1. An image fusion method for medical applications, comprising: a. acquiring a first image with a planned radiation region; b. acquiring a second image with an actual radiation region; c. determining, by an image processor, if user defined landmarks have been placed on said first and second images, if user defined landmarks are present go to step (d), if not go to step (e); d. pre-transforming said first image or second image or both images; e. performing a first delineation step on said actual radiation region using active contour model with adaptive weighting on said second region; f. determining if said delineation is correct, if yes go to step (g), if not go to step (h); g. fusing said first and second image and exit process, wherein fusing comprises the step of forming a mask that encloses said second region using said region contour vector with distinct values inside and outside of said mask, the mask tagging pixels in the radiation and non-radiation regions differently; h. selecting multiple contour points around said actual radiation region in said second image; and i. performing a second delineation step on said actual radiation region and go to step (f).