Essentials of Medical Ultrasound

Essentials of Medical Ultrasound

Medical Methods Essentials of Medical Ultrasound: A Practical Introduction to the Principles, Techniques, and Biomedical Applications, Edited by Michael H. Repacholi and Deirdre A. Benwell, 1982

Essentials of Medical Ultrasound A Practical Introduction to the Principles, Techniques, and Biomedical Applications Edited by Michael H. Repacholi and Deirdre A. Benwell Health and Welfare Canada Ottawa, Ontario, Canada

Library of Congress Cataloging in Publication Data Main entry under title: Essentials of medical ultrasound. (Medical methods) Includes bibliographies and index. 1. Ultrasonic waves-physiological effect. 2. Ultrasonics in medicine. I. Repacholi, Michael H. II. Benwell, Deirdre A. III. Series. [DNLM: 1. Ultrasonics. OT 34 E775] OP82.2.U37E78 616.07'543 80-85522 ISBN-13: 978-1-4612-5807-0 e-isbn-13: 978-1-4612-5805-6 001: 10.1007/978-1-4612-5805-6 1982 The HUMANA Press Inc. Softcover reprint of the hardcover 15t Edition 1982 Crescent Manor PO Box 2148 Clifton, NJ 07015 All rights reserved No part of this book may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, microfilming, recording, or otherwise without written permission from the Publisher.

Preface One of the first applications of ultrasound was in submarine sonar equipment. Since then ultrasound has found increasing applications, particularly in industry, but increasingly in biomedicine. For many years ultrasound has been used in physical therapy, although only in the past decade or two has it evolved from laboratory curiosity to a well-established diagnostic imaging modality. Ultrasound is now a widely accepted, indeed pervasive, diagnostic and therapeutic tool in the medical field, and its applications are increasing rapidly. Our intent in developing this book is to provide a coherent tutorial introduction to the field of medical ultrasound at a level suitable for those entering the area from either medical or scientific backgrounds. The topics discussed should be of interest to nearly all medical and health care personnel needing to understand or operate ultrasonic devices, including clinicians, medical technicians, physiotherapists, medical physicists, and other biomedical scientists interested in the field. The book opens with a description of the basic principles of propagating acoustic waves, explains how they interact with a wide range of biological systems, and outlines the effects they produce. To provide practical information to operators of ultrasound equipment, we have included thorough coverage of the details of ultrasonic instrumentation and measurement techniques, and set forth the framework for an effective quality assurance program. Regulations and safe-use guidelines have also been described and distinguished in an effort to acquaint people with the philosophy upon which standards are based, as well as some of the details of those currently proposed or in use. This is especially important in medical ultrasound, and even now a number of professional organizations have developed, or are drafting, standards on ultrasound equipment and its proper uses, standards that will effect operators directly. Although each chapter was written by an expert in the particular area of ultrasound covered, an attempt has also been made to ensure that the chapters are interactive. Topics discussed in one article are often intended to complement information provided in others, so that readers are ultiv

vi PREFACE mately provided with an integrated, but practical survey of all the basic concepts, instrumentation, techniques, standards, and applications likely to be encountered in the day-to-day use of medical ultrasound. We would like to thank our coauthors for their enthusiam and forbearance during the compilation of this text. Ottawa, Canada May, 1982 Michael H. Repacholi Deirdre A. Benwell

Table of Contents Preface... v Chapter 1 Physical Characteristics of Ultrasound............ 1 Alan J. Mortimer 1. Introduction... 1 2. Acoustic Waves.................................... 2 2.1. Wave Motion................................. 2 2.2. Periodic Wave Motion......................... 2 3. Parameters on an Ultrasonic Wave................... 4 3.1. Modes of Wave Propagation................... 5 3.2. Standing Waves.............................. 6 4. Ultrasonic Transducers............................. 7 4.1. Piezoelectric Materials........................ 8 4.2. Medical Transducers......................... 8 5. Characteristics of Ultrasound Beams................. 10 5.1. Huygen's Principle........................... 11 5.2. Circular Transducers.......................... 11 5.3. Far Field..................................... 12 5.4. Near Field................................... 13 5.5. Pulsed Transducers........................... 15 6. Reflection and Refraction... 18 6.1. Matching.................................... 20 6.2. Mode Conversion............................. 20 7. Absorption and Scattering........................... 20 7.1. Absorption................................. 21 7.2. Dispersion................................... 23 7.3. Scattering................................... 25 7.4. Doppler Effect................................ 27 8. Conclusion... 28 Appendix: Mathematical Derivations of Physical Characteristics................................... 28 vii

viii CONTENTS A.1. Acoustic Waves.............................. 28 A.2. Modes of Propagation of Acoustic Waves....... 31 References........................................ 33 Chapter 2 Biophysical Mechanisms of Ultrasound... 35 Wesley L. Nyborg 1. Introduction... 35 2. Thermal Mechanism... 37 2.1. Temperature Rise Without Heat Transfer... 37 2.2. Temperature Rise During a Single Pulse-No Heat Transfer... 38 2.3. Thermal Method of Intensity Measurement-No Heat Transfer... 38 2.4. Temperature Rise with Heat Transfer... 39 2.5. Temperature vs Time in an Absorbing Sphere-Influence of Conduction... 39 2.6. Applications to Biomedical Ultrasound... 44 2.7. Summary of Findings for Thermal Mechanism... 48 3. Stress Mechanisms... 49 3.1. First-Order and Second-Order Quantities-Radiation Pressure... 49 3.2. Radiation Force... 50 3.3. Radiation Torque... 54 3.4. Acoustic Microstreaming... 55 3.5. Stress Fields of Gas-Filled Pores-Low Megahertz Frequencies... 64 3.6. Summary of Findings for Stress Mechanism... 67 4. Cavitation... 70 5. Conclusions... 71 References... 72 Chapter 3 Ultrasonic Measurement Techniques and Equipment Output Levels... 77 Harold F. Stewart 1. ~ntroduction... 77 2. Measurement Parameters........................... 78

CONTENTS ~ 3. Techniques and Instrumentation..................... 80 3.1. Total Power-Radiation Force.................. 81 3.2. Radiation Force-Intensity Techniques.......... 92 3.3. Thermal Methods............................. 93 3.4. Optical Techniques........................... 98 3.5. Reciprocity Calibration... 101 3.6. Electrical Determination of Ultrasonic Output for Quartz Transducers............... 102 3.7. Miniature Hydrophones... 103 4. Ultrasound Equipment Output Levels................. 105 4.1. Therapy Equipment........................... 105 4.2. Diagnostic Equipment..., 105 4.3. Output Levels and Biological Effect Levels... 109 References........................................ 111 Chapter 4 Selected Biological Effects of Ultrasound......... 117 F.Dunn 1. Introduction... 117 2. Whole-Body Radiation.............................. 120 2.1. Vertebrates.................................. 120 2.2. Insects...................................... 121 3. Tissues and Organs................................ 121 3.1. Central Nervous System....................... 122 3.2. Liver........................................ 123 3.3. Testes... 124 3.4. Blood Stasis................................. 124 3.5. Tissue Regeneration.......................... 125 3.6. Neoplastic Tissues and Synergism............. 125 4. Cells and Microorganisms........................... 126 5. Biomacromolecules and Their Assemblages.......... 128 5.1. Biomacromolecules........................... 130 5.2. Macromolecular Assemblages................. 130 6. Concluding Remarks............................... 133 7. Acknowledgments... 134 References........................................ 134

x CONTENTS Chapter 5 Clinical Applications of Diagnostic Ultrasound................................ 141 Edward A. Lyons 1. Introduction....... 141 1.1. Limited Significance Method... 142 1.2. Useful Ancillary Method of Investigation........ 143 1.3. Most Efficacious Method of Non-Invasive Examination... '"... 143 1.4. Sole Investigative Tool........................ 143 2. Head... 144 2.1. Brain... 144 2.2. Eyes........................................ 146 3. Neck... 149 3.1. Thyroid and Parathyroid Glands................ 149 3.2. Carotid Artery................................ 151 4. Chest... 151 4.1. Heart........................................ 151 4.2. Pleural Space................................ 158 4.3. Breast... " 159 5. Abdomen... 160 5.1. Liver........................................ 161 5.2. Kidneys..................................... 162 5.3. Pancreas.................................... 164 5.4. Spleen................................... 165 5.5. Biliary Tract.................................. 166 5.6. Aorta.................................... 168 5.7. Lymph Nodes................................ 170 5.8. Peritoneal Space............................. 170 6. Pelvis... 171 6.1. Uterus (Pregnant)............................. 171 6.2. Uterus (Nonpregnant)......................... 175 6.3. Fallopian Tubes and Ovaries.................. 175 6.4. Bladder..................................... 176 6.5. Prostate and Scrotum......................... 177 7. Extremities... 178 8. Conclusion... 178

CONTENTS xi Chapter 6 Ultrasound Therapy............................ 181 by Harold F. Stewart, Michael H. Repacholi, and Deirdre A. Benwell 1. Introduction... 181 2. Therapeutic Devices and the Ultrasound Field......... 182 2.1. Ultrasound Therapy Devices................... 182 2.2. Temporal (Time) Variations of the Ultrasound Field............................ 183 2.3. Spatial Variations of Ultrasound Fields.......... 186 3. Qual ity Assurance and Standards.................... 191 3.1. Power and Intensity........................... 192 3.2. Power Output and Exposure Time.............. 193 3.3. Quality Assurance of Equipment............... 194 4. Ultrasound Transmission and Absorption in Biolog ical Materials.............................. 195 5. Applications of Therapeutic Ultrasound... 203 6. Minimizing Operator and Patient Exposure... 206 7. Contraindications for the Application of Ultrasound in Therapy............................ 207 8. Summary... 208 References........................................ 209 Chapter 7 Quality Assurance in Diagnostic Ultrasound... 215 Albert Goldstein 1. Introduction... 215 2. Description of Equipment Displays... 216 2.1. A-Mode... 217 2.2. B-Mode... 218 2.3. M-Mode..................................... 218 2.4. Two-Dimensional Cross-Section Images........ 220 2.5. Gray-Scale... 220 2.6. Real-Time Displays... " 220 2.7. Continuous-Wave Techniques... 222 2.8. Holographic Display... 222

xii CONTENTS 3. Equipment Operation... 222 3.1. Operator Controls........................... 223 3.2. Scanning Technique... 224 3.3. Potential Hazards............................. 227 3.4. Warmup Procedure........................... 229 3.5. Hardcopy Care... 230 3.6. Hospital Electrical Noise... 236 4. Routine Preventive Maintenance..................... 237 4.1. Hard Copy................................... 237 4.2. Air Filters... 238 4.3. Scanning Arm Stability... 238 4.4. Integrity of Enclosures........................ 239 4.5. Worn or Frayed Cables........................ 239 5. System Performance and Testing... 239 5.1. Transducer... " 240 5.2. Receiver..................................... 243 5.3. Analog Scan Converter... 244 5.4. Digital Scan Converter........................ 245 5.5. Gray-Scale Display... 246 5.6. B-Mode Reg istration.......................... 248 5.7. Display Size and Linearity... 249 5.8. Document System Performance................ 249 6. Routine Performance Tests.......................... 250 6.1. Introduction.................................. 250 6.2. AlUM 1 OO-mm Test Object.... 251 6.3. Test of Test Object Liquid Acoustic Velocity... 255 6.4. Other Performance Tests...................... 258 Performance Test Worksheets.................. 270 7. Summary...................... 270 Sample Service Logs... 270 References........................................ 275 Bibliography: Selected Quality Assurance Publications... 275 Chapter 8 Ultrasound Standards: Regulations and Guidelines... 281 Michael H. Repacholi and Deirdre A. Benwell 1. Philosophy of Developing Standards... 282 2. Biological Effects... 284

CONTENTS xiii 3. Types of Standards................................. 287 4. Device or Emission Standards....................... 288 4.1. Diagnostic Ultrasound........................ 288 4.2. Therapy Devices............................. 291 4.3. Surgical Devices... 293 4.4. Dentistry..................................... 295 5. Safe-Use Guidelines and Education... 296 5.1. Guidelines... 296 5.2. Education................................... 297 6. International Activities.............................. 297 7. National Standards... 298 8. Summary................ 300 References........................................ 300 Glossary of Ultrasound Terminology.... 305 Index...... 325

Contributors DEIRDRE A. BENWELL Radiation Protection Bureau, Health and Welfare Canada, Ottawa, Ontario, Canada F. DUNN Department of Electrical Engineering, University of Illinois, Urbana Illinois ALBERT GOLDSTEIN Department of Diagnostic Radiology, Henry Ford Hospital, Detroit, Michigan EDWARD A. LYONS Department of Diagnostic Ultrasound, Health Sciences Centre, Winnipeg, Manitoba, Canada ALAN J. MORTIMER National Research Council, Ottawa, Ontario Canada WESLEY L. NYBORG Department of Physics, The University of Vermont, Burlington, Vermont MICHAEL H. REPACHOLI Radiation Protection Bureau, Health and Welfare Canada, Ottawa, Ontario, Canada HAROLD F. STEWART Bureau of Radiological Health, Food and Drug Administration, Rockville, Maryland xv