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

Abstract

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.

Acknowledgement

Supported by Varian Medical System and CIRRO – The Lundbeck Foundation Center for Interventional Research in Radiation Oncology and The Danish Council for Strategic Research. We gratefully thank Tomas Gustafsson, Roman Iustin, and Andreas Bergqvist (Micropos Medical AB) for modifications of the RayPilot system to allow integration with the tracking program. Thomas Schack Kinnari, Isak Wahlstedt and Jakob Fester (Aarhus University) as well as Henrik Svensson and Sofie Ceberg (Skåne University Hospital/Lund University) are acknowledged for their contribution to manufacturing of gel dosimeters.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.