On tradeoffs between treatment time and plan quality of volumetric-modulated arc therapy with sliding-window delivery

TL;DR

This paper formulates the optimization problem for VMAT with sliding-window delivery, analyzing how reducing the number of sweeps impacts treatment plan quality and proposing algorithm modifications for improved results.

Contribution

It provides an exact formulation of VMAT optimization with sliding-window delivery and introduces a modified algorithm for better plan quality with fewer sweeps.

Findings

Fewer sweeps can improve plan quality under tight treatment time constraints.

The modified algorithm yields better objective values and dose accuracy.

Plan quality benefits are more pronounced with fewer sweeps.

Abstract

The purpose of this study is to give an exact formulation of optimization of volumetric-modulated arc therapy (VMAT) with sliding-window delivery, and to investigate the plan quality effects of decreasing the number of sliding-window sweeps made on the 360-degree arc for a faster VMAT treatment. In light of the exact formulation, we interpret an algorithm previously suggested in the literature as a heuristic method for solving this optimization problem. By first making a generalization, we suggest a modification of this algorithm for better handling of plans with fewer sweeps. In a numerical study involving one prostate and one lung case, plans with varying treatment times and number of sweeps are generated. It is observed that, as the treatment time restrictions become tighter, fewer sweeps may lead to better plan quality. Performance of the original and the modified version of the algorithm is evaluated in parallel. Applying the modified version results in better objective function values and less dose discrepancies between optimized and accurate dose, and the advantages are pronounced with decreasing number of sweeps.