Background: Deep learning has been widely used to detect lesions in brain MRIs. However, a major challenge is the systematic low accuracy of deep learning in detecting small diffuse lesions, where the Dice overlap between expert- and computer-detected lesion regions is typically 0.3-0.7, compared to the high accuracy of deep learning in detecting big focal lesions, where the Dice overlap is usually 0.8-0.95 [Zhang2021a].

Algorithm: