Monte Carlo characterization of a new Yb-169 high dose rate source for brachytherapy application.

Purpose: The objective was to characterize a new Yb-169 high dose rate source for brachytherapy application.

Methods: Monte Carlo simulations were performed using the MCNP5 F6 energy deposition tallies placed around the Yb-169 source at different radial distances in both air-vacuum and water environments. The calculations were based on a spherical water phantom with a radius of 50 cm. The output from the simulations was converted into radial dose rate distribution in polar coordinates surrounding the brachytherapy source.

Results: The results from Monte Carlo simulations were used to calculate the AAPM Task Group 43 dosimetric parameters: Anisotropy function, radial dose function, air kerma strength, and dose rate constant. The results indicate a dose rate constant of 1.12 +/- 0.04 cGy h(-1) U(-1), anisotropy function ranging from 0.44 to 1.00 for radial distances of 0.5-10 cm and polar angles of 0 degrees-180 degrees.

Conclusions: The data from the Yb-169 HDR source, Model M42, presented in this study show that this source compares favorably with another source of Yb-169, Model 4140, already approved for brachytherapy treatment.