Relationship between apparent diffusion coefficient and subsequent hemorrhagic transformation following acute ischemic stroke

Background and Purpose-A method for identifying patients at increased risk for developing secondary hemorrhagic transformation (HT) after acute ischem ic stroke could be of significant value, particularly in patients being con sidered for thrombolytic therapy. We hypothesized that diffusion-weighted M RI might aid in the identification of such patients. Methods-We retrospectively analyzed 17 patients with ischemic stroke who re ceived diffusion-weighted MRI within 8 hours of symptom onset and who also received follow-up neuroimaging within 1 week of initial scan. The apparent diffusion coefficient (ADC) for each pixel in the whole ischemic area was calculated, generating a histogram of values. Areas subsequently experienci ng HT were then compared with areas not experiencing HT to determine the re lationship between ADC and subsequent HT. Results-A significantly greater percentage of pixels possessed lower ADCs ( less than or equal to 550X10(-6) mm(2)/s) in HT lesions compared with non-M T lesions (47% versus 19%; P<0.001). Moreover, >40% of the pixels possessed values less than or equal to 550X10(-6) mm(2)/s in all lesions experiencin g secondary HT, compared with <31% of the pixels in the non-MT-destined les ions. Conclusions-HT-destined stroke regions possess a significantly great percen tage of low ADC values than non-HT-destined regions. Early measurement of A DC values may be a useful tool for assessing secondary HT risk.