KEY POINTS
- The system was developed for intracavitary and hybrid interstitial cervical HDR brachytherapy planned in Oncentra and treated with a Flexitron Ir-192 afterloader. Clinical evaluation included 85 treatment plans.
- Automated integrity checks covered patient identifiers, prescription consistency, treatment interval, TRAK, source activity, catheter number, catheter length, applicator-specific offsets and other parameters that are vulnerable to manual transcription or reconstruction errors.
- Deliberately generated test plans containing predefined errors were used before clinical implementation. The software identified all embedded errors and reported the specific cause, including catheter-order, length, offset and prescription inconsistencies.
- In the 85 clinical plans, 79 passed the integrity check and 6 triggered warnings. These included four unusually high air-kerma values related mainly to large target volumes, one outdated prescription label and one elevated dwell-time loss ratio.
- The QA module also checked imaging and dosimetric criteria including CT slice thickness, contour integrity, HR-CTV coverage, OAR D2cc limits, conformity and dwell-point location. One plan was automatically rejected because of 5-mm CT slice thickness, exceeding the predefined ≤2-mm requirement.
- Independent dose verification used a separate TG-43 implementation and source database. Across all 85 plans, mean gamma passing rate was 98.70% ± 0.5% using 3%/2 mm, and every plan exceeded 97%.
- Gamma agreement varied modestly with target size: mean passing rate increased from 98.18% for HR-CTV <25 cm³ to 99.02% for volumes >50 cm³, because small targets contain a greater proportion of steep dose-gradient voxels.
- The system still has important limitations. Both Oncentra and the secondary calculation use TG-43 water-based formalism, applicator position relative to anatomy and digitization accuracy are not yet independently verified, and validation was limited to one institution and predominantly cervical brachytherapy.
CLINICAL TAKEAWAY
HDR brachytherapy QA can be automated beyond simple dose recalculation by checking the complete planning dataset for internal consistency and clinical constraints. This system provides a useful secondary safety net, but it does not replace physicist review, applicator reconstruction checks or independent assessment of patient anatomy.