Diffusion-Weighted MR Imaging of the Brain

411 Pages·2009·19.65 MB·English

by  Toshio Moritani MD

Diff usion-Weighted MR
Imaging of the Brain
Moritani · Ekholm · Westesson
T. Moritani
S. Ekholm
P.-L. Westesson
Diffusion-Weighted
MR Imaging
of the Brain
Second Edition
Toshio Moritani, MD, PhD Per-Lennart Westesson, MD, PhD, DDS
Assistant Professor Professor of Radiology
Department of Radiology and Director of Division of Diagnostic
University of Iowa Hospitals and Clinics and Interventional Neuroradiology
200 Hawkins Drive Department of Radiology and
Iowa City, IA 52242-1009 Professor of Clinical Dentistry
USA University of Rochester
School of Medicine and Dentistry
Sven Ekholm, MD, PhD 602 Elmwood Avenue
Professor of Radiology and Director of Research Rochester, NY 14624-8623
Division of Diagnostic USA
and Interventional Neuroradiology
Department of Radiology
University of Rochester
School of Medicine and Dentistry
602 Elmwood Avenue
Rochester, NY 14642-8623
USA
ISBN 978-3-540-78784-6 e-ISBN 978-3-540-78785-3
DOI 10.1007/978-3-3540-78785-3
Springer Dordrecht Heidelberg London New York
Library of Congress Control Number: 2009926632
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V
Foreword
Few advances in MR imaging have had the impact degenerative neurologic disorders, white matter dis-
that diff usion-weighted (DW) imaging has had in the eases, toxic/metabolic disorders, and tumors. As one
evaluation of brain. From the time of the early de- can easily see from the table of contents, the authors
scriptions by LeBihan and colleagues of the ability have systematically covered all major areas of neuro-
to image and measure the micromovement of water radiology. Th is will allow cross-referencing to prob-
molecules in the brain to the present time, diff usion lematic cases which one may encounter. Additionally,
imaging and its derivatives have made an impact in knowledge of what represents a normal adult brain
the evaluation of multiple disease processes, primar- and a normal developing brain along with an expla-
ily in ischemia, but also in other conditions of the nation of artifacts seen in DW imaging makes this a
brain. In most medical centers diff usion imaging is valuable book. It is noteworthy that the authors have
no longer considered a sequence to be used in spe- chosen to abundantly illustrate the clinical material,
cial circumstances, but rather it is employed as part drawing on pathologic correlations in a number of
of routine MR imaging of the brain. Because the in- areas.
formation derived from diff usion measurements can I believe that this book will benefi t not only those
improve our understanding of pathologic processes who deal routinely with neuro-MR imaging, but also
and can infl uence patient care, knowledge of the prin- those who want to establish a basis for understand-
ciples and applications of DW imaging is critical. ing of diff usion images in the hope of taking these
It is therefore of great interest that the group from principles of diff usion further into more exotic areas
the University of Rochester (Drs. Moritani, Ekholm, of neuroimaging such as white matter tract mapping
and Westesson) have assembled under one cover a with diff usion tensor imaging, analyzing alterations
collection of material which encompasses all the clini- in highly organized structures with fractional anisot-
cal aspects of DW imaging. Th ose who have attended ropy, or delving into macromolecular alterations with
recent meetings of the ASNR know the quality of the ever-higher b values. Th e authors are to be congratu-
exhibits and presentations which have come from this lated for putting their considerable experience to-
group. Th ey, early on, demonstrated the wide spectra gether in this form, and I am sure that the collection
of diseases that can cause restricted diff usion and they of cases herein will serve to educate not only those
warned us of mimickers of infarction and ischemia. who are just entering the clinical neurosciences, but
In this richly illustrated volume the authors take also those who daily use diff usion imaging to arrive at
the reader from the basic principles of DW imaging, a proper clinical diagnosis.
through the pulse sequences used, to mathematical
concepts behind the derivation of apparent diff usion Robert M. Quencer, M.D.
coeffi cients. Following explanations of the diff erent Chairman, Department of Radiology
types of edema which can eff ect the brain and the ap- Th e Robert Shapiro, M.D. Professor of Radiology
pearance of DW images, this book allows the reader University of Miami/Jackson Memorial
to see the variety of conditions that alter diff usion, in- Medical Center
cluding infarction, hemorrhage, cerebral infections, Miami, Florida, USA
VVIIII
PPrreeffaaccee
Progress in the fi eld of diff usion imaging is occurring to the pathophysiological mechanisms. I included my
at a very fast pace, with many papers on the clinical own hypothesis of “excitotoxic mechanisms,” which ac-
application of diff usion-weighted (DW) imaging being counts for cytotoxic/cellular edema in diff erent patho-
published in the last few years. Today, DW imaging has logical conditions. For instance, cytotoxic/cellular ede-
become one of the routine MR imaging sequences of ma (Chap. 4) is seen not only in ischemia/infarction
the brain; therefore, the correct interpretation of brain (Chap. 5), but also in epilepsy (Chap. 8), demyelination
MR images is mandatory. Without accurate knowledge and degeneration (Chap. 9), toxic and metabolic dis-
of DW imaging, correct diagnoses are oft en diffi cult to ease (Chap. 10), infectious disease (Chap. 11), trauma
make. (Chap. 12), or sometimes in relation to brain neoplasm
Furthermore, remarkable progress has been made (Chap. 13). Interestingly, their distributions are some-
in the fi elds of diff usion tensor imaging, including times similar even though the pathological processes
fractional anisotropy mapping, diff usion tensor color are quite diff erent.
mapping, and fi ber tractography, as well as in high- Each chapter presents correlations between many
b-value diff usion imaging, as exemplifi ed by numer- DW images and pathological tissues. In Chap. 13, we
ous articles published recently. Th e second edition of have classifi ed brain neoplasms based on the WHO
Diff usion-Weighted Imaging of the Brain contains new 2007 classifi cation, and displayed many cases with pa-
cutting-edge images from these fi elds. Th ose images thology. All pathology reports and fi gure legends were
that are clinically most useful were carefully selected reviewed and checked by two experienced neuropathol-
for inclusion, as the clinical applications are sometimes ogists, namely, Patricia Kirby MD (Neuropathology,
not straightforward. Department of Pathology, Th e University of Iowa
For this second edition, almost all the chapters were Hospitals and Clinics) and Barbara Germin, MD
rewritten and new cases were added – particularly the (Neuropathology, Department of Pathology, University
most clinically useful cases with recent references and of Rochester).
images, including diff usion tensor imaging and high- Th e pediatric brain is not a “small adult brain”; dif-
b-value imaging. Consequently, the total number of ferent types of diseases and their mechanisms in the
images in this edition is almost double that of the fi rst pediatric brain are remarkably diff erent from those
one. of the adult brain. For example, the postnatal period
In Chap. 1, the description of the principle of dif- of brain development is vulnerable to excitotoxic in-
fusion tensor imaging, including fractional anisotropy jury. In Chap. 14, we have collected DW and diff usion
mapping, diff usion tensor color mapping, and fi ber tensor images of pediatric conditions encompassing
tractography, was added. In Chaps. 2 and 3, we display various common and uncommon diseases. We also
the normal fi ndings in adult and pediatric brain imag- added a new chapter (Chap. 15) on scalp and skull
ing, along with the pitfalls and artifacts encountered, lesions, since DW imaging is executed routinely in
and explain the anatomy of white matter fi ber tracts this area.
by using diff usion tensor color maps and fi ber tractog- I hope that Diff usion-Weighted Imaging of the Brain
raphy. will be useful for the understanding of the anatomy and
Abnormal fi ndings in DW imaging are based on the pathophysiological background of brain diseases,
such diverse pathological conditions as edema (cyto- contributing to a better interpretation of DW images
toxic /cellular edema vs vasogenic edema), necrosis and thereby to correct clinical diagnoses in daily clini-
(coagulative necrosis vs liquefactive necrosis), cellu- cal work.
larity of tissue or tumor (hypercellular vs hypocellular
tumor), viscosity of fl uid (abscess, hematoma), etc. In Toshio Moritani MD, PhD
the present volume, we have given more consideration April 2009
IX
Preface to the 1st Edition
Th is book is the result of many years of clinical and Chapters 5–13 cover DW imaging characteristics of
academic interest in diff usion-weighted MR (DW) diff erent pathologic conditions and in Chap. 14 (pe-
imaging of the brain. Researchers and clinicians at diatrics) we have collected DW images of pediatric
the University of Rochester started to collect DW conditions.
images of a spectrum of abnormalities aff ecting the Th e book is organized according to major disease
brain immediately aft er this technique became avail- categories. Th is brings structure to the book, but is
able. Several case series with clinical and radiograph- not optimal for the clinician sitting in front of a set
ic correlations have been presented at the annual of images and wondering what they might represent.
meetings of the American Society of Neuroradiology For that reason we have a summary chapter entitled
and the Radiological Society of North America via “How to Use Th is Book” (Chap. 15, Chap. 16 in 2nd
posters and scientifi c reports. Over time it became ed), which is organized from the opposite perspective.
quite clear that we had a collection of DW images Th us, in Chap. 15 we have started with DW images
representing the majority of conditions that aff ect the and grouped them according to imaging characteris-
brain and we felt a need to put them all together un- tics. In each table we have listed diff erential diagnoses
der one cover. for each specifi c set of DW imaging characteristics
MR imaging has evolved dramatically since its and added thumbnail images with references to the
introduction into clinical work in the mid-1980s. corresponding chapters. Th e clinician can go directly
Looking back, there are several major steps that took to Chap. 15, determine the signal on the DW imag-
MR imaging of the central nervous system to the next ing, combine it with the T2 and ADC signal charac-
level. One of the fi rst steps was the introduction of teristics, and get a list of the conditions that match
the clinical usefulness of contrast agents. Other steps these imaging characteristics. Th e thumbnail images,
were the development of fat suppression techniques, the reference to corresponding chapter and knowl-
fast spin echo imaging, and,more recently, the devel- edge about the patient’s clinical presentation should
opment of a clinically useful DW imaging technique. allow the clinician to formulate a relatively narrow
DW imaging has revolutionized the imaging diagno- diff erential diagnosis for most clinical conditions. We
sis of acute infarction in the brain. It is,however,quite think that this “reversed” chapter will make the book
clear from the series of cases shown in this book that very useful for everyday work with DW imaging of
DW imaging is useful for many other conditions.Th e the brain.
time it takes to obtain a DW image is so short that in We are grateful for many pathological slides and
many institutions it is now being used as a routine fruitful discussions with Barbara Germin, MD,
part of any MR imaging of the brain. Department of Pathology, University of Rochester.
Th e initial chapters on principles of DW imaging, We acknowledge the case contribution from the
normal DW appearance, and pitfalls and artifacts Department of Radiology,Showa University, Japan,
provide the bases for understanding DW imaging. collected during the primary author’s time at Showa
Th is technique is complex and is associated with University. We would also like to thank Masahiro
many pitfalls and artifacts. Th e following chapter on Ida,MD,Department of Radiology, Ebara Municipal
brain edema provides the basis for understanding the Hospital, Japan; Minoru Morikawa, MD, Department
pathophysiology of signal alterations in DW images of Radiology, Nagasaki University, Japan; R.Nuri
related to various pathological conditions. Th e im- Sener,MD, Department of Radiology, Ege University
ages are correlated to corresponding neuropathologic Hospital, Turkey; and Ryutarou Ukisu,MD,Department
slides and aid the understanding of the DW imag- of Radiology, Showa University, Japan, all of whom
ing representation of various types of brain edema. contributed case studies. Our deepest gratitude goes to
X Preface to the 1st Edition
Ms Margaret Kowaluk and Ms Th eresa Kubera,Med- fellows and coworkers at the University of Rochester.
ical Graphic Designers, Department of Radiology, Finally, but not least, we thank our families for giving
University of Rochester, and Ms Belinda De Libero us the time to complete this project.
for her secretary work.We also wish to thank Yuji It is our hope that our readers will fi nd this book
Numaguchi, MD, PhD, Department of Radiology, on “Diff usion-Weighted Imaging of the Brain” in-
University of Rochester and St. Luke’s Hospital, Japan, structional and clinically useful.
who gave us encouragement and support.
We want to thank the editorial staff at Springer- Toshio Moritani
Verlag, without whose guidance, skills and knowl- Sven Ekholm
edgeable advice this book would not have become a Per-Lennart Westesson
reality. We would also like to thank our colleagues, October 2003
Chapter 1 XXII
Acknowledgments
Many new images, such as those of diff usion tensor im- Sergei MD (Department of Pathology, Th e University of
aging, fi ber tractography, high-b-value imaging, as well Iowa Hospitals and Clinics, USA); Takashi S. Sato MD
as new cases were provided by leading neuroradiologists (Th e University of Iowa Carver College of Medicine,
who take active roles in neuroradiology. We are deeply USA); Bruno Policeni MD, Andres Capizzano MD,
grateful to: Matthew L. White MD and Yan D. Zhang MD and Limin Yang MD (Department of Radiology, Th e
(Department of Radiology, Th e University of Nebraska University of Iowa Hospitals and Clinics, USA).
Medical Center, USA); Jinsuh Kim MD (Department of We would like to especially thank James M. Powers
Radiology, Th e University of Iowa Hospitals and Clinics, MD (Former Director, Neuropathology, Department of
USA); Noriko Salamon MD (Department of Radiology, Pathology, Th e University of Rochester Medical Center),
Th e University of California, Los Angeles, USA); who gave me valuable advice on brain cutting.
Shigeki Aoki MD (Department of Radiology, Juntendo Most of the new adult and pediatric cases come from
University, Japan); Kei Yamada MD (Department of the University of Iowa Hospitals and Clinics, and we are
Radiology, Kyoto Prefectural University of Medicine, sincerely grateful to Wendy R.K. Smoker MD (Director
Japan); Toshiaki Taoka MD (Department of Radiology, of Neuroradiology) and Yutaka Sato MD (Director of
Nara Medical University, Japan); Keiko Toyoda MD Pediatric Radiology, Department of Radiology, Th e
(Department of Radiology, Kameda Medical Center, University of Iowa Hospitals and Clinics).
Japan); and Hidetsuna Utsunomiya MD (Department of I also wish to thank Laurie Fajardo MD (Chairman,
Radiology, Graduate School of Radiology, International Department of Radiology, Th e University of Iowa
University of Health and Welfare, Japan). Hospitals and Clinics), Takehiko Gokan MD
Many neuroradiologists and clinicians kindly pro- (Chairman, Department of Radiology, Showa
vided us with valuable cases and pathology reports. University of School of Medicine, Japan), Hirotsugu
We hereby express our deepest gratitude to: R. Nuri Munechika MD (Department of Radiology, Southern
Sener MD (Department of Radiology, Ege University Tohoku Research Institute for Neuroscience, Japan,
Hospital, Turkey); Michael Sacher MD (Department and Former Chairman, Showa University of School
of Radiology, Mount Sinai Medical Center, USA); Ho of Medicine, Japan), and Yuji Numaguchi, MD
Kyu Lee MD (Department of Radiology, Wayne State (Department of Radiology, University of Rochester,
University Detroit Medical Center, USA); Jain Vikas USA, and St. Luke’s International Hospital, Japan), who
MD (Metro Health Hospital, Case Western Reserve gave us encouragement and support.
University, USA); Edip M. Gurol MD (Department Th is book is also an outcome of the daily clini-
of Neurology, Massachusetts General Hospital, USA); cal work, lectures, and seminars at the University of
Andrew Lee MD (Department of Ophthalmology, Iowa Hospitals and Clinics. I hereby wish to thank
Methodist Hospital, Houston, USA); Toshibumi the residents, fellows, colleagues, and coworkers at the
Kinoshita MD (Research Institute for Brain and Blood University of Iowa who constantly provided insight-
Vessels, Akita, Japan); Masaki Oka MD (Department of ful comments, stimulating discussions, and interesting
Radiology, Kikuna Memorial Hospital, Japan); Harushi questions.
Mori MD (Department of Radiology, Th e University I also wish to express my deepest gratitude to the
of Tokyo, Japan); Masahiro Ida MD (Department of editorial staff at Springer for their skills and knowl-
Radiology, Ebara Municipal Hospital, Japan); Minoru edgeable advice.
Morikawa MD (Department of Radiology, Nagasaki Last but not least, I would like to thank my wife
University, Japan); Ryutaro Ukisu, MD (Department for her support and secretarial work. I also thank my
of Radiology, Showa University Northern Yokohama parents in Japan for their warm support.
Hospital, Japan); Hisao Nakamura MD and Takashi
Kitanosono MD (Department of Radiology, Th e Toshio Moritani MD, PhD
University of Rochester Medical Center, USA); Syrbu April 2009
XIII
Contents
1 Basics of Diff usion Measurements 3 Pitfalls and Artifacts of DW Imaging . . . . . 23
by MRI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
1.1 Diff usion Imaging in MR . . . . . . . . . . . . . . . . 1 3.2 Infl uence of ADC and T2
1.2 Diff usion Imaging of the Brain . . . . . . . . . . . 1 on the DW Appearance . . . . . . . . . . . . . . . . . 23
1.3 Magnetic Resonance Principles 3.2.1 Concepts . . . . . . . . . . . . . . . . . . . . . . 23
of Diff usion Imaging . . . . . . . . . . . . . . . . . . . . 1 3.2.2 Apparent Diff usion
1.4 Apparent Diff usion Coeffi cient . . . . . . . . . . . 2 Coeffi cient Maps . . . . . . . . . . . . . . . . 23
1.5 Diff usion Represents a Molecular Event . . . 3 3.2.3 Exponential Images . . . . . . . . . . . . . 23
1.6 Requirements in Clinical 3.3 Clinical Conditions . . . . . . . . . . . . . . . . . . . . . 23
Diff usion Imaging . . . . . . . . . . . . . . . . . . . . . . 3 3.3.1 T2 Shine-through . . . . . . . . . . . . . . . 23
1.7 Setting the b-Value in Clinical 3.3.2 T2 Washout . . . . . . . . . . . . . . . . . . . . 26
DW Imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.3.3 T2 Blackout . . . . . . . . . . . . . . . . . . . . 27
1.8 Future Trends in Clinical 3.4 Artifacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Diff usion Imaging . . . . . . . . . . . . . . . . . . . . . . 4 3.4.1 Eddy Current Artifacts . . . . . . . . . . 28
3.4.2 Susceptibility Artifacts . . . . . . . . . . . 30
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.4.3 N/2 Ghosting Artifact
(Nyquist Ghost) . . . . . . . . . . . . . . . . 30
3.4.4 Chemical Shift . . . . . . . . . . . . . . . . . 30
2 Diff usion-Weighted and Tensor Imaging 3.4.5 Motion Artifacts . . . . . . . . . . . . . . . . 33
of the Normal Brain . . . . . . . . . . . . . . . . . . . . . 7 3.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.2 Adult Brain . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2.1 Low Signal in Basal Ganglia . . . . . . 7
2.2.2 Diff usion-Weighted Imaging 4 Brain Edema . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
of Gray and White Matter . . . . . . . . 7
2.2.3 Choroid Plexus . . . . . . . . . . . . . . . . . 7 4.1 Characterizationand Classifi cation
2.3 Pediatric Brain . . . . . . . . . . . . . . . . . . . . . . . . . 7 of Brain Edema . . . . . . . . . . . . . . . . . . . . . . . . 37
2.3.1 Diff usion-Weighted Imaging 4.2 Defi nition and Classifi cation
and ADC of the Pediatric Brain . . . 7 of Cytotoxic Edema . . . . . . . . . . . . . . . . . . . . . 37
2.4 Diff usion Tensor Imaging 4.3 Pathophysiology of Cytotoxic Edema . . . . . . 38
and White Matter Anatomy . . . . . . . . . . . . . . 12 4.3.1 Energy Failure . . . . . . . . . . . . . . . . . 38
2.4.1 Association Fibers . . . . . . . . . . . . . . . 12 4.3.2 Excitotoxic Brain Injury . . . . . . . . . . 39
2.4.2 Projection Fibers . . . . . . . . . . . . . . . . 12 4.4 Diff usion-Weighted Imaging
2.4.3 Commissural Fibers . . . . . . . . . . . . . 14 and Cytotoxic Edema . . . . . . . . . . . . . . . . . . . 41
2.4.4 Fibers of the Brain Stem 4.4.1 Conditions that Cause Cytotoxic
and Cerebellum . . . . . . . . . . . . . . . . 15 Edema, and Reversibility . . . . . . . . . 41
2.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 4.5 Vasogenic or Interstitial Edema . . . . . . . . . . 50
4.5.1 Conditions Th at Cause
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Vasogenic Edema . . . . . . . . . . . . . . . 51
4.6 Diff usion Tensor Imaging and Edema . . . . . 51