Imaging of the Spine

557 Pages·2010·117.55 MB·English

by  Thomas P. Naidich

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IMAGING OF THE SPINE ISBN: 978-1-4377-1551-4
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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
CHAPTER 1 ● Imaging Techniques in the Adult Spine 5
(STIR) techniques may be used instead. The dose of Gd-
chelate contrast agent is based on the patient’s weight.
A typical lumbar spine protocol employs a spin-echo
T1W sagittal sequence and a FSE T2W sagittal sequence.
Additional axial FSE T1W and T2W images are obtained
from the thoracolumbar junction to include the conus
medullaris through at least the S1 level of the sacrum.
Axial T2W FSE images are optimal in the lumbar region
because CSF pulsation artifact is not as signifi cant a
problem as in the cervical and thoracic spine. Additional
inversion recovery sequences are useful for trauma and
are very sensitive for edema and hemorrhage. At least one
of the axial imaging sequences should provide a series of
contiguous images to properly assess the facet and liga-
mentous structures. Oblique axial images oriented with
the disc space may be added.
The cervical and thoracic spine are often imaged using
sagittal and axial FSE techniques, but a multiplanar gradi-
ent-echo axial sequence may substitute for or be used in
addition to FSE technique to obtain high resolution and
contrast while reducing CSF pulsation artifact. Sagittal
images should extend suffi ciently far laterally to include
the neural foramen and proximal portions of the exiting
spinal nerve.
Fast fl uid-attenuated inversion recovery (FLAIR) is a
T2W spin-echo sequence that suppresses the high signal
of CSF. It has the potential advantage of displaying subtle
edema or demyelination of the spinal cord, particularly
■ FIGURE 1-1 Sagittal T2W MR image of the cervical and thoracic near the surface of the cord. It is not limited by the CSF
spine used for localization. A vitamin B external marker (arrow) has been
12 motion artifacts seen on T2W FSE images and can be
placed on the back to allow accurate correlation as to vertebral level on
performed rapidly using FSE techniques. Despite these
axial and smaller fi eld-of-view sagittal images of the thoracic spine.
inherent advantages, the literature has reported varying
sensitivities that may result from (1) variations in the spe-
cifi c techniques used to acquire this sequence and (2) the
short TR. A 3D low fl ip angle GRE sequence may be used decrease in lesion contrast that occurs with heavily T2W
for axial T2W images of the cervical spine. A 2D GRE sequences. Additional FLAIR sagittal images are often
sequence may be better for T2W axial imaging of the useful when there is a suggestion of demyelinating disease
thoracic spine or if motion artifact is present at either site. such as multiple sclerosis.
Both spoiled GRE and steady-state GRE sequences are 3-T MRI has the theoretical advantage of doubling the
available. Steady-state GRE sequences provide very good signal-to-noise ratio (SNR) over imaging on a 1.5-T system
“myelographic” effect when used in tissues with long TR (Fig. 1-2). Eight-channel phased-array coils are currently
such as CSF. available for high-quality spinal imaging at 3 T. Long echo
Phased-array coils may be used in the thoracic and train, high-bandwidth acquisitions provide high resolution
lumbar regions to provide high-resolution images. Ante- and can be achieved with shorter acquisition times than
rior and posterior neck coils and a large imaging matrix 1.5 T. Conventional T2W FSE sequences usually provide
(512 or 256) are typically used to image the cervical spine. high quality images at 3 T. FSE or turbo spin-echo
Anterior saturation bands should be employed to reduce sequences are necessary for best image contrast. Free
artifacts from respiratory and bowel motion. Imaging of induction decay related artifacts may be reduced by using
the thoracic spine should include an external marker a greater number of acquisitions or fl ow compensation
to allow identifi cation of the correct spine level (Fig. techniques. However, a challenge inherent to 3-T spine
1-1). imaging is the increase in T1 relaxation time of tissue at
Gadolinium (Gd)-chelate contrast enhancement is used the higher magnetic fi eld strength. This increased T1
to evaluate suspected infection, tumor, arteriovenous mal- relaxation time requires increased time for image
formation, and diseases of the leptomeninges. It is also acquisition.
used to evaluate the postoperative lumbar spine but is MR myelography can be performed using FSE tech-
usually not needed in patients with uncomplicated cervi- niques such as rapid acquisition with relaxation enhance-
cal spine surgery. At least one of the Gd-enhanced imaging ment (RARE) and 3D fast imaging with steady-state
sequences should be obtained with fat suppression to precession (FISP) but is best accomplished using EPI. We
better evaluate fat-containing structures such as the bone have modifi ed a single-shot turbo spin-echo technique
marrow and epidural space. In the spine, both frequency- described by Demaerel and colleagues to improve resolu-
selected and spectrally selected fat-suppression techniques tion (Fig. 1-3).1 Each image is acquired in 8 seconds
are susceptible to artifact, so short-tau inversion recovery using the following parameters: TE 199.5 ms, TR 8000 ms,
6 PART ONE ● Introduction
■ FIGURE 1-2 Sagittal T1W
images acquired on 1.5-T (A) and 3-
T (B) MRI systems and sagittal T2W
images acquired at 1.5 T (C) and 3 T
(D). These studies were acquired 2
years apart. One can easily see,
however, the increased signal-to-
noise ratio on 3-T images by compar-
ing similar structures on both T1W
and T2W images. Note the increased
defi nition of the bone marrow, nerve
roots (short arrows), and longitudinal
ligaments (long arrows).
A B
C D
256 × 256 matrix, 1 acquisition, 200 × 200-mm fi eld of 2.5-mm thickness for the thoracic and lumbar spine. Sagit-
view (FOV), and 20-mm slice thickness. A presaturation tal and coronal reformatted images are usually used for
fat pulse is used to improve resolution. interpretation. The 3D reconstructions and oblique refor-
CT of the spine is performed in the axial plane using matted images may be reconstructed at the workstation
thin contiguous sections. Multislice scanners can image to assist in interpretation.
very thin slices very rapidly over substantial lengths of Intravascular contrast is not routinely utilized for spine
tissue. The resulting data loads are often very large, par- CT. It may be administered in cases of suspected tumor
ticularly if the images are obtained with near isotropic or infection. Intrathecal contrast is typically used when
resolution. The most important imaging parameters for CT myelography is performed and allows greater contrast
MDCT are section collimation, table feed per rotation, between CSF within the thecal sac and structures of the
and pitch. spinal canal. This is useful in the evaluation of spinal
Slice thickness is typically 0.625 mm, with axial images cord or nerve compression (Fig. 1-4). Nonionic contrast
reconstructed at 1.25-mm thickness for cervical spine and agent that is specifi cally formulated without preservatives
CHAPTER 1 ● Imaging Techniques in the Adult Spine 7
NORMAL APPEARANCE
CSF and fat act as natural contrast agents in spinal MRI.
They provide excellent contrast for outlining the spinal
cord, the thecal sac, and the nerve roots and veins within
the neural foramina. CSF has low signal characteristics on
T1W images and high signal on T2W images. The spinal
cord has intermediate signal on T1W images in part owing
to the abundance of myelinated fi ber tracts (lipid) within
the cord substance. It has very low signal on T2W images
because of the predominance of dense fi ber tracts and low
water content (Fig. 1-5). Fat has high signal on T1W images
and low signal on T2W images. On contrast-enhanced
images, the high signal from the fat may obscure the
high signal, resulting from contrast enhancement.
Therefore, fat-suppression techniques are commonly
used to eliminate the high signal from fat and thereby
display the high signal from contrast enhancement in stark
relief. These fat suppression techniques aid in detecting
enhancement within the epidural space and within the
spinal cord.
Normal adult bone marrow has intermediate to slightly
increased signal intensity on T1W images owing to the
presence of fatty marrow. Intermediate to slightly low
signal is seen on T2W images in part from the fast imaging
techniques used to acquire these images. The facet joints
are easily evaluated on both sagittal and axial imaging.
Sagittal imaging best illustrates the full articulation between
■ FIGURE 1-3 Frontal projection MR myelogram obtained using 3D the superior and inferior facets, but axial T1W imaging is
fast imaging with steady-state precession. This rapid technique uses
best to evaluate the integrity of the articular hyaline carti-
the natural contrast effects of CSF to produce a myelographic effect. The
descending nerve roots (short arrow) are easily identifi ed, including lage. The structures within the neural foramen are easily
the CSF-fi lled nerve root sleeve (long arrow). evaluated on parasagittal images.
The cartilaginous endplates of the vertebral body are
best evaluated in the sagittal or coronal planes using a fat-
suppressed 3D spoiled-gradient-echo sequence.2 This
technique may detect subtle morphologic abnormalities
for safe use in myelography is administered through a of the endplate, including cartilaginous thinning, irregular-
standard lumbar puncture or cervical puncture at the C1-2 ity, erosions, defects, and Schmorl’s nodes. These lesions
level. Because the dense myelographic contrast will fl ow are the earliest fi ndings seen with degeneration of the
through the CSF by gravity before becoming mixed with intervertebral disc and may be a source of axial back pain.
and diluted by the CSF, consideration must be given to (1) The normal cartilaginous endplate has slightly hypoin-
the relative positions of the puncture site, the site of tense to isointense signal on spin-echo T1W images and
expected pathology, and the specifi c curvature of the hypointensity on fast spin-echo T2W images when com-
patient’s spine and (2) the volume of contrast adminis- pared with the normal intervertebral disc. High signal is
tered versus the volume of the spinal canal. Correct assess- observed within the cartilage on fat-suppressed spoiled
ment of both factors will bring the contrast to the site of GRE images.
the pathologic process in proper concentration to dem- CT excels at delineating bony detail of the spine and
onstrate the lesion. Imaging the patient in the prone or adjacent soft tissues (Fig. 1-6). The bone cortex is very
symptomatic position may assist in revealing the cause of dense and easily evaluated. The underlying trabeculae of
neural compression. the medullary bone can also be easily identifi ed on CT. CT
Postprocessing of the images on a workstation improves clearly displays early reactive or reparative changes such as
CT of the spine, because varying the window levels and sclerosis, subchondral cyst formation, and osteophytosis.
widths provides optimal image review. Bone is typically Parasagittal images are useful for evaluating the integrity of
reviewed with a level of 300 and width of 3000, whereas the neural foramen, facet alignment, and the effect of bone
soft tissue is viewed with a level of 50 and width of 350. remodeling (Fig. 1-7). The posterior bony structures of the
By manually adjusting the contrast and window levels at spine including the pedicle, lamina, and spinous and trans-
the workstation one can accentuate the differences in verse processes are easily defi ned on CT.
tissue densities and detect subtle abnormalities such as The spinal cord is diffi cult to evaluate on CT, given the
small disc protrusions. Curved plane reconstructions can inherent contrast limitations. The addition of intrathecal
display lengths of the spinal column, canal, and cord that contrast during myelography allows evaluation of spinal
make interpretation easier in patients with kyphoscoliosis cord size and morphology. It also permits adequate evalu-
or other deformities. ation of the intradural nerve roots.