To extract the brain from cerebral MR image automatically and stably

an improved BET (brain extraction tool) algorithm is proposed in this paper. The improved algorithm simplifies the smoothing force used in BET which makes the contour of edge smooth and modifies the expansionary force used in BET to evolve the edge of brain according to the intensity distribution and the gradient of images. The modified expansionary force puts the contour fast when the contour is in the brain and puts the contour slowly when the contour is close to the edge of brain. The experiment results of the MR images from 100 patients processed by the improved algorithm are satisfying

but BET leads to 8 unsatisfying results whatever the parameters are set as

which shows the improved algorithm is more robust than BET algorithm when processing real MR images.