The study, the largest of its kind, found that diffusion-weighted MR imaging was about 90 percent accurate in diagnosing stroke, says Mark Mullins, MD, PhD, of Massachusetts General Hospital. Dr. Mullins was the lead author of the study. Diffusion-weighted MR imaging was 91% accurate if the test was done 0-6 hours after the patient first began having symptoms; accuracy was 89% at 6-12 hours, then 90% at 12-24 hours, says Dr. Mullins.
The earlier we can accurately detect stroke and treat these patients, the less likely the stroke will be debilitating, says Dr. Mullins.
"Diffusion-weighted MR imaging was 100% specific, meaning that every patient we identified as having had a stroke, had indeed had one. It was 90% sensitive; of the 122 patients studied, 12 had had a stroke, however it wasn't clear on the diffusion weighted MR images," says Dr. Mullins.
These results are superior to previously reported studies on CT, which has about a 40-60% accuracy rate. CT of the brain, with the radiologist looking for hemorrhage, is the technique currently used most often to detect stroke, adds Dr. Mullins.
Diffusion-weighted MR imaging is a relatively new technique that creates images based on the diffusion properties of water in human cells. "The technique allows us to create two sequences of images. We can tell if a patient has had a stroke because in one sequence there is a very bright spot; we call it the light bulb sign. In the other sequence that same area is dark," says Dr. Mullins.
The study will be presented May 7 during the American Roentgen Ray Society Annual Meeting in San Diego, CA.
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