The Novel Homogeneity Index Evaluation Tool for Radiotherapy Treatment Plans

Objective One of the primary goals of radiotherapy is to deliver the prescribed dose homogeneously to each voxel of the target volume. The homogeneity index (HI) serves as a quantitative tool to assess the uniformity of the dose distribution within a target volume. The goal of this study is to introduce novel Homogeneity Index (HI) and UnHomogeneity Index (UHI) evaluation tool algorithms that are universally applicable for all radiotherapy treatment planning methods. Methods The deficiencies of existing HIs were analyzed for universal applicability and performance. Novel HI and UHI algorithms that address these deficiencies were derived and validated using fifteen prostate cancer cases. Results Existing HIs were found to measure only deviations in specific point doses without identifying the cause or magnitude of inhomogeneity. The proposed novel HI considers cold spots and/or hot spots in the target volume and accurately quantifies dose homogeneity. Clinical analysis demonstrated that the novel HI aligns with the theoretical definitions of homogeneity. The results for the novel HI consistently range between 0 and 1, where 1 corresponds to perfect homogeneity and 0 indicates complete inhomogeneity. Conclusions The novel HI effectively quantifies dose homogeneity, identifies the magnitude and cause of inhomogeneity via UHI algorithms, and provides actionable insights for improving treatment plans. It can serve as a cost function for automated radiotherapy treatment planning, significantly enhancing the dose distribution and reducing the planning time.