This article deals with the so called GVF (Gradient Vector Flow) introduced by C. Xu, J.L. Prince [14, 15]. We give existence and uniqueness results for the front propagation flow for boundary extraction that was initiated by Paragios, Mellina-Gottardo et Ralmesh [11, 12]. The model combines the geodesic active contour flow and the GVF to determine the geometric flow. The motion equation is con...