An Independent Three-Dimensional (3D) Dose Verification System for Elekta Unity MR-Linac Online Plans

Abstract PurposeTo implement an independent 3D dose verification system with RayStation (RaySearch, Stockholm, Sweden) for online adaptive radiotherapy on Elekta Unity MR-Linac (MRL). MethodsPlan quality of simple-single-field and intensity-modulated radiotherapy (IMRT) plans were investigated in a comparison of (1) Monte-Carlo calculated data using MRL Monaco with high magnetic field (1.5 T) and (2) Collapsed-Cone calculated data using RayStation. The dose quality of RayStation plans, compared to corresponding Monaco plans, was (1) visually inspected in percentage depth-dose curves, inline and crossline profiles, and (2) quantified in 3D gamma-passing-rates. Processing time was measured to evaluate the practical efficacy of our system using 5 prostate IMRT plans.ResultsCompared to Monaco simple-single-field plans as ground truth, RayStation simple-single-field plans achieved an average 95.7% and 98.5% in 2%/2mm and 3%/3mm of 3D gamma criteria, respectively. Gantry angle dependency in simple-single-field plans was <2% in both 2%/2mm and 3%/3mm, and field size dependency was <5% in 2%/2mm and <2% in 3%/3mm. Compared to Monaco IMRT plans, RayStation IMRT plans achieved an average 95.1% (3%/3mm). The entire processing time of the independent 3D dose verification system was an average approximately 200 s. ConclusionsThis was the study to implement an independent 3D dose verification process using RayStation with an in-house 3D gamma analysis software. This led to an average 95% plan quality in 3%/3mm gamma criteria and added an average 200 s throughout the entire verification processes. These results demonstrate that this approach can be applicable and efficient for online quality assurance for MRL online adaptive radiotherapy planning.