Photon-based Medical Imagery E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 511

Veröffentlichungsjahr: 2013

Beschreibung

This book describes the different principles and equipments used in medical imaging. Importance of medical imaging for diagnostic is strongly increasing and it is now necessary to have a good knowledge of the different physical possible principles. Researchers, clinicians, engineers and professionals in this area, along with postgraduate students in the signal and image processing field, will find this book of great interest.

Leseprobe

Table of Contents

Foreword

Chapter 1. Interactions between Radiation and Matter: Consequences for Detection and Medical Imaging

1.1.The limits of imaging using light

1.2.Imaging with other types of radiation

1.3.X-rays: their interaction with matter

1.4.Radiological imaging relies on the X-ray-matter interaction

1.5.Consequences of interaction modes on detection

1.6.Conclusion

1.7.Bibliography

Chapter 2. Detectors for Medical Imaging

2.1.Radiation-matter interaction and signal formation

2.2.Flux, energy, time and position measurements

2.3.Semi-conductor detectors

2.4.Scintillation and measurement channel

2.5.Pixel detectors

2.6.Bibliography

Chapter 3. Quantitative Digital Radiography Image Processing

3.1.Introduction to flat-panel sensors

3.2.Relation between physical quantities and radiographic acquisition

3.3.Access to linear attenuation coefficients from the attenuation image

3.4.Access to physical dimensions by combining several X-rays of a flat sensor

3.5.Conclusion

3.6.Bibliography

Chapter 4. X-Ray Tomography

4.1.Introduction

4.2.Principle of the first acquisition systems

4.3.Physical aspects and the direct problem

4.4.Principle of tomographic image reconstruction

4.5.Evolution of X-ray scanners and reconstruction algorithms

4.6.Examples of clinical applications

4.7.From tomography to micro-tomography

4.8.Conclusion

4.9.Bibliography

Chapter 5. Positron-Emission Tomography: Principles and Applications

5.1.Introduction

5.2.PET: principle and performance

5.3.PET systems

5.4.PET for cancer staging

5.5.Conclusion

5.6.Bibliography

Chapter 6. Single Photon Imaging

6.1.Introduction

6.2.Overview of single photon imaging

6.3.Conventional detection systems in single photon imaging: the scintillation gamma camera

6.4.Innovative systems: semiconductor detectors

6.5.Tomographic reconstruction and corrections

6.6.Hybrid detectors

6.7.Applications

6.8.Future developments

6.9.Conclusion

6.10.Bibliography

Chapter 7. Optical Imaging

7.1.Introduction

7.2.Physics of luminous propagation in biological tissue

7.3.Different optical imaging techniques for different applications

7.4.Conclusion

7.5.Bibliography

First published 2011 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc. Adapted and updated from Imagerie médicale à base de photons : radiologie, tomographie X, tomographie gamma et positons, imagerie optique published 2010 in France by Hermes Science/Lavoisier © LAVOISIER 2010

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

John Wiley & Sons, Inc.

27-37 St George’s Road

111 River Street

London SW19 4EU

Hoboken, NJ 07030

UK

USA

www.iste.co.uk

www.wiley.com

© ISTE Ltd 2011

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 Cataloging-in-Publication Data

Photon-based medical imagery / edited by Hervé Fanet.

      p. ; cm. Includes bibliographical references and index. ISBN 978-1-84821-241-1

1. Diagnostic imaging. 2. Photons--Diagnostic use. I. Fanet, Hervé. [DNLM: 1. Diagnostic Imaging. 2. Photons--diagnostic use. WN 180] RC78.7.D53P46 2011 616.07'54--dc23

2011012245

British Library Cataloguing-in-Publication Data

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

ISBN 978-1-84821-241-1

Foreword

After 100 years of latency, medical imaging has been the subject of considerable evolution in the last 30 years. This is mainly the result of the convergence of major innovations in the field of detection, information processing, and instrumentation. This convergence would not have happened without the extraordinary progress of computation power, which is necessary because of the considerable increase in data processing. Previously radiography, nuclear medicine, magnetic resonance imaging (MRI), and ultrasound used to represent “single spectral” methods, independent from one another; however, today emerging techniques called multispectral imaging combine two imaging techniques in the same device, the most accomplished example is positron-emission tomography-computed tomography (PET-CT). This convergence enables us to go beyond the diagnostic stage and reach that of therapy: MRI-based high-energy focused ultrasound is a perfect example.

Information sciences and the development of “physiological” models opened up functional imaging to methods initially used for their physical properties: the extraction of circulation parameters from dynamic scanners or MRI sequences has become an essential tool in the study of tumor response to therapy.

Initially intended for the study of the whole body, high-resolution imaging techniques are starting to emerge: the same can be said for optical imaging, but this is limited because of low sampling. However, its use on man, notably in the endoscopy methods and in the future, probably in imaging-guided biopsy methods, seems very promising.

Imaging is the subject of very intense intrinsic research, and conversely, is considered as an essential tool in physiological and metabolic, or even cognitive, research, because of the integration of physiological signals to imaging data. In this way, magnetic tattoo methods on the cardiac muscle have elucidated the physiology of contraction; the study of aortic stiffness shows that it can presently be considered as an early marker for ageing. In addition, these imaging methods have become vital in preclinical studies in animals: the development of new drugs greatly benefits from these methods. In a more general way, small animal imaging platforms have been developed in a context of multidisciplinarity, and show the interconnection of imaging with physical sciences, information sciences, chemistry, and biology.

In this context, the setup and development of markers and tracers represent a common issue for all imaging methods; having already been developed in nuclear medicine, contrast materials for molecular and other forms of imaging in animals or man should be the subject of future progress. Substances with diagnostic and therapeutic properties are starting to emerge and are being developed. Imaging progress is also achieved through advances in the field of chemistry.

This book is an attempt to define the progress achieved in the different imaging fields; undoubtedly, the reader will come out with a richer understanding.

Guy FRIJA

Chapter 1

Interactions between Radiation and Matter: Consequences for Detection and Medical Imaging1

The goal of medical imaging is to provide the practitioner with information to reveal, examine, or diagnose disease. Light is absorbed, scattered, or reflected by most types of matter over a very short distance, a few dozen to a few hundred microns for biological tissues, for example.

1.1. The limits of imaging using light

Medical imaging must provide the practitioner with information on the internal organs to provide a better diagnosis or to direct surgery. Endoscopy provides high-quality visual images of the body's cavities, such as bronchial tubes, the stomach, or the intestine. However, these tests are often complex, requiring preparation and/or anesthesia, and can be risky; therefore, they are usually reserved for cases where visual information provides a real advantage, particularly when surgery can be performed at the same time as the observation (a colonoscopy or an arthroscopy for example). With the aim of extracting information on organs or internal lesions, numerous studies are trying to develop light-scattering techniques in live tissue.

Hemoglobin greatly absorbs wavelengths shorter than 600 nm, and water absorption strongly increases beyond 900 to 1,000 mn. The result is a spectral window between 650 nm and 1 μm for which the absorption of light in animal tissueis minimal. Despite weak transmission, a measurable quantity of light remains in the tissue at a depth of a few centimeters. However, the heterogeneity of the envirormient causes very strong scattering, so much so that there are no longer any direct rays (so-called ballistic photons) providing optical imaging.

A digital reconstruction of the three-dimensional structure of the area observed is possible from the distribution of scattered light on the outside surface for different positions of a source located on the other side of the observation. This is the principle of optical tomography.

The use of a fluorescent marker with a specific affinity for the examined object, for example a tumor, makes it possible to detect the object within the tissue. As fluorescence occurs at a different wavelength than excitation, and as it comes completely from the inside, we can use more sensitive detection processes, because direct light does not impede the light to be detected, as in the case of optical tomography. This method is particularly useful for small animal imaging [KOE 07], and for the human body in applications involving superficial organs or areas where endoscopy can be considered.

1.2. Imaging with other types of radiation

In order to provide a complete image of the internal organs regardless of distance, we must use penetrating radiation, which is able to traverse 1030 cm of tissue of low attenuation.

X-rays have this power of penetration through tissue. They have been used for this purpose ever since they were discovered by Röntgen in 1895. At first, they offered projection imaging; the contrast was the result of the absorption differences associated with the composition of organs. y-rays, in the same vein as X-rays, are also used.

True three-dimensional imaging appeared in the mid-1970s with tomographic reconstruction. We can pick up several projections from different angles, and the structure of the object is reconstituted with the help of mathematical transformations from these projections. As with fluorescence imaging, the source can be incorporated into the patient in the form of radio-active markers, which reside in an organ or a lesion; for example in scintigraphy, or positron-emission tomography (PET).

Radiofrequencies are easily transmitted, but the wavelengths are too long to provide sufficient resolution of transmission imaging. An interesting case, however, is that of nuclear magnetic resonance (NMR) imaging.

In NMR, we measure the intensity and frequency of radiation transmitted by the precession of the magnetic moment of the nucleus in a magnetic field, after a brief magnetogenic excitation. Most of the time, we focus on the hydrogen atom nucleus. The radiation wavelength is no longer a limit to resolution, because the size and position of the small volume observed are defined by the characteristics of the applied field, the signal only indicates the quantity of interacting nucleus in that area.