Stroke represents the second leading cause of mortality worldwide. The key component for immediate diagnosis is the localization (over CT scans) and delineation of lesions ( over MRI studies). The lesions are nonetheless poorly delineated, only visible at advanced stages, and analysis uses manual delineation. This challenge introduces a paired dataset of CT and ADC studies. The researchers are invited to propose computational strategies that approach paired data, during training, and deal with lesion segmentation over CT onset sequences. During training will be available annotated paired sequences (from one expert), and resultant segmentation for testing will be compared regarding two experts.