MRI in Practice

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.

• Preface to the Fifth Edition ixAcknowledgments xiList of Acronyms xiiiEquation symbols xviiAbout the Companion Website xixChapter 1 Basic principles 1 Introduction 1Atomic structure 2Motion in the atom 2MR active nuclei 4The hydrogen nucleus 5Alignment 6Net magnetic vector (NMV) 8Precession and precessional (Larmor) frequency 10Precessional phase 13Resonance 13MR signal 18The free Induction decay(FDI) signal 20Pulse timing parameters 22Chapter 2 Image weighting and contrast 24 Introduction 24Image contrast 25Relaxation 25T1 recovery 26T2 decay 27Contrast mechanisms 31Relaxation in different tissues 32 /p>T1 contrast 36T2 contrast 40Proton density contrast 41Weighting 42Other contrast mechanisms 51Chapter 3 Spin echo pulse sequences 58 Introduction 58RF rephasing 59Conventional spin echo 65Fast or turbo spin echo FSE/TSE) 68Inversion recovery (IR) 78Short tau inversion recovery (STIR) 82Fluid attenuated inversion recovery (FLAIR) 84Chapter 4 Gradient echo pulse sequences 89Introduction 89Variable flip angle 90Gradient rephasing 91Weighting in gradient echo pulse sequences 94Coherent or rewound gradient echo 106Incoherent or spoiled gradient echo 109Reverse-echo gradient echo 113Balanced gradient echo 119Fast gradient echo 122Echo planar imaging (EPI) 122Chapter 5 Spatial encoding 128 Introduction 128Mechanism of gradients 129Gradient axes 134Slice-selection 135Frequency encoding 142Phase encoding 145  Bringing it all together – pulse sequence timing 152Chapter 6 k-space 158 Introduction 158Part 1 – what is k-space? 159Part 2 - how are data acquired and how are images created from this data? 165Part 3 –some important facts about k-space 184Part 4: how do pulse sequences fill k-space? 197Part 5: options that fill k-space 199Chapter 7 Protocol optimization 209 Introduction 209Signal-to-noise ratio (SNR) 210Contrast-to-noise ratio (CNR) 226Spatial resolution 232Scan time 237Trade-offs 238Protocol development and modification 238Chapter 8 Artefacts 240Introduction 242Phase mismapping 243Aliasing 253Chemical shift artefact 261Out-of-phase signal cancellation 265Magnetic susceptibility artefact 269Truncation artefact 272Cross-excitation/cross-talk 273Zipper artefact 275Shading artefact 276Moiré artefact 277Magic angle 279Equipment faults 280Flow artefacts 280Flow-dependent (non-contrast enhanced) angiography 298Black-blood imaging 303Phase contrast MRA 304Chapter 9 Instrumentation 311 Introduction 311Magnetism 313Scanner configurations 315Magnet system 318Magnet shielding 326Shim system 328Gradient system 330RF system 337Patient transport system 343Computer system and graphic user interface 344Chapter 10 MRI safety 346 Introduction (and disclaimer) 346Definitions used in MRI safety 347Psychological effects 350The spatially-varying static field 351Electromagnetic (radiofrequency) fields 357Time-Varying Gradient Magnetic Fields 363Cryogens 365Safety tips 367Additional resources 368Glossary 370Index 387

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