A Web-Based Semi-Automated Film Analysis Tool for Repeated Verification of Varian GYN Ring Applicator Dwell Positions In HDR Brachytherapy
Abstract
Purpose
The Varian GYN ring applicator exhibits known dwell position dependence on source wire behavior and rotational orientation. For the Bravos HDR afterloader, the vendor recommends repeated periodic verification of ring dwell positions, including following Ir-192 source wire exchanges, to account for potential differences in mechanical properties between source wires rather than an expected increase in uncertainty. Conventional film-based verification is effective but labor-intensive, limiting the practicality of repeated measurements. This work presents a web-based, semi-automated film analysis tool designed to streamline repeated dwell position verification for the Varian GYN ring applicator.
Methods
A standalone HTML/JavaScript application was developed for analysis of scanned film images acquired from Varian GYN ring applicator irradiations. The tool supports direct import of common image formats, including TIFF, without proprietary software. Interactive functions include image rotation, cropping, applicator center definition, and DPI-based spatial calibration. Image processing capabilities include adjustable brightness/contrast, binary thresholding with automated Otsu-based initialization, and geometric masking aligned with the ring orientation. A semi-automated detection algorithm identifies candidate dwell locations using connected-component analysis constrained by expected ring radius, dwell size, and angular distribution. Detected dwell positions are merged, angularly sorted, and presented for user verification. Manual refinement is supported through interactive point editing and keyboard nudging. Final dwell coordinates are exported in a spreadsheet-ready format for direct comparison with treatment planning system data.
Results
The application enables rapid and reproducible identification of Varian GYN ring dwell positions with substantially reduced user interaction compared to manual film digitization. The streamlined workflow facilitates efficient implementation of vendor-recommended repeated and periodic verification for the Bravos HDR system.
Conclusion
This web-based film analysis tool provides a practical and efficient solution for implementing Varian-recommended repeated verification of GYN ring applicator dwell positions in the Bravos HDR afterloader, supporting routine clinical QA without additional software or hardware requirements.