A theoretical multileaf collimator model for fast Monte Carlo dose calculation of linac 6/10 MV photon beams

Abstract

A complete linac photon beam Monte Carlo dose calculation, even on a fast computer, requires generally a substantial computation time. The existing approaches developed to improve the efficiency are mainly based on the use of variance reduction techniques, phase space sources or virtual source models. The collimation of the simulated photon beam, involving particle transport through the multileaf collimator, considerably increases the calculation time especially for intensity modulation radiation therapy, where multiple small and medium field shapes are taking place. In this paper an improvement of a previous model will aim to significantly enhance the calculation efficiency for fast intensity modulation computations mainly by the use of an analytical collimator. The linac photon beam and multileaf collimator model is controlled by several parameters, such as, the geometrical dimensions of the primary collimator, the flattening filter and the number of leaves of the linac's collimator. The model uses only correlated energy spectra and particle fluence distributions derived from the International Atomic Energy Agency phase space files of Elekta PreciseVarian TrueBeam. RECEIVED

A phase space model of a Versa HD linear accelerator for application to Monte Carlo dose calculation in a real‐time adaptive workflow

“…They also demonstrate good agreement between dose calculations resulting from the virtual source model and from the standard phase space, when using GEANT4 as the Monte Carlo engine. Their work 17 is for rectangular fields, and a subsequent report 18 describes the incorporation of a multileaf collimator into the virtual source model. Compared to these studies, the method in the current paper has the advantage of being related to a clinically commissioned commercial treatment planning system.…”

“…They apply the model to 6 and 10 MV beams from an Elekta Precise head and to the 6 MV beam from a Varian Truebeam accelerator. A more detailed model of a multileaf collimator allows for fast calculation of IMRT fields in the case of Elekta and Varian accelerators 18 . These works show that accurate modeling of the linear accelerator head to produce a deterministic phase space is possible.…”

“…A more detailed model of a multileaf collimator allows for fast calculation of IMRT fields in the case of Elekta and Varian accelerators. 18 These works show that accurate modeling of the linear accelerator head to produce a deterministic phase space is possible.Similar results are also obtained in the field of particle therapy. 19,20 There is currently considerable interest in fast dose calculation for application to dose reconstruction during adaptive radiotherapy.…”