Room: Exhibit Hall | Forum 6
Purpose: Fast, volumetric independent dose calculation (vIDC) tool for image guided adaptive high-dose-rate brachytherapy (BT-HDR) was developed to facilitate comprehensive dose evaluation beyond a point-based plan decision. The feasibility and clinical practicality of the vIDC was evaluated for previously treated patient cases.
Methods: Five cervical cancer patients were selected to evaluate dose distributions in BT-HDR using tandem and ring applicator. A fractional dose of 550 cGy was prescribed to 90% of the high-risk clinical target volume (HR-CTV) across 5 fractions. The vIDC adopts an updated version of the TG-43 formalism and the same air-kerma rate for iridium-192 with a clinical treatment planning system (TPS). Volumetric dose evaluation using the vIDC was perfromed by an accuracy test at the ICRU reference points, namely point A and B, and rectal points. Dose differences were presented with dose-volume histograms (DVHs) and primary dose-volume parameters such as D2cc for organs-at-risk (OAR). A grid size of 1.0 x 1.0 mmÂ² (G-1.0) was selected for dose calculation. To test the effect of grid size at the high-dose gradient, dose were compared at a sparse and a fine grid resolution of 2.5 x 2.5 mmÂ² (G-2.5) and 0.5 x 0.5 mmÂ² (G-0.5), respectively.
Results: The averaged difference throughout an entire volume of dose points was less than -1.79%. When the 1-mm grid resolution was used, the DVHs for the HR-CTV and OAR showed minimal difference between the vIDC and the TPS. While D2cc of OAR showed averaged dose deviation less than 10 cGy, D90 of CTV showed the averaged difference of -12.90%, -8.26%, and -6.18% in G-2.5, G-1.0, and G-0.5, respectively.
Conclusion: The vIDC was developed as an efficient second-check 3D dose evaluation tool for BT-HDR using iridium-192. Volumetric dose calculation using the sparse grid size can affect delivered dose distributions using volume-based dose prescription.