Clinical Magnetic Resonance Spectroscopy

285 Pages·1990·8.013 MB·English

by  Ernest B. Cady (auth.)

Clinical Magnetic
Resonance Spectroscopy
Clinical Magnetic
Resonance Spectroscopy
Ernest B. Cady
University College Hospital
London, United Kingdom
Plenum Press • New York and London
Library of Congress Cataloging-in-Publication Data
Cady, Ernest B.
Clinical magnetic resonance spectroscopy I Ernest B. Cady.
p. em.
Includes bibliographical references.
Inc I udes index.
ISBN-13: 978-1-4684-1335-9 e-ISBN-13: 978-1-4684-1333-5
DOl: 10_1007/978-1-4684-1333-5
1. Nuclear magnetic resonance spectroscopy--Oiagnostic use.
r. Title.
[ONLM: 1. Nuclear Magnetic Resonance. 00 96.NS C126cl
RC7S.7.N83C33 1990
616.07·548--dc20
DNLM/OLC
for Library of Congress 90-7400
CIP
© 1990 Plenum Press, New York
Softcover reprint of the hardcover 1s t edition 1990
A Division of Plenum Publishing Corporation
233 Spring Street, New York, N.Y. 10013
All rights reserved
No part of this book may be reproduced, stored in a retrieval system, or transmitted
in any form or by any means, electronic, mechanical, photocopying, microfilming,
recording, or otherwise, without written permission from the Publisher
Foreword
Nobody can know everything. For the successful application of techniques
based on nuclear magnetic resonance to clinical problems, it is a vital
necessity that individuals with widely different skills should learn a little of
each others' trades by co-operation and communication. Ernest Cady has long
proved himself a master of these arts to his colleagues at University College
London, and by writing this excellent book he extends his experience to a wide
circle of readers.
Although the nuclear magnetic resonance (NMR) phenomenon had been
predicted theoretically (and to some degree demonstrated experimentally)
appreciably earlier, it required the advances in electronics that took
place during World War II to turn NMR into a practical technique, as
demonstrated independently in 1946 by Bloch and Purcell. Since then, NMR
has been used extensively and increasingly by chemists and physicists.
In the 1970s the first applications of NMR to animal organs yielded
important advances in our knowledge of the biochemical and physiological
processes as they occur in genuinely intact tissues. They showed incidentally
that some conventional techniques introduce significant artifacts.
More importantly, when combined with massive technical advances in
the design of superconducting magnets and in radiofrequency technology, this
work laid the foundations for the explosive expansion of human clinical
applications that has occurred within the past decade. One casualty of this
expansion has been in terminology. The very word "nuclear" sent shudders
down the spines of many patients even though the energy per quantum of the
radiofrequencies employed is some 1010 times less than that of ionizing radia
tions. Nevertheless for clinical purposes the "N" has been dropped from the
name; "MR" is used instead throughout this book. This may seem trivial but
v
vi Foreword
it is not; the mental equanimity of patients is just as important as their physical
condition.
The change is distinctly confusing to other scientists, who wonder
whether the clinicians are employing a totally different technique, especially
since in some new developments they are! Another loss is that the name NMR
is succinctly descriptive-Nuclear because the fundamental phenomenon
arises from the spin of those atomic nuclei that have it (all those containing
uneven numbers of protons and/or neutrons ); Magnetic because the spin and
positive charge make the nucleus behave like a tiny magnet which will interact
with externally applied magnetic fields; and Resonance because the use of the
technique depends on first exciting and then detecting resonant frequencies.
This book deals almost exclusively with MR spectroscopy (MRS), one of
whose main uses is the noninvasive chemical analysis of tissues. MRS has had
some success in solving clinical problems, notably in assessing the condition of
the brain and the prognosis in new-born human babies. Enzyme defects in
muscle, which are easily detected by MRS, tum out on survey to be rare. The
real and well-justified clinical success of the decade has been in MR imaging
(MRI). In this technique, the resonances from the IH nuclei, so plentiful
in the body, and also intrinsically the most sensitive, are manipulated in such
a way that they produce pictures of high quality of sections in any plane within
the body. Because radio-frequency technique is so versatile, these sections can
be "stained" in different ways so as to show up contrasts that are impossible
when using X-ray tomography.
Nevertheless, the appearance of a book on clinical MRS now is singularly
well timed. MRS is increasingly being combined with MRI in the same wide
bore, high-field spectrometer. In this way a certain volume of tissue can be
located using MRI and its chemical composition determined by MRS. The
possibilities seem endless and the excellent reference listings not only describe
the past but also put up many pointers to the future.
Since clinical MR is such a multifaceted subject, it is hard to know how
to begin to present it optimally to readers whose own knowledge will also be
very variable. My advice to them is that they need not necessarily start at the
beginning of the book but should start from topics that they already know
something about and are especially interested in. They can then work outward,
colloquially speaking, to less familiar but very important territory. Anyone
who wants to learn about MRS but feels daunted by every part of this book can
take heart from the fact that Ernest Cady's first degree was in astronomy!
Prof. D. R. Wilkie MD FRCP FRS
Department of Physiology
University College London
Preface
I have found the production of this book an exhilarating and self-educative
experience. The initial impetus for its production occurred during the
production of a chapter on the same subject, which was coauthored with
S. R. Williams. It was apparent that enough material was available and
that the subject had reached a sufficient degree of maturity to proceed
with a more substantial work. It is hoped not only that the reader will
find the text interesting as a description of the medical applications of
magnetic resonance spectroscopy (MRS) but also that those who are
actively involved in clinical investigations will find the work useful for
reference purposes. Furthermore, it is anticipated that clinicians and other
researchers entering the field without prior experience will find that the text
gives useful information about both the practical implementation of MRS
systems and the physiological information which can be derived from the
spectra.
Over the last decade, the in vivo MRS field has always been exciting
-from the first collections of the P spectra of in situ human muscle using
31
surface coils to the recent acquisition of highly resolved proton spectra with
full three-dimensional 1H image-guided localization from the living human
brain. The field is still developing rapidly, with continuous publication of
technical advances in data collection, localization, spectral editing, and
spectral-analysis methods. I have attempted to ensure that as many recent
"state of the art" publications as possible have been cited in the text.
My initial interest in the clinical aspects of MRS was aroused by D. R.
Wilkie, E. O. R. Reynolds, and R. H. T. Edwards; for this, and for the
leadership shown by these individuals, I am eternally thankful. I am also
grateful for discussions with various colleagues concerning the application
vii
viii Preface
of MRS in the clinic. These include P. L. Hope, P. A. Hamilton, J. S.
Wyatt, A. D. Edwards, A. M. de L. Costello, R. M. Gardiner, P. S. Tofts,
S. Wray, M. J. Dawson, and D. T. Delpy. I must express my thanks to D. J.
Newham, R. Aldridge, D. A. Jones, and J. K. Nicholson for assistance with
collecting some of the spectra used in the present work and to
H. Greenwood for secretarial assistance.
Finally, but by no means least, I must thank my wife, Lorna, and my
sons, Henry and Douglas, for their tolerance and patience during my many
periods of absence while preparing the manuscript.
Ernest B. Cady
Hornsey, London
Contents
1. An Introduction to Medical Magnetic Resonance Spectroscopy . . . . . .. 1
1.1. The Magnetic Resonance Phenomenon. . . . . . . . . . . . . . . . . . . .. 1
1.2. Magnetic Resonance in a Clinical Context. . . . . . . . . . . . . . . . . .. 4
1.3. Nuclei with Potential Clinical Applications. . . . . . . . . . . . . . . . .. 6
1.3.1. Phosphorus e1p). .................................. 6
1.3.2. Hydrogen eH). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 8
1.3.3. Carbon (l3C) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9
1.3.4. Nitrogen eSN) ..................................... 10
1.3.5. Oxygen (170) ...................................... 10
1.3.6. Fluorine (19F) ..................................... 10
e
1.3.7. Sodium 3Na) ..................................... 11
1.4. The Development of Biological MRSI ....................... 11
1.4.1. Skeletal Muscle .................................... 12
1.4.2. Cardiac Muscle .................................... 15
1.4.3. Smooth Muscle .................................... 17
1.4.4. Brain ............................................ 19
1.4.5. Liver ............................................. 31
1.4.6. Kidney ........................................... 33
1.4.7. Adipose Tissue .................................... 34
1.4.8. Lung(s) .......................................... 35
1.4.9. Testes ............................................ 36
1.4.10. Ovaries ........................................... 37
1.4.11. Skin ............................................. 38
1.4.12. Neoplastic Tissues ................................. 39
References .................................................. 40
ix
x Contents
2. Fundamentals of Clinical Magnetic Resonance. . . . . . . . . . . . . . . . . . .. 47
2.1. The Origin of the Magnetic Resonance Signal. . . . . . . . . . . . . . .. 47
2.1.1. The Behavior of Nuclear Spins in a Magnetic Field. . . . .. 47
2.1.2. The Rotating Frame of Reference ..................... 49
2.1.3. The Bloch Equations and Relaxation Phenomena ....... 51
2.2. The Magnetic Resonance Signal . . . . . . . . . . . . . . . . . . . . . . . . . .. 53
2.2.1. The Free Induction Decay. . . . . . . . . . . . . . . . . . . . . . . . . .. 54
2.2.2. The Spin Echo. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 57
2.2.3. Fourier Transformation. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 58
2.3. The Spectrum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 59
2.3.1. Chemical Shifts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 60
2.3.2. The Shapes and Widths of Spectral Peaks. . . . . . . . . . . . .. 69
2.3.3. Metabolite Concentrations. . . . . . . . . . . . . . . . . . . . . . . . . .. 74
2.4. The Signal-to-Noise Ratio. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 74
2.4.1. The SNR from a Single 90° Pulse ..................... 75
2.4.2. The Effect of T, and T2 on SNR ...................... 76
References ................................................. 79
3. Clinical Studies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 83
3.1. Introduction............................................ 83
3.2. Studies ofthe Human Brain ............................... 84
3.2.1. Studies ofthe Neonatal Brain. . . . . . . . . . . . . . . . . . . . . . .. 85
3.2.2. Spectroscopic Studies of the Adult Brain. . . . . . . . . . . . . .. 95
3.3. Studies of Human Skeletal Muscle .......................... 109
3.3.1. 3'p Spectroscopy of Human Muscle ................... 109
3.3.2. 'H Spectroscopy of Human Muscle ................... 121
3.3.3. 13C Spectroscopy of Muscle .......................... 122
3.4. Studies of Human Cardiac Metabolism ..................... 124
3.4.1. 3'p Studies of Human Cardiac Metabolism ............. 124
3.4.2. 'H Studies of the Human Heart ...................... 126
3.5. Studies of the Human Liver ............................... 126
3.5.1. 3' P Studies of the Human Liver ....................... 126
3.5.2. 13C Studies of Human Liver Metabolism ............... 129
3.6. Studies of Human Kidneys ................................ 130
3.7. Studies of Human Testes .................................. 131
3.8. In Vitro Studies of Human Body Fluids ..................... 132
3.8.1. 'H Studies of Urine ................................. 132
3.8.2. 'H Studies of Amniotic Fluid ......................... 135
3.8.3. 'H Studies of Human Blood Plasma ................... 136
3.9. Studies of Human Red Blood Cells ......................... 136
3.9.1. Results from 3'p Spectroscopy ........................ 137
3.9.2. 'H Spectroscopy of Red Blood Cells ................... 138
3.9.3. 23Na Spectroscopy of Red Blood Cells ................. 139
References ................................................. 139
Contents xi
4. Practical Aspects of Clinical Magnetic Resonance
Spectroscopy Systems ......................................... 149
4.1. An Overview of the System ................................ 149
4.2. The Magnet. ............................................ 151
4.2.1. Permanent Magnets ................................ 152
4.2.2. Resistive Electromagnets ............................ 153
4.2.3. The Liquid-Helium Superconducting Magnet. .......... 154
4.2.4. Shim, Gradient, and Profiling Coils ................... 159
4.3. The Spectrometer ........................................ 159
4.3.1. The RF Probe ..................................... 160
4.3.2. RF Coils .......................................... 160
4.3.3. The Preamplifier ................................... 176
4.3.4. The Receiver ....................................... 178
4.3.5. The Analog-to-Digital Converter ..................... 179
4.3.6. The Computer System .............................. 181
4.4. Safety Requirements. ..................................... 182
4.4.1. The Static Magnetic Field ........................... 183
4.4.2. Rapid Magnetic Field Changes ....................... 185
4.4.3. Radio-Frequency Fields ............................. 186
4.4.4. Other Hazards ..................................... 187
4.5. Patient Handling ........................................ 187
References ................................................. 188
5. Data Acquisition in Clinical Magnetic Resonance Spectroscopy ...... 193
5.1. Fundamental Considerations .............................. 193
5.1.1. Collecting Data Using Repeated Single Pulses .......... 193
5.1.2. Reduction of Spectrum-Baseline Artifacts .............. 196
5.2. Signal Localization ...................................... 196
5.2.1. Surface-Coil-Localization Methods .................... 197
5.2.2. Magnetic Field Gradient Techniques .................. 201
5.3. Spin-Echo Techniques .................................... 213
5.3.1. Simplification of Spectra ............................. 213
5.3.2. Spin Echoes with Surface Coils ....................... 214
5.4. Solvent Suppression ...................................... 216
5.4.1. Composite Pulses ................................... 216
5.4.2. Spin Echoes ....................................... 217
5.4.3. Saturation Methods ................................ 218
5.4.4. Binomial Pulses .................................... 218
5.5. Spectral Editing ......................................... 220
5.5.1. Reduction of Bone and Phospholipid Signals ........... 221
5.5.2. Spectral Editing in IH Spectroscopy ................... 222
5.6. Absolute Quantitation .................................... 225
5.6.1. External Concentration References .................... 226