Abstract: Based on modified brain extraction tool(BET)， an automatic extraction algorithm is proposed for brain MRI(magnetic resonance imaging). Firstly， the algorithm combining image gradient information can estimate the center of gravity(COG) of brain more accurately; secondly， it builds a new brain surface deformation force. Edge force is introduced into the expansion force perpendicular to the tangent of brain surface， which could suppress the brain tissue leaking and over-segmentation problem. Experiments are conducted on the algorithm proposed to automatically extract brain tissue of MRI brain images， and the results show the more accurate extraction of brain tissue， especially at brain tissue edges， compared with the BET method.

Key words: brain extraction, MRI, BET(brain extraction tool), COG(center of gravity) of brain, edge force