Program Information
Evaluation of Electron Monte Carlo Dose Calculation of RayStation Treatment Planning System in Heterogeneous Media
S Mossahebi*, M Lin , S Chen , H Xu , M Guerrero , University of Maryland School of Medicine, Baltimore, MD
Presentations
SA-B-BRD-5 (Saturday, March 5, 2016) 10:30 AM - 12:30 PM Room: Grand Ballroom D
Purpose:
To evaluate the dosimetric performance of the Electron Monte Carlo (EMC) algorithm of RayStation treatment planning system (v.4.5)
Methods:
The dose calculation of RayStation TPS was compared with ion chamber, OSLD, and EBT2 film measurements for straight incidence and with EBT2 film measurements for oblique incidence in heterogeneous, multi-layer phantoms to mimic the chest wall irradiation conditions. Both setups were irradiated (200 MUs) with 6, 9, and 16 MeV electron beams. For straight incidence, films were placed at the top polystyrene-cork interface with two OSLDs around the center and the farmer-type ion chamber was positioned at the center of the bottom polystyrene layer. The phantom was irradiated with an open field and 3x6 cm² cut-out at SSD 100 cm. For oblique incidence, films were placed vertically between two phantom sets. A 3x6 cm² cut-out was irritated at gantry angles 0°, 10°, 20°, and 45°. Extended SSD (110 cm) was employed for 20° and 45°. The RayStation dose calculations were compared with the measurements for each energy and field size combination.
Results:
Agreements within 3% and 4% were found between TPS calculations vs OSLD (high-dose region) and ion chamber (low-dose region) measurements, respectively. In the straight incidence, gamma analysis (3mm/3%) showed an excellent agreement passing rate (>96%) between RayStation and film for all energies. In the small angle oblique incidence, >91% passing rate was observed at the high-dose region for 6 and 9 MeV beams comparing to >82% for 16 MeV. However, a poor agreement was observed for high angles and extended SSD for all energies (64%-81%).
Conclusion:
The Electron Monte Carlo algorithm of RayStation treatment planning system (v.4.5) is clinically acceptable for standard treatment and small angle incidence in heterogeneous treatment conditions. Caution should be paid when large angle incidence and extended SSD are utilized.
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