A constraint-normalized robustness index for HDR brachytherapy

The authors aim to develop a normalized robustness index for high-dose-rate brachytherapy that quantifies the sensitivity of treatment plans to geometric uncertainties, such as applicator displacement and catheter deflection. This index is designed to be dimensionless and clinically relevant, providing a single interpretable metric that reflects the plan's performance against dose-limit constraints. By incorporating various perturbation scenarios, the proposed framework enhances the evaluation of brachytherapy plans under uncertainty, complementing traditional dose volume histogram analyses.