An Improved Method of Heterogeneity Compensation for the Convolution / Superposition Algorithm

17th International Conference on the Use of Computers in Radiation Therapy

物理学;计算机科学

Jacques, Robert^1 ; McNutt, Todd^2

Elekta / IMPAC Medical Systems, Inc., Maryland Heights, MO, United States^1

Department of Radiation Oncology, Molecular Radiation Sciences, Johns Hopkins University, Baltimore, MD, United States^2

关键词: Convolution/superposition;    Cooperative agreements;    Direction sensitive;    GPU-based algorithms;    Heterogeneous materials;    Johns hopkins universities;    Monte Carlo results;    Recursive filters;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/489/1/012019/pdf
DOI  :  10.1088/1742-6596/489/1/012019

学科分类：计算机科学（综合）

来源: IOP

【 摘 要 】

Purpose: To improve the accuracy of convolution/superposition (C/S) in heterogeneous material by developing a new algorithm: heterogeneity compensated superposition (HCS). Methods: C/S has proven to be a good estimator of the dose deposited in a homogeneous volume. However, near heterogeneities electron disequilibrium occurs, leading to the faster fall-off and re-buildup of dose. We propose to filter the actual patient density in a position and direction sensitive manner, allowing the dose deposited near interfaces to be increased or decreased relative to C/S. We implemented the effective density function as a multivariate first-order recursive filter and incorporated it into GPU-accelerated, multi-energetic C/S implementation. We compared HCS against C/S using the ICCR 2000 Monte-Carlo accuracy benchmark, 23 similar accuracy benchmarks and 5 patient cases. Results: Multi-energetic HCS increased the dosimetric accuracy for the vast majority of voxels; in many cases near Monte-Carlo results were achieved. We defined the per-voxel error, %|mm, as the minimum of the distance to agreement in mm and the dosimetric percentage error relative to the maximum MC dose. HCS improved the average mean error by 0.79 %|mm for the patient volumes; reducing the average mean error from 1.93 %|mm to 1.14 %|mm. Very low densities (i.e.