Peter Sandwall

Novel validation of HDR brachytherapy dosimetry for cervical cancer using egs_brachy Monte Carlo simulations: a comparative analysis with Oncentra treatment planning system

Abstract Purpose This study aims to validate HDR brachytherapy dosimetry for cervical cancer patients utilizing the egs_brachy Monte Carlo (MC) simulation. Methods Three cervical cancer patients treated with 192 Ir HDR brachytherapy were included. Dose distributions were calculated by the Oncentra Brachy v4 treatment planning system (TPS) based on AAPM TG‐43. The newly developed eb_gui, an egs_brachy graphical user interface for MC simulations, was applied in recalculating dose distributions for 12 fractions using digital imaging and communications in medicine‐radiotherapy (DICOM‐RT) anatomical information. Comparisons were made for clinical target volume (CTV), bladder, and rectum using dose–volume histograms (DVH) and clinically relevant plan quality indices. Results TPS‐calculated doses were greater than those obtained from MC simulations. For the CTV, the median percentage differences were 7.9% (Q1: 6.4%, Q3: 9.8%; range: 0.4%–10.4%) for D 90 . For the bladder, the median percentage differences were 0.7% (Q1: 0.4%, Q3: 2.3%; range: −9.4–5.4%) for D 2cc . For the rectum, the median percentage differences were 3.6% (Q1: 2.8%, Q3: 5.6%; range: 0.9%–6.4%) for D 2cc . Conclusion CTV and critical organ doses calculated by the TPS were consistently greater than those obtained from MC simulations. This suggests that the TPS may overestimate dose distributions, especially in heterogeneous regions like the pelvis. These results emphasize the need for continued validation of TPS algorithms in HDR brachytherapy for cervical cancer.