Systematic end-to-end testing of multiple target treatments using the modular RUBY phantom

The RUBY head phantom in combination with the System QA insert MultiMet can be used for simultaneous point dose measurements at an isocentric and two off-axis positions. This study investigates the suitability of the system for systematic integral end-to-end testing of single-isocenter multiple target stereotactic treatments. Several volumetric modulated arc therapy plans were optimized on a planning CT of the phantom positioned in a stereotactic mask on the stereotactic treatment board. The plans were created for three artificial spherical target volumes centred around the measurement positions in the MultiMet insert. Target diameters between 5 and 40 mm were investigated. Coplanar and non-coplanar plans were optimized using the collapsed cone algorithm of the Oncentra Masterplan treatment planning system and recalculated with the Monte Carlo algorithm of the Monaco treatment planning system. Measurements were performed at an Elekta Synergy linear accelerator. The head phantom was positioned according to clinical workflow comprising immobilization and CBCT imaging. Simultaneous point dose measurements at all target positions were performed with three PinPoint 3D chambers (type 31022) as well as three microDiamond (type 60019) detectors and compared to the treatment planning system calculations. Furthermore, the angular dependence of the detector response was investigated to estimate the associated impact on the measured point dose values. Considering all investigated plans, PTV diameters and positions, the point doses calculated with the Monaco treatment planning system and the microDiamond measurements differed within 3.5%, whereas the PinPoint 3D showed differences of up to 6.9%. Point dose differences determined in comparison to the Oncentra Masterplan dose calculations were larger. The RUBY system was shown to be suitable for end-to-end testing of complex treatment scenarios such as single-isocenter multiple target plans.

Analyzing the Treatment Delivery Accuracy of the uRT Treatment Planning System and uRT-Linac 506C by Use of AAPM TG 119 Test Cases

ObjectiveThe objective of this study was to investigate accuracy of the United Imaging Healthcare's uRT treatment planning system (uRT-TPS), by creating AAPM TG 119 test plans with respectively IMRT and VMAT techniques by homogeneous and heterogeneous phantom. Materials and MethodsThe plans were delivered to the homogeneous and heterogeneous phantom using the United Imaging Healthcare's uRT-Linac 506C. The overall dose calculation accuracy by uRT-TPS with Collapsed Cone Convolution (CC) and Monte Carlo (MC) algorithm was measured and analyzed by creating IMRT and VMAT plans for the 5 test geometries specified in TG 119, by using two kinds of beams FF photon beam and FFF photon beam. The point doses were measured with a Farmer type ion chamber and the fluences were measured with films respectively. Results The result of position accuracy was shown that the worst position accuracy is 0.36 mm and the repeated positioning accuracy of MLC field location was less than 0.25mm. The symmetry deviation of MLC was less than 0.08mm. In this study, the CLs of sMLC, dMLC and VMAT plans with FF photon beams were 2.74%, 2.12%, and 1.36% respectively. As for FFF photon beams, they were 3.76%, 2.14% and 2.90% respectively, whereas the counterpart CL specified in TG119 were 4.5% for the high dose regions and 4.7% for OAR regions. The CLs of Gamma Passing rates for sMLC, dMLC and VMAT plans were 4.59%, 5.35% and 2.15% for FF beam mode, and were 1.82%, 6.12% and 4.82% for FFF beam mode. For the heterogeneous phantom, the maximum deviation is 2.35% for CC and 2.63% for MC algorithm respectively.Conclusion Based on this analysis which were performed in accordance with the TG 119 recommendations, it is evident that the URT treatment planning system and URT-Linac 506C have commissioned IMRT and VMAT techniques with adequate accuracy. and all uRT_TPS treatment plans were recognized as clinically acceptable.

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

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.