Room: ePoster Forums
Purpose: To determine the effect of calculation grid-size, statistical uncertainty and CT slice-thickness on dose and calculation time for Monte Carlo(MC) and Collapsed Cone(CC) algorithms in the Elekta Monaco Treatment Planning System (TPS).
Methods: Three patients were created in the Monaco TPS. To evaluate CC, Head and Neck, Brain and SBRT Lung plans were created varying CT slice-thickness and calculation grid-size. To evaluate MC, plans were created for the same anatomical sites varying statistical uncertainty and calculation grid-size. Calculation times were recorded and dose planes for each plan were analyzed using SNC Patient software. DVH statistics for various structures were compared.
Results: Dose plane analysis for CC showed all points passed above 99% except one using 3%/3mm criteria, all passed above 96% using 2%/2mm, and a minimum of 52.4% passed using 1%1mm criteria. Analysis for MC showed 100% of the points passed using 3%/3mm and 2%/2mm criteria and minimum of 92.4% using 1%/1mm criteria. For CC, the DVH statistics showed the mean dose for the PTV within 1.5% for all plans, while variation up to 11% was found for other structures. For MC, the DVH statistics showed mean doses for all structures within 1% for all plans. Point dose variations above 5% were observed but deemed clinically insignificant.CC calculation times ranged from 7 to 150 seconds, while MC calculation times ranged from 4 to 60 minutes.
Conclusion: Higher pass rates using smaller grid sizes and CT slice-thicknesses for CC Monaco plans demonstrated that planning using these parameters will have the smallest impact on dose agreement with minimal increase in calculation time. Conversely, the small variation in pass rates among MC Monaco plans with differing grid-sizes and statistical uncertainties demonstrated that planning with the shortest calculation times will have insignificant impact on dose agreement.