An MRI-Based Nomogram for Palladium and Iodine Prostate Brachytherapy Quality Assurance

While the dose prescribed for permanent seed, prostate brachytherapy has been standardized, the amount of activity per volume can vary significantly with ultrasound-based planning, potentially Resulting in compromised clinical outcomes. We hypothesized that MR-planned, low-dose rate (LDR) prostate brachytherapy (BT) with Palladium-103 (103Pd) and Iodine-125 (125I) results in a decrease in activity-to-volume ratio, given the ability to spare the external urinary sphincter (EUS) and reduce planning target volume (PTV) margins. Further, because MR post-implant dosimetry (day zero, D0) provides well-defined prostate boundaries, we expected greater deviations between pre-planned and D0 dosimetry compared to U/S planning. Based on institutional experience, we developed an activity nomogram for MR-planned prostate brachytherapy to improve quality assurance through a secondary dosimetric check.