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Physical Principles of Medical Ultrasonics Second Edition Editors C. R. Hill J. C. Bamber G. R. ter Haar Physics Department, Institute of Cancer Research, Royal Marsden Hospital, Sutton, Surrey, UK Physical Principles of Medical Ultrasonics Physical Principles of Medical Ultrasonics Second Edition Editors C. R. Hill J. C. Bamber G. R. ter Haar Physics Department, Institute of Cancer Research, Royal Marsden Hospital, Sutton, Surrey, UK First Edition published in 1986 by Ellis Horwood Limited, Chichester, West Sussex Copyright u 2004 John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex PO19 8SQ, England Telephone (+44) 1243 779777 Email (for orders and customer service enquiries): cs-books@wiley.co.uk Visit our Home Page on www.wileyeurope.com or www.wiley.com All Rights Reserved. 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British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN 0 471 97002 6 Typeset in 9/11pt Times by Dobbie Typesetting Ltd, Tavistock, Devon Printed and bound in Great Britain by TJ International Ltd, Padstow, Cornwall This book is printed on acid-free paper responsibly manufactured from sustainable forestry in which at least two trees are planted for each one used for paper production. To Dr John Wild – Who had the vision – ‘My Dear Strutt, I am glad you are writing a book on Acoustics . . . . You speak modestly of a want of Sound books in English. In what language are there such, except Helmholtz, who is sound not because he is German but because he is Helmholtz . . . .’ (Letter from James Clerk Maxwell to John William Strutt, Lord Rayleigh, 20th May 1873, referring to Rayleigh’s Theory of Sound, which he had started writing earlier that year whilst on a honeymoon trip up the river Nile) ‘Compound utterances addressed themselves to their senses, and it was possible to view by ear the features of the neighbourhood. Acoustic pictures were returned from the darkened scenery; . . . ’ (From The Return of the Native, 1878, Thomas Hardy) Contents List of Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii Chapter 1 Chapter 2 Chapter 3 Basic Acoustic Theory . . . . . . . . . . . . . . . . . . . . . . S. J. Leeman 1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 The Canonical Inhomogeneous Wave Equation of Linear Acoustics . . . . . . . . . . . . . . . . . . . . 1.3 Acoustic Wave Variables . . . . . . . . . . . . . . . . 1.4 Some Special Solutions . . . . . . . . . . . . . . . . . 1.5 Green’s Function and Rayleigh’s Integral . . . . 1.6 Transducer Fields . . . . . . . . . . . . . . . . . . . . . 1.7 Propagation Across Planar Boundaries . . . . . . 1.8 Finite Amplitude Waves. . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . ............... 1 ................ 1 . . . . . . . . . . . . . . . . Generation and Structure of Acoustic Fields . . . . . . . . . C. R. Hill 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Piezoelectric Devices . . . . . . . . . . . . . . . . . . . . . 2.3 The Fields of ‘Simple’, CW Excited Sources. . . . . 2.4 The Pulsed Acoustic Field . . . . . . . . . . . . . . . . . 2.5 Focused Fields . . . . . . . . . . . . . . . . . . . . . . . . . 2.6 Effects of the Human Body on Beam Propagation 2.7 Beam Formation by Transducer Arrays. . . . . . . . 2.8 The Field of the Toronto Hybrid . . . . . . . . . . . . 2.9 Generation of Therapy Fields . . . . . . . . . . . . . . . 2.10 Magnitudes of Acoustic Field Variables. . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . Detection and Measurement of Acoustic Fields C. R. Hill 3.1 Introduction . . . . . . . . . . . . . . . . . . . . 3.2 Piezoelectric Devices . . . . . . . . . . . . . . 3.3 Displacement Detectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. .. . . . . . 2 7 9 13 15 26 34 39 ............. 41 . . . . . . . . . . . . . . . . . . . . . . 41 42 46 48 48 56 56 59 59 62 63 .................... 69 .................... .................... .................... 69 70 77 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .