Magnetic Resonance Imaging: Physical Principles and Applications (Electromagnetism)

197 Pages·2000·11.49 MB·English

by  Vadim Kuperman

Magnetic Resonance
Imaging
PHYSICAL PRINCIPLES AND
APPLICATIONS
This is a volume in
ELECTROMAGNETISM
.... o .......... o ............ o ..............
ISAAK MAYERGOYZ~ SERIES EDITOR
UNIVERSITY OF MARYLAND
COLLEGE PARK, MARYLAND
Magnetic Resonance
Imaging
PHYSICAL PRINCIPLES AND
APPLICATIONS
VADIM KUPERMAN
University of Chicago
Chicago, Illinois
ACADEMIC PRESS
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To my dear wife Leslie,
whose constant love and support are precious to me.
I could not have written this book without her by my side.
This Page Intentionally Left Blank
Contents
Foreword xi
Acknowledgements xiii
Introduction 1
References 7
Chapter I Basic Principles of Nuclear Magnetic
Resonance 9
1.1. The Phenomenon of NMR 9
1.2. Motion of Magnetic Moments 12
1.3. The Bloch Equations 15
1.4. Basic NMR Experiment 17
1.5. T~ Decay 19
1.6. Spin Echoes 21
1.7. Signal Attenuation Due to Diffusion 24
References 26
Chapter 2 Excitation of the Transverse Magnetization 29
2.1. Dynamics of Repeatedly Excited Magnetization 29
2.2. Ernst Angle 34
2.3. Spatially Selective Excitation 35
References 39
VIo. I
viii Contents
Chapter 3 Basic Techniques for 2D and 3D MRI 41
3.1. Image Reconstruction from Discrete Samples 41
3.2. Frequency and Phase Encoding 44
3.3. Basic Gradient and Spin-echo Pulse Sequences 49
3.4. K-space 53
References 56
Chapter 4 Contrast in MR Imaging 57
4.1. Main Contrast Mechanisms in 1H MRI 58
4.2. Contrast Agents 64
4.3. Magnetization Transfer Contrast 67
4.4. Diffusion-Weighted Images 71
References 73
Chapter 5 Signal-to-Noise Ratio in MRI 77
5.1. Noise Variance in MR Images 77
5.2. SNR in 2D and 3D MRI 80
5.3. SNR Field Dependence 83
References 85
Chapter 6 Image Artifacts 87
6.1. Artifacts Due to Magnetic Field Nonuniformity 87
6.2. Chemical Shift Artifacts 90
6.3. Artifacts Due to Motion and Flow 95
6.4. MRI Techniques for Motion Artifact Reduction 100
References 107
Chapter 7 Rapid MR Imaging 111
7.1. Rapid Gradient-Echo Imaging 111
7.2. Echo-Planar Imaging 116
7.3. Fast Spin-Echo Imaging 120
Contents ix
7.4. Spiral Imaging 125
7.5. Partial k-Space Acquisition 128
References 133
Chapter 8 MR Imaging of Flow 135
8.1. Time-of-Flight Techniques 135
8.2. Phase-contrast MRA 143
8.3. Contrast-enhanced MRI of Flow 146
References 147
Chapter 9 MRI Instrumentation: Magnets, Gradient
Coils, and Radiofrequency Coils 151
9.1. Magnets 151
9.2. Gradient Coils 161
9.3. Radiofrequency Coils 164
References 171
Appendix 173
A. Phase-sensitive Detection 173
B. Image Display 175
Index 177