QUANTITATIVE METHODS IN BONE DENSITOMETRY QUANTITATIVE METHODS IN BONE DENSITOMETRY ALAN L. HUDDLESTON, PH.D. Chief, Medical Physics Baylor University Medical Center Charles A. Sammons Cancer Center Division of Radiation Oncology Dallas, Texas 75246 ..... " KLUWER ACADEMIC PUBLISHERS BOSTON/DORDRECHT/LONDON © 1988 by Kluwer Academic Publishers, Boston. Softcover reprint of the hardcover 15t edition 1988 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publishers. Kluwer Academic Publishers, 101 Philip Drive, Assinippi Park, Norwell, MA 02061 Distributors for the United States and Canada: Kluwer Academic Publishers, 101 Philip Drive, Assinippi Park, Norwell, MA 02061 for the UK and Ireland: Kluwer Academic Publishers, Falcon House, Queen Square, Lancaster LAI1RN, UK for all other countries: Kluwer Academic Publishers Group, Distribution Centre, P.O. Box 322, 3300 AH Dordrecht, The Netherlands Library of Congress Cataloging-in-Publication Data Huddleston, Alan. Quantitative methods in bone densitometry. Includes index. 1. Osteoporosis - Diagnosis. 2. Bone densitometry. 1. Title. [DNLM: 1. Bone and Bones - radiography. 2. Densitometry - methods. 3. Osteoporosis - radiography. 4. Tomography, X-Ray Computed-methods. WE 200 H884q] RC931.073H831988 616.7'10754 87-35241 ISBN-13: 978-1-4612-8971-5 e-ISBN-13: 978-1-4613-1725-8 DOl: 10.1007/978-1-4613-1725-8 To the memory of my brother, Gary Lee Huddleston, M.D. CONTENTS Preface and Acknowledgments Xl 1 Introduction 1 Composition of Bone Tissue 4 Bone Strength and Bone Mass 6 Bone Mass Measurements 7 2 Radiographic Film Methods 13 Radiographic Diagnosis (Radioscopy) 14 Trabecular Indices 15 Principles of Radiogram met ry 18 Combined Cortical Thickness 19 Barnett-Nordin Index 19 Cortical Area 19 Percent Cortical Area 20 Exton-Smith Index 20 Principles of Metacarpal Measurements 20 Magnification Techniques 22 Vertebral Measurements 23 vii viii Radius Measurements 23 Precision and Accuracy (Radiogrammetry) 25 Clinical Measurements 26 Radiographic Photodensitometry 28 Precision and Accuracy (Photodensitometry) 31 Videodensitometry 31 3 Single-Photon Absorptiometry 33 Principles of Measurement 34 X-ray Tube Sources for SPA 39 Multiwire Proportional Counters 40 Two-Dimensional SPA 42 Precision and Accuracy (SPA) 43 Effects of Adipose Tissue 45 Clinical Measurements 46 SPAin Children 51 Fracture Risk 54 Radiation Dose to Patients 54 4 Dual-Photon Absorptiometry 57 Principles of Measurement 57 Instrumentation and System Design 60 Beam Hardening and Crossover Corrections 68 Correction for Fat 70 Precision and Accuracy 71 Total-Body Bone Mineral Measurements 73 Clinical Measurements 79 Fracture Threshold 82 Radiation Dose to Patients 82 5 Quantitative Computed Tomography 85 Monoenergetic (Gamma) CT 86 Precision and Accuracy (Gamma-CT) 88 Single-Energy X-ray Quantitative CT 89 Precision and Accuracy (Single-Energy X-ray CT) 97 Beam-Hardening Effects 101 Partial Volume Effects 104 ix Effects of Marrow Fat 105 Dual-Energy X-ray Quantitative CT 106 Precision and Accuracy (Dual-Energy CT) 108 Clinical Measurements 108 Radiation Dose to Patients 110 6 Scattering Methods in Densitometry 113 Compton-Scatter Imaging Methods 114 Fixed-Point Compton-Scatter Methods 125 Dual-Source/Dual-Detector Methods 127 Dual-Source/Single-Detector Methods 133 Single-Source/Single-Detector Methods 134 Single-Source/Dual-Detector Method 139 Finite Geometry Effects 139 Multiple Scattering 140 Clinical Measurements 140 Coherent/Compton-Scatter Methods 144 7 Activation Analysis Methods 161 Principles of Measurement 162 Partial-Body NAA 167 Precision and Accuracy (NAA) 168 Clinical Measurements 170 Radiation Dose to Patients (NAA) 176 Proton Activation Analysis (P AA) 176 Muonic X-ray Excitation 177 8 Clinical Applications and Comparison of Methods 179 References 195 Index 215 PREFACE Interest in bone densitometry methods has recently experienced a resurgence within the medical community. Physicians have become more interested than ever before in the diagnosis and treatment of degenerative diseases of bone such as osteoporosis. The public perception of osteoporosis and its prevention has been recently heightened. Because osteoporosis is widespread, especially in women, and leads to an increase in fractures in our population, many re searchers and clinicians are strongly motivated in their search for more sensi tive and accurate methods of diagnosis. This book was written for physicians, scientists, engineers, medical phy sicists, and others desiring an introduction or further understanding of this exciting field. Beginning with the early development of x-ray film methods for assessing bone status, the field has steadily grown throughout the years. Novel and interesting devices have been designed for the measurement of bone mass, bone density, cortical thickness, and other parameters of bone changes. Both qualitative and quantitative bone methods are described. The techniques include imaging devices such as CT and radiography as well as fixed point methods in which bone characteristics of a region of interest are analyzed. Clinical applications of these bone densitometry methods are included as an indication of the usefulness of the various techniques, although the complete analysis of clinical data was not exhaustive nor intended in this work. How ever, it is intended that an appreciation of the extensive efforts of the many re searchers who have worked to develop these techniques and an understanding xi xii of the basic physical principles will be realized by this book. Further develop ment of the field of bone densitometry will require new insights for the integra tion of technology and biomedical knowledge. Further investigation of the methodology is necessary to increase the sensitivity, precision, and accuracy with which bone parameters may be assessed by noninvasive means in the human body. It is hope that this work may inspire others to meet this challenge. ACKNOWLEDGMENTS Grateful acknowledgment is made for the interest and appreciation expressed by the many authors of published works in this field. Special thanks are con veyed to those authors who have granted permission to reproduce or extract information from their published works and to the publishers of the many referenced journals and books on the subject. In particular, I would like to acknowledge Moses A. Greenfield, Ph.D., my mentor and adviser as a gra duate student, without whose encouragement and enthusiasm this work would not have been written. Appreciation is expressed for the patience of my wife, Diane, and my daughters, Lisa and Katherine, and for the encourage ment of my family and friends. Alan L. Huddleston QUANTITATIVE METHODS IN BONE DENSITOMETRY