CLINICAL-EXPERIENCE WITH DIFFUSION-WEIGHTED MR IN PATIENTS WITH ACUTESTROKE

PURPOSE: Our purpose was to evaluate the clinical efficacy, sensitivit y, and specificity of echo-planar diffusion-weighted MR imaging in pat ients with acute infarction, METHODS: We retrospectively analyzed 194 cases of acute ischemic stroke diagnosed clinically within 24 hours of onset and studied with echo-planar diffusion-weighted MR imaging. Exa minations were considered to be positive for infarction when an increa se in signal was noted on images acquired at a high b value but absent on images with a low b value. A final clinical diagnosis of acute str oke was used as the standard of reference. A subset of 48 patients sca nned within 6 hours was also analyzed, RESULTS: Diffusion-weighted MR imaging studies were positive in 133 of 151 cases of infarction (88% s ensitivity) and negative in 41 of 43 cases with no infarction (95% spe cificity). Two cases identified as positive on diffusion-weighted imag es had nonischemic diagnoses (1.5% false-positive rate). Diffusion-wei ghted imaging had a positive predictive value of 98.5% and a negative predictive value of 69,5%. Use of T2-weighted sequences as well as dif fusion-weighted imaging produced no false-positive findings. Of the ne gative scans, 69.5% corresponded to transient ischemic attacks or infa rcts (mostly small brain stem infarcts), When only cases scanned withi n 6 hours of onset were considered, the sensitivity rose to 94% and th e specificity to 100%. CONCLUSION: Despite bias due to dependence betw een diffusion-weighted imaging and the final diagnosis, this analysis suggests high sensitivity and specificity for echo-planar diffusion-we ighted imaging in the diagnosis of acute cerebral infarction, although negative scans did not rule out an ischemic pathogenesis.