—This paper presents an Improved Snake Model (ISM) effective for performing fast image segmentation. The work takes advantage of two well-known snake models of Balloon [1] and GGVF (Generalized Gradient Vector Flow) [2]. The Balloon model [1] is well known for its capability of fast locating object boundary using an extra pressure force field, but it may easily cause the contour to overwhelm the boundary. The more accurate GGVF model [2], however, requires lengthy computation time due to the need to specify a relatively large range in order to cover all the control points inside the range. Our goal is to obtain the exact field provided by GGVF while at the same time to expand the capture range with the Balloon pressure force. To this end, in ISM the force fields of Balloon [1] and GGVF [2] are integrated and a dynamic scheme for setting the control points is employed to avoid the time-consuming “re-sampling process”in both GVF (Gradient Vector Flow) and GGVF. The key attribute of...