Calculation of Dosimetry Parameters for 192Ir and 125I Brachytherapy Sources Using Geant4

In brachytherapy cancer treatments, methods for calculation of dose delivered to tumours and organs have been continuously improving. Monte Carlo methods are na important tool in dose calculation for brachytherapy cancer treatments, where the exposition to the source planning aims at the maximization of dose deposition in the target volume, while minimizing the deposition in healthy tissues. The use of interstitial brachytherapy sources follows the recommendations of AAPM REPORT No.51. The present work is based on Monte Carlo simulations with the Geant4 toolkit of the dose quantities recommended by that report. An Iridium-192 Buchler HDR source and an Iodine-125 LDR source were simulated and the geometry of dose deposition in media and energy spectra have been obtained. Calculations also include the Dose Rate Constant Lambda, the Geometry Factor G(r, theta), the Anisotropy Function F(r, theta) and the Radial Dose Function g(r, theta).