MRI in Practice

Catherine Westbrook, Senior Lecturer and Course Leader, Magnetic Resonance Imaging (MRI), Faculty of Medical Science, Anglia Ruskin University, Cambridge, UK.

John Talbot, Senior Lecturer in Magnetic Resonance Imaging (MRI), Research Methodology and Medical Education, Faculty of Medical Science, Anglia Ruskin University, Cambridge, UK.

Preface to the Fifth Edition


Acknowledgments


List of Acronyms


Equation symbols


About the Companion Website


Chapter 1 Basic principles


Introduction


Atomic structure


Motion in the atom


MR active nuclei


The hydrogen nucleus


Alignment


Net magnetic vector (NMV)


Precession and precessional (Larmor) frequency


Precessional phase


Resonance


MR signal


Pulse timing parameters


Further reading


Chapter 2 Image weighting and contrast


Introduction


Image contrast


Relaxation


T1 recovery


T2 decay


Contrast mechanisms


Relaxation in different tissues


T1 contrast


T2 contrast


Proton density contrast


Weighting


Other contrast mechanisms


Further reading


Chapter 3 Spin echo pulse sequences


Introduction


RF rephasing


Conventional spin echo


Fast or turbo spin echo FSE/TSE)


Inversion recovery (IR)


Short tau inversion recovery (STIR)


Fluid attenuated inversion recovery (FLAIR)


Further Reading


Chapter 4 Gradient echo pulse sequences


Introduction


Variable flip angle


Gradient rephasing


Weighting in gradient echo pulse sequences


Weighting mechanism 1 extrinsic contrast parameters


Weighting mechanism 2 the steady state


Weighing mechanism 3 residual transverse magnetization


Coherent or rewound gradient echo


Incoherent or spoiled gradient echo


Reverse-echo gradient echo


Balanced gradient echo


Fast gradient echo


Echo planar imaging (EPI)


Further reading


Chapter 5 Spatial encoding


Introduction


Mechanism of gradients


Gradient axes


Slice selection


Frequency encoding


Phase encoding


Sampling


Data collection and image formation


Bringing it all together pulse sequence timing


Further reading


Chapter 6 k-space


Introduction


Part 1 what is k-space?


Part 2 - how are data acquired and how are images created from this data?


Part 3 some important facts about k-space


Part 4: how do pulse sequences fill k-space?


Part 5: options that fill k-space


Further reading


Chapter 7 Protocol optimization


Introduction


Signal to noise ratio (SNR)


Contrast to noise ratio (CNR)


Spatial resolution


Scan time


Trade-offs


Protocol development and modification


Further reading


Chapter 8 Artefacts


Introduction


Phase mismapping


Aliasing


Chemical shift artefact


Out of phase signal cancellation


Magnetic susceptibility artefact


Truncation artefact


Cross-excitation/cross-talk


Zipper artefact


Shading artefact


Moire artefact


Magic angle


Equipment faults


Flow artefacts


Flow-dependent (non-contrast enhanced) angiography


Black-blood imaging


Phase contrast MRA


Further reading


Chapter 9 Instrumentation


Introduction


Magnetism


Scanner configurations


Magnet system


Magnet shielding


Shim system


Gradient system


RF system


Patient transport system


Computer system and graphic user interface


Further reading


Chapter 10 MRI safety


Introduction (and disclaimer)


Definitions used in MRI safety


Psychological effects


The spatially-varying static field


Electromagnetic (radiofrequency) fields


Time-Varying Gradient Magnetic Fields


Cryogen safety


Cryogen safety


Additional resources


Further reading


Appendix


Glossary


Index