This paper proposes a local minimization method for an active contour model, instead of the traditional minimization method used in other works. A new external force is also proposed, called hybrid force, which brings together balloon force and GVF force obtained from a GVF field of reduced diffusion. The balloon force and GVF force are combined in such a way that, while active contour is not placed on GVF defined areas, active contour is deformed by a balloon force. If active contour is placed on GVF defined areas, balloon force will be suddenly reduced, completely losing its preponderance on the snake. Therefore, balloon force acts on the first frame of the sequence, when the initial contour is placed on areas where GVF field is not defined.