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RESEARCH PRODUCT

SU-E-T-467: Monte Carlo Dosimetric Study of the New Flexisource Co-60 High Dose Rate Source.

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Recently, a new HDR 60Co brachytherapy source, Flexisource Co-60, has been developed (Nucletron B.V.). This study aims to obtain quality dosimetric data for this source for its use in clinical practice as required by AAPM and ESTRO.Penelope2008 and GEANT4 Monte Carlo codes were used to dosimetrically characterize this source. Water composition and mass density was that recommended by AAPM. Due to the high energy of the 60Co, dose for small distances cannot be approximated by collisional kerma. Therefore, we have considered absorbed dose to water for r0.75 cm and collisional kerma from 0.75r20 cm. To provide adequate spatial resolution, cells were 0.01 cm in thickness for r2 cm from the source and a factor of 10 thicker for 2r20 cm respectively. Angular sampling was taken every 2°. Additional simulations were performed to obtain SK as recommended by AAPM. Mass-energy absorption coefficients in water and air were consistently derived and used to calculate collisional kerma. Along-away tables and TG-43 formalism parameters and functions were derived. Dosimetric data were also provided following the primary and scatter dose separation for the collapsed cone technique.TG-43 dosimetry parameters with L = 0.35 cm were obtained. Results performed with both radiation transport codes showed agreement typically within 0.2% for r0.8 cm and up to 2% closer to the source. Using Penelope2008 and GEANT4, an average of Î= 1.085±0.003 cGy/(h U) (with k = 1, Type A uncertainties) was obtained. Dose rate constant, radial dose function and anisotropy functions for the Flexisource Co-60 are compared with published data for other Co-60 sources.Dosimetric data are provided for the new Flexisource Co-60 source not studied previously in the literature. Using the data provided by this study in the treatment planning systems, it can be used in clinical practice. This project has been funded by Nucletron BV.