The traditional active contour model is limited to capture range
and poor convergence to boundary concavities. GVF was proposed
by Xu and Prince [8] as a new external force for active contour
model to overcome these issues. It is a dense vector field, gener-
ated by diffusing the gradient vectors of a gray-level or binary edge
map derived from an image. The GVF field is defined as a vector
field V(x, y)=[u(x, y), v(x, y)] that minimizes the following energy
functional: