Abstract: Transrectal ultrasound guided transperineal low dose-rate brachytherapy has been emerged as one of the definitive treatments of low-risk prostate cancer. Ultrasound has been an excellent tool in guiding the implant needles with respect to prostate anatomy, yet it cannot show reliably the location of radioactive seeds after they are released in the prostate. Intraoperative C-arm fluoroscopy can show the implanted seeds, but it cannot detect prostate anatomy. Intra-operative fusion of these two complementary modalities offers significant clinical benefit by allowing for real-time optimization of the brachytherapy implant as the procedure progresses in the operating room. Disclosed is a system and method for mitigating this problem and providing registration of seeds seen by fluoroscopy with live prostate anatomy visualized by transrectal ultrasound.