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DIAGNOSTIC ULTRASOUND Imaging and Blood Flow Measurements © 2006 by Taylor & Francis Group, LLC A CRC title, part of the Taylor & Francis imprint, a member of the Taylor & Francis Group, the academic division of T&F Informa plc. DIAGNOSTIC ULTRASOUND Imaging and Blood Flow Measurements Boca Raton London New York K. Kirk Shung © 2006 by Taylor & Francis Group, LLC Published in 2006 by CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2006 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group No claim to original U.S. Government works Printed in the United States of America on acid-free paper 10 9 8 7 6 5 4 3 2 1 International Standard Book Number-10: 0-8247-4096-3 (Hardcover) International Standard Book Number-13: 978-0-8247-4096-2 (Hardcover) Library of Congress Card Number 2005048513 This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. A wide variety of references are listed. Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use. No part of this book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers. For permission to photocopy or use material electronically from this work, please access www.copyright.com (http://www.copyright.com/) or contact the Copyright Clearance Center, Inc. (CCC) 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400. CCC is a not-for-profit organization that provides licenses and registration for a variety of users. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Library of Congress Cataloging-in-Publication Data Shung, K. Kirk. Diagnostic Ultrasound : imaging and blood flow measurements / by K. Kirk Shung. p. cm. Includes bibliographical references and index. ISBN 0-8247-4096-3 Diagnosis, Ultrasonic. 2. Blood flow – Measurement. 3. Laser Doppler blood flowmetry. I. Title. RC78.7.U4S53 2005 616.07’543–dc22 2005048513 Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com Taylor & Francis Group is the Academic Division of T&F Informa plc. DK1305_Discl.fm Page 1 Monday, July 11, 2005 1:33 PM © 2006 by Taylor & Francis Group, LLC This book is dedicated to my wife, Linda, and three children: Albert, Simon, and May DK1305_C000.fm Page v Friday, August 5, 2005 1:36 PM © 2006 by Taylor & Francis Group, LLC Preface The field of medical imaging is advancing at a rapid pace. Imaging modalities like x-ray radiography, x-ray computed tomography (CT), ultrasound, nuclear imaging, magnetic resonance imaging (MRI), and optical imaging have been used in biology and medicine to visualize anatomical structures as large as the lung and liver and as small as molecules. Ultrasound is considered the most cost-effective among them. It is used routinely in hospitals and clinics for diagnosing a variety of diseases. It is the tool of choice in obstetrics and cardiology because it is safe and capable of providing images in real time. New applications in small-animal imaging and cellular imaging are being explored. Although many clinical books on ultrasound have been published, very few technical books are available. This has been a major problem for the author in teaching graduate courses in ultrasonic imaging at the Department of Bioengineer- ing, Pennsylvania State University, and Department of Biomedical Engineering, University of Southern California, over the past 25 years. It is for this purpose that this book was written. The book is intended as a textbook for a senior or first-year graduate-level course in ultrasonic imaging in a biomedical engineering, electrical engineering, medical physics, or radiological sciences curriculum. An attempt has been made to minimize mathematical derivation and to place more emphasis on physical concepts. Chapter 1 gives an overview of the field of ultrasonic imaging and its role in diagnostic medicine relative to other imaging modalities. Chapter 2 and Chapter 3 are relatively longer and describe the fundamental physics involved and a crucial device in ultrasound, ultrasonic transducers. Conventional imaging approaches and Doppler measurements are discussed in Chapter 4 and Chapter 5. More recent developments, including contrast imaging and four-dimensional imaging, are described in Chapter 6 through Chapter 9. In Chapter 10, current status and standards on ultrasound bioeffects are reviewed. Chapter 11 discusses methods that have been used to measure ultrasonic properties of tissues. This chapter is optional and may be eliminated at the discretion of the instructor. A list of relevant references is found at the end of each chapter and some of the chapters suggest further reading materials. Material contained in the book should be more than sufficient for a one-semester graduate senior-level course. The book should also be of interest to radiologists with some technical back- ground and practicing engineers and physicists working in the imaging industry. K. Kirk Shung DK1305_C000.fm Page vii Friday, August 5, 2005 1:36 PM © 2006 by Taylor & Francis Group, LLC Acknowledgment The author gratefully acknowledges the financial support provided by NIH Grant No. P41-EB2182 during the period when this book was written. DK1305_C000.fm Page ix Friday, August 5, 2005 1:36 PM © 2006 by Taylor & Francis Group, LLC The Author K. Kirk Shung, Ph. D., obtained a B.S. in electrical engineering from Cheng-Kung University in Taiwan in 1968, an M.S. in electrical engineering from the University of Missouri, Columbia, in 1970, and a Ph.D. in electrical engineering from the University of Washington, Seattle, in 1975. He did postdoctoral research at Provi- dence Medical Center in Seattle, Washington, for 1 year before being appointed a research bioengineer holding a joint appointment in the Institute of Applied Physi- ology and Medicine. He became an assistant professor in the bioengineering pro- gram, Pennsylvania State University, University Park in 1979 and was promoted to professor in 1989. He was a Distinguished Professor of Bioengineering at Penn State until September 1, 2002, when he joined the department of biomedical engineering, University of Southern California, Los Angeles, as a professor. He has been the director of NIH Resource on Medical Ultrasonic Transducer Technology since 1997. Dr. Shung is a fellow of the IEEE, the Acoustical Society of America, and the American Institute of Ultrasound in Medicine. He is a founding fellow of the American Institute of Medical and Biological Engineering. He served two terms as a member of the NIH Diagnostic Radiology Study Section. He received the IEEE Engineering in Medicine and Biology Society Early Career Award in 1985 and coauthored a best paper published in IEEE Transactions on Ultrasonics, Ferroelec- trices, and Frequency Control in 2000. He was the distinguished lecturer for the IEEE UFFC Society from 2002 through 2003 and was elected an outstanding alumnus of Cheng-Kung University in Taiwan in 2001. Dr. Shung has published more than 200 papers and book chapters. He is the author of a textbook, Principles of Medical Imaging , published by Academic Press in 1992, and coedited a book, Ultrasonic Scattering by Biological Tissues , published by CRC Press in 1993. Dr. Shung’s research interests are ultrasonic transducers, high-frequency ultrasonic imaging, and ultrasonic scattering in tissues. DK1305_C000.fm Page xi Friday, August 5, 2005 1:36 PM © 2006 by Taylor & Francis Group, LLC Contents Chapter 1 Introduction ..........................................................................................1 1.1 History..............................................................................................................1 1.2 Role of Ultrasound in Medical Imaging .........................................................2 1.3 Purpose of the Book ........................................................................................3 Reference ...................................................................................................................3 Further Reading .........................................................................................................3 Chapter 2 Fundamentals of Acoustic Propagation ...............................................5 2.1 Stress and Strain Relationships .......................................................................8 2.2 Acoustic Wave Equation ................................................................................11 2.2.1 Compressional Wave..........................................................................11 2.2.2 Shear Wave.........................................................................................12 2.3 Characteristic Impedance...............................................................................13 2.4 Intensity ..........................................................................................................14 2.5 Radiation Force ..............................................................................................17 2.6 Reflection and Refraction ..............................................................................17 2.7 Attenuation, Absorption, and Scattering .......................................................20 2.7.1 Attenuation .........................................................................................21 2.7.2 Absorption..........................................................................................21 2.7.3 Scattering............................................................................................25 2.8 Nonlinearity Parameter B/A ..........................................................................32 2.9 Doppler Effect ................................................................................................35 References................................................................................................................36 Chapter 3 Ultrasonic Transducers and Arrays....................................................39 3.1 Piezoelectric Effect ........................................................................................39 3.2 Piezoelectric Constitutive Equation...............................................................41 3.3 Ultrasonic Transducers...................................................................................46 3.4 Mechanical Matching.....................................................................................53 3.5 Electrical Matching ........................................................................................55 3.6 Transducer Beam Characteristics ..................................................................55 3.6.1 Beam Profiles .....................................................................................57 3.6.2 Pulsed Ultrasonic Field......................................................................61 3.6.3 Visualization and Mapping of the Ultrasonic Field ..........................62 3.6.4 Axial and Lateral Resolution.............................................................63 3.6.5 Focusing .............................................................................................63 DK1305_C000.fm Page xiii Thursday, August 11, 2005 2:38 PM © 2006 by Taylor & Francis Group, LLC 3.7 Arrays .............................................................................................................68 References................................................................................................................77 Chapter 4 Gray-Scale Ultrasonic Imaging .........................................................79 4.1 A (Amplitude)-Mode and B (Brightness)-Mode Imaging ............................79 4.1.1 Resolution of B-Mode Ultrasonic Imaging Systems ........................88 4.1.2 Beam Forming....................................................................................88 4.1.3 Speckle ...............................................................................................90 4.1.4 Image Quality.....................................................................................91 4.1.4.1 Point Spread Function ........................................................92 4.1.4.2 Contrast ...............................................................................92 4.1.4.3 Noises..................................................................................94 4.1.5 Phase Aberration Compensation........................................................94 4.1.6 Clinical Applications..........................................................................94 4.2 M-Mode and C-Mode ....................................................................................95 4.3 Ultrasound Computed Tomography (CT)......................................................97 4.4 Coded Excitation Imaging .............................................................................98 4.5 Compound Imaging........................................................................................99 4.6 Synthetic Aperture Imaging ...........................................................................99 References..............................................................................................................101 Chapter 5 Doppler Flow Measurements...........................................................103 5.1 Nondirectional CW Flow Meters ................................................................103 5.2 Directional Doppler Flow Meters................................................................108 5.2.1 Single Sideband Filtering.................................................................108 5.2.2 Heterodyne Demodulation ...............................................................109 5.2.3 Quadrature Phase Demodulation .....................................................110 5.3 Pulsed Doppler Flow Meters .......................................................................113 5.4 Clinical Applications and Doppler Indices..................................................115 5.5 Potential Problems in Doppler Measurements ............................................115 5.6 Tissue Doppler and Multigate Doppler .......................................................116 References..............................................................................................................117 Chapter 6 Flow and Displacement Imaging.....................................................119 6.1 Color Doppler Flow Imaging ......................................................................119 6.2 Color Doppler Power Imaging ....................................................................125 6.3 Time-Domain Flow Estimation ...................................................................127 6.4 Elasticity Imaging ........................................................................................129 6.4.1 Elastography.....................................................................................130 6.4.2 Sonoelasticity Imaging.....................................................................131 6.5 B-Flow Imaging ...........................................................................................131 References..............................................................................................................133 DK1305_C000.fm Page xiv Friday, August 5, 2005 1:36 PM © 2006 by Taylor & Francis Group, LLC Chapter 7 Contrast Media and Harmonic Imaging ..........................................135 7.1 Contrast Agents ............................................................................................135 7.1.1 Gaseous Agents ................................................................................135 7.1.2 Encapsulated Gaseous Agents .........................................................139 7.1.3 Dilute Distribution of Bubbles of Varying Size ..............................140 7.2 Nonlinear Interactions between Ultrasound and Bubbles...........................141 7.3 Modified Rayleigh–Plesset Equation for Encapsulated Gas Bubbles .................................................................................................142 7.4 Solutions to Rayleigh–Plesset Equation ......................................................142 7.5 Harmonic Imaging .......................................................................................146 7.6 Native Tissue Harmonic Imaging ................................................................148 7.7 Clinical Applications of Contrast Agents and Harmonic Imaging .............149 References..............................................................................................................150 Chapter 8 Intracavity and High-Frequency (HF) Imaging...............................153 8.1 Imaging.........................................................................................................153 8.1.1 Transesophageal Cardiac Imaging...................................................153 8.1.2 Transrectal and Transvaginal Imaging.............................................155 8.1.3 Endoluminal Imaging.......................................................................156 8.2 Intravascular Imaging...................................................................................157 8.3 High-Frequency Imaging .............................................................................158 8.4 Acoustic Microscopes ..................................................................................162 References..............................................................................................................162 Chapter 9 Multidimensional Imaging...............................................................163 9.1 Parallel Processing .......................................................................................163 9.2 Multidimensional Arrays..............................................................................164 9.2.1 Two-Dimensional Arrays .................................................................166 9.2.2 Sparse Arrays ...................................................................................170 9.3 Three-Dimensional Imaging ........................................................................173 References..............................................................................................................175 Chapter 10 Biological Effects of Ultrasound .....................................................177 10.1 Acoustic Phenomena at High-Intensity Levels ...........................................177 10.1.1 Wave Distortion...............................................................................177 10.1.2 Heating ............................................................................................177 10.1.3 Cavitation ...................................................................................