Photon-based Medical Imagery

Transcription

1 Photon-based Medical Imagery

2 Photon-based Medical Imagery Edited by Hervé Fanet

3 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 St George s Road 111 River Street London SW19 4EU Hoboken, NJ UK USA ISTE Ltd 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 Library of Congress Cataloging-in-Publication Data Photon-based medical imagery / edited by Hervé Fanet. p. ; cm. Includes bibliographical references and index. ISBN Diagnostic imaging. 2. Photons--Diagnostic use. I. Fanet, Hervé. [DNLM: 1. Diagnostic Imaging. 2. Photons--diagnostic use. WN 180] RC78.7.D53P '54--dc British Library Cataloguing-in-Publication Data A CIP record for this book is available from the British Library ISBN Printed and bound in Great Britain by CPI Antony Rowe, Chippenham and Eastbourne.

4 Table of Contents Foreword... Guy FRIJA xi Chapter 1. Interactions between Radiation and Matter: Consequences for Detection and Medical Imaging... 1 Jean-Pierre MOY 1.1. The limits of imaging using light Imaging with other types of radiation X-rays: their interaction with matter The production of X-rays Beer-Lambert s law The photoelectric effect Creation of pairs Deviation and loss of energy. The Compton effect Absorption and attenuation Chemical effects The dose Radiological imaging relies on the X-ray-matter interaction Image constitution Role of scattered radiation Consequences of interaction modes on detection Signal, noises Counting, integration Specific imaging problems Conclusion Bibliography... 33

5 vi Photon-based Medical Imagery Chapter 2. Detectors for Medical Imaging Hervé FANET 2.1. Radiation-matter interaction and signal formation A simple case of a plane detector: phenomenological explanation General case of the multi-electrode detector and weighting field Case with a real detector Examples of the silicon detector and the strip or pixel detector Influence of the dimension of the detector How the problem can be made more complicated Uses of current pulses for measurement Flux, energy, time and position measurements Flux measurements Measurement of energy Electronic noise Time measurement Position measurements Semi-conductor detectors The solid state ionization chamber Junction semi-conductor detectors Photoconduction Semi-conductor materials for detection Silicon detectors Germanium detectors Cadmium telluride detectors Scintillation and measurement channel Scintillator-based channel Scintillation mechanisms Inorganic materials Organic materials Quality of time and energy measures Principlesand use of photomultipliers Photocathode technology Coupling the scintillator and the photomultiplier Photodiodes Pixel detectors Major characteristics Imaging system technologies Bibliography

6 Table of Contents vii Chapter 3. Quantitative Digital Radiography Image Processing Jean RINKEL and Jean-Marc DINTEN 3.1. Introduction to flat-panel sensors X-ray detection techniques Performance evaluation Clinical applications Relation between physical quantities and radiographic acquisition Attenuation distribution Poly-chromaticity Scattered radiation Response of the sensor Synthesis Access to linear attenuation coefficients from the attenuation image Processes linked to sensor effects Correction of radiation scattered by the patient Access to physical dimensions by combining several X-rays of a flat sensor Dual-energy imaging Computed tomography with a flat sensor Conclusion Bibliography Chapter 4. X-Ray Tomography Françoise PEYRIN and Philippe DOUEK 4.1. Introduction Principle of the first acquisition systems Translation-rotation systems: first and second generations Fan-beam systems: third and fourth generations Physical aspects and the direct problem Nature of the tomographic image Modeling of the physical phenomenon Data modeling Principle of tomographic image reconstruction Problem positioning Analytical methods Discrete methods Conclusion Evolution of X-ray scanners and reconstruction algorithms Spiral systems Truly 3D systems

7 viii Photon-based Medical Imagery Spiral divergent systems Dual-source systems Introduction to dosimetry Examples of clinical applications Introduction Cardiac CT: ECG synchronization Perfusion imaging From tomography to micro-tomography Osteo-articular applications Peripheral tomography systems Micro-tomography systems Conclusion Bibliography Chapter 5. Positron-Emission Tomography: Principles and Applications Régine TRÉBOSSEN 5.1. Introduction Definition PET compared with other molecular imaging techniques PET: principle and performance Radiopharmaceuticals The physical principle of PET Acquired data processing Reconstruction of images Main PET performance PET systems Detector PET systems Disposition of detectors Uniformity of spatial resolution in the field of view: measurement of interaction depth Measurement of time of flight PET for cancer staging Physiological basis Acquisition and reconstruction protocol Image interpretation: sensitivity and specificity Conclusion Bibliography

8 Table of Contents ix Chapter 6. Single Photon Imaging Irène BUVAT 6.1. Introduction Overview of single photon imaging Radiopharmaceuticals Detectors Signal processing Conventional detection systems in single photon imaging: the scintillation gamma camera Overview of a conventional scintillation gamma camera Options in the components of the scintillation camera Performances and use of conventional scintillation cameras Innovative systems: semiconductor detectors Tomographic reconstruction and corrections Tomographic reconstruction Corrections Hybrid detectors Applications Future developments Conclusion Bibliography Chapter 7. Optical Imaging Anabela DA SILVA 7.1. Introduction Physics of luminous propagation in biological tissue Scales of measurement and resolution: different imaging techniques Light-matter interaction From direct to inverse problem Different optical imaging techniques for different applications Selecting ballistic or snake photons Multiscattered photons Conclusion Bibliography List of Authors Index

9 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

10 xii Photon-based Medical Imagery 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