文摘
The objective of this study was to evaluate the differences in dose-volumetric data obtained using the analytical anisotropic algorithm (AAA) vs the x-ray voxel Monte Carlo (XVMC) algorithm for stereotactic body radiation therapy (SBRT) for lung cancer. Dose-volumetric data from 20 patients treated with SBRT for solitary lung cancer generated using the iPlan XVMC for the Novalis system consisting of a 6-MV linear accelerator and micro-multileaf collimators were recalculated with the AAA in Eclipse using the same monitor units and identical beam setup. The mean isocenter dose was 100.2 % and 98.7 % of the prescribed dose according to XVMC and AAA, respectively. Mean values of the maximal dose (Dmax), the minimal dose (Dmin), and dose received by 95 % volume (D95) for the planning target volume (PTV) with XVMC were 104.3 % , 75.1 % , and 86.2 % , respectively. When recalculated with the AAA, those values were 100.8 % , 77.1 % , and 85.4 % , respectively. Mean dose parameter values considered for the normal lung, namely the mean lung dose, V5, and V20, were 3.7 Gy, 19.4 % , and 5.0 % for XVMC and 3.6 Gy, 18.3 % , and 4.7 % for the AAA, respectively. All of these dose-volumetric differences between the 2 algorithms were within 5 % of the prescribed dose. The effect of PTV size and tumor location, respectively, on the differences in dose parameters for the PTV between the AAA and XVMC was evaluated. A significant effect of the PTV on the difference in D95 between the AAA and XVMC was observed (p = 0.03). Differences in the marginal doses, namely Dmin and D95, were statistically significant between peripherally and centrally located tumors (p = 0.04 and p = 0.02, respectively). Tumor location and volume might have an effect on the differences in dose-volumetric parameters. The differences between AAA and XVMC were considered to be within an acceptable range (<5 percentage points).
