SU-E-J-150: To Design a Methodology Based on Numerical Phantom for Reconstruction of Dose Delivered to Moving Lung Tumors

Medical Physics
D Tewatia, R Tolakanahalli

Abstract

To design a methodology based on numerical phantom for reconstruction of dose delivered to moving lung tumors. MatlabTM 7.6 was used to generate a 4D numerical lung phantom (NLP). Customer parameter files were used as input to this NLP, which consists of multiple ellipsoids representing body, lung, cord and tumor. In this study, we studied the impact of varying breathing pattern on a left lower lobe tumor, where the tumor motion was simulated on the daily breathing pattern of the patient acquired using real time positioning management (RPMTM) system from Varian Medical Systems. Based on the daily breathing pattern, the original RPM signal and the original tumor trajectory, 5 sets of motion trajectories were simulated. This was then used to build 10 different phases of the numerical phantom. Average Intensity Projection (AIP) was then generated from the different phases. The actual delivered dose on the 5 AIP sets were compared to the intended dose on the original planning AIP image set. The mean target coverage (TC) recomputed on the 5 AIP sets was approximately 18% lower than the TC for the planning AIP image set. The mean homogeneity index (HI) recomputed on the 5 sets, was approximately 5 times higher than HI for the plannin...Continue Reading

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