Imaging Techniques in the Adult Spine

603 Pages·2012·20.82 MB·English

OTHER VOLUMES IN THE
EXPERT RADIOLOGY SERIES
Imaging of the Chest
Imaging of the Musculoskeletal System
Image-Giuded Interventions
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EXPERT RADIOLOGY SERIES
Imaging of the Brain
Pediatric Neuroimaging
Imaging of the Abdomen
Imaging of the Cardiovascular System
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IMAGING OF THE SPINE ISBN: 978-1-4377-1551-4
Copyright © 2011 by Saunders, an imprint of Elsevier Inc.
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Library of Congress Cataloging-in-Publication Data
Imaging of the spine / Thomas P. Naidich . . . [et al.].—1st ed.
p. ; cm.
Includes bibliographical references.
ISBN 978-1-4377-1551-4
1. Spine—Imaging. 2. Spine—Imaging—Atlases. I. Naidich, Thomas P.
[DNLM: 1. Spine—pathology—Atlases. 2. Diagnostic Imaging—Atlases. 3. Spinal Cord
Diseases—diagnosis—Atlases. 4. Spinal Cord Injuries—diagnosis—Atlases. 5. Spinal Diseases—
Diagnosis—Atlases. 6. Spinal Injuries—diagnosis—Atlases. WL 17 I31 2010]
RD768.I45 2010
617.5′60754—dc22 2009053174
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Contributors
Krisztina Baráth, MD Mary Elizabeth Fowkes, MD, PhD
Senior Staff Neuroradiologist, Institute of Assistant Professor, Division of Neuropathology,
Neuroradiology, University Hospital Zurich, Department of Pathology, Mount Sinai Hospital,
Zurich, Switzerland New York, New York
David Mark Capper, MD Sosikhan Geibprasert, MD
Department of Neuropathology, Institute of Lecturer, Neuroradiology, Mahidol University; Staff,
Pathology, Ruprecht-Karls University, Neuroradiology, Ramathibodi Hospital,
Heidelberg, Germany Bangok, Thailand
Francis Michael Castellano, MD
Ronit Gilad, MD
Neuroradiology Fellow, Department of Radiology,
Resident, Mount Sinai School of Medicine,
University of North Caroline at Chapel Hill,
New York, New York
Chapel Hill, North Carolina
Mauricio Castillo, MD Yakov Gologorsky, MD
Professor and Chief of Neuroradiology, Department of Resident, Department of Neurosurgery, Mount Sinai
Radiology, University of North Carolina at Chapel School of Medicine, New York, New York
Hill School of Medicine and University of North
Carolina Hospital, Chapel Hill, North Carolina Serap Gultekin, MD
Faculty of Medicine, Department of Radiology,
Cynthia T. Chin, MD Gazi University School of Medicine,
Associate Professor of Radiology and Neurosurgery, Ankara, Turkey
University of California at San Francisco,
San Francisco, California Victor M. Haughton, MD
Professor, Department of Radiology, University of
Tanvir Fiaz Choudhri, MD Wisconsin; Radologist, University of Wisconsin
Assistant Professor of Neurosurgery, Department of Hospitals and Clinics, Madison, Wisconsin
Surgery, and Co-Director, Neurosurgery Spine
Program, Mount Sinai School of Medicine,
Michael Christian Hollingshead, MD
New York, New York
Neuroradiology Fellow, Department of Radiology,
University of North Carolina at Chapel Hill,
David L. Daniels, MD
Chapel Hill, North Carolina
Professor of Radiology, Medical College of Wisconsin,
Milwaukee, Wisconsin
Sundar Jayaraman, MD
Bradley Neil Delman, MD Clinical Assistant Professor, Department of Radiology,
Associate Professor of Radiology and Director of State University of New York-Upstate Medical
Radiology Quality and Performance Improvement, University, Binghamton; Attending Radiologist,
Mount Sinai School of Medicine, Department of Radiology, Wilson Regional Medical
New York, New York Center, Johnson City, New York
Girish Manohar Fatterpekar, MBBS, DNB, MD David M. Johnson, MD
Assistant Professor of Radiology, James J. Peters Associate Professor of Radiology and Neurosurgery,
Veterans Administration Medical Center, Mount Fletcher Allen Health Care, University of Vermont,
Sinai Medical Center, New York, New York Burlington, Vermont
v
vi Contributors
Spyros S. Kollias, MD Joy S. Reidenberg, PhD
Professor of Radiology (Neuroradiology), Department Professor, Center for Anatomy and Functional
of Medical Radiology, and Chief of Neuro-MRI, Morphology, Mount Sinai School of Medicine,
Institute of Neuroradiology, University of Zurich, New York, New York
Zurich, Switzerland
Jose Conrado Rios, MD
Timo Krings, MD, PhD Neuroradiology Fellow, Department of Radiology,
Professor of Neuroradiology, Tornonto Western
Mount Sinai Medical Center, New York, New York
Hospital, University Health Network,
Toronto, Ontario, Canada
Nadja Saupe, MD
Department of Radiology, University Hospital Balgrist,
Pierre L. Lasjaunias, MD, PhD†
Zurich, Switzerland
Professor of Neuroradiology, University Paris Sud,
University Hospital Bicetre, Le Kremlin-Bicetre,
Paris, France Marta Martínez Schmickrath, MD
Staff Neuroradiologist, La Paz Hospital, Madrid, Spain
Patrick A. Lento, MD
Associate Professor, Departments of Pathology, J. Keith Smith, MD, PhD
Internal Medicine, and Medical Education, Mount Associate Professor, Department of Radiology,
Sinai Medical Center, New York, New York University of North Carolina at Chapel Hill School
of Medicine, Chapel Hill, North Carolina
Kenneth Michael Lury, MD
Assistant Professor, Department of Radiology, Medical
Maria Vittoria Spampinato, MD
University of South Carolina, Charleston, Assistant Professor, Department of Radiology, Medical
South Carolina University of South Carolina, Charleston,
South Carolina
Kenneth R. Maravilla, MD
Professor, Radiology and Neuroradiology, and
Director, MR Research Laboratory, University of Evan Gary Stein, MD
Resident, Neuroradiology Division, Department of
Washington, Seattle, Washington
Radiology, Mount Sinai Medical Center,
Michel Guy André Mittelbronn, MD New York, New York
Institute of Brain Research, University of Tuebingen,
Tuebingen, Germany Jeffrey Stone, MD
Associate Professor of Radiology, Mayo Clinic,
Thomas Paul Naidich, MD, FARC Rochester, Minnesota
Professor of Radiology and Neurosurgery, Irving and
Dorothy Regenstreif Research Professor of E. Turgut Tali, MD
Neuroscience (Neuroimaging); Director of Professor and Director, Division of Neuroradiology,
Neuroradiology, Mount Sinai School of Medicine, Department of Radiology, Gazi University School of
New York, New York Medicine, Ankara, Turkey
Matthew F. Omojola, MB, FRCPC
Cheuk Ying Tang, PhD
Professor, Section of Neuroradiology, Department of
Assistant Professor, Mount Sinai School of Medicine;
Radiology, University of Nebraska Medical Center,
Director, Neurovascular Imaging Research,
Omaha, Nebraska
Translational and Molecular Imaging Institute,
Irina Oyfe, BS, MS Eng Departments of Radiology and Psychiatry; Director,
Post Processing Analyst, Department of Radiology, In Vivo molecular Imaging SRF, Mount Sinai
Mount Sinai Medical Center, New York, New York Medical Center, New York, New York
Paola Carmina Valbuena Parra, MD Armin K. Thron, MD
Institute of Neuroradiology, University Hospital Professor, Department of Radiology, University
Zurich, Zurich, Switzerland Hospital Aachen, Aachen, Germany
Aman B. Patel, MD
Carrie L. Tong, MD
Associate Professor, Department of Neurosurgery and
Faculty Lecturer, Department of Radiology, Mount
Radiology, Mount Sinai School of Medicine,
Sinai School of Medicine; Attending Radiologist,
New York, New York
Good Samaritan Hospital, Suffern, New York
Sumit Pruthi, MD, DNB
Assistant Professor, Department of Radiology, Donald J. Weisz, PhD
University of Washington; Attending, Children’s Associate Professor, Department of Neurosurgery,
Hospital and Regional Medical Center, Mount Sinai School of Medicine,
Seattle, Washington New York, New York
†Deceased.
Preface
Over the years, the imaging of spinal disease has evolved decompressing spinal stenosis and disc disease. Three
from plain fi lm diagnosis and polytomography to advanced fi nal chapters address the brachial plexus, the sacral
computed tomography (CT) and magnetic resonance plexus, and peripheral nerve compression at the carpal
(MR) imaging (I). Year by year, what is considered to be tunnel. The congenital malformations of the spine will
“modern imaging” morphs from advanced techniques to be presented in a companion volume on pediatric
basic diagnostic tests to quaint old studies. Year by year, neuroimaging.
cruder and more invasive procedures are replaced by In successive chapters, this text also provides strategies
safer, faster, and more precise methods for detecting and for effi ciently analyzing spinal images and includes sample
characterizing spinal disease. reports to illustrate one way to convey key fi ndings to the
Through all of these changes, however, the constants clinicians and achieve “useful reporting” of our studies.
of medical diagnosis have remained the anatomy, physiol- The increasingly sophisticated imaging techniques
ogy, and pathology of the spinal column and cord. The require of us increasingly sophisticated knowledge of
human body has evolved more slowly than the techniques how to perform the studies effectively, how to recognize
used to display it, so the anatomy, physiology, and pathol- their limitations, and how to interpret them to under-
ogy of the spine remain the foundation of all medical stand the state of the patient in health and disease.
diagnosis. For this volume, therefore, the editors have selected a
To be useful, the data derived from the imaging studies group of highly skilled physician-authors who know their
need to be communicated concisely and effectively to the subject and who can present it concisely and thoroughly.
clinicians who care for the patient. Too often, imaging These authors specifi cally include neuropathologists,
reports are cluttered with technical details about the study whose contributions underlie our imaging appreciation of
but limited in their discussion of the key pathophysiologic neuropathology.
data needed to direct patient management toward one This volume, then, is intended to provide a concise but
or another path. The generations-long debate: “Who reads thorough review of the imaging diagnosis of spinal disease.
the studies better, the clinician or the imager?” is resolved It emphasizes the constant anatomy and physiology of the
when it is appreciated that these physicians read the spinal column and cord in the detail that is now required
studies for two fundamentally different sets of data. Useful to understand “modern” imaging. It illustrates how pathol-
interpretation of the images provides the pertinent posi- ogy affects the spine and reviews which patterns of pathol-
tive and negative data clinicians need to make their man- ogy lead to secure imaging diagnosis. It also deliberately
agement decisions as well as the detailed physical data includes selected data that we feel may aid us in interpret-
imagers need to reach their diagnoses and to understand ing the “modern” imaging of the future.
the limitations of their studies. We hope that the readers will enjoy learning about the
In successive chapters, therefore, this text addresses spine as much as we have in researching this text and in
imaging techniques for the spine, the paraspinal soft making the anatomic and pathologic images that illustrate
tissues, the normal anatomy of the spinal column and the text. It is hoped further, that the readers may discern
cord, age-related changes of the spine, degenerative defects in our knowledge, be stimulated by them to pursue
disorders of the spine, the normal vascularization of their own investigations, and thus join us to
the spinal cord, spinal ischemia and vascular malforma- “Perform an act whereof what’s past is prologue;
tions, spinal trauma, spinal tumors and cysts, metabolic what to come, [is] in your and my discharge.” William
disorders of the spine, infl ammation and infection of the Shakespeare, The Tempest Act 2, scene 1, 245-254.
spine, preoperative mapping of spinal pathology, intra-
operative monitoring of spinal physiology, vertebro- THOMAS P. NAIDICH
plasty-kyphoplasty, and the complications of surgery for
vii

11
C H A P T E R
IImmaaggiinngg TTeecchhnniiqquueess iinn tthhee
AAdduulltt SSppiinnee
Jeffrey Stone
Imaging of the adult spine is typically accomplished using curvature, effects of gravity, dilution of contrast, or size
CT and MRI. Although conventional radiography may play of the thecal sac. It is, however, more sensitive to motion
a role in the evaluation of spinal disorders, the sensitivity, and may not permit imaging the patient in the symptom-
specifi city, availability, and trends in medical practice atic position.
have resulted in a paradigm shift to the use of cross-sec-
tional imaging. CT is frequently used to study spinal frac-
PHYSICAL PRINCIPLES
tures. Multidetector CT (MDCT) is signifi cantly faster than
routine CT, so it is very useful for evaluating the unstable MRI relies on the spin of unpaired protons around the
or elderly patient who may not be able to hold still for atomic nucleus. The spin of the unpaired proton of hydro-
lengthier examinations. MDCT signifi cantly reduces arti- gen is typically utilized due to the abundance of hydrogen
facts related to beam hardening, so it also is useful for in the body. Hydrogen protons spin or precess around the
evaluating bone adjacent to surgical hardware. axis of the applied magnetic fi eld used in MRI. The fre-
MRI is used for evaluation of suspected degenerative quency of precession is proportional to (1) the strength
disc disease, infection, tumor, and soft tissue trauma, of the applied magnetic fi eld (typically 0.7 to 3 T for diag-
including suspected spinal cord injury or spinal canal nostic MRI) and (2) an intrinsic property of the nucleus
hemorrhage. MRI is motion sensitive, so adequate image referred to as the gyromagnetic ratio. The base magnetic
resolution can be a challenge in the claustrophobic or fi eld results in a slightly greater number of hydrogen
elderly patient. Such patients may require the use of seda- protons becoming aligned parallel with the magnetic fi eld
tion. The recent availability of 3-T MRI has presented new (longitudinal magnetization) versus antiparallel and a
opportunities for spinal imaging and may allow better resultant net magnetization of the tissue.
functional and dynamic imaging of the spinal column. Once the protons are aligned, a radiofrequency (RF)
Conventional contrast myelography has seen a decrease pulse is applied to tilt the axes of spin away from their
in use over the past decade mostly in response to better alignment with the applied magnetic fi eld. This creates a
MRI. Myelography is useful in evaluating extrinsic com- net magnetization in the plane perpendicular to the origi-
pression of the neural elements in and around the spinal nal axis (transverse magnetization). Once the RF pulse is
canal. It is typically performed when there is a contrain- removed, these protons (1) begin to realign parallel to the
dication to MRI. The increased use of non-ferromagnetic applied magnetic fi eld in exponential fashion and (2) emit
implants and medical devices has reduced the number of a weak signal that can be detected by a receiver coil. The
such patients. Contrast myelography may also be consid- time after the RF pulse that 63% of the original magnetiza-
ered in a patient whose symptoms or physical fi ndings are tion has returned to its alignment with the applied mag-
not explained on CT or MRI. MR myelography is an alter- netic fi eld is a constant that depends on the anatomic
native approach to evaluation and can be performed environment of the proton. This constant is referred to as
without the injection of a contrast agent. MR myelography T1. The applied RF pulse also causes the precession of the
has the advantage of not being dependent on spine individual protons to synchronize with each other. This
3
4 PART ONE ● Introduction
synchrony of precession is lost exponentially on removal CT uses x-ray radiation to acquire and reconstruct thin,
of the RF pulse. The loss of synchronization results from cross-sectional images of an object. Measurements of
the effect of the local environmental on each proton and attenuation are obtained throughout a defi ned thickness
from interactions among adjacent protons (spin-spin inter- of the object being imaged, and the data are used to recon-
action). Protons lose transverse magnetization exponen- struct a cross-sectional image. Each pixel within the image
tially as they return parallel to the magnetic fi eld. The time represents a measurement of the mean attenuation within
at which protons have lost 63% of their transverse mag- the voxel (volume of tissue) that extends through the
netization is a second constant referred to as T2. thickness of the section. The attenuation measurement
The weak signal emitted by the spins as they realign quantifi es the amount of radiation removed from the beam
with the main magnetic fi eld can be made detectable as as the beam traverses the voxel. This reduction in beam
an “echo” by applying an additional 180-degree RF pulse. strength is expressed as an average attenuation coeffi -
The echo is created when the dephased protons come cient. Many rays from many different rotational angles are
back into phase. The echo occurs after the 180-degree used to calculate the average attenuation coeffi cient. The
pulse at a time equal to the time between the 90-degree CT number, or Hounsfi eld unit (HU), is then calculated by
pulse and 180-degree pulse. The echo time (TE) equals normalizing the average attenuation coeffi cient of a voxel
the time between the initial RF pulse and the time at to the value of water (water = 0). Voxels that contain
which the echo is detectable. Spatial information is material that attenuates the x-ray beam more than water
encoded in these echoes by using gradient coils to vary (i.e., muscle, bone) have positive values. Voxels that
the magnetic fi eld strength across the applied magnetic contain material that attenuates the x-ray beam less than
fi eld. Frequency encoding along an excited slice (x-axis) water (i.e., fat, air) have negative values. The attenuation
provides spatial resolution between slices. It is achieved of water is obtained at the time the CT scanner is cali-
by applying a magnetic gradient along one direction of the brated. The absolute CT number of materials other than
region being sampled. This gradient causes the protons in air or water may vary with changes in x-ray tube potential
each slice to precess at a frequency slightly different from and between different manufacturers. A HU may be
the protons in the adjacent slice. Phase encoding allows assigned between −1000 and 1000. Only a limited number
spatial resolution within a slice. It is achieved by applying of all HU are actually presented on the display monitor
an additional magnetic gradient along the tangential axis used for interpretation. The window width is the range of
(y-axis) of an excited slice at a time between the RF pulse HU displayed on the monitor, whereas the window level
and the sampling of the signal. This new applied pulse represents the central HU of all the numbers within that
causes the spins in each row of the selected slice to window width.
precess at a slightly different frequency than the spins in CT scanners have quickly evolved from single-row
an adjacent row. The raw data collected during scanning detector confi gurations to helical scanners and more
of each slice are then used to generate an image by fi lling recently to multiple-row or multislice scanning technol-
in the k-space. The k-space is a mathematical construct—a ogy. By increasing detectors along the z-axis, multiple
matrix that provides a graphical representation of the raw image slices can be acquired simultaneously. Therefore,
data obtained within a slice. The amplitude of the signal large volumes of tissue can be rapidly scanned with near-
detected at time points during the echo is used to assign isotropic resolution even when the slices are very thin.
a specifi c numerical value to each point in the k-space This results in an image that is equally sharp in any plane
matrix. By repeating the process for each phase-encoding within the scanned volume. From these image data, mul-
gradient applied to the slice being imaged, a matrix con- tiplanar reformatted images and 3D reconstructions can
sisting of rows and columns is created with each number be performed at amazingly high resolution and with reduc-
representing the signal strength. The data acquired at one tion in artifact.
phase-encoding gradient are represented by a single row,
and the data obtained at different times of the echo are
contained within a single column. 2D Fourier transforma- IMAGING
tion is then used to generate an image.
Parameters/Protocols
MR myelography takes advantage of the intrinsic con-
trast between cerebrospinal fl uid (CSF) and soft tissue Protocols for MRI of the spine include T1-weighted (T1W)
structures such as the spinal cord, nerves, and fat within and T2-weighted (T2W) imaging in the axial and sagittal
the epidural space. Echoplanar imaging (EPI) is especially planes. Coronal imaging may be used to evaluate coronal
suited for MR myelography and allows image acquisition imbalances such as scoliosis. T1W images provide excel-
in seconds. It decreases the effects of patient motion and lent spatial resolution and are very useful for evaluating
is an easy addition to routine imaging protocols. EPI is the bone marrow, ligaments, and soft tissue structures.
accomplished by using a rapid series of gradient reversals T2W images are excellent for displaying the spinal cord
in the frequency-encoding phase to continuously fi ll k- and the CSF within the spinal canal. Fast spin-echo (FSE)
space. The resultant short repetition time (TR) allows very techniques are usually used to obtain sagittal T2W images.
rapid acquisition of images in the 100- to 200-ms range. Because FSE techniques are subject to degradation by CSF
Whereas EPI is sensitive to chemical shift and magnetic pulsation, however, FSE sequences may not provide excel-
susceptibility artifacts, this is not critical when imaging lent axial images of the cervical and thoracic spine.
larger structures such as the spinal column. However, Instead, gradient-recalled-echo (GRE) sequences may be
these effects may degrade resolution when EPI is used to used for axial imaging of the cervical and thoracic regions.
display the spinal cord. The GRE sequences allow for rapid imaging with a very