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  4. Obtaining the Phase Space of An Electronic Brachytherpy Equipment for Surfaces Treatments Through Monte Carlo Simulations

Obtaining the Phase Space of An Electronic Brachytherpy Equipment for Surfaces Treatments Through Monte Carlo Simulations

C Valdes*1,2, Yury Niatsetski3, J Perez-Calatayud1,4, J Vijande1, F Ballester1, (1) University of Valencia, Valencia, Spain, (2) Centro Oncologico de Antofagasta, Antofagasta, Chile, (3) Elekta Brachyhtherapy, Veenendal, The Neetherlands, (4) La Fe Hospital, Valencia, Spain

Presentations

(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: The aim of this work is to obtain the phase-space file that will be used in the in the dosimetric characterization of an electronic brachytherapy equipment for surface treatments, finding the optimal use of some Monte Carlo (MC) enhancing efficiency strategies, as the variance reductions tools (VRT) and the user-defined transport parameters (TrP) supported by the used code.

Methods: The simulations of the Esteya® system (Elekta Brachytherapy, Veenendaal, The Netherlands), which emits a flattened bremsstrahlung beam of 69.5 kVp, were performed with penEasy for PENELOPE2014. The VRT evaluated was the interaction forcing (VRIF) for hard bremsstrahlung emission. The PENELOPE TrP evaluated were the cutoff energy EABS, and C1/C2. The energy spectrum was compared against a control simulation, which use the optimum VRIF previously found, EABS = 1 keV and C1 = C2 = 0.

Results: The simulation efficiency was increased by factor ~20, using a VRIF factor equal to 150. We did not find any further improvement using C1/C2.The control energy spectrum show a minimum energy bin equal to 11 keV, with an average energy of 35.43 +/- 0.19 keV (k = 2). At least, the 98.78 +/- 0.44% of the photons detected at the applicator exit were created in the target, without any further electron interaction. Moreover, the electron contamination found was 0.005 +/- 0.005% of the photon energy fluence. The use of EABS = 10 keV (disabling the electron transport for all materials except the target), allowed a time saving of 90%, showing an average photon energy of 35.48 +/- 0.13 keV, without any noticeable difference in the energy spectrums, which are in agreement with the findings published by other authors.

Conclusion: In our opinion, the methodology here exposed show a good compromise between computation speed and accuracy, allowing an efficient characterization of the Esteya system.

Keywords

Brachytherapy, Monte Carlo, Dosimetry

Taxonomy

TH- Brachytherapy: Monte Carlo dosimetry

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