GPU-based fast gamma index calcuation

TL;DR

This paper presents a GPU-accelerated method for fast gamma-index calculation in radiotherapy dose comparison, achieving significant speedups over CPU methods and enabling rapid analysis of 3D dose distributions.

Contribution

The authors develop a GPU-based gamma-index calculation tool combining geometric and radial pre-sorting techniques, significantly reducing computation time compared to traditional CPU methods.

Findings

GPU implementation achieves 20-30x speedup over CPU.

Pre-sorting voxels speeds up calculation by 2-4 times.

Calculation time scales quadratically with resolution on CPU, less so on GPU.

Abstract

The gamma-index dose comparison tool has been widely used to compare dose distributions in cancer radiotherapy. The accurate calculation of gamma-index requires an exhaustive search of the closest Euclidean distance in the high-resolution dose-distance space. This is a computational intensive task when dealing with 3D dose distributions. In this work, we combine a geometric method with a radial pre-sorting technique , and implement them on computer graphics processing units (GPUs). The developed GPU-based gamma-index computational tool is evaluated on eight pairs of IMRT dose distributions. The GPU implementation achieved 20x~30x speedup factor compared to CPU implementation and gamma-index calculations can be finished within a few seconds for all 3D testing cases. We further investigated the effect of various factors on both CPU and GPU computation time. The strategy of pre-sorting voxels based on their dose difference values speed up the GPU calculation by about 2-4 times. For n-dimensional dose distributions, gamma-index calculation time on CPU is proportional to the summation of gamma^n over all voxels, while that on GPU is effected by gamma^n distributions and is approximately proportional to the gamma^n summation over all voxels. We found increasing dose distributions resolution leads to quadratic increase of computation time on CPU, while less-than-quadratic increase on GPU. The values of dose difference (DD) and distance-to-agreement (DTA) criteria also have their impact on gamma-index calculation time.