An image fusion method for medical applications, comprising: a. acquiring a first image with a planned radiation region; b. acquiring a second image with actual radiation region; c. determining if user defined landmarks have been placed on the first and second images, if user defined landmarks are present go to step (d), if not go to step (e); d. pre-transforming the first image or second image or both images; e. performing a first delineation step on the actual radiation region; f. determining if the delineation is correct, if yes go to step (g), if not go to step (h); g. fusing the first and second image and exit process; and h. selecting multiple contour points around the actual radiation region in the second image; i. performing a second delineation step on the actual radiation region and go to step (f).