FUNDAMENTALS OF MEDICAL IMAGING
Paul Suetens
Katholieke Universiteit Leuven
With contributions from
Bruno De Man, Jan D'hooge, Frederik Maes, Johan Michiels,
Johan Nuyts, Johan Van Cleynenbreugel, and Koen Vande Velde
Cambridge University Press 2002
FROM THE BACK COVER
Medical imaging has become a very important technology in medical diagnosis and
treatment. This book explains the mathematical and physical principles of medical
imaging and image processing, from how medical images are obtained to how they
are used.
The book begins with an introduction to digital image processing. The following
chapters explain the most important imaging modalities in use today: radiography,
computed tomography, magnetic resonance imaging, ultrasonic imaging, and nuclear
medicine imaging. Each chapter includes a short history of the imaging modality, the
physics of the signal and its interaction with tissue, the image formation or
reconstruction process, a discussion of the image quality, the different types of
equipment, examples of clinical applications, a brief description of the biological
effects and safety issues, and future expectations The remainder of the book deals
with image analysis and visualization for diagnosis, therapy, and surgery after images
are available. Color plates complement the text, and a CD-Rom packaged with the
book includes all the images in color, as well as animations.
Both students and beginning biomedical engineers will welcome this well-balanced,
copiously illustrated treatment of medical imaging.
Paul Suetens is Professor of Medical Imaging and Image Processing and Head of
the Center for Processing Speech and Images in the Department of Electrical
Engineering (ESAT/PSI) at Katholieke Universiteit Leuven. He is also head of the
interdisciplinary research unit Medical Image Computing, a joint initiative of the
Faculty of Engineering and the Faculty of Medicine located in the Department of
Radiology of the University Hospital Leuven.
CONTENTS
Preface xi
Acknowledgments xiii
Part One: Introduction to Digital Image Processing
1. Definitions 3
1.1 Digital Images 3
1.2 Image Quality 5
2. Linear Systems Theory 8
2.1 Introduction 8
2.2 Signals 8
2.2.1 Definitions and Examples 8
2.2.2 The Dirac Impulse 11
2.3 Systems 12
2.3.1 Definitions and Examples 12
2.3.2 Convolution 14
2.3.3 Response of an LSI System 15
2.4 The Fourier Transform 16
2.4.1 Definitions 16
2.4.2 Examples 17
2.4.3 Properties 20
2.4.4 Polar Form of the Fourier Transform 22
2.5 Sampling 22
3. Image Operations 27
3.1 Introduction 27
3.2 Gray Level Transformations 27
3.3 Multi-Image Operations 29
3.4 Geometric Operations 31
3.5 Filters 32
3.5.1 Linear Filters 32
3.5.2 Nonlinear Filters 37
3.6 Multiscale Image Enhancement 38
3.6.1 Multiscale Image Representation 40
3.6.2 Image Enhancement by Nonlinear Mapping 42
Part Two: Medical Imaging Modalities
4. Radiography 47
4.1 Introduction 47
4.2 X rays 47
4.3 Interaction with Matter 49
4.3.1 Interaction of Photons with Matter 49
4.3.2 Interaction of an X-ray Beam with Tissue 49
4.4 X-ray Detectors 51
4.4.1 Screen-Film Detector 51
4.4.2 Image Intensifier 53
4.4.3 Detectors for Computed Radiography 54
4.5 Image Quality 56
4.5.1 Resolution 56
4.5.2 Noise 57
4.5.3 Contrast 57
4.5.4 Artifacts 57
4.6 Equipment 57
4.7 Clinical Use 58
4.8 Biologic Effects and Safety 62
4.9 Future Expectations 64
5. X-ray Computed Tomography 66
5.1 Introduction 66
5.2 X-ray Detectors in CT 68
5.2.1 Scintillation Crystal with Photomultiplier Tube 68
5.2.2 Gas Ionization Chambers 69
5.2.3 Scintillation Crystals with Photodiode 69
5.3 Imaging 69
5.3.1 Data Acquisition 69
5.3.2 Image Reconstruction 74
5.3.3 Imaging in Three Dimensions 81
5.4 Image Quality 83
5.4.1 Resolution 83
5.4.2 Noise 84
5.4.3 Contrast 85
5.4.4 Image Artifacts 85
5.5 Equipment 87
5.5.1 Scanner Generations 88
5.5.2 Internal Geometry 89
5.5.3 Multislice CT 90
5.5.4 Dynamic Spatial Reconstructor 92
5.5.5 Electron Beam Tomography 93
5.6 Clinical Use 95
5.7 Biologic Effects and Safety 96
5.8 Future Expectations 97
6. Magnetic Resonance Imaging 99
6.1 Introduction 99
6.2 Physics of the Transmitted Signal 99
6.2.1 Angular Momenta and Magnetic Moments 99
6.2.2 Dynamic Equilibrium: The Net Magnetization Vector of Matter 104
6.3 Interaction with Tissue 105
6.3.1 Disturbing the Dynamic Equilibrium: The RF Field 105
6.3.2 Return to Dynamic Equilibrium: Relaxation 106
6.4 Signal Detection and Detector 108
6.5 Imaging 109
6.5.1 Introduction 109
6.5.2 Slice or Volume Selection 110
6.5.3 Position Encoding: The k-Theorem 111
6.5.4 Dephasing Phenomena 113
6.5.5 Basic Pulse Sequences 115
6.5.6 Three-Dimensional Imaging 118
6.5.7 Acquisition and Reconstruction Time 119
6.5.8 Very Fast Imaging Sequences 120
6.5.9 Imaging of Moving Spins 122
6.5.10 Functional Imaging 129
6.6 Image Quality 130
6.6.1 Contrast 130
6.6.2 Resolution 131
6.6.3 Noise 134
6.6.4 Artifacts 134
6.7 Equipment 135
6.8 Clinical Use 138
6.9 Biologic Effects and Safety 141
6.9.1 Biologic Effects 141
6.9.2 Safety 141
6.10 Future Expectations 143
7. Ultrasonic Imaging 145
7.1 Introduction 145
7.2 Physics of Acoustic Waves 146
7.2.1 What Are Ultrasonic Waves? 146
7.2.2 Generation of Ultrasonic Waves 147
7.2.3 Wave Propagation in Homogeneous Media 147
7.2.4 Wave Propagation in Inhomogeneous Media 153
7.2.5 Wave Propagation and Motion: Doppler 156
7.3 Generation and Detection of Ultrasound 158
7.4 Gray Scale Imaging 159
7.4.1 Data Acquisition 159
7.4.2 Image Reconstruction 161
7.4.3 Acquisition and Reconstruction Time 163
7.5 Doppler Imaging 164
7.5.1 Data Acquisition 164
7.5.2 Reconstruction 164
7.5.3 Acquisition and Reconstruction Time 168
7.6 Image Quality 168
7.6.1 Spatial Resolution 168
7.6.2 Noise 170
7.6.3 Image Contrast 171
7.6.4 Gray Scale Image Artifacts 171
7.6.5 Doppler Image Artifacts 172
7.7 Equipment 172
7.7.1 One-Dimensional Array Transducers 172
7.7.2 Transducers for 3D Imaging 174
7.7.3 Special-Purpose Transducers 175
7.8 Clinical Use 175
7.8.1 Gray Scale Imaging 176
7.8.2 Doppler Imaging 181
7.8.3 Contrast Echography 181
7.9 Biologic Effects and Safety 182
7.10 Future Expectations 182
8. Nuclear Medicine Imaging 184
8.1 Introduction 184
8.2 Radionuclides 185
8.2.1 Radioactive Decay Modes 185
8.2.2 Statistics 187
8.3 Interaction of Photons with Matter 187
8.4 Data Acquisition 188
8.4.1 The Detector 188
8.4.2 Detected Number of Photons 191
8.4.3 Energy Resolution 191
8.4.4 Count Rate 191
8.5 Imaging 192
8.5.1 Planar Imaging 192
8.5.2 2D Fourier Reconstruction and Filtered Backprojection 192
8.5.3 2D Iterative Reconstruction 193
8.5.4 3D Reconstruction 197
8.6 Image Quality 199
8.6.1 Contrast 199
8.6.2 Spatial Resolution 199
8.6.3 Noise 200
8.6.4 Artifacts 200
8.7 Equipment 201
8.7.1 Gamma Camera and SPECT Scanner 201
8.7.2 PET Scanner 202
8.8 Clinical Use 204
8.9 Biologic Effects and Safety 207
8.10 Future Expectations 209
Part Three. Image Analysis and
Visualization for Diagnosis, Therapy, and Surgery
9. Medical Image Analysis 213
9.1 Introduction 213
9.2 Manual Analysis 214
9.3 Automated Analysis 216
9.4 Computational Strategies for
Automated Medical Image Analysis 220
9.4.1 Pixel Classification 223
9.4.2 Fitting Rigid Models to Photometry 228
9.4.3 Fitting Flexible Models to Photometry 231
9.5 Validation 239
9.6 Future Expectations 241
10. Image-Guided Interventions 243
10.1 Introduction 243
10.2 Stereotactic Neurosurgery, the
Pioneer of Image-Guided Interventions 244
10.3 Stereotactic Neurosurgery Based on Digital Image Volumes 247
10.3.1 Image Acquisition 247
10.3.2 Planning 249
10.3.3 Transfer 250
10.4 Evolutions in Stereotactic Neurosurgery 251
10.4.1 Image Acquisition 252
10.4.2 Planning 254
10.4.3 Transfer 256
10.5 Image Guidance for Rigid Structures 259
10.5.1 Complex Trajectories 260
10.5.2 Templates 260
10.5.3 Tracking Moving Anatomical Structures 263
10.6 Intraoperative Imaging 263
10.6.1 Intraoperative Diagnostic Imaging 263
10.6.2 Transfer by Matching Preoperative with Intraoperative Images 263
10.6.3 Augmented Reality (AR) 264
10.7 Future Expectations 266
References 269
Bibliography 271
Index 273
Color plates follow p. 281
PREFACE
This book explains the applied mathematical and physical principles of medical
imaging and image processing. It gives a complete survey of how medical images
are obtained and how they can be used for diagnosis, therapy, and surgery.
It has been written principally as a course text on medical imaging intended for
graduate and last-year undergraduate students with a background in physics,
mathematics, or engineering. Although a large proportion of the book covers the
physical principles of imaging modalities, the emphasis is always on how the image
is computed. Equipment design, clinical considerations, and image interpretation are
treated in less detail. Presently, books on medical imaging fall into two groups,
neither of which is suitable for this readership. The first group is the larger and
comprises books directed primarily at the less numerate professions such as
physicians, surgeons, and radiologic technicians. These books cover the physics and
mathematics of all the major medical imaging modalities, but mostly in a superficial
way. They do not allow any real understanding of these imaging modalities. The
second group comprises books suitable for professional medical physicists or
researchers in the field. Although these books have a numerate approach, they tend
to cover the topics too deeply for the beginner and to have a narrower scope than
this book.
The text reflects what I teach in class, but there is somewhat more material than I can
cover in a module of 30 contact hours. This means that there is scope for the stronger
student to read around the subject and also makes the book a useful purchase for
those going on to do research. Nevertheless, there are no unnecessary details.
Premature techniques or topics under investigation have been omitted.
The book consists of three parts. In Part One, an introduction to digital image
processing is given. It summarizes the jargon used by the digital image community,
the theory about linear systems needed to understand most of the medical imaging
methods, and basic image operations to process digital images. Some sections
may seem rather dry, but the topics are an essential basis for the subject.
Nevertheless, the reader who has studied this matter elsewhere may skip the
related paragraphs or chapters in this part of the book.
Part Two explains how medical images are obtained. The most important imaging
modalities today are discussed: radiography, computed tomography, magnetic
resonance imaging, ultrasonic imaging, and nuclear medicine imaging. Each chapter
includes (1) a short history of the imaging modality, (2) the theory about the physics
of the signal and its interaction with tissue, (3) the image formation or reconstruction
process, (4) a discussion of the image quality, (5) the different types of equipment
today, (6) examples of the clinical use of the modality, (7) a brief description of the
biologic effects and safety issues, and (8) future expectations.
Part Three deals with image analysis and visualization for diagnosis, therapy, and
surgery once images are available. Medical images can, for example, be analyzed
to obtain quantitative data, or they can be displayed in three dimensions and actively
used to guide a surgical intervention. Most courses separate the imaging theory from
the postprocessing, but I strongly believe that they should be taken together
because the topics are integrated. The interest in clinical practice today goes beyond
the production and diagnosis of an image, and the objective then is to calculate
quantitative information or to actively use the images during patient treatment.
The field of medical imaging and image processing can also be approached from the
perspective of information and communication and the supporting technology, such
as hospital information systems, the electronic patient record, and PACS (picture
archiving and communication systems). However, this focus would put the emphasis
on informatics, such as networking, data bases, user interfaces, internet technology,
and computer graphics, which is not the purpose of this book.
In the bibliography, references to untreated topics can be found as well as a list of
more specialized works on a particular subdomain and some other generic
textbooks related to the field of medical imaging and image processing.
Paul Suetens
WHERE TO ORDER
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Phone: 1-800-872-7423
Fax: 914-937-4712
Web site: http://www.cambridge.org
Price: $100.00(Hardbound) ISBN: 0-521-80362-4
URL: http://www.primate.wisc.edu/pin/review/fundamentals.html
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