We propose a modification of the generalized gradient vector flow field techniques based on a continuous force filed analysis. At every iteration the generalized gradient vector flow method obtains a new, improved vector field. However, the numerical procedure always employs the original image to calculate the gradients used in the source term. The basic idea developed in this paper is to use the resulting vector field to obtain an improved edge map and use it to calculate a new gradient based source term. The improved edge map is evaluated by new continuous force filed analysis techniques inspired by a preceding discrete version. The approach leads to a better convergence and better segmentation. The numerical experiments with synthetic and real ultrasound images show that the proposed technique overperforms the conventional gradient vector flow method. Furthermore, we propose a method of feature extraction based on tumor regions via filter blank technique. The multi-resolution filter blank is applied to rotationally invariants moments to construct numerical features of tumors after segmentation which they are noise-insensitive features.