Purpose: Modern radiotherapy technique allows normal tissues to have a minimal dose while maintaining a prescription dose of target volume with its complex dose distributions. Specifically, intensity₋modulated radiotherapy (IMRT) delivers the radiation doses to target in a few minutes using intricate multiple beam segments determined with multi₋leaf collimators (MLC). Therefore, we propose a scintillator-based dosimetry system capable of assessing the dosimetric quality of IMRT as well as MLC performance in real₋time.
Methods: The developed dosimetry is equipped with a scintillator plate and two complementary metal₋oxide₋semiconductor (CMOS) cameras. Due to the position of CMOS cameras, recorded images have geometric distortions. The geometric distortions of recorded images were corrected by tomographic image reconstruction techniques. Dosimetric evaluations were performed by gamma analysis in comparison with dose maps calculated from treatment planning system (TPS) in three clinical cases: brain, head and neck, and pelvis. Average differences of MLC positions for six different square fields measured between the developed system and the machine log files were used to evaluate the applicability for mechanical quality assurance of MLCs.
Results: The agreements of the dose distribution were 99.75% in brain, 96.22% in head and neck, and 99.46% in pelvis case with a 3%/3 mm gamma criterion between the corrected dose images and TPS dose maps. Average differences of MLC positions in six fields were 1.32, 1.23, 1.15, 0.78, 0.26, and 0.35 mm, respectively, and the mean value of prediction errors in six cases was 0.81 mm.
Conclusion: In this study, we developed a real₋time scintillator-based dosimetry. The feasibility of the proposed system was investigated with dosimetric and mechanical evaluations in IMRT plans. The developed system has clinically acceptable accuracy both in dosimetric and mechanical QAs of the IMRT plans. With a further evaluation for clinical implementation, the proposed system can be an alternative in modern radiotherapy dosimetry.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by Korea Institute for Advancement of Technology (KIAT) grant funded by the Korea Government (MOTIE) (P0012971) and the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (2021M2E8A1048108).
Scintillation Cameras, Dosimetry, MLC