Abstract: Complex targets of medical image are usually difficult to be completely segmented,so an image segmentation algorithm of modified Li model combining mark watershed algorithm was proposed.A symbol pressure function replaces the traditional stop function in Modified Li model,and the problem of unidirectional curve evolution is solved.Mark watershed has both stronger ability to suppress noise and stronger ability to capture weak edge of medical image.Firstly,mark watershed algorithm is used for image segmentation pretreatment,positioning information of target edge fast and accurately.Then,the modified Li model algorithm is introduced,and the symbol pressure function is used to guide curve evolution direction and control the size of the evolution speed,realizing full segmentation of complex object.The experimental results show that global information and edge information can be gooten,and the combination algorithm of complex targets can get satisfactory effect in the medical image segmentation.

Key words: Medical image segmentation,Mark watershed,Modified Li model,Sign pressure function