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Edition History

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Library of Congress Cataloging-in-Publication Data

Names: Westbrook, Catherine, author. | Talbot, John (Writer on magnetic

resonance imaging), author.

Title: MRI in practice / by Catherine Westbrook, John Talbot.

Description: Fifth edition. | Hoboken, NJ : Wiley, 2018. | Includes

bibliographical references and index. |

Identifiers: LCCN 2018009382 (print) | LCCN 2018010644 (ebook) | ISBN

9781119391999 (pdf) | ISBN 9781119392002 (epub) | ISBN 9781119391968

(pbk.)

Subjects: | MESH: Magnetic Resonance Imaging–methods | Magnetic Resonance

Imaging–instrumentation

Classification: LCC RC78.7.N83 (ebook) | LCC RC78.7.N83 (print) | NLM WN 185

| DDC 616.07/548–dc23

LC record available at https://lccn.loc.gov/2018009382

Cover image: Courtesy of John Talbot

Cover design by Wiley

CONTENTS

Preface

Acknowledgments

Acronyms

Nomenclature

About the companion website

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
The free induction decay (FID) signal
Pulse timing parameters
References

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
References

3 Spin-echo pulse sequences

Introduction
RF rephasing
Conventional spin-echo
Fast or turbo spin-echo (FSE/TSE)
References

4 Gradient-echo pulse sequences

Introduction
Variable flip angle
Gradient rephasing
Weighting in gradient-echo pulse sequences
Coherent or rewound gradient-echo
Incoherent or spoiled gradient-echo
Reverse-echo gradient-echo
Balanced gradient-echo
Fast gradient-echo
Echo planar imaging
References

5 Spatial encoding

Introduction
Mechanism of Gradients
Gradient Axes
Slice-Selection
Frequency Encoding
Phase Encoding
Bringing it All Together – Pulse Sequence Timing
References

6 k-Space

Introduction
Part 1: What is k-Space?
Part 2: How are Data Acquired and How are Images Created from These 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
References

7 Protocol optimization

Introduction
Signal-to-Noise Ratio (SNR)
Contrast-to-Noise Ratio (CNR)
Spatial Resolution
Scan Time
Trade-Offs
Protocol Development and Modification
References

8 Artifacts

Introduction
Phase Mismapping
Aliasing
Chemical Shift Artifact
Out-of-Phase Signal Cancellation
Magnetic Susceptibility Artifact
Truncation Artifact
Cross-Excitation/Cross-Talk
Zipper Artifact
Shading Artifact
MoirÉ Artifact
Magic Angle
Equipment Faults
Flow Artifacts
Flow-Dependent (Non-Contrast-Enhanced) Angiography
Black-Blood Imaging
Phase-Contrast MRA
References

9 Instrumentation

Introduction
Magnetism
Scanner Configurations
Magnet System
Magnet Shielding
Shim System
Gradient System
RF System
Patient Transport System
Computer System and Graphical User Interface
References

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
Cryogens
Safety Tips
Additional Resources
References

Glossary

Index

End User License Agreement

List of Tables

Table 1.1
Table 1.2
Table 1.3
Table 1.4
Table 1.5
Table 1.6

Table 2.1
Table 2.2
Table 2.3
Table 2.4
Table 2.5
Table 2.6
Table 2.7
Table 2.8
Table 2.9
Table 2.10
Table 2.11
Table 2.12
Table 2.13
Table 2.14

Table 3.1
Table 3.2
Table 3.3
Table 3.4
Table 3.5
Table 3.6
Table 3.7
Table 3.8

Table 4.1
Table 4.2
Table 4.3
Table 4.4
Table 4.5
Table 4.6
Table 4.7
Table 4.8
Table 4.9
Table 4.10
Table 4.11
Table 4.12
Table 4.13
Table 4.14
Table 4.15
Table 4.16
Table 4.17
Table 4.18
Table 4.19

Table 5.1
Table 5.2
Table 5.3
Table 5.4
Table 5.5
Table 5.6
Table 5.7

Table 6.1
Table 6.2
Table 6.3
Table 6.4
Table 6.5
Table 6.6
Table 6.7
Table 6.8

Table 7.1
Table 7.2
Table 7.3
Table 7.4
Table 7.5
Table 7.6

Table 8.1
Table 8.2
Table 8.3
Table 8.4
Table 8.5
Table 8.6
Table 8.7
Table 8.8
Table 8.9
Table 8.10
Table 8.11
Table 8.12
Table 8.13

Table 9.1
Table 9.2
Table 9.3
Table 9.4

Table 10.1
Table 10.2

List of Illustrations

Figure 1.1 The atom.
Figure 1.2 The magnetic moment of the hydrogen nucleus.
Figure 1.3 Alignment – classical theory.
Figure 1.4 Alignment – quantum theory.
Figure 1.5 The net magnetic vector.
Figure 1.6 Precession.
Figure 1.7 Precession of the spin-up and spin-down populations.
Figure 1.8 The electromagnetic spectrum.
Figure 1.9 In phase (coherent) and out of phase (incoherent).
Figure 1.10 Energy transfer during excitation.
Figure 1.11 Phase and frequency (the watch analogy).
Figure 1.12 Generation of the signal.
Figure 1.13 Longitudinal and transverse magnetization.
Figure 1.14 A basic pulse sequence.

Figure 2.1 The T1 recovery curve.
Figure 2.2 T2* decay and field inhomogeneities.
Figure 2.3 Dephasing and free induction decay.
Figure 2.4 The T2 decay curve.
Figure 2.5 The magnitude of transverse magnetization vs amplitude of signal.
Figure 2.6 T1 recovery in fat.
Figure 2.7 T1 recovery in water.
Figure 2.8 T2 decay in fat.
Figure 2.9 T2 decay in water.
Figure 2.10 T1 contrast generation.
Figure 2.11 Saturation with a short TR.
Figure 2.12 No Saturation with a long TR.
Figure 2.13 T2 contrast generation.
Figure 2.14 The difference in T1 recovery between fat and water.
Figure 2.15 Coronal T1-weighted image of the knee.
Figure 2.16 The difference in T2 decay between fat and water.
Figure 2.17 Axial T2-weighted image of the wrist.
Figure 2.18 Sagittal proton density weighted image of the ankle.
Figure 2.19 T1 weighting and the heat analogy.
Figure 2.20 T2 weighting and the heat analogy.
Figure 2.21 Proton density weighting and the heat analogy.
Figure 2.22 Midline sagittal T1-weighted image of the brain.
Figure 2.23 Free and restricted diffusion in water.
Figure 2.24 BOLD images of the brain. Functional areas are shown in red.

Figure 3.1 T2* dephasing.
Figure 3.2 180° RF rephasing.
Figure 3.3 A basic spin-echo pulse sequence.
Figure 3.4 The Larmor Grand Prix.
Figure 3.5 Tau.
Figure 3.6 Spin-echo with one echo.
Figure 3.7 Spin-echo with two echoes.
Figure 3.8 Spatial encoding in conventional spin-echo.
Figure 3.9 The echo train.
Figure 3.10 Phase-encoding gradient slopes.
Figure 3.11 Phase encoding vs signal amplitude.
Figure 3.12 k-Space filling and phase reordering.
Figure 3.13 Sagittal TSE T2-weighted image of a female pelvis. Source: Westbrook 2014 [5]. Reproduced with permission of John Wiley & Sons.
Figure 3.14 Axial T1-weighted TSE image of a male pelvis. Source: Westbrook 2015 [6]. Reproduced with permission of John Wiley & Sons.
Figure 3.15 Coronal TSE PD-weighted image of a knee. Source: Westbrook 2014 [5]. Reproduced with permission of John Wiley & Sons.
Figure 3.16 The DRIVE pulse sequence.
Figure 3.17 Axial DRIVE image through the right internal auditory meatus. Note high signal intensity in the CSF.
Figure 3.18 The 180° inverting pulse in an IR pulse sequence.
Figure 3.19 The inversion recovery sequence.
Figure 3.20 T1 weighting in inversion recovery.
Figure 3.21 PD weighting in inversion recovery.
Figure 3.22 Axial T1-weighted inversion recovery sequence of the brain. A T1 of 700 ms was used.
Figure 3.23 The STIR sequence.
Figure 3.24 Coronal STIR of the knee. Source: Westbrook 2014 [5]. Reproduced with permission of John Wiley & Sons.
Figure 3.25 Axial T2-weighted FLAIR of the brain. Source: Westbrook 2014 [5]. Reproduced with permission of John Wiley & Sons.
Figure 3.26 Coronal IR-TSE T2-weighted image with a TI selected to null white matter. Source: Westbrook 2014 [5]. Reproduced with permission of John Wiley & Sons.

Figure 4.1 How gradients dephase.
Figure 4.2 How gradients rephase.
Figure 4.3 A basic gradient-echo sequence showing how a bipolar application of the frequency- encoding gradient produces a gradient-echo.
Figure 4.4 T1 contrast in gradient-echo.
Figure 4.5 T2* contrast in gradient-echo.
Figure 4.6 T1 weighting in gradient-echo and the heat analogy.
Figure 4.7 T2* weighting in gradient-echo and the heat analogy.
Figure 4.8 PD weighting in gradient-echo and the heat analogy.
Figure 4.9 The steady state.
Figure 4.10 Ernst angle graphs in the brain using a TR of 30 ms.
Figure 4.11 Axial steady state image.
Figure 4.12 Echo formation in steady state I.
Figure 4.13 Echo formation in steady state II.
Figure 4.14 The coherent gradient-echo sequence.
Figure 4.15 Axial coherent gradient-echo sequence of the abdomen. Source: Westbrook 2014 [6]. Reproduced with permission of John Wiley & Sons.
Figure 4.16 Sagittal coherent gradient-echo sequence of the knee. Source: Westbrook 2014 [6]. Reproduced with permission of John Wiley & Sons.
Figure 4.17 RF spoiling in the incoherent gradient-echo sequence.
Figure 4.18 Sagittal incoherent gradient-echo sequence of the ankle. Source: Westbrook 2014 [6]. Reproduced with permission of John Wiley & Sons.
Figure 4.19 Coronal incoherent gradient-echo after contrast enhancement. Source: Westbrook 2014 [6]. Reproduced with permission of John Wiley & Sons.
Figure 4.20 The reverse-echo sequence.
Figure 4.21 Axial reverse-echo gradient-echo in the brain.
Figure 4.22 Perfusion imaging using an echo shifting sequence. Source: Westbrook 2015 [9]. Reproduced with permission of John Wiley & Sons.
Figure 4.23 Echo formation in coherent gradient-echo.
Figure 4.24 Echo formation in incoherent gradient-echo.
Figure 4.25 Echo formation in reverse-echo gradient-echo.
Figure 4.26 Balanced gradient system in balanced gradient-echo.
Figure 4.27 Maintenance of the steady state in balanced gradient-echo.
Figure 4.28 Axial balanced gradient-echo image of the lumbar spine.
Figure 4.29 GE-EPI sequence.
Figure 4.30 SE-EPI sequence.
Figure 4.31 GRASE sequence.
Figure 4.32 Axial SE-EPI of the abdomen. Source: Westbrook 2015 [9]. Reproduced with permission of John Wiley & Sons.

Figure 5.1 How gradients change field strength and precessional frequency.
Figure 5.2 Three-terminal gradient coil.
Figure 5.3 (a) Steep and (b) shallow gradient slopes.
Figure 5.4 Gradient axes in a typical superconducting system.
Figure 5.5 Slice-selection and the tuning fork analogy.
Figure 5.6 X, Y, and Z as slice selectors.
Figure 5.7 Timing of the slice-select gradient in a spin-echo pulse sequence.
Figure 5.8 Transmit bandwidth, gradient slope, and slice thickness.
Figure 5.9 Frequency encoding and the keyboard analogy.
Figure 5.10 Timing of the frequency-encoding gradient in a spin-echo pulse sequence.
Figure 5.11 Phase encoding.
Figure 5.12 Timing of the phase-encoding gradient in a spin-echo pulse sequence.
Figure 5.13 (a) Steep and (b) shallow phase-encoding gradients.
Figure 5.14 Gradient timing in a spin-echo pulse sequence.
Figure 5.15 How a waveform is produced from a change of phase over distance.
Figure 5.16 Spatial frequency vs amplitude of phase-encoding gradient.

Figure 6.1 The axes of k-space.
Figure 6.2 k-space – the chest of drawers.
Figure 6.3 k-Space – phase matrix and the number of drawers.
Figure 6.4 k-Space – labeling.
Figure 6.5 k-Space filling in a spin-echo sequence.
Figure 6.6 Waveforms from three different magnet moments precessing at three different frequencies and their amplitude modulation.
Figure 6.7 Data points in k-space. The number in each column is the phase matrix. The number in each row is the frequency matrix.
Figure 6.8 The Nyquist theorem.
Figure 6.9 Sampling time (acquisition window) and the TE.
Figure 6.10 FFT.
Figure 6.11 Signals in k-space from one voxel.
Figure 6.12 Generation of pseudo-frequency from one voxel.
Figure 6.13 k-Space symmetry – phase.
Figure 6.14 k-Space symmetry – frequency.
Figure 6.15 Phase gradient amplitude vs signal amplitude.
Figure 6.16 k-Space – signal and resolution.
Figure 6.17 k-Space using all data.
Figure 6.18 k-Space using resolution data only.
Figure 6.19 k-Space using signal data only.
Figure 6.20 TR vs slice number.
Figure 6.21 How gradients traverse k-space in a gradient-echo sequence.
Figure 6.22 Partial Fourier.
Figure 6.23 Partial echo.
Figure 6.24 Parallel imaging.
Figure 6.25 k-Space filling in EPI.
Figure 6.26 Spiral k-space filling.
Figure 6.27 Data acquisition methods.

Figure 7.1 Coil position vs SNR.
Figure 7.2 (a) TR 700 ms, (b) TR 500 ms, (c) TR 300 ms, (d) TR 140 ms.
Figure 7.3 Changing TR at 3 T.
Figure 7.4 Flip angle vs SNR.
Figure 7.5 Axial gradient-echo image of the brain using a flip angle of 10° at 3 T.
Figure 7.6 Axial gradient-echo image of the brain using a flip angle of 90° at 3 T.
Figure 7.7 SNR vs TE.
Figure 7.8 (a) TE 11 ms, (b) TE 20 ms, (c) TE 40 ms, (d) TE 80 ms.
Figure 7.9 Changing TE at 3 T.
Figure 7.10 SNR vs NSA.
Figure 7.11 Sagittal brain using 1 NSA.
Figure 7.12 Sagittal brain using 4 NSA.
Figure 7.13 SNR vs receive bandwidth.
Figure 7.14 The voxel. The large blue square is the FOV.
Figure 7.15 Voxel volume and SNR (spin numbers are not representative).
Figure 7.16 SNR vs slice thickness.
Figure 7.17 Sagittal brain using 128 phase matrix.
Figure 7.18 Sagittal brain using 256 phase matrix.
Figure 7.19 SNR vs FOV.
Figure 7.20 Sagittal brain using a square FOV of 240 mm.
Figure 7.21 Sagittal brain using a square FOV of 120 mm.
Figure 7.22 A heavily T2-weighted image of the buttock. A very long TE was used in this image. The CNR is optimized showing pathology clearly.
Figure 7.23 Fat saturation.
Figure 7.24 Sagittal ankle with fat saturation. Source: Westbrook 2014 [9]. Reproduced with permission of John Wiley & Sons.
Figure 7.25 Water saturation.
Figure 7.26 Sagittal T2-weighted image of the pelvis without fat saturation.
Figure 7.27 Sagittal T2-weighted image of the pelvis with fat saturation.
Figure 7.28 Square and rectangular FOV and the chest of drawers.

Figure 8.1 Axial image through a breathing abdomen showing phase mismapping.
Figure 8.2 One of the causes of phase mismapping.
Figure 8.3 Axial T1-weighted image of the chest. Phase is anterior to posterior. Source: Westbrook 2014 [3]. Reproduced with permission of John Wiley & Sons.
Figure 8.4 Axial T1-weighted image of the chest. Phase is right to left. Source: Westbrook 2014 [3]. Reproduced with permission of John Wiley & Sons.
Figure 8.5 Placement of respiratory compensation and cardiac gating leads.
Figure 8.6 Respiratory compensation and k-space.
Figure 8.7 Image showing respiratory motion.
Figure 8.8 Image without respiratory motion.
Figure 8.9 (a) Respiratory triggering and (b) gating.
Figure 8.10 Sagittal image of the brain showing aliasing or wrap around.
Figure 8.11 Aliasing and undersampling.
Figure 8.12 Phase wrap.
Figure 8.13 Antialiasing along the frequency axis.
Figure 8.14 Antialiasing along the phase axis.
Figure 8.15 With wrap.
Figure 8.16 Without wrap.
Figure 8.17 Chemical shift. In this image, the signal from the fatty bone marrow in the talus has been shifted inferiorly in the frequency-encoding direction. This is more apparent on the 16 KHz image where the signal void mimics a thickening of cortical bone.
Figure 8.18 Chemical shift and pixel shift.
Figure 8.19 Out-of-phase signal cancellation show as a black line around the abdominal organs border at the boundaries between fat and muscle.
Figure 8.20 Out-of-phase signal cancellation and the watch analogy.
Figure 8.21 The periodicity of fat and water.
Figure 8.22 Axial gradient-echo images when the magnetic moments of fat and water nuclei are out of phase (below) and in phase (above). Source: Westbrook 2014 [3]. Reproduced with permission of John Wiley & Sons.
Figure 8.23 Magnetic susceptibility from a dental implant causing massive distortion of the image.
Figure 8.24 Sagittal gradient-echo images of the knee with pins in the tibia. Magnetic susceptibility has produced a large distortion of the image.
Figure 8.25 Sagittal spin-echo images of the same patient as shown in Figure 8.24. The artifact is reduced.
Figure 8.26 Truncation artifact.
Figure 8.27 Contrast changes between slices as a result of cross-excitation.
Figure 8.28 Cross-excitation.
Figure 8.29 Zipper artifact. In both examples shown, there is a line of high signal running perpendicular to the frequency-encoding direction. This represents external interference at a discrete frequency.
Figure 8.30 Various appearances of multiple noise spikes.
Figure 8.31 Moiré artifact seen as zebra lines on the edge of the FOV.
Figure 8.32 Magic angle artifact shown with a high signal intensity at the lower border of the patellar tendon.
Figure 8.33 Inflow and flow-related enhancement.
Figure 8.34 Entry-slice phenomenon and direction of flow.
Figure 8.35 Entry-slice phenomenon: slice 1 (most inferior).
Figure 8.36 Entry-slice phenomenon: slice 2 (middle inferior).
Figure 8.37 Entry-slice phenomenon: slice 3 (middle superior).
Figure 8.38 Entry-slice phenomenon: slice 4 (most superior).
Figure 8.39 Time-of-flight phenomenon.
Figure 8.40 Time of flight vs TE.
Figure 8.41 The different types of flow.
Figure 8.42 Intravoxel dephasing.
Figure 8.43 Gradient moment rephasing (nulling).
Figure 8.44 Without GMN.
Figure 8.45 With GMN.
Figure 8.46 Spatial presaturation.
Figure 8.47 Without presaturation.
Figure 8.48 With presaturation.
Figure 8.49 Axial 3D inflow MRA images of the brain to evaluate vasculature in the circle of Willis. These images were acquired at 3 T (a) and 1.5 T (b). Note the improvement in vascular contrast due to greater SNR and CNR in the 3 T image.
Figure 8.50 In-plane flow. Tortuous vessels or vessels in which the flow is along the plane of the slice may not be demonstrated on a MIP. The spins become saturated by numerous excitation pulses.
Figure 8.51 MIP reformatting. The maximum intensity projection ascertains the maximum intensity in each row or column of pixels and assigns this value to a pixel in a projected plane. In this diagram, there are two such planes representing an anterior and lateral projection of the data.
Figure 8.52 Image reconstructions from MOTSA acquisition (multiple overlapping thin slabs). Signal saturation has occurred at the edge of a slab resulting in an apparent (and highly suspicious) bilateral “stenosis.”
Figure 8.53 8.53 Spatial presaturation to produce black blood. Note that the magnetic moments of nuclei in the vessel (at the top of the illustration) are aligned with the magnetic field (B₀) along the z-axis. As the blood within the vessel flows down into the saturation volume, they receive a 90° RF pulse and their vectors enter the transverse plane. As blood continues to flow down into the slice, nuclei receive another 90° RF pulse and are aligned 180° from their original position at the top of the diagram. At this point (and with no time to recover), nuclei with the blood are saturated and are dark on the image.
Figure 8.54 8.54 Black-blood imaging. Normal flow may return a similar signal intensity to the vessel lumen. In the event of an arterial dissection, stationary blood trapped in the intima may also exhibit a similar intensity. By saturating inflowing blood, the signal is removed resulting in a more accurate and conspicuous representation of vessel patency.
Figure 8.55 PCA gradient.
Figure 8.56 VENC.
Figure 8.57 VENC aliasing.
Figure 8.58 8.58 EKG-triggered subtraction imaging. This technique exploits the T2 contrast difference between blood (a fluid) and the background tissue. Data acquisition is synchronized to the EKG permitting the visualization of arteries or veins. The mechanism is related to the speed of flow.

Figure 9.1 Closed-bore MRI scanner in axial cross-section revealing the principal components to be arranged in concentric circles, most of them being cylindrical electromagnets.
Figure 9.2 Effect of a diamagnetic substance on a homogenous magnetic field.
Figure 9.3 Effect of a paramagnetic substance on a homogenous magnetic field.
Figure 9.4 Ferromagnetic substance in a homogenous magnetic field.
Figure 9.5 Differences in solenoid configuration in (a) closed-bore and (b) open MRI scanners.
Figure 9.6 Typical design of a permanent-magnet open scanner. The flux lines of the static field run vertically in this type of scanner.
Figure 9.7 Right-hand grip rule.
Figure 9.8 Construction of an MRI cryostat.
Figure 9.9 Bobbin used to create a segmented solenoid electromagnet.
Figure 9.10 Parallel circuit and persistent switch used for ramping a magnet.
Figure 9.11 Passive shielding causes the lines of flux to pass through steel cladding in preference to air.
Figure 9.12 Passive shim system.
Figure 9.13 Mechanism of a gradient coil.
Figure 9.14 How gradients change field strength.
Figure 9.15 Characteristics of a magnetic field gradient.
Figure 9.16 RF transmit and receive chain.
Figure 9.17 The RF transmit coil. This is a birdcage resonator coil consisting of two end rings linked by a symmetrical array of straight conductors.
Figure 9.18 Schematic diagram showing surface coil configurations.
Figure 9.19 Phased array spine coil.

Figure 10.1 MRI safety zones as recommended by the ACS Guidance Document on MR-Safe Practices 2013.
Figure 10.2 Device-labeling icons developed by the American Society for Testing and Materials International and recognized by the FDA.
Figure 10.3 Static magnetic field gradient of an actively shielded closed-bore MRI scanner. The values shown will vary with scanner model.
Figure 10.4 Ferromagnetic wheelchair taken into an actively shielded magnet room. No attraction was appreciated until the chair was moved close to the end of the bore.
Figure 10.5 An implanted device or clip may experience torque. This is a turning force that causes the long axis of a device to become aligned with the static field.
Figure 10.6 Anatomy may form “biological circuits” through which an induced current may flow. Contact areas such as the hands or heels may concentrate the current flow through a small area causing burns.
Figure 10.7 Dipole heating in a conductive wire such as a pacemaker lead.

Preface to the fifth edition

The MRI in Practice brand continues to grow from strength to strength. The fourth edition of MRI in Practice is an international best-seller and is translated into several languages. At the time of writing, the accompanying MRI in Practice course is 26 years old. We have delivered the course to more than 10 000 people in over 20 countries and have a large and growing MRI in Practice online community. Our readers and course delegates include a variety of professionals such as radiographers, technologists, radiologists, radiotherapists, veterinary practitioners, nuclear medicine technologists, radiography students, postgraduate students, medical students, physicists, and engineers.

The unique selling point of MRI in Practice has always been its user-friendly approach to physics. Difficult concepts are explained as simply as possible and supported by clear diagrams, images, and animations. Clinical practitioners are not usually interested in pages of math and just want to know how it essentially “all works.” We believe that MRI in Practice is so popular because it speaks your language without being oversimplistic.

This fifth edition has had a significant overhaul and specifically plays to the strengths of the MRI in Practice brand. We have created a synergy between the book and the course so that they are best able to support your learning. We purposefully focus on physics in this edition and on essential concepts. It is important to get the fundamentals right, as they underpin more specialist areas of practice. There are completely new chapters on MRI equipment and safety, and substantially revised and expanded chapters on gradient-echo pulse sequences, k-space, artifacts, and angiography. The very popular learning tips and analogies from previous editions are expanded and revised. There is also a new glossary, lots of new diagrams and images, and suggestions for further reading for those who wish to delve deeper into physics. The accompanying website includes new questions and additional animations. We also include some equations in this edition, but don’t worry: they are there only for those who like equations, and we explain what they mean in a user-friendly style.

However, probably the most significant change in this edition is the inclusion of scan tips. Throughout the book, your attention is drawn to how theory applies to practice. Scan tips are specifically used to alert you to what is going on “behind the scenes” when you select a parameter in the scan protocol. We hope this helps you make the connection between theory and practice. Physics in isolation is of little value to the clinical practitioner. What is important is how this knowledge is applied. We stand by the MRI in Practice philosophy that physics does not have to be difficult, and we hope that our readers, old and new, find these changes helpful. Richard Feynman, who is considered one of the finest physics teachers of all time, was renowned for his ability to transfer his deep understanding of physics to the page with clarity and a minimum of fuss. He believed that it is unnecessary to make physics more complicated than it need be. Our aspiration is that the fifth edition of MRI in Practice emulates his way of thinking.

We hope that the many fans of MRI in Practice around the world continue to enjoy and learn from it. A big thank you for your continued support and happy reading!

Catherine Westbrook

John Talbot

November 2017

United Kingdom

Acronyms

Generic	Siemens	GE	Philips	Hitachi	Toshiba
Pulse sequences
Conventional spin-echo (SE)	SE	SE	SE	SE	SE
Turbo spin-echo (TSE)	TSE	FSE	TSE	FSE	FSE
Single-shot TSE (SS-TSE)	HASTE	SS-FSE	SS-TSE	SS-FSE	FASE
TSE (with restoration pulse)	RESTORE	FRFSE	DRIVE	driven equilibrium FSE	T2 Puls FSE
Inversion recovery (IR)	IR	IR/MPIR	IR	IR	IR
Fast inversion recovery	TIR	Fast IR	IR-TSE	IR	IR
Short tau IR (STIR)	STIR	STIR	STIR	STIR	fast STIR
Fluid-attenuated IR (FLAIR)	turbo dark fluid	FLAIR	FLAIR	FLAIR	fast FLAIR
Gradient-echo (GRE)	GRE	GRE	FFE	GE	field echo
Coherent gradient-echo	FISP	GRASS	FFE	rephased SARGE	SSFP
Incoherent gradient-echo	FLASH	SPGR	T1 FFE	spoiled SARGE	fast FE
Reverse-echo gradient-echo	PSIF	SSFP	T2 FFE	time-reversed SARGE	—
Balanced gradient-echo	true FISP	FIESTA	BFFE	balanced SARGE	true SSFP
Echo-planar imaging (EPI)	EPI	EPI	EPI	EPI	EPI
Double-echo steady state	DESS	—	—	—	—
Balanced dual excitation	CISS	FIESTA-C	—	phase balanced SARGE	—
Multi-echo-data-image-combination	MEDIC	MERGE	MFFE	—	—
Fast gradient-echo	turbo FLASH	fast GRE, fast SPGR	TFE	RGE	Fast FE
Hybrid sequence	TGSE	—	GRASE	—	Hybrid EPI
Contrast parameters
Repetition time (TR)	TR	TR	TR	TR	TR
Time to echo (TE)	TE	TE	TE	TE	TE
Time from inversion (TI)	TI	TI	TI	TI	TI
Flip angle	flip angle	flip angle	flip angle	flip angle	Flip angle
Number of echoes (in TSE)	turbo factor	ETL	turbo factor	shot factor	ETL
b factor/value	b factor	b factor	b factor	b factor	b factor
Geometry parameters
Field of view (FOV)	FOV (mm)	FOV (cm)	FOV (mm)	FOV (mm)	FOV (mm)
Rectangular FOV	FOV phase	PFOV	rectangular FOV	rectangular FOV	rectangular FOV
Slice gap	distance factor	gap	gap	slice interval	gap
Data acquisition parameters
Averages	average	NEX	NSA	NSA	NSA
Bandwidth	bandwidth (Hz/pixel)	receive bandwidth (KHz)	fat water shift (pixel)	bandwidth (KHz)	bandwidth (KHz)
Variable bandwidth	optimized bandwidth	variable bandwidth	optimized bandwidth	variable bandwidth	matched bandwidth
Partial averaging	half Fourier	fractional NEX	half scan	half scan	AFI
Partial echo	asymmetric echo	partial echo	partial echo	half echo	matched bandwidth
Parallel imaging (image based)	mSENSE	ASSET	SENSE	RAPID	SPEEDER
Parallel imaging (k-space based)	GRAPPA	ARC	—	—	—
Artifact reduction techniques
Radial k-space filling	BLADE	PROPELLOR	multiVane	RADAR	JET
Gradient moment rephasing	GMR/flow comp	flow comp	flow comp/FLAG	GR	FC
Presaturation	pre SAT	Sat	REST	Pre SAT	Pre SAT
Moving sat pulse	travel SAT	walking SAT	travel REST	Sequential pre SAT	BFAST
Fat saturation	fat SAT	chem SAT	SPIR	Fat Sat	MSOFT
Out-of-phase imaging	DIXON	IDEAL	ProSET	Water excitation	PASTA
Respiratory compensation	respiratory gated	respiratory compensation	PEAR	MAR	respiratory gated
Antialiasing (frequency)	oversampling	antialiasing	frequency oversampling	frequency oversampling	frequency wrap suppression
Antialiasing (phase)	phase oversampling	no phase wrap	fold-over suppression	antiwrap	phase wrap suppression
Special techniques
Volume TSE variable flip angle	SPACE	CUBE	VISTA	—	—
Volume gradient-echo	VIBE	LAVA-XV	THRIVE	TIGRE	—
Dynamic MRA	TWIST	TRICKS-SV	keyhole (4d Trak)	—	—
Noncontrast MRA gradient-echo	NATIVE – true FISP	inhance inflow IR	B-TRANCE	VASC ASL	TIME-SLIP
Noncontrast MRA spin- echo	NATIVE-SPACE	—	TRANCE	VASC FSE	FBI
Susceptibility weighting	SWI	SWAN	Venous BOLD	—	—
High-resolution breast imaging	VIEWS	VIBRANT-XV	BLISS	—	RADIANCE
Diffusion-weighted imaging	DWI	DWI	DWI	DWI	DWI
Diffusion tensor imaging	DTI	DTI	diffusion tensor imaging	—	DTI
Body diffusion imaging	REVEAL	—	DWIBS	—	body vision

Nomenclature

S	spin quantum number
N⁺	number of spins in the high-energy population (Boltzmann)
N⁻	number of spins in the low-energy population (Boltzmann)
ΔE	energy difference between high- and low-energy populations (Boltzmann)	J
k	Boltzmann’s constant	J/K
T	temperature of the tissue	K
ω₀	precessional or Larmor frequency	MHz
γ	gyromagnetic ratio	MHz/T
B₀	external magnetic field strength	T
E	energy of a photon	J
h	Planck’s constant	J/s
θ	flip angle	°
ω₁	precessional frequency of B₁	μT
B₁	magnetic field associated with the RF excitation pulse	mT
τ	duration of the RF excitation pulse	ms
ϵ	emf	V
N	number of turns in a coil
dΦ	changing magnetic flux in a single loop	V/s
dt	changing time	s
Mz_t	amount of longitudinal magnetization at time t
Mz	full longitudinal magnetization
Mxy_t	amount of transverse magnetization at time t
Mxy	full transverse magnetization
SI	signal intensity in a tissue
ΔB₀	variation in magnetic field	ppm
G	gradient amplitude	mT/m
δ	gradient duration	ms
Δ	time between two gradient pulses	ms
b	b value or b factor	s/mm²
ST	scan time	s
E_S	echo spacing in turbo spin-echo (TSE)	ms
t	time from inversion (TI)	ms
Ernst	Ernst angle	°
TE_eff	effective TE	ms
TE_act	TE set at the console	ms
B_p	magnetic field strength at a point along the gradient	T
Sl_t	slice thickness	mm
TBW	transmit bandwidth	KHz
ω_sampling	digital sampling frequency	KHz
ΔT_s	sampling interval	ms
ω_Nyquist	Nyquist frequency	KHz
RBW	receive bandwidth	KHz
W_s	sampling window	ms
M(f)	frequency matrix
M(p)	phase matrix
N_s	number of slice locations
G(p)	max amplitude of the phase encoding gradient	mT/m
φ	incremental step between each k-space line
G(f)	amplitude of the frequency encoding gradient	mT/m
FOV(f)	frequency FOV	cm
σ	standard deviation of background signal or noise
S_p	separation between ghosts due to motion p	pixels
T_m	period of motion of something moving in the patient	ms
Re	Reynolds number
d	density of blood	g/cm³
v	velocity of flow	cm/s
m	diameter of a vessel	cm
vis	viscosity of blood	g/cm s
f_p	perceived frequency	KHz
f_t	actual frequency	KHz
ω_csf	chemical shift frequency difference between fat and water	Hz
C_s	chemical shift (3.5 ppm or 3.5 × 10⁻⁶)	ppm
CS_p	pixel shift	mm
H₀	magnetic intensity	A/m
q	charge of a particle	C
F	Lorentz force (total emf on a charged particle)	V
E	electric field vector
B	magnetic field vector

MRI in Practice

Fifth Edition

Catherine Westbrook

EdD, MSc, FHEA, PgC (Learning & Teaching), DCRR, CTC

Senior Lecturer
Anglia Ruskin University
Cambridge
UK

John Talbot

EdD, MSc, FHEA, PgC (Learning & Teaching), DCRR

Senior Lecturer
Anglia Ruskin University
Cambridge
UK

Preface to the fifth edition

Acknowledgments

Acronyms

Nomenclature

About the companion website

Fifth Edition

Catherine Westbrook

EdD, MSc, FHEA, PgC (Learning & Teaching), DCRR, CTC

Senior Lecturer Anglia Ruskin University Cambridge UK

John Talbot

EdD, MSc, FHEA, PgC (Learning & Teaching), DCRR

Senior Lecturer Anglia Ruskin University Cambridge UK

Senior Lecturer
Anglia Ruskin University
Cambridge
UK

Senior Lecturer
Anglia Ruskin University
Cambridge
UK