(Sunday, 7/29/2018) 3:00 PM - 6:00 PM
Room: Exhibit Hall
Purpose: To quantify the accuracy of Scientific RT’s SciMoCa Monte Carlo algorithm for a 6MV Elekta Agility linac.
Methods: Beam model data for the 6MV Elekta Agility linac was acquired using IBA’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 Nuclear’s EDGE diode. All other measurements were acquired using IBA’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 0.2±0.17%. PDDs varied by 0.23±0.20%. In- and out-of-field doses varied by 0.43±0.35% and 0.20±0.31% respectively. Penumbral DTA, penumbral width, and field width varied by 0.58±0.68mm, 1.22±1.35mm, and 0.38±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
Keywords
Taxonomy
TH- External beam- photons: Monte Carlo
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