SDSU Department of Physics Master’s Thesis Defense: Phillip Lopez

Speaker:  Phillip Lopez, M.S. Candidate

Title:  “Dosimetric Comparison of Pinnacle3, EclipseTM 11.0, and iPlan 4.1 Algorithms with Heterogeneous Phantoms”

Time:   2-3 pm, Wednesday, August 6, 2014

Place:  P-245



Our goal is to compare the dosimetric accuracy of the EclipseTM 11.0 Anisotropic Analytical Algorithm (AAA) and Acuros® XB (AXB), Pinnacle3 9.2 Collapsed Cone Convolution Superposition, and the iPlan 4.1 Monte Carlo (MC) and Pencil Beam (PB) algorithms using measurement as the gold standard. Measurements were taken for 6, 10, and 18 megavoltage (MV) beams in heterogeneous block phantoms and an E2E®stereotactic body radiation therapy* (*SBRT) Lung Phantom. The measurements were taken using a pinpoint chamber and EDGE diode. Data from the planning systems were computed for each scenario, and compared to our benchmark measurements using percent differences.The best results between data from the algorithms and our measurements occur after the buildup region in solid water for scenarios 1 and 2, and at the treatment isocenter in scenario 3.  The cumulative results from scenarios 1 and 2, using a 3% difference from benchmark as our passing criteria, indicate that AXB performs the best overall.  All algorithms except PB were within 5% difference from our benchmark measurements at the isocenter.  Differences between our measurements and algorithm data are much greater for the off-axis points. In summary there is an obvious lack of accuracy for doses to critical structures outside any primary beam.  Further studies will need to be done to understand the risk of dose to OAR’s outside the primary fields.  The data for the anthropomorphic phantom indicates that all the algorithms accurately calculate dose to targets within lung, excluding PB. Finally, our first two scenarios display the possible power behind AXB, overall outperforming iPlan MC code.


Committee Members:

Dr. Mauro Tambasco (Chair)

Dr. Usha Sinha

Dr. Faramarz Valafar



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