Samane Golmakani
Alfred Health Radiation Oncology, The Alfred Hospital, Melbourne, 3004 VIC, Australia
Medical Physicist

Sarah Elliott
Senior Medical Physicist
Alfred Health Radiation Oncology, The Alfred Hospital, Melbourne, 3004 VIC, Australia

Background and Purpose:

Despite TG 56 [1] recommendations for an independent dose verification check for brachytherapy, this is not routinely performed. This may be attributed to the simple calculation algorithm or the fast paced HDR workflow. However, we should not underestimate the importance of an independent dose verification program in preventing major dose delivery errors in HDR treatments, where any error is extremely difficult to compensate.

This work describes the commissioning and implementation of BrachyCheck in our HDR program, with its first annual review.

Methods:

BrachyCheck v.8.3.1 (Oncology Data System) has been installed and configured for Ir192 HDR treatments at AHRO. Data used for dose calculations, based on TG 43 formalism, has been validated. The correct transfer of DICOM data from our treatment planning system Oncentra has been verified. The software has been tested for basic (single dwell position) and more complex (real prostate patient plans) configurations.

In our workflow, the plan checker is responsible for the BrachyCheck calculation and preparing a report with patient and source details, as well as the percentage variation between BrachyCheck and Oncentra for the calculated point.

The software has been implemented in the clinic with a monthly QA program. Tolerances have been updated following regular reviews.

Results:

The preloaded tables for anisotropy and radial dose factors were compared to the Monte Carlo calculated data of Daskalov et al [2], and also to the data in Oncentra tables. BrachyCheck factors were identical to both references. BrachyCheck geometry factors were similar to within 2% to manually calculated factors for radius ≥ 1 cm for all angles.

BrachyCheck showed good agreement with both manual and Oncentra calculations for the selected 49 points around a single dwell position, with the maximum difference of 1.3% (< 0.14 Gy) and 0.5% respectively.

All ~400 points checked by BrachyCheck in real patient plans were within 0.4% of Oncentra calculations.

BrachyCheck contributes less than three minutes to the plan checking process. Although BrachyCheck uses the same algorithm as Oncentra, it uses independent data tables to confirm the source activity and dose calculated to a point.

More than 30 patient plans have been checked using Brachycheck during last year. The maximum variation between Oncentra and BrachyCheck has been <0.3% for all plans.

Conclusions:

BrachyCheck is an efficient, user-friendly program, which provides an independent verification of calculated dose that has improved the safety and overall quality of our HDR program. BrachyCheck will be commissioned for LDR plans in the future.

References:

Ravinder, N., et al. (1997). “Code of practice for brachytherapy physics: Report of the AAPM Radiation Therapy Committee Task Group No. 56.” Med. Phys. 24, 1557–98.

Daskalov, G.M., Löffler, E., Williamson, J.F., (1998). “Monte Carlo-aided dosimetry of a new high dose-rate brachytherapy source.” Med. Phys. 25, 2200–2208.


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