BEaST: Brain extraction using multiresolution nonlocal segmentation

Brain extraction is an important step in the analysis of brain images. Variability in brain morphology and intensity characteristics due to different imaging sequences makes the development of a general pur- pose brain extraction algorithm challenging. Purpose: To address this issue, we propose a new robust method (BEaST) for brain extraction. Methods: The method is based on nonlocal segmentation embedded in a multiresolution framework. A library of 50 priors are semi-automatically constructed from the NIHPD, ICBM, and ADNI databases. Results: A mean Dice coefficient of 0.9834±0.0053 is obtained when performing leave-one-out cross validation. Validation using the online available Seg- mentation Validation Engine resulted in a top ranking position with a mean Dice coefficient of 0.9781±0.0047. Conclusions: The segmentation accuracy of the method is comparable to that of a recent label fusion ap- proach, while being 40 times faster and requiring a much smaller library of priors.