Medical Imaging Based on Magnetic Fields and Ultrasounds E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 460

Veröffentlichungsjahr: 2014

Beschreibung

This book describes the different principles and equipment used in medical imaging. The importance of medical imaging for diagnostics is rapidly increasing. A good working knowledge of all the different possible physical principles involved in medical imaging is now imperative. This book covers many of these principles including matter photon interactions, the principles of detectors, detectors and information processing for radiology, X-ray tomography, positron tomography, single photon tomography and optical tomography.

Leseprobe

Table of Contents

Foreword

Chapter 1: Ultrasound Medical Imaging

1.1. Introduction

1.2. Physical principles of echography

1.3. Medical ultrasound systems

1.4. The US image

1.5. Recent advances in ultrasound imaging

1.6. A bright future for ultrasound imaging

1.7. Bibliography

Chapter 2: Magnetic Resonance Imaging

2.1. Introduction

2.2. Fundamental elements for MRI

2.3. Instrumentation

2.4. Image prope

2.5. Imaging sequences and modes of reconstruction

2.6. Application of MRI: uses and evolution in the biomedical field

2.7. Bibliography

List of Authors

Index

First published 2014 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc.

Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address:

ISTE Ltd

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www.iste.co.uk

John Wiley & Sons, Inc.

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USA

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© ISTE Ltd 2014

The rights of Hervé Fanet to be identified as the author of this work have been asserted by him in accordance with the Copyright, Designs and Patents Act 1988.

Library of Congress Control Number: 2013956559

British Library Cataloguing-in-Publication Data

A CIP record for this book is available from the British Library

ISBN 978-1-84821-502-3

Foreword

After almost a century of quiescence, medical imaging has experienced considerable progress over the past thirty years. This progress has resulted primarily from the convergence of major innovations in the fields of detection, information processing and instrumentation. It should be stressed from the very outset that this convergence would never have happened without the extraordinary progression of computing power, the use of which is an absolute necessity nowadays, in view of the enormous increase in the volume of data needing to be handled. Although originally, X-rays, nuclear medicine, MRI and ultrasounds represented mutually independent “monospectral” methods, it is evident today that another convergence is coming about: that of multispectral imaging, stemming from the combination of two imaging techniques in the same piece of equipment. The best example of this would be positron emission tomography – computed tomography (PET-CT). Let us also point out that the capabilities offered by this convergence go beyond the diagnosis stage – the device can also be used in a therapeutic capacity: a very typical example is focused high-energy ultrasounds under MRI.

Information sciences and the development of “physiological” models have opened up functional imaging for the use of methods initially used for their morphological properties: the extraction of circulatory parameters from dynamic scanner or MRI sequences has become an essential tool in the study of tumor response.

Initially developed with a view to studying the whole body, high-resolution imaging techniques are beginning to emerge: an example is optical imaging, but the weakness of this technique is the small sample size. However, its use on humans, particularly in endoscopy and likely, in tomorrow’s world, in imaging-guided biopsy methods, appears to have a very bright future.

While imaging is the subject of very intense intrinsic research, it is also considered a crucial tool in physiological and metabolic research, or even cognitive research by integration of physiological signals with imaging data. Thus, methods for magnetic tattooing of cardiac muscle have opened up numerous avenues for the physiology of heart contraction; the study of aortic distendibility is now considered an early sign of aging. In addition, these imaging methods have become absolutely essential in pre-clinical trials on animals: thus, the development of new medicines benefits greatly from such methods. More generally, platforms for imaging of small animals have developed in the context of multidisciplinarity, and demonstrate the interconnection of imaging with the physical sciences, information sciences, chemical sciences and biological sciences.

In this context, the development and fine-tuning of markers and tracers represent a common goal for all imaging methods; the molecular imaging which has already been developed in the field of nuclear medicine should see future progress with other imaging techniques, both in animals and in humans. Substances with diagnostic and therapeutic properties are beginning to come to light, and are developing with no difficulty at all. Thus, progress is also being made in imaging, by way of the advances made in the field of chemistry.

The aim of this book is to provide an overview of the progress made in the various domains of imaging from various different angles: there can be no doubt that readers will find it enriching.

Guy FRIJAJanuary 2014

Chapter 1

Ultrasound Medical Imaging

1.1. Introduction

Ultrasound imaging accompanies each of us, from several months before we are born, throughout our lives. To monitor our development, 17 million ultrasound examinations are performed each year in France in the private sector, and around twice that if we add those done in the public sector. Thus, ultrasound imaging is the most widely used type of imaging for diagnostics after radiography. The world market for ultrasonography is still growing, and is worth an estimated 4.9 billion dollars (data from 2009). Ultrasonography plays a central role, both in hospitals and in doctors’ surgeries. The reasons for its ever-growing success are mainly based on its portability, its reasonable cost in comparison with other methods, its performances in terms of yielding results in real time and the fact that it uses non-ionizing waves. Historically, ultrasonography is associated with specialties in obstetrics for pregnancy-monitoring and cardiology. Today, ultrasound medical imaging covers a far wider range of specialties like no other type of imaging. Imaging of the digestive system, breasts, liver with elastography, thyroid or prostate, are examples of the most commonly performed operations [HTT 09].

In the future, significant progress is expected which will enable a doctor to reach a more certain diagnosis in a shorter period of time. For this to happen, technological innovations will be accompanied by methodological developments in signal- and image processing. 3D or 4D imaging techniques, particularly in the area of cardiovascular care, are likely to emerge in the near future, with the development of new probes and new modes of acquisition, e.g. using sparse sampling techniques. At the same time, progress in modeling, simulation and image processing will be at the heart of new quantitative analysis software built into ultrasound machines. The diagnosis of myocardial infarction, the replacement of the heart valves or the detection of atherosclerosis are examples of medical exams for which these innovations will be essential (Figure 1.1).

Figure 1.1.Program for measuring the volume of the left ventricle of the heart, running on a Vivid 6 clinical echogram machine (GE HealthCare). For a color version of this figure, seewww.iste.co.uk/fanet/medimagnet.zip

Other means of imaging based on estimation of the physical properties of healthy and diseased tissues will also supplement conventional imaging tools. Different modes of quasi-static, dynamic or transient elastography should be able to quantify the elasticity of tissues for diagnosing liver disorders or quantify the development of cancer, for instance.

In this chapter, we are going to present both the physical basics of ultrasound (US) imaging and the main advances expected of the echography of tomorrow. The chapter begins with a presentation of the physical principles upon which ultrasound imaging is based. Then, we shall detail the different modes of imaging in ultrasound systems: B-mode, M-mode, Doppler modes, contrast and harmonic imaging. The hardware aspects will also be touched upon, with a discussion of the different types of linear or sectorial probes used in clinical practice, depending on the compromise between resolution and penetration. We shall then return to statistical analysis of the US image using the properties of the ultrasound speckle. This knowledge will help to simulate realistic images and sequences which are useful to validate the image formation models and processing methods. The final part of this chapter will be given over to the advances in ultrasound image acquisition and processing which will serve as a diagnostic aid to doctors. We shall present the most recent probe technologies which are based on new materials to transmit and receive ultrasounds in 2D and 3D with sensor matrices. These probes can be based on innovative methods of image formation using the methods of synthetic aperture, “tagging” or sparse sampling. We shall also illustrate the contribution made by new techniques such as elastography, nonlinear imaging or parametric imaging, and the performances of real-time tracking methods or motion estimation more generally. The end of the chapter will be devoted to multimodality imaging. Using the example of bi-modal US/Optical imaging, we shall show that the combination of the anatomical information provided by the US image with the functional or metabolic information provided by the other modes of imaging facilitates a more effective aid to diagnosis and monitoring of the evolution of diseases.