Feasibility of a GATE Monte Carlo platform in a clinical pretreatment QA system for VMAT treatment plans using TrueBeam with an HD120 multileaf collimator

Abstract

PurposeTo evaluate the quality of patient‐specific complicated treatment plans, including commercialized treatment planning systems (TPS) and commissioned beam data, we developed a process of quality assurance (QA) using a Monte Carlo (MC) platform. Specifically, we constructed an interface system that automatically converts treatment plan and dose matrix data in digital imaging and communications in medicine to an MC dose‐calculation engine. The clinical feasibility of the system was evaluated.Materials and MethodsA dose‐calculation engine based on GATE v8.1 was embedded in our QA system and in a parallel computing system to significantly reduce the computation time. The QA system automatically converts parameters in volumetric‐modulated arc therapy (VMAT) plans to files for dose calculation using GATE. The system then calculates dose maps. Energies of 6 MV, 10 MV, 6 MV flattening filter free (FFF), and 10 MV FFF from a TrueBeam with HD120 were modeled and commissioned. To evaluate the beam models, percentage depth dose (PDD) values, MC calculation profiles, and measured beam data were compared at various depths (Dmax, 5 cm, 10 cm, and 20 cm), field sizes, and energies. To evaluate the feasibility of the QA system for clinical use, doses measured for clinical VMAT plans using films were compared to dose maps calculated using our MC‐based QA system.ResultsA LINAC QA system was analyzed by PDD and profile according to the secondary collimator and multileaf collimator (MLC). Values for MC calculations and TPS beam data obtained using CC13 ion chamber (IBA Dosimetry, Germany) were consistent within 1.0%. Clinical validation using a gamma index was performed for VMAT treatment plans using a solid water phantom and arbitrary patient data. The gamma evaluation results (with criteria of 3%/3 mm) were 98.1%, 99.1%, 99.2%, and 97.1% for energies of 6 MV, 10 MV, 6 MV FFF, and 10 MV FFF, respectively.ConclusionsWe constructed an MC‐based QA system for evaluating patient treatment plans and evaluated its feasibility in clinical practice. We observed robust agreement between dose calculations from our QA system and measurements for VMAT plans. Our QA system could be useful in other clinical settings, such as small‐field SRS procedures or analyses of secondary cancer risk, for which dose calculations using TPS are difficult to verify.

Development of clinical application program for radiotherapy induced cancer risk calculation using Monte Carlo engine in volumetric-modulated arc therapy

“…We utilized a previously developed clinically available automatic VMAT QA system for this study [ 37 ]. The system is designed to re-calculate the beam sequence of equipment and treatment plan using the Monte Carlo engine, so it is possible to accurately calculate and evaluate scatter and leakage radiation, difficult to calculate in TPS [ 38 ].…”

“…In the case of Monte Carlo calculation, after the physical calculation of the dose deposit was completed based on the voxel value of 1.27 × 1.27 × 2.5 mm 3 , it was reconstructed into a pixel size of 2 mm 3 to represent the dose distribution [ 44 , 45 ]. Information regarding the number of fields, position of the gantry, field weight, and MLC of the patient treatment plan is converted to a macro file and stored in the system [ 37 ]. GATE v8.1, officially released in 2018, was employed for system configuration because it has the advantage of easy geometry configuration and fast calculation time with parallel computing using job split.…”

“…The organ dose estimation utilizing Monte Carlo simulation has the advantage that the dose can be calculated accurately. In a previous study, we have developed a phantom-based dose calculation system for VMAT using GATE Monte Carlo that directly apply scatter dose, difficult to calculate using TPS [ 37 ]. And, the system developed in previous studies has been improved to allow direct calculation of patient dose by adding new modules.…”

“…In this study, we developed a clinical application program to apply a SCR evaluation process into the workflow of patient treatment. In addition, the automatic quality assurance (QA) system [ 37 ] for VMAT based on GATE Monte Carlo simulation which is useful for accurate dose calculation, has added and automated a module that enables calculation using patient specific CT data for direct evaluation in a system developed through previous research. By combining SCR evaluation program and Monte Carlo based automatic QA system for VMAT to improve the accuracy, we intend to apply clinical evaluation of SCR that may be caused by radiotherapy as an indicator of patient treatment.…”

Validation of a secondary dose check tool against Monte Carlo and analytical clinical dose calculation algorithms in VMAT

“…34,35 These software packages provide useful dosimetric tools especially in treatment centers with many available treatment machines and a large number of patients treated per day. Among the most used, Mobius3D (Varian/Mobius Medical Systems, Houston, TX, USA) 36 performs a full recalculation of the dose on the patient computed tomography (CT) dataset based on an independent Collapsed Cone Convolution Superposition (CCCS) algorithm; 37,38 the open-source toolkit GATE 39 is a Geant4based 40 MC platform typically used for dose calculations and features 3D simulation and parallel computation 41 ; MUCheck is an EGSnrc-based 42 MC calculation system used as secondary MU check method for VMAT plans. 35 In this study, the recently released SciMoCa software package (version 1.4.2, Scientific RT GmbH, Munich, Germany), 43 a MC secondary dose check and plan verification software, is validated against a CCCS algorithm and, to our knowledge for the first time, against a widely used MC software.…”