Room: ePoster Forums
Purpose: To present a methodology for commissioning a facility-specific Beam Data Library (BDL) for a fast and open-source MC code, MCsquare, for pencil beam scanning (PBS) proton therapy.
Methods: A proton BDL for MCsquare simulation was initially constructed based on measured beam data for commissioning of PBS delivery system and commercial TPS, including determination of the phase space, energy spectrum and number of protons per MU for all 30 commissioning energies. BDL parameters listed above were fine-tuned by fitting the in-air spot fluence with a single Gaussian and reproducing the respectively measured Bragg peaks in water. Then, relative dose verification of Spread-Out-Bragg-peaks (SOBP) depth dose profiles and absolute dose verification in water were investigated against measurements, TOPAS and TPS MC calculations for every commissioned energy, various field sizes, modulation widths and spot spacings, and at various depths from plateau to SOBP. Through implementing the commissioned BDL and a test plan with a stair-like target, differences among MCsquare, TOPAS and TPS MC calculations were evaluated using a 2D gamma index analysis (using 3%/3mm criteria) of planar dose distribution at various depths.
Results: Comparison among MCsquare, measurements, TOPAS and TPS MC showed less than 2% difference for all relative SOBP depth dose profiles, and the absolute dose results were also in good agreement with the maximum difference within 3%. Comparison of planar dose distribution of the test plan resulted in a 2D gamma analysis passing rate for all three depths in excess of 97%.
Conclusion: A PBS Proton BDL for fast MC calculations has been commissioned. Further validations will be investigated for patient specific QA (PSQA) plans against TPS calculations and measurements. MCsquare with well commissioned and validated BDL will be feasible as an independent check tool for PSQA in our facility.