Room: Exhibit Hall
Purpose: To quantify the accuracy of Scientific RTâ€™s SciMoCa Monte Carlo algorithm for a 6MV Elekta Agility linac.
Methods: Beam model data for the 6MV Elekta Agility linac was acquired using IBAâ€™s Blue Phantom2. Inline/crossline profiles, PDDs, and output factors were acquired for various field sizes as shown in Tables 1 and 2. Output factors less than 5x5, PDDs less than 5x5, and profiles less than 20x20 were acquired using Sun Nuclearâ€™s EDGE diode. All other measurements were acquired using IBAâ€™s CC13 ion chamber. Crossplane profiles were offset half a leaf width in the inplane direction to minimize the effect of interleaf leakage. All profiles were measured at 1.5/5/10/20 cm depths. Matching dose profiles were calculated in physics mode using 1mm dose grid resolution in the direction of interest. Per-field comparison metrics included (1) absolute percent difference in output factor, (2) mean absolute percent global difference in PDD from 0-35cm, (3) mean absolute percent local difference in in-field dose, (4) mean absolute percent global difference in out-of-field (<10% max dose) dose, (5) mean absolute distance-to-agreement in the penumbra, (6) mean absolute difference in penumbra width (80%-20%), and (7) mean absolute difference in field width (50%-50%). Due to insufficient scan length, penumbra and out-of-field data for the 40x40cm field was not analyzed.
Results: Output factors varied by 0.2Â±0.17%. PDDs varied by 0.23Â±0.20%. In- and out-of-field doses varied by 0.43Â±0.35% and 0.20Â±0.31% respectively. Penumbral DTA, penumbral width, and field width varied by 0.58Â±0.68mm, 1.22Â±1.35mm, and 0.38Â±0.34mm respectively.
Conclusion: Calculated and measured doses matched well for both small and large field sizes in a homogenous medium.
Funding Support, Disclosures, and Conflict of Interest: This research is partially funded by an Elekta research grant