Diffusion-Weighted MR Imaging of the Spinal Cord
Roland Bammera,
Franz Fazekas
,a,
Michael Augustina,
Josef Simbrunnera,
Siegrid Strasser-Fuchsa,
Thomas Seiferta,
Rudolf Stollbergera and
Hans-Peter Hartunga
a From the Department of Neurology (R.B., F.F., M.A., S.S.-F., T.S., H.-P.H.) and the Magnetic Resonance Institute (R.B., F.F., M.A., J.S., R.S.), Karl-Franzens University, Graz, Austria.
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FIG 1. Diffusion-weighted images obtained from volunteers in three mutually orthogonal directions.
Top row, Direction-dependent diffusion-weighted interleaved echo-planar images of the cervical spine in a healthy male volunteer (images 1 to 3) with corresponding calculated trace-weighted diffusion and T2-weighted interleaved echo-planar images (images 4 and 5, from left to right). Diffusion gradients were applied in anteroposterior, cephalocaudal, and left-right directions (from left to right) at a b-value of 709 s/mm².
Bottom row, Calculated maps of apparent diffusion coefficient for diffusion weighting along anteroposterior, cephalocaudal, and left-right directions and trace of the diffusion tensor (from left to right).
Diffusion anisotropy can be clearly appreciated in the corpus callosum, the pontine region, and the spinal cord itself. Contrast between gray and white matter is most apparent with diffusion weighting in the left-right direction (arrows).
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FIG 2. Images of a 41-year-old male patient who was suffering from spondylotic myelopathy with evolution of spastic tetraparesis over the course of 3 to 4 weeks.
A, Diffusion-weighted interleaved echo-planar image clearly shows a hyperintense lesion (straight arrow) surrounded by a hypointense, presumably edematous, area (curved arrows).
B, T2-weighted interleaved echo-planar image shows corresponding hyperintensity (straight arrow).
C, Reduced diffusion, confirmed by a region of interest–based analysis of apparent diffusion coefficient maps, is likely caused by vascular compromise with cell swelling (black arrow). Note that fiber structures of the pyramidal tract running in a cephalocaudal direction are clearly apparent in the pontine region and medulla oblongata (arrowheads) because of left-right diffusion gradient application. Cord hyperintensity from C1 to the proximity of the lesion in A is from white matter anisotropy, similar to that observed in volunteers.
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FIG 3. Only mild hyperintensity was seen on diffusion-weighted MR images of a patient with myelitis.
A, Diffusion-weighted interleaved echo-planar image shows diffuse signal hyperintensity and swelling of the cervical spinal cord (open arrows). Note the signal cancellation due to ghosting artifacts (closed arrows) caused by bulk motion.
B, T2-weighted interleaved echo-planar image shows diffuse signal hyperintensity and swelling of the cervical spinal cord (open arrows), consistent with myelitis.
C, Region-of-interest measurements on corresponding apparent diffusion coefficient maps reveal moderately increased apparent diffusion coefficient values. Therefore, hyperintensity in diffusion-weighted MR imaging seems to be related to the so-called "T2-shine-through" effect that compensates for increased apparent diffusion coefficient.
D, Diffusion-weighted interleaved echo-planar image obtained at follow-up 7 months later. No pathologic signal alteration is seen.
E, T2-weighted interleaved echo-planar image obtained at follow-up 7 months later. The cord volume appears normal, and only faint intramedullary hyperintensities have remained.
F, Apparent diffusion coefficient map shows a small area with elevated apparent diffusion coefficient at the level between the medulla oblongata and C1 (arrowhead), which may represent residual damage.
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AJNR - American Journal of Neuroradiology