Dose calculation algorithm of fast fine-heterogeneity correction for heavy charged particle radiotherapy

TL;DR

This paper introduces an improved dose calculation algorithm for heavy charged particle radiotherapy that enhances accuracy and efficiency by addressing distortions and artifacts in heterogeneity correction methods.

Contribution

The paper presents a novel combination of grid-dose spreading and Gaussian beam splitting techniques to improve dose calculation accuracy in proton and ion therapy.

Findings

Reduced dose distribution distortion for tilted beams

Effective correction of artifacts due to beam-grid interplay

Calculation time increased only marginally with complex beam splitting

Abstract

This work addresses computing techniques for dose calculations in treatment planning with proton and ion beams, based on an efficient kernel-convolution method referred to as grid-dose spreading (GDS) and accurate heterogeneity-correction method referred to as Gaussian beam splitting. The original GDS algorithm suffered from distortion of dose distribution for beams tilted with respect to the dose-grid axes. Use of intermediate grids normal to the beam field has solved the beam-tilting distortion. Interplay of arrangement between beams and grids was found as another intrinsic source of artifact. Inclusion of rectangular-kernel convolution in beam transport, to share the beam contribution among the nearest grids in a regulatory manner, has solved the interplay problem. This algorithmic framework was applied to a tilted proton pencil beam and a broad carbon-ion beam. In these cases, while the elementary pencil beams individually split into several tens, the calculation time increased only by several times with the GDS algorithm. The GDS and beam-splitting methods will complementarily enable accurate and efficient dose calculations for radiotherapy with protons and ions.