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GATE-RTion is a clinical GATE/GEANT4 release since May 2018. The Independent DosE cAlculation for Light ion beam therapy (IDEAL) project includes GATE-RTion as dose engine. It focuses on the implementation of a CE-marked IDC system for facilities equipped with Scanned Ion Beam Delivery systems. A first prototype is available since 2018 and was transferred in 2019 into a clinical environment of a Light Ion Beam Therapy center. This work presents the first commissioning results of IDEAL/GATE-RTion for scanned proton and carbon ion beams.

DICOM input files (CT, Plan, Dose and Structure) are imported into IDEAL and run on a dedicated cluster of modular capacity (currently equipped with 48 cores). Commissioning work is divided into 1D beam delivery (depth-dose profiles, spot sizes, and nuclear halo), 2D (spot maps, output factors) and 3D (targets of various shapes and complexity: square, cylinder, L-shape, etc.). TEDD (a Toolkit for the Evaluation of DICOM Doses) was developed to analyze 1D/2D/3D beam delivery parameters. Proton and carbon ion beam models were generated and validated in terms of energy and optical properties and then calibrated in dose. 3D commissioning of IDEAL is performed using TEDD. IDEAL recomputed treatment plan doses are evaluated with TEDD against measurements performed in water using a 3D-block featured with 24 pin-point ionization chambers.

The proton beam model was found to be within clinical tolerances of 0.5 mm in range and 10% in spot size in the air-gap from the nozzle exit to the isocenter. So far, 26 targets of various shapes were simulated in water for protons. Averaged dose differences were always better than +/-3% and mostly within 1% or 2%. These plans included field sizes from 3 to 20 cm, target volumes from 0.03 to 2 liters and more, with and without range shifter and were centered between 3 and 31 cm depth. Overall, more than 2000 pin-point measurements were analyzed. An example is provided in Figure 1.

As of today, proton commissioning is on-going and promising preliminary results have been obtained. More complex plans including inhomogeneities and various phantom geometries and compositions will be analyzed. In parallel, carbon ion commissioning will start by the end of 2019 and preliminary results will be obtained early 2020. To our knowledge, this work is the first attempt of transferring general purpose MC codes such as GATE/Geant4 into a CE certified IDC product, making this project very unique.