The essential physics of medical imaging

1044 Pages·2012·47.454 MB·English

by  Jerrold T. Bushberg

The Essential
Physics of
Medical Imaging
T H I R D
E D I T I O N
JERROLD T. BUSHBERG, PhD
Clinical Professor of Radiology and Radiation Oncology
University of California, Davis
Sacramento, California
J. ANTHONY SEIBERT, PhD
Professor of Radiology
University of California, Davis
Sacramento, California
EDWIN M. LEIDHOLDT JR, PhD
Clinical Associate Professor of Radiology
University of California, Davis
Sacramento, California
JOHN M. BOONE, PhD
Professor of Radiology and Biomedical Engineering
University of California, Davis
Sacramento, California
Executive Editor: Charles W. Mitchell
Product Manager: Ryan Shaw
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2nd edition © 2002 by LIPPINCOTT WILLIAMS & WILKINS
1st edition © 1994 by LIPPINCOTT WILLIAMS & WILKINS
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Library of Congress Cataloging-in-Publication Data
Bushberg, Jerrold T.
The essential physics of medical imaging / Jerrold T. Bushberg. — 3rd ed.
p. ; cm.
Includes bibliographical references and index.
ISBN 978-0-7817-8057-5
1. Diagnostic imaging. 2. Medical physics. I. Title.
[DNLM: 1. Diagnostic Imaging—methods. WN 200]
RC78.7.D53E87 2011
616.07'54—dc22
2011004310
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consequences from application of the information in this book and make no warranty, expressed or implied,
with respect to the currency, completeness, or accuracy of the contents of the publication. Application of the
information in a particular situation remains the professional responsibility of the practitioner.
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set forth in this text are in accordance with current recommendations and practice at the time of publication.
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10 9 8 7 6 5 4 3 2 1
First and foremost, I offer my most heartfelt love, appreciation and apology to my wife Lori and our children,
Alex and Jennifer, who endured my many absences to focus on completing this text with “almost” infinite
patience (especially during the last 4 months, when I was typically gone before they woke and got home long
after they had gone to sleep). I look forward to spending much more time with my family and even to starting
to make a dent in the list of “chores” my wife has been amassing in my absence. I have also had the good fortune
to be supported by my extended family and my Oakshore neighbors who never missed an opportunity to offer
an encouraging word after my response to their question “Is the book done yet?”
Second, I would like to express my profound gratitude to my coauthors, colleagues, and friends Tony, Ed,
and John for their herculean efforts to bring this 3rd edition into existence. Not only would this text not exist
without them, but the synergy of their combined skills, expertise, and insights was an invaluable resource at
every stage of development of this edition. We all have many more professional obligations now than during the
writing of the previous editions. The willingness and ability of my coauthors to add another substantial com-
mitment of time to their already compressed professional lives were truly remarkable and greatly appreciated.
While all of my staff and colleagues have been very helpful and supportive during this effort (for which I
am very grateful), two individuals deserve special recognition. Linda Kroger’s willingness to proof read several
chapters for clarity along with the countless other ways she provided her support and assistance during this
effort with her typical intelligent efficiency was invaluable and greatly appreciated. Lorraine Smith has been the
coordinator of our annual radiology resident physics review course for as long as I can remember. This course
would not be possible without her considerable contribution to its success. Lorraine is one of the most helpful,
resourceful, patient, and pleasant individuals I have ever had the pleasure to work with. Her invaluable assistance
with this course, from which this book was developed, is gratefully acknowledged and deeply appreciated.
I would also like to thank our publisher Lippincott Williams and Wilkins, Charley Mitchell, Lisa
McAllister, and in particular Ryan Shaw (our editor) for the opportunity to develop the 3rd edition. Your
patience, support, and firm “encouragement” to complete this effort are truly appreciated.
I dedicate this edition to my parents. My mother, Annette Lorraine Bushberg (1929–1981), had a gift for
bringing out the best in me. She cheered my successes, reassured me after my failures, and was an unwavering
source of love and support. My father, Norman Talmadge Bushberg, brightens everyone’s world with his effort-
less wit and sense of humor. In addition to his ever present love and encouragement, which have meant more to
me than I can find the words to fully express, he continues to inspire me with his belief in each person’s ability
and responsibility to make a unique contribution. To that end, and at the age of 83, he recently published his
first literary contribution, a children’s story entitled “Once Upon a Time in Kansas.” It is slightly lighter reading
than our text and I highly recommend it. However, if getting your child to fall asleep is the problem, then any
chapter in our book should do the trick.
J.T.B.
Thanks, TSPOON, for your perseverance, patience, and understanding in regard to your often AWOL dad
during these past several years—it’s very gratifying to see you prosper in college, and maybe someday you
will be involved in writing a book as well! And to you, Julie Rainwater, for adding more than you know to my
well-being and happiness.
J.A.S.
To my family, especially my parents and my grandmother Mrs. Pearl Ellett Crowgey, and my teachers, especially
my high school mathematics teacher Mrs. Neola Waller, and Drs. James L. Kelly, Roger Rydin, W. Reed Johnson,
and Denny D. Watson of the University of Virginia. To two nuclear medicine physicists, Drs. Mark W. Groch
and L. Stephen Graham, who contributed to earlier editions of this book, but did not live to see this edition.
And to Jacalyn Killeen, who has shown considerable patience during the last year.
E.M.L.
Susan Fris Boone, my wife, makes life on this planet possible and her companionship and support have made my
contribution to this book possible. Emily and Julian, children extraordinaire and both wild travelers of the world,
have grown up using earlier editions of this book as paperweights, lampstands, and coasters. I appreciate the per-
spective. Marion (Mom) and Jerry (Dad) passed in the last few years, but the support and love they bestowed on
me over their long lives will never be forgotten. Sister Patt demonstrated infinite compassion while nurturing our
parents during their final years and is an angel for all but the wings. Brother Bob is a constant reminder of dedica-
tion to patient care, and I hope that someday he and I will both win our long-standing bet. Friends Steve and Susan
have elevated the fun in life. My recent students, Nathan, Clare, Shonket, Orlando, Lin, Sarah, Nicolas, Anita, and
Peymon have helped keep the flag of research flying in the laboratory, and I am especially in debt to Dr. Kai Yang
and Mr. George Burkett who have helped hold it all together during my too frequent travel. There are many more
to thank, but not enough ink. This book was first published in 1994, and over the many years since, I have had
the privilege of sharing the cover credits with my coauthors and good friends Tony, Jerry, and Ed. This has been a
wild ride and it would have been far less interesting if not shared with these tres amigos.
J.M.B.

Preface to the Third Edition
The first edition of this text was written in 1993, and the second edition followed in
2002. This third edition, coming almost 10 years after the second edition, reflects the
considerable changes that have occurred in medical imaging over the past decade.
While the “digitization” of medical images outside of nuclear medicine began in ear-
nest between the publication of the first and second editions, the transformation of
medical imaging to an all-digital environment is largely complete at the time of this
writing. Recognizing this, we have substantially reduced the treatment of analog mo-
dalities in this edition, including only a short discussion on screen-film radiography
and mammography, for example. Because the picture archiving and communication
system (PACS) is now a concrete reality for virtually all radiological image interpre-
tation, and because of the increasing integration between the radiology information
systems (RISs), the PACS, and the electronic medical record (EMR), the informatics
section has been expanded considerably.
There is more to know now than 10 years ago, so we reduced some of the detail
that existed in previous editions that may be considered nonessential today. Detailed
discussions of x-ray tube heating and cooling charts, three-phase x-ray generator
circuits, and CT generations have been shortened or eliminated.
The cumulative radiation dose to the population of the United States from medi-
cal imaging has increased about sixfold since 1980, and the use of unacceptably
large radiation doses for imaging patients, including children, has been reported. In
recent years, radiation dose from medical imaging and radiation therapy has become
the focus of much media attention, with a number of radiologists, radiobiologists,
and medical physicists testifying before the FDA and the U.S. Congress regarding the
use of radiation in imaging and radiation therapy. The media attention has given rise
to heightened interest of patients and regulatory agencies in the topics of reporting
and optimizing radiation dose as well as limiting its potentially harmful biological
effects. In this edition, we have added an additional chapter devoted to the topic of
x-ray dose and substantially expanded the chapters on radiation biology and radia-
tion protection. The current International Commission on Radiological Protection
system of estimating the potential detriment (harm) to an irradiated population;
the calculation of effective dose and its appropriate use; as well as the most recent
National Academy of Sciences Biological Effects of Ionizing Radiation (BEIR VII) report
recommended approach of computing radiation risk to a specific individual are dis-
cussed in several chapters.
Our publisher has indicated that the second edition was used by increasing num-
bers of graduate students in medical imaging programs. While the target audience of
this text is still radiologists-in-training, we have added appendices and other sections
with more mathematical rigor than in past editions to increase relevance to scientists-
in-training. The goal of providing physicians a text that describes image science and
the radiological modalities in plain English remains, but this third edition contains
an appendix on Fourier transforms and convolution, and Chapter 4 covers basic
image science with some optional mathematics for graduate student readers and for
radiologists with calculus-based undergraduate degrees.
v
vi Preface to the Third Edition
A number of new technologies that were research projects 10 years ago have
entered clinical use, and this edition discusses the more important of these: tomos-
ynthesis in mammography, cone beam CT, changes in mammography anode com-
position, the exposure index in radiography, flat panel fluoroscopy, rotational CT
on fluoroscopy systems, iterative reconstruction in CT, and dual modality imaging
systems such as PET/CT and SPECT/CT. Some new technologies offer the possibility
of substantially reducing the radiation dose per imaging procedure.
All of the authors of this book are involved in some way or another with national
or international advisory organizations, and we have added some perspectives from
published documents from the American Association of Physicists in Medicine, the
National Council on Radiation Protection and Measurements, the International Com-
mission on Radiation Units and Measurement, and others.
Lastly, with the third edition we transition to color figures, tables, text headings,
and photographs. Most of the figures are newly designed; some are colorized versions
of figures from previous editions of the text. This edition has been completely rewrit-
ten and a small percentage of the text remains as it was in previous editions. We hope
that our efforts on this third edition bring this text to a completely up-to-date status
and that we have captured the most important developments in the field of radiology
so that the text remains current for several years to come.
Foreword
Dr. Bushberg and his coauthors have kept the title The Essential Physics of Medical
Imaging for this third edition. While the first edition in 1994 contained the “ essentials,”
by the time the second edition appeared in 2002, the book had expanded signifi-
cantly and included not only physics but also a more in depth discussion of radiation
protection, dosimetry, and radiation biology. The second edition became the “go to”
reference book for medical imaging physics. While not light weekend reading, the
book is probably the only one in the field that you will need on your shelf. Residents
will be happy to know that the third edition contains the topics recommended by the
AAPM and thus likely to appear on future examinations.
Although there are shorter books for board review, those typically are in outline
form and may not be sufficient for the necessary understanding of the topics. This
book is the one most used by residents, medical imaging faculty, and physicists. On
more than one occasion I have heard our university biomedical physicists ask, “What
does Bushberg’s book say?”
The attractive aspects of the book include its completeness, clarity, and ability
to answer questions that I have. This is likely a consequence of the authors having
run a resident review course for almost 30 years, during which they have undoubt-
edly heard every question and point of confusion that a nonphysicist could possibly
raise. I must say that on the door to my office I keep displayed a quote from the
second edition: “Every day there is an alarming increase in the number of things I
know nothing about.” Unfortunately, I find this true regarding many things besides
medical physics.
My only suggestion to the authors is that in subsequent editions they delete the
word “Essentials” from the title, for that word does not do justice to the staggering
amount of work they have done in preparing this edition’s remarkably clear text or to
the 750+ illustrations that will continue to set the standard for books in this field.
Fred A. Mettler Jr, MD, MPH
Clinical and Emeritus Professor
University of New Mexico School of Medicine
vii
Acknowledgments
During the production of this work, several individuals generously gave their time
and expertise. Without their help, this new edition would not have been possible.
The authors would like to express their gratitude for the invaluable contributions of
the following individuals:
Craig Abbey, PhD Jiang Hsieh, PhD Fred A. Mettler Jr, MD, MPH
University of California, Santa General Electric Medical Systems University of New Mexico
Barbara School of Medicine
Kiran Jain, MD
Ramsey Badawi, PhD University of California, Davis Stuart Mirell, PhD
University of California, Davis University of California at Los
Willi Kalender, PhD
Angeles
John D. Boice Jr, ScD Institute of Medical Physics,
Vanderbilt University Erlangen, Germany Norbert Pelc, ScD
Vanderbilt-Ingram Cancer Stanford University
Frederick W. Kremkau, PhD
Center
Wake Forest University School Otto G. Raabe, PhD
Michael Buonocore, MD, PhD of Medicine University of California, Davis
University of California, Davis
Linda Kroger, MS Werner Roeck, Dipl Eng
Dianna Cody, PhD University of California, Davis University of California, Irvine
MD Anderson Cancer Center Health System
John Sabol, PhD
Michael Cronan, RDMS Ramit Lamba, MD General Electric Medical
University of California, Davis University of California, Davis Systems
Brian Dahlin, MD Karen Lindfors, MD D.K. Shelton, MD
University of California, Davis University of California, Davis University fo California, Davis
Robert Dixon, PhD Mahadevappa Mahesh, PhD Jeffrey Siewerdsen, PhD
Wake Forest University Johns Hopkins University Johns Hopkins University
Raymond Dougherty, MD Cynthia McCollough, PhD Michael G. Stabin, PhD
University of California, Davis Mayo Clinic, Rochester Vanderbilt University
Ken Eldridge, RT(R)(N) John McGahan, MD Steve Wilkendorf, RDMS
University of California, Davis University of California, Davis
William Erwin, MS
UT MD Anderson Cancer Sarah McKenney Sandra Wootton-Gorges, MD
Center Houston, TX University of California, Davis University of California, Davis
Kathryn Held, PhD Michael McNitt-Gray, PhD Kai Yang, PhD
Massachusetts General Hospital University of California. Los University of California, Davis
Harvard Medical School Angeles
viii
Contents
Preface to the Third Edition v
Foreword vii
Acknowledgements viii
Section I: Basic Concepts ..........................................1
1 Introduction to Medical Imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
1.1 The Modalities 3
1.2 Image Properties 15
2 Radiation and the Atom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
2.1 Radiation 18
2.2 Structure of the Atom 24
3 Interaction of Radiation with Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
3.1 Particle Interactions 33
3.2 X-ray and Gamma-Ray Interactions 38
3.3 Attenuation of X-rays and Gamma Rays 44
3.4 Absorption of Energy from X-rays and Gamma Rays 52
3.5 Imparted Energy, Equivalent Dose, and Effective Dose 55
4 Image Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60
4.1 Spatial Resolution 60
4.2 Convolution 65
4.3 Physical Mechanisms of Blurring 68
4.4 The Frequency Domain 69
4.5 Contrast Resolution 76
4.6 Noise Texture: The Noise Power Spectrum 86
4.7 Contrast 87
4.8 Contrast-to-Noise Ratio 91
4.9 Signal-to-Noise Ratio 91
4.10 Contrast-Detail Diagrams 92
4.11 Detective Quantum Efficiency 94
4.12 Receiver Operating Characteristic Curves 96
5 Medical Imaging Informatics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101
5.1 Analog and Digital Representation of Data 101
5.2 Digital Radiological Images 109
5.3 Digital Computers 111
5.4 Information Storage Devices 112
5.5 Display of Digital Images 116
5.6 Computer Networks 133
5.7 PACS and Teleradiology 143
5.8 Image Processing 159
5.9 Security, Including Availablility 163
Section II: Diagnostic Radiology ..................................169
6 x-ray Production, x-ray Tubes, and x-ray Generators . . . . . . . . . . . . . . . .171
6.1 Production of X-rays 171
6.2 X-ray Tubes 176
6.3 X-ray Generators 190
6.4 Power Ratings and Heat Loading and Cooling 199
6.5 Factors Affecting X-ray Emission 202
7 Radiography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .207
7.1 Geometry of Projection Radiography 207
7.2 Screen-Film Radiography 209
ix