Comparison of TG43 and Hounsfield Unit-based TG186 brachytherapy dose metrics in Oncentra Brachy for 100 patients receiving interstitial partial breast irradiation.

PURPOSE: The aim of the study was to conduct a retrospective analysis of 100 patients who received interstitial accelerated partial breast irradiation at a single institution, comparing the standard American Association of Physicists in Medicine Task Group (TG) 43 dose calculation algorithm to the model-based dose calculation algorithms (MBDCAs) available in the Oncentra Brachy treatment planning system. METHODS AND MATERIALS: Dose-volume histogram parameters were compared between the different dose calculation algorithms for the planning target volume and organs at risk. and a statistical analysis was performed. The resulting changes in isodose distribution were assessed, with the worst-case data presented. RESULTS: The TG43 algorithm calculated higher doses to all structures compared with the MBDCAs. The largest discrepancy was observed for the skin, with maximum doses on average 2.0% lower with the MBDCA. The newly released Hounsfield Unit-based algorithm further decreased the skin dose compared with TG43 by <0.5%. CONCLUSIONS: This study demonstrates that the differences between TG43 and MBDCA as implemented in Oncentra Brachy for accelerated partial breast irradiation are clinically insignificant in the treatment area and nearby organs at risk. Justification for investing in MBDCAs for this treatment site is limited when considering the additional calculation time, introduced uncertainties, and cost.

Towards real time in-vivo rectal dosimetry during trans-rectal ultrasound based high dose rate prostate brachytherapy using MOSkin dosimeters.

PURPOSE: To compare the dose measured by MOSkin dosimeters coupled to a trans-rectal ultrasound (TRUS) probe to the dose predicted by the brachytherapy treatment planning system (BTPS) during high dose rate (HDR) prostate brachytherapy (pBT), and to examine the feasibility of performing real-time catheter-by-catheter analysis of in-vivo rectal dosimetry during TRUS based HDR pBT. METHOD: Four MOSkin dosimeters were coupled to a TRUS probe during 20 TRUS-based HDR pBT treatment fractions. The measured MOSkin doses were retrospectively compared to those predicted by the BTPS for the total treatment fraction, as well as on a per catheter basis. RESULTS: The average relative percentage difference between MOSkin measured and BTPS predicted doses for a total treatment fraction was 0.3% ± 11.6% (k = 1), with a maximum of 23.2% and a minimum of -29.0%. The average relative percentage difference per catheter was +2.5% ± 16.9% (k = 1). The majority (64%) of per catheter MOSkin measured doses agreed with the treatment planning system within the calculated uncertainty budget of 12.3%. CONCLUSION: The results of the study agreed well with previously published data, despite differences in clinical workflows. To improve the redundancy to potential dosimeter errors, a minimum of 4 MOSkin dosimeters should be used when performing real-time in-vivo rectal dosimetry for HDR pBT, and error thresholds should be based off the total combined uncertainty estimate of measurement. 'Real time' error thresholds can be more confidently applied in the future through enhanced integration between IVD systems with both the imaging device and the BTPS/afterloader.

A risk-based approach to development of ultrasound-based high-dose-rate prostate brachytherapy quality management.

PURPOSE: The purpose of this study was to apply a risk-based approach to the development of a quality management (QM) program for ultrasound-based high-dose-rate (HDR) prostate brachytherapy (pBT) treatment planning and delivery. METHODS AND MATERIALS: A QM program was developed by a multidisciplinary team, using both an in-house risk-and-benefit balance impact template (RABBIT) tool and a failure modes and effect analysis (FMEA). FMEA scores were determined by three physicists, one radiation therapist and two radiation oncologists who were familiar with the protocol. The QM program produced by both risk-based techniques was then compared and consolidated. RESULTS: The RABBIT tool identified 26 potential risks during the treatment planning and delivery process. During the FMEA, a total of 35 potential failure modes were identified from the seven major processes in ultrasound-based HDR pBT. For the 35 potential failure modes, risk priority number scores ranged from 14 to 267. The highest ranked failure mode was identified to be mislabeling/connection of the transfer tubes/catheters. From the risks analyses, a comprehensive QM program was developed. CONCLUSION: Both the RABBIT tool and process mapping and FMEA were shown to be valuable tools in developing a QM program for ultrasound-based HDR pBT treatments. A considerable number of the potential failure modes identified in both tools were related to human or procedural errors, highlighting the importance of checklists and protocols in delivering a safe and effective ultrasound-based HDR pBT treatment.