Abstract: An interactive segmentation method based on graph cuts and improved fast level set is proposed to segment abdominal CT image.In our approach,an initial contour is sketched and dilated,a graph for graph cuts method is constructed while inner contour vertices based on morphologic dilation are identified as source and outer contour vertices as sink,the Pre-CT image segmentation is achieved by graph cuts method roughly,and then with the initial inner contour of dilation,the fast level set algorithm based on the Region Competition Based Active Contour(RCAC)model is applied to re-segment the result image by graph cuts.Thus,the low speed and leakage error in traditional level set methods are avoided.Furthermore,we extend this segmentation method to three dimensions,and several 3-D abdominal organs are segmented.Doctors could straightforwardly visualize the organs'relationship and structure topologically after 3-D reconstruction.Experimental results show that the proposed method is with interactive simply,robustness and high accuracy,and can support doctors for diagnosis and surgical planning effectively.