Accuracy and efficiency of graphics processing unit (GPU) based Acuros XB dose calculation within the Varian Eclipse treatment planning system

To evaluate, in terms of dosimetric accuracy and calculation efficiency, the implementation of a graphic processing unit (GPU)-based Acuros XB dose calculation engine within version 15.5 of the Varian Eclipse treatment planning system. Initial phantom based calculations and a range of 101 clinical cases were analyzed on a dedicated test system. Dosimetric differences, based on dose-volume histrogram parameters and plan comparison, were compared between central processing unit (CPU) and GPU based calculation. Calculation times were also compared between CPU and GPU, as well as PLAN and FIELD modes. No dosimetric differences were found between CPU and GPU. CPU based calculations ranged from 25 to 533 seconds per plan, reducing to 13 to 70 seconds for GPU. GPU was 4.4 times more efficient than CPU. FIELD mode was up to 1.3 times more efficient than PLAN mode. For the clinical cases and version of Eclipse used, no dosimetric differences were found between CPU and GPU. Based on this, GPU architecture has been safely implemented and is ready for clinical use. GPU based calculation times were superior to CPU, being on average, 4.4 times faster.