Abstract: A method and system for imaging and treating an internal organ of a patient is disclosed. In an illustrative method embodying the invention, a method of imaging and treating prostate cancer includes first stabilizing the prostate using a tube, with imbedded fiducial markers, inserted into the rectum of the patient and attached to an external perineal template and support. Ultrasound images of the prostate and surroundings are then taken with an ultrasound imaging probe inserted into the tube. The radioisotope seeds are implanted with the guidance of the ultrasound images. Afterwards, CT and/or fluoroscopic images are taken to examine the adequacy of the implantation. Image fusion of ultrasound and CT and/or fluoroscopic images is then achieved. If necessary, further or corrective implantation procedures can be carried out under ultrasound guidance, with follow-up CT and or fluoroscopic imaging. The process can be repeated until the implantation is deemed satisfactory.