Kelsey Charles A. - Radiation Biology of Medical Imaging

Table of Contents

Copyright 2014 by John Wiley & Sons, Inc. All rights reserved.

Published by John Wiley & Sons, Inc., Hoboken, New Jersey.

Published simultaneously in Canada.

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Library of Congress Cataloging-in-Publication Data:

Kelsey, Charles A., author.

Radiation Biology of Medical Imaging / Charles A. Kelsey, Philip H. Heintz, Daniel J. Sandoval, Gregory D. Chambers, Natalie L. Adolphi, Kimberly S. Paffett

p. ; cm

Includes bibliographical references.

ISBN 978-0-470-55177-6 (cloth)

I. Heintz, Philip, author. II. Sandoval, Daniel, author. III. Chambers, Gregory D. (Gregory Daniel), author. IV. Adolphi, Natalie, author. V. Paffett, Kimberly, author. VI. Title

[DNLM: 1. Radiobiology. 2. Diagnostic Imaging. 3. Tissuesradiation effects. WN 600]

QP82.2.R3

612'.01448dc23

2013012759

Acknowledgments

The authors want to acknowledge and thank the many individuals who contributed their thoughts and views regarding the impact of radiation biology in the practice of medicine. While the authors are fully responsible for the content of this book, we thank these individuals for their generous time and effort in reducing the number and egregiousness of the errors and in suggesting better ways in which to explain things.

In particular, we would like to thank Bret Heintz, PhD, and Phillip Berry, PhD, for their careful review of several chapters, and Ruth Anne Bump, Tanner Adams, and Sage Byrne for their efforts in tirelessly working their way through the seemingly endless revision of the illustrations. And also, we thank the numerous students who struggled through the earlier versions of the course. Their challenging questions and perceptive views have immeasurably improved this text.

The authors would like to thank our spouses and families for their seemingly everlasting support in this project, specifically, Judy Kelsey, Lillian Heintz, Kristen Sandoval, Jennifer Chambers, Andrew McDowell, and Michael Paffett.

Introduction

This book evolved from courses taught over the past several years to medical professionals, technologists, scientists, and engineers at the University of New Mexico. The medical professionals in our classes were primarily radiology and cardiology residents and fellows. Our students included X-ray, nuclear medicine, radiation oncology, and ultrasound technology students. The residents, fellows, and students were studying for board certification or registry examinations to establish their competence to practice their professions. We needed a book for these users of radiation with questions of the type they would face in their examinations. The authors consist of a team of scientists and engineers with over 75 years combined experience working with and teaching about radiation. We have included a chapter on radiation therapy because it is also deeply involved in imaging. The biological effects of magnetic resonance and ultrasound are included, although they employ nonionizing radiation because their biological effects may be cause for concern at higher power levels.

Within a year of Roentgen's discovery of X-rays in 1895, their biological effects were evident because radiation burns and ulcers were observed in early users. Clarence Daly, one of Edison's assistants, died from radiation-induced cancer less than 10 years after their discovery. In the years between X-ray's discovery and Watson and Crick's unraveling of the DNA structure in 1953, radiobiology studies concentrated on radiation in the treatment of cancer and on the effects of radiation on those exposed to radiation during World War II. Since 1953, radiobiology studies have focused on radiation damage to the DNA molecule. For a number of years before 9/11, there was a lull in the study of radiation effects. Since 9/11, there has been an increased effort to understand the effect of low levels of ionizing radiation. With recent developments in the study of DNA, now is an exciting time for the field of radiation biology.

Medical radiation, which is responsible for about half the U.S. population exposure, comes primarily from three sources: radiation therapy, interventional/diagnostic, and nuclear medicine. Radiation therapy, often called radiation oncology, uses high doses to cure cancer. Interventional/diagnostic uses lower doses to guide the insertion of devices into the body or determine what ails the patient. Nuclear medicine follows radioactive materials injected into the body to determine body functions. The effects of medical radiation depend on the dose and the parts of the body irradiated, but do not depend on how or why the radiation was delivered.

The first quarter of the book is designed to establish an essential background knowledge base in biology and physics. For many readers, this will be a straightforward review. The book next covers DNA structure and function, DNA damage and repair, genetic effects, and the characteristics of cancer. The third quarter of the book covers the effects of radiation on various body organs and on the whole body, including a brief discussion of radiation-induced bystander effects. The final quarter concentrates on radiation effects from medical and natural sources of radiation and the regulations designed to protect workers and the general public. Particular attention is directed to the effects of low-dose, long-term exposures and the limitations of the linear no-threshold (LNT) hypothesis. A brief discussion of hormesis is included in this section.