Program Information
An Independent Dose Calculation Engine for Proton PBS Patient-Specific QA
C Lee1*, B Chiang2 , H Huang3 , T Chao4 , (1) Chang Gung University, Guishan Dist, Taoyuan City, (2) Chang Gung University, Kweishan, Taoyuan, Taiwan, (3) Chang Gung Memorial Hospital, Kweishan, Taoyuan, Taiwan, (4) Chang Gung University, Guishan Dist, Taoyuan City
Presentations
SU-I-GPD-T-120 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: The purpose of this study is to establish an independent dose calculation engine to reduce the amount of measurement required for patient-specific quality assurance (PSQA) of proton therapy using the continuous pencil beam scanning (PBS) technique.
Methods: This dose calculation algorithm adopted the pencil beam convolution (PBC) technique and a divergent grid system to handle beam and spot propagation along the beam axis. Fluence distribution was reconstructed from both the scanning patterns recorded in the treatment planning DICOM-RN output files (Varian Eclipse 13.7) and the measured in-air spot distributions. This study also applied the double-Gaussian (DG) model to process dose effect due to nuclear halo. For in-phantom propagation, integral depth dose (IDD) curves measured by the PTW Bragg peak chamber (BPC) were used to inherently include dose contributions from ionizational energy loss and nuclear interaction. This study also applied the Highland theory to simulate beam lateral spreading due to multiple Coulomb scattering in phantom.
Results: Simulation results for 10x10 cm^2 fields with 3-cm SOBP at high, medium and low energy beams show good depth dose agreement with those measured by IBA Zebra. Maximum deviations of distal R90s were kept under 1 mm and FWHM deviations of the SOBPs were within 2 mm.
Conclusion: An independent dose calculation engine for PSQA was successfully created based on fluence patterns decoded from the Varian Eclipse treatment planning DICOM-RN output files for our continuous PBS delivery technique.
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