Utility of relative ADC ratio in patient selection for endovascular revascularization of large vessel occlusion.

Purpose: The relative apparent diffusion coefficient (ADC) ratio on magnetic resonance imaging (MRI) can be used to evaluate the degree of ischemia. Here, we assessed the predictability of ischemic reversibility and the risk of hemorrhagic transformation using the relative ADC ratio.

Methods: This single-center retrospective study analyzed 56 patients with acute occlusion of the internal carotid artery (ICA) or the middle cerebral artery (M1) with endovascular revascularization. Diffusion-weighted imaging (DWI) lesions were classified as reversible lesions, final infarct lesions, and hemorrhagic or non-hemorrhagic regions. The relative ADC ratio was calculated in each DWI lesion and was defined as the ratio of ADC pixel values within affected territory to ADC pixel values in contralateral normal brain regions.

Results: The average relative ADC ratio was 0.890±0.045 in reversible DWI lesion and 0.640±0.041 in final infarct DWI lesion (P<0.001). In 4 cases with hemorrhagic transformation, hemorrhagic transformation regions were 0.557±0.049 and non-hemorrhagic transformation regions were 0.762±0.042 (P<0.001). In addition, percentage DWI improvement was inversely correlated with DWI lesion volume at the time of hospitalization (r=-0.840) and onset-to-reperfusion time (r=-0.765), but no correlation was noted with patient age (r=-0.043) or the first NIHSS score (r=-0.277).

Conclusions: The relative ADC ratio may be useful for predicting DWI reversibility and post-reperfusion hemorrhagic transformation, even in patients with an unknown time of onset.