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IMRT Monte Carlo Dose Calculations for a Novalis TX LINAC Equipped with HD-120 MLC

L Vazquez Quino

L Vazquez Quino*, S Stathakis, A Gutierrez, C Esquivel, N Papanikolaou, University of Texas Health Science Center at San Antonio, SAN ANTONIO, TX

SU-E-T-365 Sunday 3:00:00 PM - 6:00:00 PM Room: Exhibit Hall

Purpose: : To investigate the accuracy of a Monte Carlo dose calculation engine for IMRT using a Novalis Tx LINAC with the HD-120 MLC.

Methods: PDD and beam profiles ranging from 1x1 to 20x20 cm² were calculated and compared against measured data in water to commission the LINAC built on the BEAMNRC platform. An in-house, MATLAB-based software was used to extract the parameters needed for the MC simulation from the DICOM-RT plan and create input files for the MCSim egs4 Monte Carlo code. MCSim egs4 software was used to simulate the IMRT treatment plans in a cylindrical solid-water phantom and ultimately used to compute the dose. In-house software using a MATLAB platform was utilized to convert the 3D dose file obtained from the Monte Carlo simulation to a universal file which can be read on the RIT Software platform. Within RIT, the MC and treatment planning system (TPS) dose calculations could be compared.

Results: 5 IMRT plan simulations were performed and good agreement results were achieved for TPS and MC dose comparison. Gamma analysis with a 3% dose and 3 mm DTA criteria shows a mean gamma index value of 92% for the cases studied.

Conclusions: Based on our preliminary results, the Monte Carlo based Novalis Tx linear accelerator and the MCSim simulations of the IMRT treatments on a cylindrical phantom demonstrate good accuracy with regards to the treatment planning dose calculation.

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