(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: To validate Brainlab’s elements Monte Carlo and pencil beam algorithm with the measured data and eclipse AAA model.
Methods: For this purpose a 1D water tank was filled with water and scanned it using the GE Optima scanner. A simple AP field was created to deliver dose on this phantom for a predetermined MU and field sizes. The dose calculation was done using both MC and Pencil Beam algorithm using Brainlab element system. A comparison for measured and calculated data was done for a) Monte Carlo, and a comparison with Eclipse AAA calculation was done for b) Pencil Beam Algorithm. The dose in Elements was calculated for field sizes: 1x1, 2x2, 4x4, 6x6, 10x10, and 15x15. The PDD at 10cm and the output factor were calculated and compared to what was measured using a PTW 31022 pinpoint (0.015cc) ion chamber. For Pencil beam validation, the dose was calculated in Elements for field sizes: 2x2, 4x4, 6x6, 8x8, and 10x10. Equivalent plans were also calculated in Eclipse v13.6 using Analytical Anisotropic Algorithm (AAA). A comparison of PDD at 10cm, output factor, qualitative profile and an OAF (off axis factor) was compared between the two algorithms
Results: Both Monte Carlo calculations agreed with measurements within 1% for all values except for PDD at 10cm at 1x1 where the difference was 1.6%. Calculation time increased by a factor of 20 when changing between 2%/2mm and 1%/1mm for a 10x10 field. Pencil Beam calculations in general agreed with Eclipse AAA calculations within 1% for all values except the output factors for 2x2 and 4x4 cm, and the off axis factor for 2x2 field with a difference of 1.40%.
Conclusion: The Monte Carlo based model calculation was validated. The differences between 2%/2mm and 1%/1mm calculations were found to be clinically insignificant.
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