Medical Imaging Based on Magnetic Fields and Ultrasounds (eBook)

Hervé Fanet is a Senior Scientist at CEA LETI in France. Previously head of the medical instrumentation department, he is now in charge of low power research programs.

Foreword ix

Guy FRIJA

Chapter 1. Ultrasound Medical Imaging 1

Didier VRAY, Elisabeth BRUSSEAU, Valérie DETTI,
François VARRAY, Adrian BASARAB, Olivier BEUF, Olivier BASSET,
Christian CACHARD, Hervé LIEBGOTT, Philippe
DELACHARTRE

1.1. Introduction 1

1.2. Physical principles of echography 3

1.2.1. Ultrasound waves 3

1.2.2. Wavefronts 4

1.2.3. Stress/Strain relation 5

1.2.4. Propagation equation 6

1.2.5. Acoustic impedance 7

1.2.6. Acoustic intensity 7

1.2.7. Mechanical Index 9

1.2.8. Generation, emission 9

1.2.9. Resolution 10

1.2.10. Propagation of a plane wave in a finite isotropic medium
11

1.2.11. Propagation of a plane wave in a non-homogeneous medium
13

1.2.12. Speckle 15

1.2.13. Nonlinear waves 16

1.2.14. Contrast agents 17

1.3. Medical ultrasound systems 18

1.3.1. Principle 18

1.3.2. The different stages in image formation 19

1.3.3. Ultrasound imaging probe 21

1.3.4. Modes of imaging, B-mode and M-mode, and harmonic imaging
modes 24

1.3.5. Doppler imaging 27

1.4. The US image 34

1.4.1. Properties of speckle, echostructure and statistical
laws 34

1.4.2. Segmentation of US images 38

1.4.3. Simulation of US images 41

1.5. Recent advances in ultrasound imaging 44

1.5.1. Generation/emission of ultrasounds 44

1.5.2. Signal- and image processing 49

1.5.3. Multimodal imaging 60

1.6. A bright future for ultrasound imaging 65

1.7. Bibliography 65

Chapter 2. Magnetic Resonance Imaging 73

Dominique SAPPEY-MARINIER and André BRIGUET

2.1. Introduction 73

2.2. Fundamental elements for MRI 76

2.2.1. Introduction 76

2.2.2. Vectorial description of nuclear magnetic resonance (NMR)
78

2.2.3. RF pulses and their effect on magnetizations 88

2.2.4. Elementary pulse sequences using the refocusing
technique 97

2.2.5. Spatial discrimination of signals using gradients:
fundamental principle of MRI 106

2.2.6. Multi-parameter aspect of MRI 110

2.3. Instrumentation 115

2.3.1. Introduction 115

2.3.2. Recording the signal 117

2.3.3. Magnetic systems 129

2.3.4. A typical MRI installation in a clinical environment
136

2.3.5. Operation and safety 139

2.4. Image properties 144

2.4.1. Introduction 144

2.4.2. Field of view 144

2.4.3. Spatial resolution 148

2.4.4. Contrast and signal 155

2.4.5. Contrast elements in MRI practice 162

2.5. Imaging sequences and modes of reconstruction 168

2.5.1. Introduction 168

2.5.2. Overall view of acquisition sequences 168

2.5.3. Modes of reconstruction 195

2.6. Application of MRI: uses and evolution in the biomedical
field 208

2.6.1. Introduction 208

2.6.2. Spectroscopy and imaging: technical and clinical
complementarity 210

2.6.3. Diffusion MRI: a morphological and functional
approach 217

2.6.4. Functional MRI (fMRI) of cerebral activation 236

2.6.5. Bi-modal approach to MRI: the example of
MR/PET 239

2.7. Bibliography 244

List of Authors 263

Index 265