SU‐F‐T‐111: Investigation of the Attila Deterministic Solver as a Supplement to Monte Carlo for Calculating Out‐Of‐Field Radiotherapy Dose

Abstract

Purpose:To use the Attila deterministic solver as a supplement to Monte Carlo for calculating out‐of‐field organ dose in support of epidemiological studies looking at the risks of second cancers. Supplemental dosimetry tools are needed to speed up dose calculations for studies involving large‐scale patient cohorts.Methods:Attila is a multi‐group discrete ordinates code which can solve the 3D photon‐electron coupled linear Boltzmann radiation transport equation on a finite‐element mesh. Dose is computed by multiplying the calculated particle flux in each mesh element by a medium‐specific energy deposition cross‐section. The out‐of‐field dosimetry capability of Attila is investigated by comparing average organ dose to that which is calculated by Monte Carlo simulation. The test scenario consists of a 6 MV external beam treatment of a female patient with a tumor in the left breast. The patient is simulated by a whole‐body adult reference female computational phantom. Monte Carlo simulations were performed using MCNP6 and XVMC. Attila can export a tetrahedral mesh for MCNP6, allowing for a direct comparison between the two codes. The Attila and Monte Carlo methods were also compared in terms of calculation speed and complexity of simulation setup. A key perquisite for this work was the modeling of a Varian Clinac 2100 linear accelerator.Results:The solid mesh of the torso part of the adult female phantom for the Attila calculation was prepared using the CAD software SpaceClaim. Preliminary calculations suggest that Attila is a user‐friendly software which shows great promise for our intended application. Computational performance is related to the number of tetrahedral elements included in the Attila calculation.Conclusion:Attila is being explored as a supplement to the conventional Monte Carlo radiation transport approach for performing retrospective patient dosimetry. The goal is for the dosimetry to be sufficiently accurate for use in retrospective epidemiological investigations.