Totally Accessible MRI: A User’s Guide to Principles, Technology, and Applications

334 Pages·2008·22.08 MB·English

by  Michael L. Lipton MD

Totally Accessible MRI
Totally Accessible MRI
A User's Guide to Principles,
Technology, and Applications
Michael L. Lipton, MD, PhD
With a Foreword by Emanuel Kanal, MD, FACR, FISMRM, AANG
~
Springer
Michael L.Lipton, MD, PhD
Associate ProfessorofClinicalRadiology, Psychiatry and BehavioralSciences
Medical Director,MRI Services
DirectorofRadiology Research
AlbertEinstein College ofMedicine and Montefiore Medical Center
Bronx, NY
USA
and
Senior ResearchScientist
The Centerfor Advanced Brain Imaging
The NathanS.Kline Institutefor Psychiatric Research
Orangeburg, NY
USA
ISBN:978-0-387-48895-0 e-ISBN: 978-0-387-48896-7
DOl:10.1007/978-0-387-48896-7
Libraryof CongressControlNumber:2007932970
©2008SpringerScience+BusinessMedia,LLC
All rightsreserved.Thisworkmaynotbe translatedor copiedinwholeorinpartwithoutthe
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Dedicated to the memory ofmy grandfathers:
Samuel Parelman
Samuel B. Lipton
Meyer Light
Herman Blitz
Siegfried Rosenthal
Stature ofcharacter and ethic,
Unqualified love and support
Justifiable pride in their enduring legacy
Stand as an example for us all.
May their memory be a blessing.
Foreword
BS"D
Allmagnetic resonance technologists and allradiologistswhowork with
magnetic resonance (MR) technology can be divided into two subgroups:
(1) those who understand the underlying physics principles and how to
apply them; and (2) those who do not.
For so many patients and for so many diagnostic considerations, the
difference between membership in these two groups is minimal. One
can easilydiagnose avestibularschwannoma and accurately differentiate
it from a cerebellopontine angle meningioma without being that well
versed with many of the concepts underlying the creation of the MR
images on which these tumors are depicted. One by rote can generate
images of the pelvis that are quite diagnostic and aesthetically pleasing
without really understanding the intricate interrelationships between the
varyingimaging parameters used inthe generation ofthe obtainedimage
contrast.
There are certainsituations, however, for whichamore in-depth under-
standing isrequired. For example:Seeingtissuesignaldisappearon ashort
T1 inversion-recovery sequence yet recognizing that it does not have to
originate from fat but maycomefrom methemoglobin or some othershort
T1tissuemayprove clinicallyvitalfor arrivingat the correct diagnosis.For
suchcircumstances,understandingtheunderlyingprinciplesthat governthe
creationofthe imageand the contrastcontained thereiniscriticaland sets
oneapart-anddistinctlyahead-ofthecompetition, whocannotmake this
claim.
In the two-plus decades during which I have taught my courses on MR
physics entitled, "Clinical MR Physics: Understanding and Applying," I
have had the good fortune to teach literally thousands of eager students.
Among the most eager and most persistentwasDr. MichaelLipton. Never
satisfied with a superficial understanding, he always asked for more and
continually sought a deeper level of understanding of the underlying con-
cepts in a never-ending effort to build upon and improve upon that which
we already know.
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viii Foreword
With thistext, Dr. Liptonattemptsto impartsome ofhisvastknowledge
to one just starting out on ajourneytoward understanding this fascinating
technology. In a clearly written and disarmingly informal style more remi-
niscent ofconversationaltone thanformal lecture,Dr. Liptonbreaksdown
many of the concepts involved in the clinical magnetic resonance imaging
process into bite-sized pieces that are easy to swallowand digest. Steering
clear of most mathematics and quantum mechanics and remaining firmly
grounded in classical physics and explanations, Dr. Lipton sheds light on
manytopicsthatcanbesodifficulttosomany.Bysodoing,heisattempting
to modify the ratio of"understanders" to "rote performers" wefindin our
MR society today. I hold this to be quite a commendable objective, and I
applaudDr. Liptonforhisefforts. You, too, are tobecommended,because
reading this book is clear evidence that you have taken your first steps in
trying to switchcamps to the "understanders" group.
With G-d's Help and through the assistance of Michael's pen, may you
be granted the wisdom to attain your objectives and, more importantly,
apply them to the benefit of the patients entrusted to your care.
Emanuel Kanal, MD, FACR, FISMRM, AANG
Pittsburgh, Pennsylvania
Why This Book?
Nametipsascientiapotestasest[Knowledgeitselfispower].
-SirFrancis Bacon (OfHeresies, 1597)
The pages thatfolloware, in averylarge part, an outgrowth of an intensive
but accessible course in the physical basis and practical use of magnetic
resonanceimaging(MRI) technology thatIhave had the privilege and plea-
sure to present semiannually at Montefiore Medical Center/AlbertEinstein
College ofMedicine since 1997.It isat the urging of numerous current and
former students that I finally undertook to transform the contents of the
course and itssyllabusinto acohesivewrittenwork. Myapproachinprepar-
ingthis book has been to mirror the experience of the course, to the extent
that ispossible giventhe restrictions of a one-sided conversation.
The course remains oriented toward and open to anyone who wishes to
understand MRI, from the ground up, asused in clinicalmedicine; it isnot
merely a crash course to review for the radiology physics examinations.
Whenthe study ofphysicsand technologyisbroachedamong clinicalradi-
ologists, acommonrefrainis"why, beyondpassing our exams, do weneed
to know it." The fact isthat most clinicalradiologists, simplybecause ofits
seemingly overwhelming complexity and their heavy clinical workloads,
remain largely in the dark with regard to the physical basis of the technol-
ogythey wield.However,aswewillsee,alarge partofthe diagnosticpower
ofMRIliesinunderstandingthe physical basis ofthe images you examine.
Further, when, inevitably, images do not turn out asthey should, amodest
awarenessofthe "innerworkings" ofMRIleaves the user poisedto under-
stand and perhaps remedy the problem. I maintain that everything con-
tained in these pages has direct importance and utility in clinical imaging.
Nonetheless, asapart-timescientist, Ibelievethe materialisequallyuseful
and importantfornonclinicians. The responsesofseveralgraduatestudents
and faculty scientists who have attended the course looking for a rigorous
but very approachable introduction have borne this out.
In the interestofmakingthe materialasaccessible aspossible to aswide
an audience as possible, I assume no specific background whatsoever on
ix
x WhyThisBook?
the part of my students. (Attendees range from undergraduates to full
professors but are predominately radiology residents.) Although it iscer-
tainlytrue that mathematics isexquisitelywell-suitedfor expression ofthe
concepts underlying MRI, I choose to take an entirely nonmathematical
approach; onlyone equationneed be learned and recalled inorderto fully
absorb the information. Where I do include equations, it isfor the benefit
of those who find it a useful way to consolidate their understanding of
concepts.
Above all,thisbook isintendedfor users ofMRI; itisnot an exhaustive
reference work and not apulse sequence developer's handbook. The book
isdesigned to be read. Most importantly, however, I implore you to take
the concepts detailed inthe followingpageswithyouasyoureviewclinical
images,assessabnormalities, and confront artifacts and otherwise subopti-
mal images. One thing I can virtually guarantee: when it comes to MRI,
it is use it or lose it. Come join the users; the alternative doesn't sound
very good!
Michael L. Lipton, MD, PhD
A User's Guide
The scientistsoftoday think deeply instead ofclearly.One must be sane to think
clearly,but one canthink deeply and be quite insane.
-NikolaTesla (ModernMechanics andInventions,1934)
We are forced to livewith[scientificadvances]whether wewant or not and try to
make the best out ofit.
-RichardR. Ernst (Nobel BanquetSpeech,1991)
This book waswritten to be read. It is not a reference book but rather a
conversationofsorts that you are invited tojoin. Our common goalwillbe
a clear understanding of MRI. I begin at the beginning: the only prior
knowledge requiredisofthe mostbasicconceptsofvectors-theiraddition
and decomposition. A conciseexposition ofthis essential foundation topic
isprovided in Appendix 1.With this smallbit of background in hand, the
book canbe approached asaself-contained narrative,insequence, provid-
ingacomprehensiveunderstandingofnuclear magnetic resonance (NMR)
and basic and advanced MRI techniques.
Alwayskeep clearlyinviewthat our goalisto understandessential prin-
ciplesto the extent that they facilitate our understanding and enhance our
application of clinicallyrelevant imagingtechniques. In order to maintain
a readable narrative format, I have deliberately avoided specificliterature
references for the myriad concepts and applications described in these
pages.It goeswithout saying,however, that Icomeasanexpositor and not
an originator of these concepts. As Dr. Emanuel Kanal once remarked to
me (I paraphrase): As westruggle to understand this stuff,remember that
someone figured it out the first time around! Those readers interested in
morein-depth, specialized,ormathematicalapproachesmaywishtoconsult
one of the sources listed in Appendix 4 and the original research cited in
those references.
I have divided the book into three parts. Part I covers the concepts of
NMR, withoutcreatingan image, justanNMR signal.Thispartisimportant
because it develops all of the concepts underlying image contrast that are
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