Vfusion is a PC based Multi-Modality Registration and Display program. And it fuses the images acquired from the various medical modalities such as MR, CT, PET etc, registers its location and maps the specific diagnostic information. So it enables the clinician to use the strong points of various images from each modality. Vfusion can be applied to the images from the different modalities such as CT/PET or CT/MR etc. and in this case, the clinician can get the anatomical information from CT images and also get the functional information from MR or PET images. Usually fusion is applied to the images from the different modalities but it is also possible to apply it to the images from the same modality. For example, the clinician can fuse the pre-operation images and post-operation images that are taken from CT for the same patient. The main purposes to use Vfusion are 1) Comparison between the functional information and anatomical information 2) Tumor detection and localization 3) Planning of Surgery operation and Radiation therapy 4) Evaluation of treatment effectiveness etc So the workflow of diagnosis, treatment/operation planning, treatment evaluation etc can be much improved through Vfusion.