous pressure to reduce
doses and are responding with a number of initiatives aimed at addressing
the issue of overutilization in medical imaging. Collaborating through the
Medical Imaging and Technology Alliance (MITA) the manufacturers’ main
efforts fall under the following four categories:
• Reduction of exposures through equipment hardware features

• Standardization of dose reporting
• Integration of radiation dose into reports
• User training
It was noted that vendors are too often expected to optimize proto-
cols, making them universal rather than vendor specific and using common

nomenclature that would facilitate any method or purpose of tracking.

However, the manner in which radiation output, radiation doses, and
any corresponding radiation risks are to be presented on medical imaging
equipment must be based on a consensus by the medical imaging scientific
community. Walter Huda commented that it is unrealistic and impractical
to expect manufacturers to play a leading role in any such endeavor.
Dominic Siewko (Philips Healthcare) noted that now more than ever
it will take a coordinated effort of transparent communication between
researchers, manufacturers, regulators, and care providers to ensure that
the industry moves forward in lock-step.
Tracking the Physician’s History of Ordering

A member of the audience asked whether tracking the physician’s
ordering history could reduce unnecessary imaging. Dr. Hricak (chair,
Department of Radiology, MSKCC and workshop committee vice-chair)
responded that given the fact that the end result of this group effort is
to improve patient care, it is essential to track the physician’s history. Dr.
Sodickson (section chief, Emergency Radiology, Brigham and Women’s
Hospital) clarified that comparisons between clinical practices to assess
physicians’ ordering histories should account for justified differences due
to the patient populations being cared for.
Dr. Morin shared examples of how a system that tracks the physician’s
history of ordering improved practices at the Massachusetts General Hospi-
tal. The hospital adapted and modified the ACR appropriateness criteria for
exam ordering, and ordering physicians with low scores were consulted and
subsequently received feedback regarding their ordering behavior (personal
communication with Dr. Keith Dreyer, Harvard University, 2005). Physi-
cians do not try to do something inappropriate, Dr. Morin said, “they just
do not know.” Fred Mettler noted that easy and relatively quick checks on
the ordering habits of the physicians can happen by routine review of the
billing databases. Dr. Denison added that tracking a physician’s history with
respect to dose (rather than number of procedures) even in a somewhat
anonymized way is particularly important in interventional radiology. It
is important to share the values with all physicians and alert them when
important steps should be taken to lower doses.
3.6.3 Dose Monitoring and Individual Risk Assessment

Although they voiced no arguments against tracking radiation expo-
sures or doses and dose indices for the purposes of justification and opti-
mization, some workshop participants disagreed about the desirability of
tracking for the purposes of individual dose monitoring and risk assessment.

WORKSHOP SUMMARY 43
A member of the audience asked Dr. Huda for his opinion as to whether
patients should be given their dose periodically. In response, Dr. Huda
rephrased the question to “Do I—as a patient—want to know my cumula-
tive risk?” and categorically responded, “No! What an individual needs to
know is whether he or she will benefit from the exam that is about to be
ordered.”
Dr. Mettler added that focusing on either dose or risks may become a
problem in the future if patients refuse to have or physicians refuse to give
an exam that the patient needs because of anxiety over the risks rather than
appreciation of the benefits. Although for stochastic effects such as cancer
risk dose tracking for individual risk assessment may not be needed, for
deterministic effects, it may be good to know when those limits have been
reached.
Although not arguing with the points made, Dr. Brink reminded the
workshop participants that if the medical community does not monitor
individual doses responsibly and with control, then somebody else will
provide (in fact, already has started to provide) cumulative dose and risk
to the patient, potentially in a poor and inconsistent manner. The question
remains, however, about what one does with the tracked information. Dr.
Brink’s statement that the medical community should take the lead in track-
ing individual doses was supported by others.
What to Track and Communicate

Although patients rely on their physician to guide them through clini-
cal decisions, many workshop participants identified a trend in health care
worldwide whereby patients want to know and understand more about the
procedure they are about to have with the ultimate goal to improve their
health care. This trend was compared to that of the implementation of
nutritional information facts at the back of the products two decades ago.
Although initially consumers were unsure about how to use the informa-
tion, today many look at it for different reasons and want to know how to
use the information effectively to make good choices.
Dr. Hricak emphasized that because the physician still plays a funda-
mental role in informing the patient, the only way to provide the necessary
reassurance to the patient or help the patient understand the risks and
benefits of a procedure is by helping the physician understand the poten-
tial risks and benefits of the procedures ordered. It is important that the
physician is able to provide the answers by being familiar with the current
status and limitations of radiation dose estimations and risks. Today, many
physicians are not adequately familiar with the radiation exposure effects,
and training is crucial.
Dr. Donald Frush (chief, Division of Pediatric Radiology at Duke Uni-

versity Medical Center) identified elements of reassurance related to radia-

tion exposure that come from knowing that the patient is about to get a
good quality exam based on standard practice; the treating facility has
active programs of optimizing exams; the providers are mindful of safety;
and the scanners are accredited by an organization.
However, some patients seek more than reassurance and ask about the
dose received or the risks associated with a particular exam. Therefore the
question remains: What is the most effective way to communicate doses
or risks with those patients? Although there was no obvious approach as
to how the dose or risk would best be communicated to the patient, or
which of the two parameters should be tracked and communicated, many
workshop participants said that little would be gained by communicating
dose index metrics with the patient, especially because dose index metrics
vary by modality and therefore do not provide a uniform recording system.
Seemingly more meaningful is translating the dose index metrics to doses or
risks or communicating in some generic way the increase of risk per exam
(for example a 0.3 percent increase on top of the 42 percent baseline cancer
risk) based on current knowledge.
An alternative is to translate the risk to something more familiar to the
patients, for example, the exposure to radiation during a flight from East
to West coast, exposure to background radiation when living in Denver
versus living in New York. (This approach was found to be too simplistic
by some workshop participants including Drs. Brink and Sodickson who
spoke against it.)
Dr. Kevin Crowley (director, Nuclear and Radiation Studies Board,
National Academy of Sciences) commented that there is substantial litera-
ture on risk communication, including some National Academy of Sciences
reports. It is known that different risks mean different things to different
people based on subjective factors, and although numbers and statistical
evidence may mean less to the general public, comparisons of risks from
other sources, when risks are sufficiently similar, may prove useful to put
risks into perspective.
Regardless of the preferred method, a number of workshop participants
commented that communication must be catered to both the patient’s inter-
est to know and prior knowledge on the topic and should be done in an
appropriate language and in a way to avoid causing panic. Uncertainties in
the dose and risk estimations also should be clearly communicated.
Related to the need for effective communication is an increasing debate
regarding informed consent for ionizing radiation in diagnostic imaging
(Nievelstein and Frush, 2012).

WORKSHOP SUMMARY 45
Where to Report the Information

Dr. Mettler compared the ordering of an exam with the ordering of
a prescription, which makes it obvious that documenting the amount of
radiation used in an exam is a reasonable thing to do. The question of
where to document the amount of radiation—in the radiology report or
the medical record—was further discussed.
A member of the public pointed out that documenting doses in the
radiology report, which is a legal document, may lead to future problems
because doses are based on nonaccurate models and, in pediatrics in par-
ticular, may differ from the actual doses received. Dr. Frush responded that
these doses do not necessarily need to be recorded in the report but can be
archived in some fashion in the medical record, and whether or not they
go in the report will depend on state requirements while being mindful of
the issues mentioned.
Because the methods to estimate patient doses are not yet fully devel-
oped and it is uncertain which are the most relevant, it might be necessary
to record all parameters and dose indices provided by a scanner. This is in
agreement with the prototype used in the California’s legislation (see Sec-
tion 2.5.6), which notes that metrics such as CTDIvol and DLP or a dose
unit as recommended by AAPM should be recorded. Dr. McNitt-Gray
noted that such a recommendation is not likely to be implemented before
the July 2012 deadline, but the AAPM can make a future recommendation
for a more meaningful metric to be reported.
For patients that want more information about their exposure and the
possible health effects, different levels of information covering the different
levels of interest could be incorporated into the report. Dr. Frush suggested
that the report could include links directing the patient to the appropri-
ate organization (such as ACR, RSNA, IAEA) or federal agency (such as
FDA and NIH) for general dose information, specific dose information per
modality, or risk estimations with an option to contact the institution’s
radiology program if more patient-specific dose information is desired. The
debate of whether the reported amount of radiation should be converted
to dose or risk continued, with Dr. Brenner asserting that risk is what the
patient most cares about. Fred Mettler pointed out that the idea of report-
ing risk in relation to radiation amount in the medical record does not agree
with current practices, for example in radiotherapy, chemotherapy, and
other treatment options, which may also carry some risks.
Assuming that a dose-recording system is needed for individual pur-
poses, it has to be portable and cross boundaries to facilitate information
tracking for all, including the mobile populations, Dr. Hricak said. Several
possible approaches were discussed, including Smartphone technologies or

centralized technologies that enable patients to enter treatment information

not matter where they receive the treatment.
Past Exposure Informing Decision Making

Section 3.1 of this report discussed that insufficient information about a
patient’s history of exams (e.g., whether a procedure was done in a different
facility and its outcome) may lead to unjustified ordering of an exam. The
opinions discussed in this section regarding past exposure informing deci-
sion making are not related to the issue of insufficient information resulting
in duplicate or questionable ordering. Instead, they relate to whether and
how the history of exposure to medical radiation (e.g., too many CT exams
in a patient’s record) fits into the clinical decision of ordering the next exam
that utilizes ionizing radiation.
A member of the audience stated that, even within the walls of a hospi-
tal, a database that is easily accessed from a workstation and provides the
ordering history for a patient can affect practices and reduce the number of
exams ordered. In such a database, collecting information on the number of
procedures rather than the doses may provide a sufficient wake-up call for
the chief technologist. Dr. Sodickson agreed with the comment and added
that real-time support rather than dose registry type of implementations can
be factored into clinical decision making. Furthermore, the clinical model
of taking clinical decision today based solely on clinical presentation today
is changing; practice must move from episodic decisions to more long-term
care of the patient by looking at the entire medical history and exposure.
This may be more evident at the primary care level, when deciding whether
physicians are doing the right thing over the course of a patient’s treatment.
Ms. Gwen Darien (at the time of the workshop, executive director,
Samuel Waxman Cancer Research Foundation; currently, director, The
Pathways Project), representing the cancer survivors’ views, shared the idea
that ordering history information should fit with clinical decision mak-
ing. It is critical to have knowledge of the previous exposures to radiation
and potential harms from past, present, and future exposure as well as
how those exposures might interact with medical treatment of the specific
patient. To truly improve patient outcomes, it is vitally important to con-
sider the long term when making decisions, she said.
Other participants, including Drs. Huda, Brenner, and Frush disagreed
and stated that if an exam is clinically justified, then it is justified regardless
of the past history; however, knowing the exposure history of a patient may
serve as an important reminder that other means to diagnose a problem
are possible.
Dr. Brenner described screening as an area where a risk versus benefit
justification discussion is valid. Dr. Sodickson responded that in the emer-

WORKSHOP SUMMARY 47
gency room setting many exams border on being screening exams, and the
yield is low. For example, the positive rate for a study to rule out dissection
in a patient with chest or back pain is only 2 percent; however, the impor-
tance of making a life-or-death diagnosis in these few patients is critical.
He also emphasized that justification of an exam is often a grey area, and
the right thing to do is not always obvious.
Although past exposures might be part of the decision-making process
for ordering the next exam, there is no threshold above which you cut off
some patient from further imaging, Dr. Sodickson clarified.
Dr. Berrington de González noted that the United States could possibly
make use of the justification systems that are in place in other countries
such as the United Kingdom, where CT use is seven-fold lower than in the
United States. All requests for diagnostic imaging procedures that involve
ionizing radiation have to be approved by a radiologist, and the process
requires justification of the need for the test.22
The Patients’ Perspective

Gwen Darien discussed the patients’ perspectives on the risks and ben-
efits of radiation exposure from medical diagnostic procedures. As a cancer
survivor herself, her perspective was that of the cancer survivor rather than
the typical symptomatic or asymptomatic patient. Ms. Darien explained
that the health goals and concerns of cancer survivors may be different from
those of other patients, and therefore their perspectives and expectations
may also differ. In order to pose a question to their health care provider,
they need to know that there is a question to ask. It is not clear whether
most cancer survivors know that there is a question to ask regarding risks
associated with medical imaging. She noted that overall there is little discus-
sion between patients and health care providers on the risks and benefits of
radiation exposure from medical diagnostics.
Although the benefits are often assumed even when not explicitly dis-
cussed, the risks are rarely mentioned. In the absence of risk/benefit discus-
sions between patient and health care providers, there is often a tendency
for patients to request more procedures, Ms. Darien said. For many cancer
survivors there is fear and anxiety of “not knowing” and of disease recur-
rence. From the perspective of a cancer survivor, it is critical to understand
how radiation exposure might interact with medical treatment. With the
ultimate goal of informed decision making, patient-provider interactions
must include a discussion of the need for test, what knowledge will be
gained from the test, and how that knowledge will be used to benefit
22 Royal
College of Radiology—A guide to justification for clinical radiologists. See: http://
www.rcr.ac.uk/publications.aspx?PageID=310&PublicationID=2).

the patient. Ms. Darien noted that cancer survivors would be primarily
concerned with not being able to get the tests they perceive they need if a
tracking system for radiation dose were in place.
Are We Ready to Track?

On the topic of whether—if desirable—we are ready to track indi-
vidual doses, Dr. Sodickson described an effective system of individual dose
tracking, which is based on electronic medical records as likely the most
efficient way to store information about the patient’s history of radiation
exposure. This system would include all care sites, and as a patient moves
from one state to another his/her doses would be recorded via a unique
patient identifier. The system would be able to track all modalities and
sources of exposure and modality-specific exposure metrics or technique
parameters together with accurate patient-centric dosimetry. The database
format would be standardized, and all systems would be connected without
firewalls or barriers.
This system differs from the current reality, which involves some inde-
pendent modality-specific efforts, he said. This is because exposure metrics
and platforms are different, and most of the captured modalities are for
CT, because of its high doses and public attention, and for fluoroscopy,
because it is more regulated in terms of the deterministic effects. Impor-
tant data elements have been missing, such as exposure metrics, dose, and
parameters related to the patient’s size. Moreover, data access is limited,
and data collection processes are not often automated. The format is largely
inaccessible such as screen captures and text reports and is buried in discon-
nected systems.
For these reasons, many workshop participants asserted that—even
if desirable—tracking cumulative dose estimates from a single or multiple
modalities of a patient at the national level cannot happen today. At an
institutional level, dose indices or dose estimates of a patient associated with
a single procedure could be tracked, and possibly some institutions could
track cumulative dose estimates from a single but not multiple modalities.
In support of isolated institutional efforts to track cumulative dose
estimates from a single modality of a patient, Dr. Sodickson presented
efforts developed at the Brigham and Women’s Hospital. The team devel-
oped an open source informatics toolkit named GROK (General Radia-
tion Observation Kit), which can locate and retrieve CT exposure metrics
CTDIvol and DLP from existing digital image archives and convert them
to text. Moreover, anatomy assignment algorithms use the combined dose
report screen text and DICOM attributes data to determine the anatomic
regions irradiated, creating large repositories of historical anatomy-specific
radiation exposure metrics information from CT (Sodickson et al., 2012).

WORKSHOP SUMMARY 49
Using similar logic, an open source toolkit, PARSE (Perl Automation for
Radiopharmaceutical Selection and Extraction), was created to extract
exam- and patient-specific dosimetry from the medical records of patients,
which contain unstructured text including the administered activity and
the radiopharmaceutical name (Ikuta et al., 2012). Both methods proved
satisfactory validation yields in data retrieval (97-99 percent) and anatomic
assignment precision (94-99 percent) and may prove to be promising tools
for estimating patient-specific radiation dose and cumulative risk.
3.6.4 Research
The gaps in current knowledge and the need to explore and refine
models of biological effects at low doses were demonstrated by the presen-
tations of Drs. Brenner and Mabuchi. Dr. McNitt-Gray argued that as the
natural experiment of the effects of medical imaging procedures that use
radiation is happening, it would be wise to collect good dosimetry data.
This effort could answer the epidemiologists’ questions and improve current
knowledge of the biological effects of low-level radiation without the need
to extrapolate from other population sources, which introduces uncertainty
into measurement and interpretation.
Dr. Berrington de González responded to this idea by saying that,
although using a tracking system would be beneficial for epidemiologic
studies, capturing the study end point, such as cancer occurrence or death
from cancer, and linking it with the exposure information is necessary
for an epidemiologic investigation. In the absence of a centralized cancer
registry in the United States that could provide the cancer ascertainment
information, this is a difficult task.
Dr. Lauer added that attempting to find the potential association of
imaging and cancer risks is important, but other risks not related to cancer
also need to be tracked to assess the appropriateness of an imaging exam.
All medical procedures contain an element of danger, and a potential to
discover incidental findings that require subsequent medical evaluations.
These evaluations may not only not improve outcomes but are likely to
induce harm (Lauer, 2009).
3.7 LESSONS LEARNED FROM PEDIATRICS

Dr. Frush was invited to discuss the exposure reduction efforts and
lessons learned from pediatrics. The pediatric radiology subspecialty is not
typically on the horizon-defining medical trajectory, he said. Exceptions to
this are efforts related to medical radiation, specifically radiation dose and
potential risk from CT imaging, and education and advocacy for radiation

awareness and protection. Dr. Frush described some of the accomplish-

ments resulting from efforts through pediatric imaging.
First, he said, we can lower doses and read noisier examinations, and
we ought to do this. A number of reports in the pediatric population as well
as a growing body of literature in the adult population promote dose reduc-
tion with maintenance of image quality. There is systematic work in dose
reduction in adult and pediatric renal calculus evaluation (Karmazyn et al.,
2009; Paulson et al., 2008). A study that compared the diagnostic capabili-
ties of standard- and reduced-dose CT in the detection of nephroureteroli-
thiasis in children showed that use of the 80 mA setting for all children and
40 mA for children weighing 50 kg or less does not significantly affect the
diagnosis of pediatric renal stones (Karmazyn et al., 2009).
Second, multiphase (repeated scanning before and after contrast injec-
tion) examinations should be justified in adults, as has been promoted in
the pediatric population, although multiphase examinations in children are
generally not protocol driven, Dr. Frush said. When necessary, they could
be based on a more case-by-case approach. Overall, multiphase examina-
tions constitute fewer than 5 percent of all pediatric body CT examinations.
This philosophy is less pervasive in adult imaging. One recent investigation
noted that the frequency of “double scans” of the abdomen was highly
variable, and the mean effective dose could have been reduced by about
one-third overall with adherence to ACR appropriateness criteria (Guite et
al., 2011).
He recognized the success of the Image Gently campaign, whose main
pillars stand upon the foundations of a respected organization and leader-
ship with independence and integrity, and consensus involvement. The mes-
sages are simple, important, and promoted in a positive and constructive
(rather than alarmist) manner, with carefully controlled delivery of content,
timing of releases, and schooled spokespersons to assure consistency and
maximized penetration and impact.
He noted, however, that one must still be mindful of the various remain-
ing needs in both pediatric and adult imaging, which include helpful dose
alerts and notifications, improved dose estimations that account for the
patient’s characteristics (age, weight, size, gender), and establishment of
reference values. Although templates exist on new scanners, without rea-
sonable guidance for their use, these capabilities may be underutilized or
incorrectly utilized, and therefore ineffective.
Dose estimations for CT in children are often inaccurate. The avail-
ability of improved dose estimations, such as through the AAPM task group
204 (AAPM, 2011), is a clear improvement. Current work in many labora-
tories focuses on patient-specific (i.e., age, weight, size, gender) organ dose
estimations and resulting effective dose estimations. Dr. Frush discussed
that a pilot registry for pediatric body CT (QuIRCC) is working in parallel

WORKSHOP SUMMARY 51
with the ACR Dose Index Registry. Early results from this pediatric registry
demonstrate that the body CT dose indices at six pediatric institutions are
below those reported in the European community (personal communica-
tion, Dr. Marilyn Goske, Cincinnati, Ohio).
3.8 SOME POSSIBLE NEXT STEPS

SUGGESTED AT THE WORKSHOP
This section summarizes the key points and suggestions on some pos-
sible next steps discussed throughout the 1.5-day workshop and highlighted
during the final panel session moderated by Dr. Barbara McNeil, profes-
sor and head of the Department of Health Care Policy at Harvard Medi-
cal School and workshop committee chair. The four panelists were Drs.
Brenner, Frush, Hricak, and Mettler.
Many workshop participants noted that a primary motivator for track-
ing doses was to implement and maintain dose reduction strategies through
optimization and justification with the ultimate goal to improve care. Sev-
eral participants asserted that such strategies ought to be adopted by all
facilities that perform diagnostic imaging, including hospitals and imaging
centers, as well as free-standing private physician, dental, and chiropractor
practices. Dr. Hricak emphasized that although it may be straightforward
for major hospitals to adapt and adhere to practice guidelines, it may be
challenging for free-standing imaging centers and small community hospi-
tals to do so. Still, the goal of any imaging facility ought to be to improve
radiologic services to the patient independent of the available resources.
Some workshop participants stated that it would be desirable to have a
national registry that tracks radiation exposures and/or doses from medical
diagnostic procedures. However, such a national effort is not likely to be
implemented in the near future for many reasons, including lack of shar-
ing of medical information across different health care facilities, lack of a
unique patient identifier and integrated medical records, non-automated
dose information collection processes, and data protection and patient
privacy issues. Similarly, the current health care delivery system and cancer
registration system precludes a longitudinal study of dose for large popula-
tions in the United States that are exposed to ionizing radiation from medi-
cal diagnostic procedures.
In view of the above mentioned barriers, the key points and sugges-
tions on some possible next steps discussed by the panelists and workshop
participants were to:
• Continue to track and monitor overall trends and patterns of use

of medical imaging.

• Continue ACR dose index registry efforts and expand them to

include additional modalities (e.g., nuclear medicine, computed
radiography and digital radiography, interventional radiology) and
other sites, particularly outpatient facilities.
• Within each institution, routinely report dose metrics performance
with benchmarks.
• Create or use existing committees within institutions and outside
facilities to ensure that imaging protocols are being followed; create
routine reports for this purpose for technologists and radiologists.
• Work with industry and information technology vendors to incor-
porate dose metrics directly into medical records; ensure that dose
metric information is attached to images.
• Encourage the performance of national-level clinical trials that
quantify the benefits of imaging exams.
• Implement informed decision support systems at all stages of
patient care to optimize procedure use and ensure that only appro-
priate examinations are performed.
• Have institutions and ambulatory settings implement or continue
to implement comprehensive safety programs and educational tools
promoting awareness of radiation doses.
The above mentioned points do not represent a consensus of the

workshop participants or the authoring committee. Instead, they represent
some of the important points made by individual participants during the
workshop.

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Appendixes A
Project Statement of Task
A workshop will be organized to examine the feasibility and implica-

tions of tracking radiation doses to the U.S. population from medical diag-
nostic procedures. This workshop will examine:
• The quality and availability of data on patient doses resulting from

diagnostic procedures, including individual dose estimates, dose
uncertainties, and availability of patient dose information from
different types of health care facilities.
• Possible mechanisms and supporting technologies for collecting
and evaluating data on patient doses from diagnostic procedures.
• Potential obstacles for tracking patient radiation doses from diag-
nostic procedures and strategies for addressing them. Such impedi-
ments may include, for example, technical, logistical, regulatory, as
well as achieving patient/physician acceptance.
• Prospective uses of radiation dose information obtained from track-
ing medical diagnostic exposures and the potential consequences of
collecting such data.
A report will be prepared that summarizes the workshop presentations

and discussions.
59


Appendix B
Workshop Agenda
Chair: Barbara McNeil, Harvard Medical School
Vice-Chair: Hedvig Hricak, Memorial Sloan Kettering
Thursday , December 8, 2011

8:30 am Welcome and Introduction
Hedvig Hricak—Memorial Sloan Kettering
8:40 am Why and how to track radiation exposure

Donald Miller—U.S. Food and Drug Administration
Charles Miller—Centers for Disease Control and Prevention
Session 1: National and International Efforts in Volume and Dose

Tracking
Moderator: Fred Mettler—University of New Mexico

9:05 am Introduction to Session 1
Fred Mettler—University of New Mexico
9:15 am 1.1: IAEA activities and overview of global activities

Madan Rehani—International Atomic Energy Agency
9:35 am 1.2: Radiation exposures in medical imaging: FDA’s past

and present efforts
David Spelic—U.S. Food and Drug Administration
61

62 APPENDIX B
10:00 am 1.3: Strategies to minimize patient radiation exposure in the

Veterans Health Administration
Charles Anderson—Veterans Health Administration

10:25 am BREAK

10:45 am 1.4: American College of Radiology (ACR) Dose Index
Registry
Richard Morin—Mayo Clinic
11:10 am Discussion Session 1
Session 2: Appropriate Radiation Dose Metrics and Estimation

Techniques
Moderator: Richard Morin—Mayo Clinic

Richard Morin—Mayo Clinic
11:35 am 2.1: Radiation metrics in medical imaging

Walter Huda—Medical University South Carolina
11:50 pm 2.2: Patient Dose: What to record and track and the role of
organ dose
Michael McNitt-Gray—University of California, Los
Angeles
12:10 pm 2.3: Protocol optimization and dose variability for

CT-guided interventions
Raymond Thornton—Memorial Sloan Kettering

12:30 pm LUNCH BREAK

1:30 pm Panel: Physician’s perspective on what to report
Michael Lauer—National Heart, Lung, and Blood Institute
James Brink—Yale University
2:10 pm Discussion Session 2


APPENDIX B 63
Session 3: Volume—Methods for Collecting and Evaluating Data

Moderator: Walter Huda—Medical University South
Carolina

2:40 pm Introduction to Session 3
Walter Huda—Medical University South Carolina
2:45 pm 3.1: Measuring population utilization of medical diagnostic

procedures: data sources and challenges
Mythreyi Bhargavan Chatfield—American College of
Radiology
3:05 pm 3.2: Automated electronic medical record (EMR) dose

history extraction and monitoring
Aaron Sodickson—Brigham and Women’s Hospital

3:30 pm BREAK

3:50 pm 3.3: Procedure volume trends in the United States and
perspectives on large-scale data collection
Ashok Shah and Gail Prochaska—IMV Ltd
4:15 pm Panel: Manufacturers’ perspective on what to report

Richard Mather—Toshiba Medical Research Institute
Kenneth Denison—GE Healthcare,
Christian Eusemann—Siemens Healthcare,
Dominic Siewko—Philips Healthcare
4:55 pm Discussion Session 3
5:20 pm Closing Remarks and Adjournment

Friday , December 9, 2011

8:15 am Welcome, opening remarks
Barbara McNeil, Harvard Medical School


64 APPENDIX B
Session 4: Risk—What We Know and What We Need to Know

Moderator: Amy Berrington de González—National Cancer Institute

Amy Berrington de González—National Cancer Institute
8:30 am 4.1: Understanding radiation-induced cancer risks at

radiological doses
David Brenner—Columbia University
8:50 am 4.2: Non-cancer effects at radiological doses

Kiyohico Mabuchi—National Cancer Institute
9:10 am 4.3: Patient’s perspective

Gwen Darien—Samuel Waxman Cancer Research
Foundation
9:25 am Discussion Session 4
9:45 am Lessons learned from pediatrics

Donald Frush—Duke University
10:10 am Panel: Next Steps

Fred Mettler—University of New Mexico
Barbara McNeil—Harvard Medical School
David Brenner—Columbia University
Donald Frush—Duke University
10:25 am Discussion
11:25 am Closing Remarks and Adjournment

Barbara McNeil - Harvard Medical School

Appendix C
Committee and Staff

Biographical Sketches
Chair
BARBARA J. MCNEIL
Barbara J. McNeil, M.D., Ph.D. (IOM) is the Ridley Watts Professor and
was the founding head of the Department of Health Care Policy at Harvard
Medical School (HMS) in 1988. She was one of the first women professors
in the quad at HMS. She is also a professor of radiology at Harvard Medi-
cal School and at Brigham and Women’s Hospital (BWH). She continues to
practice nuclear medicine one day a week at BWH. She was interim dean
of Harvard Medical School during summer 2007. Dr. McNeil received her
A.B. degree from Emmanuel College, her M.D. degree from Harvard Medi-
cal School, and her Ph.D. degree from Harvard University. She is a member
of the Institute of Medicine of the National Academy of Sciences and the
American Academy of Arts and Sciences. Dr. McNeil is also a member of
the Blue Cross Technology Evaluation Commission; she formerly chaired
the Medicare Evidence Development Coverage Advisory Committee (Med-
CAC), and she is now a member of that committee. She currently chairs the
Science Board of the FDA. She serves as an advisor for several other federal
and private organizations. Dr. McNeil formerly served on the Publications
Committee of the New England Journal of Medicine as well as on the
Prospective Payment Assessment Commission. Dr. McNeil’s original career
involved research in decision analysis and cost-effective analysis. More
recently, her work has focused on quality of care and technology assess-
65

66 APPENDIX C
ment. Her research involves relationships with payers, providers, and the
federal government. Her largest ongoing study compares quality of care in
the VA system with that in the private setting for patients with cancer. For
several years she coordinated several large studies comparing the value of
alternative imaging modalities for patients with cancer.
Vice-Chair
HEDVIG HRICAK
Hedvig Hricak, M.D., Ph.D. (IOM) is chairman of the Department of Radi-

ology at Memorial Sloan-Kettering Cancer Center. She holds a senior posi-
tion within the Program of Molecular and Pharmacology Therapeutics at
the Sloan-Kettering Institute. She is a professor at Gerstner Sloan-Kettering
Graduate School of Biomedical Sciences and is a professor of radiology at
the Weill Medical College of Cornell University. She earned her M.D. degree
from the University of Zagreb and her Dr. Med. Sc. from the Karolinska
Institute. In 2005 she was awarded an honorary doctorate in medicine
(Dr.h.c.) from Ludwig Maximilian University in Munich, Germany. She
has helped develop applications in ultrasound, magnetic resonance (MR),
and CT for gynecological cancers as well as MR and MR spectroscopy for
prostate cancer. She continues to investigate diagnostic methods for cancer
detection, staging, and management and is involved in developing clinical
approaches for molecular imaging of cancer. She was elected to the Institute
of Medicine (IOM) in 2002. In recognition of her career accomplishments,
she has received the Marie Curie Award of the American Association of
Women Radiologists (2003), the gold medals of the International Society
for Magnetic Resonance in Medicine (2003) and the Association of Univer-
sity Radiologists, the Béclère medal of the International Society of Radiol-
ogy (2007), the Morocco Medal of Merit (2008), and the Katarina Zrinska
Croatian presidential award (2009).
Members
AMY BERRINGTON DE GONZÁLEZ
Amy Berrington de González, received a Ph.D. in cancer epidemiology from

the University of Oxford in 2001. She conducted post-doctoral research in
Oxford before joining the faculty there. In 2005 she became an assistant
professor in epidemiology and biostatistics at the Johns Hopkins Bloomberg
School of Public Health. She joined the Radiation Epidemiology Branch as
an investigator in 2008. She is currently serving on the UK Health Protec-
tion Agency’s Advisory Group on Ionising Radiation, and she has previ-

APPENDIX C 67
ously served on the UK Breast Screening Programme’s Advisory Group and

as a special advisor to the World Health Organization (WHO) on radiation
effects and health. Dr. Berrington has conducted a series of risk projection
studies to estimate the potential cancer risks from both diagnostic and
screening examinations, including cardiac stress tests, CT colonography,
and lung CT screening. To perform these studies, she and other collabora-
tors developed the NCI Radiation Risk Assessment Tool (RadRAT), which
is interactive computer software that uses state-of-the-art risk projection
models to estimate lifetime cancer risks and incorporates Monte Carlo
simulation methods to assess the impact of uncertainties in the assumptions
and data. She recently became the NCI principal investigator for the UK
Pediatric CT scans study, which is a retrospective cohort study of 250,000
children who had one or more CT scans as children or adolescents.
WALTER HUDA
Walter Huda, Ph.D., trained in England (B.A., physics at Oxford Univer-

sity; Ph.D., medical physics at the Hammersmith Hospital/University of
London) and worked from 1976 to 1981 at Amersham International, a
commercial company specializing in radioactive products. He has worked
as a diagnostic medical physicist at the Manitoba Cancer Treatment and
Research Foundation in Winnipeg, Canada (1982-1990), University of
Florida in Gainesville, Florida (1990-1997), and SUNY Upstate Medical
University in Syracuse, New York (1997-2007). He is currently professor of
radiology at the Medical University of South Carolina. Dr. Huda is actively
involved in the clinical use of medical imaging equipment, particularly
maximizing the diagnostic information while keeping patient doses as low
as reasonably achievable (ALARA). Dr. Huda’s primary research activities
relate to medical imaging and radiation dosimetry. Since the early 1980s,
Dr Huda pioneered the use of the effective dose to quantify the radiation
dose received by patients undergoing radiological examinations that use
ionizing radiation. Dr. Huda has also developed quantitative methods for
quantifying imaging performance. Dr. Huda is currently actively involved in
the use of Alternative Forced Choice (AFC) methods for measuring imaging
performance in CT and the investigation of the tradeoff between dose and
image quality in this imaging modality. Dr. Huda has published more than
200 scientific papers and has been awarded 24 research grants with a total
value approaching $4 million.
FRED A. METTLER, JR.
Fred A. Mettler, Jr., M.D., M.P.H., is professor emeritus and former chair of
the Department of Radiology at the University of New Mexico, School of

68 APPENDIX C
Medicine. He is currently in radiology and nuclear medicine service at the

New Mexico VA Medical Center. He earned an M.D. degree from Thomas
Jefferson University and an M.P.H. from Harvard University, and he com-
pleted his residency in radiology and nuclear medicine at Massachusetts
General Hospital. Dr. Mettler has authored more than 300 scientific pub-
lications, including 18 books, and holds 4 patents. He is currently the U.S.
representative to the United Nations Scientific Committee on the Effects of
Atomic Radiation, an emeritus commissioner of the International Commis-
sion on Radiation Protection, and a member of the National Council on
Radiation Protection.
RICHARD L. MORIN
Richard L. Morin, Ph.D., received his Ph.D. in radiological sciences from

the University of Oklahoma in 1980. His dissertation concerned the use
of Monte Carlo simulation and pattern recognition for artifact removal in
CYT. He is a fellow of the American College of Radiology and a diplomate
of the American Board of Radiology in Diagnostic Radiological Physics
and Nuclear Medical Physics. Dr. Morin is the secretary-treasurer and
trustee of the American Board of Radiology and the chair of the Board
of Trustees of the American Board of Imaging Informatics. Dr. Morin is a
former president and chairman of the Board of the American Association of
Physicist in Medicine and the Board of Chancellors of the American College
of Radiology. Dr. Morin has presented numerous lectures at international
and scientific meetings and has published more than 80 research papers. His
current research interests include computer applications in the radiological
sciences with emphasis on electronic medical imaging and CT physics with
emphasis on CT cardiovascular imaging.
Staff
OURANIA (RANIA) KOSTI
Rania Kosti, Ph.D., joined the staff of the Nuclear and Radiation Studies
Board in January 2011. Prior to her current appointment, Dr. Kosti was
a post-doctoral fellow at the Lombardi Comprehensive Cancer Center at
Georgetown University Hospital in Washington, D.C., where she conducted
research on biomarker development for early cancer detection using case-
control epidemiologic study designs. She focused primarily on prostate,
breast, and liver cancers and trying to identify those individuals who are at
high risk of developing malignancies. She contributed on hypotheses gen-
eration, study design, data analysis, and management of clinical databases
and biospecimen repositories. Dr. Kosti also trained at the National Cancer

APPENDIX C 69
Institute (NCI) (2005-2007) in the Cancer and Developmental Biology

Laboratory; during the same period she volunteered in NCI’s Division of
Cancer Epidemiology and Genetics. Dr. Kosti received a B.Sc. in biochem-
istry from the University of Surrey, United Kingdom, an M.Sc. in molecular
medicine from the University College London, and a Ph.D. in molecular
endocrinology from St. Bartholomew’s Hospital in London.


Appendix D
Workshop Speakers
Biographical Sketches
Charles M. Anderson, M. D., Ph.D., is the chief consultant for diagnostic

services in the Veterans Health Administration. He prepares policy and
coordinates national diagnostic initiatives. Dr. Anderson received a Ph.D. in
molecular biophysics and biochemistry from Yale University, an M.D. from
Stanford University, and residency training in diagnostic radiology from
University of California, San Francisco (UCSF). Dr. Anderson was a clinical
professor of radiology at UCSF until 2008. He is a practicing radiologist at
Durham North Carolina VA Medical Center.
David J. Brenner, Ph.D., is the director of the Center for Radiological

Research at Columbia University, as well as the director of the Radiologi-
cal Research Accelerator Facility and principal investigator of the Center
for High-Throughput Minimally-lnvasive Radiation Biodosimetry, which
focuses on developing mechanistic models for the effects of ionizing radia-
tion on living systems, both at the chromosomal and animal levels. He
divides his research time between the effects of high doses of ionizing radia-
tion (relating to radiation therapy) and the effects of low doses of radiation
(relating to medical, environmental, and occupational exposures).
James A. Brink, M.D., is professor and chair of the Department of Diag-

nostic Radiology at Yale University School of Medicine. He earned a B.S.
degree in electrical engineering at Purdue University and an M.D. at Indi-
ana University before completing his residency and fellowship at Mas-
sachusetts General Hospital. While he has broad experience in medical
71

72 APPENDIX D
imaging, including utilization and management of imaging resources, he

has particular interest and expertise in issues related to the monitoring and
control of medical radiation exposure, which can be compounded if testing
is superfluous, unnecessary, or redundant.
Mythreyi Bhargavan Chatfield, Ph.D., is the director of data registries at

the American College of Radiology (ACR) in Reston, Virginia. In this posi-
tion, she manages national registries focused on improving practice quality
in radiology. Dr. Chatfield’s current areas of focus include practice quality
in radiology, performance metrics, and radiation doses from medical pro-
cedures. She is a council member of the National Council on Radiation
Protection and Measurements (NCRP), an organization chartered by the
U.S. Congress to develop expert consensus on issues related to radiation
protection using independent scientific analysis. She has a Ph.D. in econom-
ics from Rutgers University.
Gwen Darien is a cancer survivor who brings a wealth of personal and

professional experiences to her position as executive director of the Samuel
Waxman Cancer Research Foundation. She was the founding director of the
American Association for Cancer Research’s (AACR) department of Survi-
vor and Patient Advocacy. Ms. Darien was editor-in-chief of CR magazine
and director of the American Association for Cancer Research Survivor
and Patient Advocacy Program. She was previously the editor-in-chief of
MAMM. Ms. Darien is chair of the National Cancer Institute (NCI) Direc-
tor’s Consumer Liaison Group and is a member of the Board of Directors
of Education Network to Advance Cancer Clinical Trials. She has served
as member of the Secretary’s Advisory Committee on Health, Genetics
and Society and the faculties of the AACR/American Society of Clinical
Oncology Methods in Clinical Cancer Research Workshop, Accelerating
Anti-Cancer Agent Development and on the advisory board of the Health
Advocacy Program at Sarah Lawrence College.
Kenneth Denison, Ph.D., is responsible for leading all dose-related activities

for General Electric (GE) Healthcare’s CT business including lower-dose
technologies, dose monitoring and tracking systems, new services and solu-
tions, education and training, and coordination of industry, public, and
government relations activities relative to the dose issue. His focus is on
helping GE Healthcare customers worldwide lower the radiation doses used
in their practices. He holds seven patents, all in the design of MRI systems.
He received both his B.S. and Ph.D. degrees in chemical engineering from
the University of Kentucky in Lexington.

APPENDIX D 73
Donald P. Frush, M.D., F.A.C.R., F.A.A.P., is professor of radiology and

pediatrics, chief of pediatric radiology and vice-chair for safety and quality,
Department of Radiology, Duke Medical Center. He is also a councilor for
NCRP, and he is on the boards of both the ACR and American Board of
Radiology (ABR). He is a fellow in the Society of Computed Tomography
and Magnetic Resonances, a steering committee member of the Alliance for
Radiation Safety in Pediatric Imaging (Image Gently Campaign), and works
with the International Atomic Energy Agency (IAEA) Smartcard Radiation
Tracking Project. Research includes CT image quality, dose assessment, and
dose reduction in children.
Katharine Grant, Ph.D., is currently a CT staff scientist for Siemens Medi-

cal Solutions USA and serves as a collaboration manager/scientific liaison
between luminary customers and Siemens’ physicists. Dr. Grant joined
Siemens in 2009 after being awarded a post-doctoral fellowship from the
Director of Central/National Intelligence and working as a research associ-
ate within the Special Purpose Processor Development Group (SPPDG) at
the Mayo Clinic. She received her B.S. in physics from Miami University in
2000 and her Ph.D. in biomedical engineering from the Mayo Clinic Col-
lege of Medicine in 2005. Dr. Grant is also an adjunct assistant professor
of radiology and physiology at the Mayo Clinic.
Michael S. Lauer, M.D., has served as director of the Division of Cardio-

vascular Sciences at the National Heart, Lung, and Blood Institute. Dr.
Lauer is a cardiologist and clinical epidemiologist noted for his work on
diagnostic testing, clinical manifestations of autonomic nervous system
dysfunction, and clinical comparative effectiveness. Dr. Lauer received a
B.S. in biology from the Rensselaer Polytechnic Institute and an M.D. from
Albany Medical College; he also participated in the Program in Clinical
Effectiveness at the Harvard School of Public. He received post-graduate
training at Massachusetts General Hospital, Boston’s Beth Israel Hospital,
and the Framingham Heart Study. Prior to joining the National Institute of
Health (NIH), Dr. Lauer was a professor of medicine, epidemiology, and
biostatistics at the Cleveland Clinic Lerner College of Medicine of Case
Western Reserve University.
Kiyohiko Mabuchi, M.D., M.P.H., deputy chief, Radiation Epidemiology

Branch, head of the Chernobyl Research Unit, and senior scientist, in the
Division of Cancer Epidemiology and Genetics at the NCI, currently directs
epidemiological studies of thyroid disease and leukemia risks following
the Chernobyl nuclear reactor accident and also is engaged in continu-
ing follow-up studies of cancer in the Japanese atomic-bombing survi-

74 APPENDIX D
vors, collaborating with the Radiation Effects Research Foundation. He

received an M.D. from Osaka University Medical School and an M.P.H./
Dr.P.H. from the John Hopkins University School of Hygiene and Public
Health. He has been a member of several international radiation commit-
tees, including the International Commission of Radiological Protection
(ICRP), the United Nations Scientific Committee on the Effects of Atomic
Radiation (UNSCEAR), and the UK National Radiological Protection
Board’s Advisory.
Richard Mather, Ph.D., has worked in medical imaging for more than 17
years including formal training at University of California, Los Angeles, in
the biomedical physics graduate program. He received his Ph.D. in 1997. At
Toshiba, Dr. Mather has been integrally involved in research projects that
validate Toshiba’s CT products in the medical community.
Michael McNitt-Gray, Ph.D., is professor of radiological sciences in the

David Geffen School of Medicine at UCLA. He is also the director of
the biomedical physics graduate program there. He received his Ph.D. in
biomedical physics from UCLA in 1993; his MSEE from Carnegie Mellon
University in 1980, and his BSEE from Washington University in St. Louis
in 1979. He currently serves on the International Commission on Radiation
Units (ICRU) Committee on Image Quality and Patient Dose in Computed
Tomography, and he chairs both the ACR CT Accreditation Program Phys-
ics subcommittee and the American Association of Physicists in Medicine
CT Subcommittee. His current research interests include investigations into
x-ray computed tomography with specific research into the physics of CT
image acquisition including estimating radiation dose and assessing image
quality.
Charles W. Miller, Ph.D., joined the Centers for Disease Control and Pre-
vention in January 1992. He is currently chief of the Radiation Studies
Branch, Division of Environmental Hazards and Health Effects, National
Center for Environmental Health. In this position, he develops goals and
objectives that integrate organization and environmental public health pro-
grams on the potential effects of exposure to radiation and radiation-related
health research, including providing leadership for the agency’s radiological
emergency response and consequence management efforts. Dr. Miller is a
member of the NCRP, and he is a fellow of the Health Physics Society. Dr.
Miller holds a B.S. in physics/math from Ball State University, a M.S. in
meteorology from the University of Michigan, and a Ph.D. in bionucleonics
(health physics) from Purdue University.

APPENDIX D 75
Donald L. Miller, M.D., is acting chief, Diagnostic Devices Branch, Divi-

sion of Mammography Quality and Radiation Programs in the Center for
Devices and Radiological Health of the FDA. He received a B.A. in molecu-
lar biophysics and biochemistry from Yale University in 1972 and an M.D.
from the New York University School of Medicine in 1976. He is a fellow
of the Society of Interventional Radiology and the ACR, a consultant to
the IAEA, a member of Council of the NCRP, and a member of Committee
3 of the ICRP.
Gail Prochaska has been with IMV since 1987 during which time she has
worked with vendors and professional societies to develop and use market
data and census databases to capture procedures, consumables, and equip-
ment for multiple diagnostic imaging modalities and radiation therapy.
Prior to IMV, Ms. Prochaska held marketing, sales, and management posi-
tions at Amersham (now GE). She has a B.S. in biology from the University
of Illinois at Champaign-Urbana.
Madan M. Rehani, Ph.D., has been working at IAEA, Vienna, Austria for
the past 10 years and manages radiation protection of patients projects
in more than 60 countries. He is responsible for initiating and directing
patient radiation exposure tracking project at IAEA. Prior to joining IAEA
he was professor and head at the Medical Physics Unit at the All India
Institute of Medical Sciences, New Delhi. He has chaired three task groups
of the ICRP, which led to Annals of ICRP.
Ashok Shah, M.B.A., is the general manager of IMV Ltd. and has more
than 30 years’ experience in the health care and scientific products markets.
Prior to IMV, Mr. Shah held positions with IMS Health, Fisher Scientific,
and Becton Dickinson & Co. He has an M.B.A. from McGill University,
Montreal, and a B.S. in microbiology.
Dominic Siewko is the radiation safety officer for Philips Healthcare and
has been in this role for two years. He previously worked for GE Healthcare
for the past 10 years in a health physicist position supporting radiopharma-
ceutical manufacturing. He currently manages the radiation/product safety
and radiation regulatory program for all nuclear and x-ray imaging modali-
ties globally for Philips and is based out of Andover, Massachusetts. He is
active in the Medical Imaging and Technology Alliance, Society of Nuclear
Medicine, and Health Physics Society, and is certified by the American
Board of Health Physics.

76 APPENDIX D
Aaron Sodickson, M.D., is the section head of emergency radiology at

Brigham and Women’s Hospital, medical director of CT for the Brigham
Radiology Network, and assistant professor of radiology at Harvard Medi-
cal School. His primary research focus is on informatics methods to auto-
matically extract radiation exposure data on a large scale from existing
sources in the electronic medical record, and use of the resultant data-
bases for quality control and patient safety applications. Related research
and clinical quality improvement efforts involve CT technology assessment
and imaging optimization to achieve high-quality imaging at low radiation
dose.
David C. Spelic, Ph.D., is a physicist with the FDA’s Center for Devices and
Radiological Health. He joined the agency in 1994, and he is involved in
public health activities regarding medical x-ray based imaging. He also has
primary responsibility for the Nationwide Evaluation of X-ray Trends sur-
vey program, a cooperative effort with the Conference of Radiation Control
Program Directors and state-level radiation control offices to character-
ize patient radiation doses from selected medical x-ray examinations per-
formed in the United States.
Raymond H. Thornton, M.D., trained as a concert pianist at the Juilliard

School before attending medical school at the University of Pittsburgh.
He completed residency in diagnostic radiology and fellowship training
in vascular interventional radiology at the University of California at San
Francisco. At Memorial Sloan-Kettering Cancer Center, he serves as vice-
chair of Radiology for Quality, Safety and Performance Improvement and
Training Program Director for the Interventional Radiology fellowship, in
addition to maintaining a busy clinical practice in interventional radiology.

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Tracking Radiation Exposure from Medical Diagnostic

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Copyright © National Academy of Sciences. All rights reserved.

Committee on Tracking Radiation Doses from

Nuclear and Radiation Studies Board

Division on Earth and Life Studies

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This study was supported by the following government agencies:

Contract No. 200-2005-13434, TO 26 Centers for Disease Control and Prevention

Any opinions, findings, conclusions, or recommendations expressed in this publica-

International Standard Book Number-13: 978-0-309-25766-4

Copyright 2012 by the National Academy of Sciences. All rights reserved.

Printed in the United States of America

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The National Academy of Sciences is a private, nonprofit, self-perpetuating society

The Institute of Medicine was established in 1970 by the National Academy of

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COMMITTEE ON TRACKING RADIATION DOSES

BARBARA J. MCNEIL (Chair), Harvard Medical School, Boston,

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NUCLEAR AND RADIATION STUDIES BOARD

JAY DAVIS (Chair), Hertz Foundation, Livermore, California

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• David Brenner, Columbia University

Although the reviewers listed above provided many constructive com-

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independent examination of this report was carried out in accordance with

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2 TRACKING RADIATION EXPOSURE

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4 TRACKING RADIATION EXPOSURE

The report is organized into three chapters:

• Chapter 1 (this chapter) provides an introduction to the workshop.

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2.1 TRENDS IN DIAGNOSTIC IMAGING

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6 TRACKING RADIATION EXPOSURE

imaging occurs in hospitals and imaging centers, as well as free-standing

1 The NCRP is a congressionally chartered organization that formulates and disseminates

information and research data related to radiation exposure and protection.

relative to whole-body exposures to facilitate radiation protection activities (ICRP, 1991).

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2.2 POTENTIAL HEALTH RISKS FROM DIAGNOSTIC IMAGING

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8 TRACKING RADIATION EXPOSURE

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(Kuehn, 2010). These events have heightened the awareness of radiation

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10 TRACKING RADIATION EXPOSURE

2.3 APPROPRIATENESS OF DIAGNOSTIC IMAGING

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medical community. In a retrospective study of 200 trauma patients, for