Magnetic Resonance Imaging: Theory and Practice

358 Pages·1996·7.866 MB·English

by  Dr. Ir. Marinus T. Vlaardingerbroek, Dr. Ir. Jacques A. den Boer (auth.)

Magnetic Resonance Imaging
Theory and Practice
Springer-Verlag Berlin Heidelberg GmbH
Marinus T. Vlaardingerbroek Jacques A. den Boer
Magnetic Resonance Imaging
Theory and Practice
With a Foreword by Freek Knoet
i
Springer
Dr. Ir. Marinus T. Vlaardingerbroek
MR Development, Philips Medical Systems
P.O. Box 10000
5680 DA Best, The Netherlands
Dr. Ir. Jacques den Boer
MR Clinical Sciences, Philips Medical Systems
P.O. Box 10000
5680 DA Best, The Netherlands
Cover figure: Front View of an MRI System. Modern System Design
Emphasizes Patient Comfort and Accessibility.
ISBN 978-3-662-03260-2 ISBN 978-3-662-03258-9 (eBook)
DOI 10.1007/978-3-662-03258-9
Library of Congress Cataloging-in-Publication Data. Vlaardingerbroek, Marinus T., 1931- . Magnetic resonance
imaging: theory and practice/Marinus T. Vlaardingerbroek, Jacques A. den Boer. p. cm. Includes bibliographical
references. 1. Magnetic resonance imaging. I. Boer, Jaques A. den.
1938- . II. Title. [DNLM: 1. Magnetic Resonance Imaging - methods. WN 185 V865m 1996] RC78.7.N83V53
1996 616.07'548-dc20 DNLMIDLC for Library of Congress 95-39241
This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned,
specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on
microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted
only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission
for use must always be obtained from Springer-Verlag Berlin Heidelberg GmbH. Violations are liable' for prosecution
under the German Copyright Law.
© Springer-Verlag Berlin Heidelberg 1996
Originally published by Springer-Verlag Berlin Heidelberg New York in 1996
Softcover reprint of the hardcover 1st edition 1996
The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the
absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and
therefore free for general use.
Product liability: The publishers cannot guarantee the accuracy of any information about dosage and application
contained in this book. In every individual case the user must check such information by consulting the relevant
literature.
Cover design: Springer-Verlag, Design & production
Typesetting: Best -set Typesetter Ltd., Hong Kong
SPIN: 10481389 55/3144/SPS - 5432 1 0 -Printed on acid-free paper
Foreword
When retired it is a blessing if one has not become too tired by the strain of one's
professional career. In the case of our retired engineer and scientist Rinus
Vlaardingerbroek, however, this is not only a blessing for him personally, but also
a blessing for us in the field of Magnetic Resonance Imaging as he has chosen the
theory of MRI to be the work-out exercise to keep himself in intellectual top
condition. An exercise which has worked out very well and which has resulted in
the consolidated and accessible form of the work of reference now in front of you.
This work has become all the more lively and alive by illustrations with live
images which have been added and analysed by clinical scientist Jacques den Boer.
We at Philips Medical Systems feel proud of our comakership with the authors
in their writing of this book. It demonstrates the value we share with them, which
is "to achieve clinical superiority in MRI by quality and imagination".
During their careers Rinus Vlaardingerbroek and Jacques den Boer have made
many contributions to the superiority of Philips MRI Systems. They have now
bestowed us with a treasure offering benefits to the MRI community at large and
thereby to health care in general: a much needed non-diffuse textbook to help
further advance the diffusion of MRI.
Freek Knoet
Director of Magnetic Resonance
Philips Medical Systems
Preface
Alles sollte so einfach wie moglich
gemacht werden, aber nicht einfacher.
Albert Einstein
Since the late 1940s the phenomenon "Nuclear Magnetic Resonance" has been
known from the work of Bloch, Purcell, and many others. The phenomenon is
based on the magnetic properties of some nuclei. When these nuclei are placed in
a magnetic field, they can absorb electromagnetic radiation of a very distinct
energy, E, and, since E = hill, of a distinct frequency, ill, and re-emit this energy
subsequently during their relaxation back to the original equilibrium situation.
Nuclear magnetic resonance became an important tool in the study of the compo
sition of chemical compounds and, in later years, also for the physical study of
matter and for biochemical studies. The Nobel Prize was awarded twice for contri
butions to the knowledge of nuclear magnetic resonance: in 1952 to Felix Bloch of
Stanford University and Edward Purcell of Harvard University, and in 1991 to
Edward R. Ernst from Zurich.
In March 1973 Lauterbur published his paper "Image Formation by Induced
Local Interaction" in Nature and introduced the idea that nuclear magnetic reso
nance can be used for medical diagnostic imaging. This was achieved by adding to
the homogeneous magnetic field (in which the nuclear magnetic resonance takes
place) small position-dependent (gradient) magnetic fields, which make the reso
nance frequency position dependent. Now the origin of the re-emitted radiation
can be traced back on the basis of the emitted frequency, which makes, in prin
ciple, imaging possible. Lauterbur's work was preceeded by a patent by Damadian
in 1972, in which the clinical use of NMR was anticipated. These inventions trig
gered enormous activity in realizing nuclear magnetic resonance systems for use
in hospitals and in the application of nuclear magnetic resonance to medical
diagnostics. The term "nuclear" is not commonly used because of its association
with nuclear warefare and nuclear radiation. The accepted name for the new
imaging technique is magnetic resonance imaging. Only a quarter of a century
after the invention of MRI one may expect that in the developed countries there
will be about one MRI system for every 105 inhabitants.
Of the many papers published nowadays on MRI (about 20000 per year) only
a small scattered minority deals with the physics of MRI. Still the number of new
ideas in this latter field is large, and in each case a good knowledge of the basic
theoretical concepts of MRI is necessary to understand them. Although there are
many excellent books and papers treating aspects of MRI theory, it is difficult (but
not impossible) to obtain from the available literature a coherent survey of the
mathematical description of MRI. The majority of MRI literature deals with the
VIII Preface
application of MRI to medical diagnostics, for which a qualitative description of
the MRI physics is considered to be sufficient. This attitude has been prompted by
the fact that the main interest in the application of MRI comes - of course - from
medical doctors, who are not in the first place interested in a quantitative physical
description of scan methods, but certainly also because early MRI systems had
many unpredictable properties, which made a quantitative understanding of the
imaging capabilities unrewarding.
However, in the last decade the reliability and reproducibility of MRI systems
has improved considerably and it may be expected that the quantitative theoretical
prediction of the results will become increasingly useful. So, both for the quantita
tive interpretation of image contrast and for the design or understanding of the
many new imaging methods, which impose new (higher) requirements on future
system design, a quantitative, hence mathematical, description of the physics of
MRI is of much value. We think here of new applications such as ultra fast dynamic
imaging, functional imaging, interventional imaging, the influence of contrast
agents and their dynamics in different applications, etc. Therefore in this textbook
we have undertaken the task of developing a coherent theoretical description of
MRI which can serve as a background for a thorough understanding of recent and
future developments. Although we start with the basic theory, the textbook is not
meant for making a first acquaintance with MRI. For this goal we refer the reader
to the textbooks mentioned in Chap. 1.
It is interesting to note here that much of the building blocks of the theory that
we need for our task were already available in the papers on NMR published long
before the invention of MRI in 1972, for example in the early works of Bloch,
Purcell, Ernst, Hahn, Hinshaw, and many others.
This textbook will also present a short global description of the system and its
components, as far as this knowledge is necessary for understanding the applica
tion capabilities of the system. The design task itself requires much more detail
and this is beyond the scope of this textbook.
The theoretical results will be illustrated with numerous MR images, which
were specially acquired for the purpose of demonstrating the effects resulting from
the MR physics, the system design, and the properties of the sequences under
consideration. The images are not taken for medical purposes: they are usually
taken from healthy volunteers. However, many problems that are met in practice
are illustrated in the image sets and are extensively discussed in the captions. Each
theoretical chapter is followed by a number of these image sets.
The image sets in this book are all generated on Philips Gyroscan systems.
This choice means that the images shown were obtained using the particular
acquisition methods available on that system type. No guarantee can be given of
the equivalence of these methods with methods that have equal names but are
implemented in MR systems of a different make. Nor will it be necessary for the
names of physically equivalent methods to be equal in MR systems of various
origins. Nevertheless, the physical basis of the design of MR acquisition methods
as treated in this book is valid for the MR systems of any manufacturer. We have
specified particularities of the methods used when these could reflect a special
Preface IX
Gyroscan idiom. Almost all the image sets are obtained at 1.5 T, making use of
volunteers. Whenever this was not true it is stated per image set.
When writing this textbook, we assumed that the reader is familiar with the
fundamentals of Fourier analysis, for which many textbooks are available. Also in
this book there is no extended theoretical description of RF pulses, which is worth
a book by itself. RF excitation pulses are treated on the basis of a simple linear
model which gives insight into some of their fundamental properties as far as we
need them for the understanding of the measuring sequences. For the detailed
design of RF pulses with large flip angles we refer the reader to the extensive
literature on that subject.
In an appendix we propose a systematic nomenclature for the imaging se
quences. This is done jointly with Prof. E.M. Haacke, one of the authors of another
book on MRI, published by Springer-Verlag.
Best, The Netherlands Marinus T. Vlaardingerbroek
July 1995 Jacques A. den Boer
Acknowledgements
This book evolved from the education that one of us (MTV) received from his co
workers during the period that he acted as project leader for (mainly) 1.5 T MRI
systems. After a long career in other fields of physics and engineering (plasma
physics, microwave devices and subassemblies, lasers, etc) and industrial manage
ment he joined the MR development group with practically no knowledge of system
design in general and MRI in particular. With much patience our colleagues
undertook the task of teaching their project leader and this education lies at the
roots of the theoretical part of this textbook. It is in a way a modest compilation of
the broad knowledge at all levels of MRI system design, system testing, and (clini
cal) application of the MR department. To mention all names here would be
unwieldy but the friendly lessons of all colleagues are highly appreciated.
The writing of this textbook was further supported by a course on system
design, which we organized within the development group. Together with a num
ber of colleagues specialized in the different disciplines we also prepared notes for
this course. We (the present authors) were allowed to use these notes for the
preparation of this textbook. We acknowledge the lecturers of this course, who
were also willing to criticize our text. They are: M. Duijvestijn, C. Ham, W.v.
Groningen, P. Wardenier, J. den Boef, F. Verschuren, L. Hofland, P. Luyten, B.
Pronk, H. Tuithof, and G.v. Yperen. Many discussions with J. Groen, P.v.d. Meulen,
M. Fuderer, R. de Boer, M. Kouwenhoven, J.v. Eggermond, A. Mehlkopf, and many
others were very stimulating.
Part of the internal Philips course was later also presented at the Institut fur
Hochfrequentztechnik of the Rheinisch Westfalische Technische Hochschule
(Technical University) in Aachen, Germany, where also the idea of preparing a
book on the basis of the college notes was born. We thank Prof. H.J. Schmitt for
opening the opportunity to organize this course and also the Rektor and Senate
for granting the "Lehrauftrag" (teaching assignment). We also thank the students
for teaching us how to explain difficult concepts such as k space.
One of us (JAdB) took the task of designing and collecting image sets for the
purpose of illustrating a number of essential problems in the interpretation of MR
images of human anatomy. The text to those images was read carefully by J.v.d.
Heuvel of the Philips MR Application department. All MR images presented in this
textbook are with the courtesy of Philips Medical Systems.
Most of the images are produced especially for this book on a 1.5 tesla, SIS
ACS (Advanced Clinical System) installed at the hospital "Medisch Spectrum