Sci-Fri PM: Planning-06: Verification of a Monte Carlo based treatment planning system in a homogeneous water phantom

In this abstract we present the results of the verification of the XVMC based treatment planning system "PrecisePLAN" (release 2.50; Elekta). We investigated a 6 MV photon beam from an Elekta Synergy linear accelerator in a homogeneous water phantom. Measurements of profiles, percentage depth dose curves (pdds) and relative output factors (ROFs) for square fields of sides 3, 5, 7, 10, 15, 20 and 30 cm were compared to calculations performed with PrecisePLAN and simulations with BEAMnrc and DOSXYZnrc. Following recommendations from the literature we investigated the deviations between measurements and calculations of the profiles and pdds in four regions and checked for the criterion of acceptability (given in parenthesis): the inner region (3 %, 2 % at the central axis), the penumbra (2 mm distance to agreement), the outer region (3 %) and the build up region (2 mm). The mean deviation +/- 1.5 times the standard deviation should lie within the confidence interval of the thresholds quoted above. For the ROFs we found very good agreement with the measurement. The deviations are lower than two and one percent for PrecisePLAN and BEAMnrc, respectively, for the investigated field sizes. Also most of the profiles and pdds fulfill the criteria of acceptability given above, but for the large field sizes some of the profiles and pdds fall outside the threshold values. The overall agreement between measurements and calculations, especially for the clinically relevant situations in modern conformal/IMRT techniques, is clinically acceptable.