The study analyzed 36 white matter plaques in 20 patients with MS who underwent both T2-weighted and diffusion tensor MRI. By measuring the degree to which water molecules spread in a particular direction--called fractional anisotropy (FA)--which is altered with damage to the nerve axons, the researchers discovered that the average area of focally abnormal white matter on diffusion tensor imaging was 87 mm2, 45% more than the average plaque area seen on T2-weighted images.
The researchers believe that besides measuring the degree of diseased white matter more accurately than T2-weighted imaging, diffusion tensor imaging may also show abnormalities earlier than T2-weighted imaging. "T2-weighted imaging does give us excellent anatomic detail of the brain and the distribution of destructive plaques in MS. However, relatively significant alteration in the tissue is necessary before we can see signal changes on T2-weighted images. Using diffusion tensor imaging, we are able to produce maps of water diffusion in the brain that help us identify damaged areas before the changes are severe enough to be detected on T2-weighted images," said Susan M. Kealey, MD, lead author of the paper.
According to Dr. Kealey, this finding could impact future treatment of MS. "Currently, many major trials of the effectiveness of various therapies for MS use the volume of affected white matter as seen on T2-weighted images as a marker of the response to therapy. Diffusion tensor imaging may be a more sensitive way of measuring the true lesion load in MS and therefore may be more sensitive in assessing the effectiveness of various therapies," she said.
The article appears in the August 2004 issue of the American Journal of Roentgenology.
Journal
American Journal of Roentgenology