MRI in Practice

Preface to the Fifth Edition ix Acknowledgments xi List of Acronyms xiii Equation symbols xvii About the Companion Website xix Chapter 1 Basic principles 1 Introduction 1 Atomic structure 2 Motion in the atom 2 MR active nuclei 4 The hydrogen nucleus 5 Alignment 6 Net magnetic vector (NMV) 8 Precession and precessional (Larmor) frequency 10 Precessional phase 13 Resonance 13 MR signal 18 The free Induction decay(FDI) signal 20 Pulse timing parameters 22 Chapter 2 Image weighting and contrast 24 Introduction 24 Image contrast 25 Relaxation 25 T1 recovery 26 T2 decay 27 Contrast mechanisms 31 Relaxation in different tissues 32 T1 contrast 36 T2 contrast 40 Proton density contrast 41 Weighting 42 Other contrast mechanisms 51 Chapter 3 Spin echo pulse sequences 58 Introduction 58 RF rephasing 59 Conventional spin echo 65 Fast or turbo spin echo FSE/TSE) 68 Inversion recovery (IR) 78 Short tau inversion recovery (STIR) 82 Fluid attenuated inversion recovery (FLAIR) 84 Chapter 4 Gradient echo pulse sequences 89 Introduction 89 Variable flip angle 90 Gradient rephasing 91 Weighting in gradient echo pulse sequences 94 Coherent or rewound gradient echo 106 Incoherent or spoiled gradient echo 109 Reverse-echo gradient echo 113 Balanced gradient echo 119 Fast gradient echo 122 Echo planar imaging (EPI) 122 Chapter 5 Spatial encoding 128 Introduction 128 Mechanism of gradients 129 Gradient axes 134 Slice-selection 135 Frequency encoding 142 Phase encoding 145 Bringing it all together - pulse sequence timing 152 Chapter 6 k-space 158 Introduction 158 Part 1 - what is k-space? 159 Part 2 - how are data acquired and how are images created from this data? 165 Part 3 -some important facts about k-space 184 Part 4: how do pulse sequences fill k-space? 197 Part 5: options that fill k-space 199 Chapter 7 Protocol optimization 209 Introduction 209 Signal-to-noise ratio (SNR) 210 Contrast-to-noise ratio (CNR) 226 Spatial resolution 232 Scan time 237 Trade-offs 238 Protocol development

ABOUT THE AUTHORS

CATHERINE WESTBROOK, Senior Lecturer and Course Leader, MSc Magnetic Resonance Imaging (MRI), Anglia Ruskin University, Cambridge, UK.

JOHN TALBOT, Senior Lecturer, MSc Magnetic Resonance Imaging (MRI), Anglia Ruskin University, Cambridge, UK.