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Validation of Small Field Dosimetry for Stereotactic SRS Cones and Effect of Angular Dependence with Respect to the Scanning System

S Kucuker Dogan*, M Gopalakrishnan , Northwestern Memorial Hospital, Chicago, IL


(Sunday, 7/14/2019)  

Room: ePoster Forums

Purpose: The purpose of this paper was to study the dosimetric characteristics of the small diameter SRS cones for Elekta 6 MV Beam modulator. The use of MC simulations allows verification and validation of measurements obtained during commissioning of stereotactic SRS cones. We also studied the effect of angular dependence with respect to the scanning system. We will be presenting the comparison between the MC calculated data and measured data for the percentage depth doses (PDDs) and profiles of each cone we studied. We will also present the relative output factor (ROF) dependence of the cones.

Methods: Nominal diameters of 5 mm, 10 mm, 15 mm, and 20 mm were used in our study. The data collection of PDDs, profiles and ROFs were done during the commissioning with an edge detector. BEAMnrc code was used for MC simulations, and DOSXYZnrc code was used to calculate the three-dimensional absorbed radiation dose distributions in water.

Results: MC calculated and measured PDDs for each cone were compared. The MC calculated profiles for each cone size were compared with the measured data. The ROF comparison results for measured and MC calculated data are in progress. We also investigated the effect of angular dependence with respect to the scanning system.

Conclusion: With this study, we can see that MC simulation can be an effective tool for validation of small field dosimetry for Stereotactic SRS cones. We have performed an experimental and theoretical investigation on the dosimetric parameters of the small SRS fields created using Elekta cones. An agreement with Monte Carlo simulations has been reached.


Monte Carlo, Small Fields, Dosimetry


TH- External beam- photons: Small/nonstandard field Monte Carlo dosimetry

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