Scintigraphic Detection of 125I Seeds After Permanent Brachytherapy for Prostate Cancer

The purpose of this investigation was to monitor the localization and migration of 125I seeds after permanent brachytherapy for prostate cancer using a new scintigraphic technique that may overcome the drawbacks of conventional x-ray methods. Methods: 125I seeds emit g-rays with an average energy peak of 28 keV. We used a g-camera equipped with low-energy high-resolution collimators that were tuned to an energy level of 35 keV with a 70%windowwidth. Sixteen patients with pros-tate cancer were examined after 125I seed insertion. The num-ber of seeds remaining in the prostate was confirmed using pelvic CT for postoperative dose planning; however, seeds that had migrated outside the prostate could not be detected. Furthermore, the migrated seeds were not completely trace-able using chest or abdominal radiography. Thus, we adopted a scintigraphic technique to perform this task. The evaluatio