AUTHOR=Gajewski Jan , Garbacz Magdalena , Chang Chih-Wei , Czerska Katarzyna , Durante Marco , Krah Nils , Krzempek Katarzyna , Kopeć Renata , Lin Liyong , Mojżeszek Natalia , Patera Vincenzo , Pawlik-Niedzwiecka Monika , Rinaldi Ilaria , Rydygier Marzena , Pluta Elzbieta , Scifoni Emanuele , Skrzypek Agata , Tommasino Francesco , Schiavi Angelo , Rucinski Antoni 

TITLE=Commissioning of GPU–Accelerated Monte Carlo Code FRED for Clinical Applications in Proton Therapy

JOURNAL=Frontiers in Physics

VOLUME=Volume 8 - 2020

YEAR=2021

URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2020.567300

DOI=10.3389/fphy.2020.567300

ISSN=2296-424X

ABSTRACT=We present commissioning and validation of Fred, a GPU-accelerated Monte Carlo (MC) code, for two proton beam therapy facilities of different beam line design: CCB (Krakow, IBA) and EMORY (Atlanta, Varian). We followed clinical acceptance tests required to admit the certified treatment planning system for clinical use. 

We implemented an automated and efficient procedure to build a parameter library characterizing the clinical proton pencil beam. Beam energy, energy spread, lateral propagation model, and a dosimetric calibration factor were parametrized based on measurements performed during the facility start-up. The Fred beam model was validated against commissioning and supplementary measurements performed with and without range shifter. 

We obtained (i) sub-millimeter agreement of Bragg peak shapes in water and lateral beam profiles in air and slab phantoms, (ii) <2% dose agreement for spread out Bragg peaks of different ranges (iii) average gamma index (2%/2mm) passing rate >95% for >1000 patient verification measurements using a 2D array of ionization chambers, (iv) GI passing rate >99% for 3D dose distributions computed with Fred and measured with an array of ionization chambers behind an anthropomorphic phantom. The results of example treatment planning study on >100 patients demonstrate that Fred simulations in patient CT enable an accurate prediction of dose distribution in patient and application of Fred as second patient quality assurance tool. Computation of a patient treatment in a CT using 10^4 protons per pencil beam took on average 2'30 min with tracking rate of 2.9x10^5 protons/s.

Fred was successfully commissioned and validated against the clinical beam model showing that it could potentially be used in clinical routine. Thanks to high computational performance due to GPU-acceleration and an automated beam model implementation method, the  application of Fred is possible for research or quality assurance purposes in most of the proton facilities.