The relative apparent diffusion coefficient (ADC) ratio can be used to evaluate the extent of ischemia. We investigated the risk factors for, and correlation between, relative ADC ratio and hemorrhagic transformation (HT) after thrombolysis.

This single-center, retrospective study involved 105 patients with acute occlusion of the anterior circulation. Relative ADC ratio was calculated as the ratio of ADC pixel values, within the affected territory to ADC pixel values in the contralateral normal region. HT was determined by computed tomography and T2* weighted magnetic resonance imaging after endovascular revascularization.

Data for 80 of the 105 patients were analyzed. Comparing the number of patients between the HT group (n=25) and the non-HT group (n=55), a significant difference was noted in tissue plasminogen activator (tPA) use (P=0.028), time from onset to reperfusion ≥380min (P<0.001), fluid-attenuated inversion recovery (FLAIR) hyperintensity (P=0.009), and relative ADC ratio<0.650 (P<0.001). Multivariable logistic regression analysis identified relative ADC ratio<0.650 as the only independent predictor of HT (odds ratio 7.79; 95% confidence interval 2.22–27.3; P=0.001). Twenty-nine patients (including 20 in the HT group) had a relative ADC ratio<0.650. Multivariable logistic regression analysis identified use of tPA as the only independent predictor of HT (odds ratio 13.8; 95% confidence interval 1.35–125.5; P=0.010).

Relative ADC ratio<0.650 with use of tPA may be important for predicting HT.