Dosimetric verification of complex radiotherapy with a 3D optically based dosimetry system - Dose painting and target tracking

Background: The increasing complexity of radiotherapy (RT) has motivated research into three-dimensional (3D) dosimetry. In this study we investigate the use of 3D dosimetry with polymerizing gels and optical computed tomography (optical CT) as a verification tool for complex RT: dose painting and target tracking. Materials and Methods: For the dose painting studies, two dosimeters were irradiated with a seven-field intensity modulated radiotherapy (IMRT) plan with and without dose prescription based on a hypoxia image dataset of a head and neck patient. In the tracking experiments, two dosimeters were irradiated with a volumetric modulated arc therapy (VMAT) plan with and without clinically measured prostate motion and a third with both motion and target tracking. To assess the performance, 3D gamma analyses were performed between measured and calculated stationary dose distributions. Results: Gamma pass-rates of 95.3 % and 97.3 % were achieved for the standard and dose-painted IMRT plans. Gamma pass-rates of 91.4 % and 54.4 % were obtained for the stationary and moving dosimeter, respectively, while tracking increased the pass-rate for the moving dosimeter to 90.4 %. Conclusions: This study has shown that the 3D dosimetry system can reproduce and thus verify complex dose distributions, also when influenced by motion