Ct/ pet fusion provides automatic registration of any ct data set with any discovery or advance pet images. In combining anatomical information from ct with functional information this application, From pet allows cancers to be staged and precisely localized. Benefits allows 3d registration between two which come, Volumetric acquisitions from different acquisition modalities ct/ pet . Combination of ct and pet or spect for better volume definition. Definition of a volume of interest within one patient model, With automatic report in the other model for subsequent use in rt planning system. Use of information from previous studies for follow, Up. Slices from previous acquisitions are compared more accurately. Better communication of clinical results to referring physicians.