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Independent MU Dose Calculation Software for S&S IMRT Using Modified Clarkson Integration Sector

C Venencia

A Adrada1 , E Miller1 , Z Tello1 , L Medina1 , E Garrigo1 , C Venencia1*, (1) Instituto de Radioterapia - Fundacion Marie Curie, Cordoba, Argentina


SU-E-T-210 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: The purpose of this work was to develop and validate an open source independent MU dose calculation software for S&S IMRT based in the algorithm proposed by Kung et.al.

Methods: Treatment plans were done using Iplan v4.5 BrainLAB TPS and S&S IMRT modality. A 6MV photon beam produced by a Primus linear accelerator equipped with an Optifocus MLC was used. TPS dose calculation algorithms were pencil beam and Monte Carlo. 230 IMRT treatments plans were selected for the study. The software was written under MALTLAB environment. Treatment plans were imported by the software using RTP format. Field fluences were reconstructed adding all segments.The algorithm implemented in the software calculates the dose at a reference point as the sum of primary and scatter dose. The primary dose is obtained by masking the fluence map with a circle of radius 1cm. The scatter dose is obtained through a shaped ring mask around the previous circle with a thickness of 0.5cm; the rings are increased one after another with constant thickness until cover the entire map of influence. The dosimetric parameters Sc, Sp and TPR vary depending on radio, the transmission effect of the MLC, inverse square law and dose profile are used for the calculation.

Results: The average difference between measured and independent calculated dose was 0.4% ± 2.2% [-6.8%, 6.4%]. For 91% of the studied plans the difference was less than 3%. The difference between the measured and TPS dose with pencil-beam algorithm was 2.6% ± 1.41% [-2.0%, 5.6%] and Monte Carlo algorithm was 0.4% ± 1.5% [-4.9%, 3.7%]. The differences obtained are comparable to that obtained with the ionization chamber and TPS.

Conclusion: The developed software is suitable for use in S&S IMRT dose calculation. This application is open and can be downloading under request.

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