Hdr-Emulating Ldr Prostate (Help) Brachytherapy Utilizing Needle Optimized Inverse Planned Intraoperative Isotope Delivery

Low dose rate (LDR) transperineal prostate brachytherapy is an effective and established treatment option for low to intermediate risk prostate cancer. An implant's ability to cure prostate cancer while sparing normal tissues often depend on the brachytherapist's experience and ability to precisely place needles in the exact location required by a treatment plan. We report a novel technique that circumvents this requirement by performing inverse planning for dose optimization after all needles are placed within the prostate in an arbitrary mostly symmetric distribution. This approach mimics the dose conformity of High Dose Rate (HDR) catheter based brachytherapy with the convenience of a single LDR transperineal prostate brachytherapy implant. Intra-operative prostate ultrasound images were imported to the treatment planning system. The prostate, rectum, and urethra were contoured and rendered in three dimensions. Needles were inserted in a generally symmetric peripheral pattern and their exact position and trajectory within the prostate was registered. Contours were updated to reflect any gland swelling during needle placement. Based on these achieved needle positions, automated inverse planning created an optimized plan that maximized target dose while minimizing urethral and rectal doses with the fixed needle positions. The Nucletron Source Selectron I-125 isotopes were robotically placed in the exact distribution as inversely planned with real-time ultrasound guidance. Post-operative evaluation with CT-MRI fusion was performed to confirm isodose coverage of the prostate and dose to the urethra and rectum. Operating room (OR) time and implant V100 and D90 were compared to cases utilizing traditional intra-operative planning. The HDR-emulating LDR (HELP) implants significantly decreased intra-operative planning time, needle placement time, and seed delivery times. The resulting concordance between the intra-operative plan's dosimetric parameters and the post-op CT/MRI-based parameters at day 1 were improved, suggesting that the delivered dose distribution was highly similar to the intra-operative inversely planned dose distribution. OR time was reduced and on average better dosimetric parameters were achieved. The HDR Emulating LDR Prostate (HELP) brachytherapy technique utilizing needle optimized inverse intra-operative planning was able to significantly decrease the time necessary to achieve consistently high quality implants by eliminating reliance on perfect needle placement. The decreased time to extremely high quality implants reduced operating room time and time under anesthesia.