Evaluation of dosimetric functions for Ir-192 source using radiochromic film

Ir-192 source is widely used in high dose rate brachytherapy. The aim of this study was to derive the brachytherapy dosimetric functions described in AAPM TG-43 to characterize the dosimetric properties of commercially available microselectron HDR Ir-192 source. All the measurements were carried out with GAFCHROMIC EBT radiochromic film in water equivalent solid phantom and the grey values were analyzed using Omnipro IMRT film dosimetry software with Vidar VXR-16 scanner. Optical density of the film was converted to dose using calibration film established in this study. Measurements were carried out by measuring the dose at radial distances from 0.5 cm to 5.0 cm with interval of 0.5 cm and at polar angle 0°-180° in 10° intervals. Dosimetric functions such as dose rate constant, radial dose functions and anisotropy of the dose distribution were found to be in good agreement with Monte Carlo calculations. This study confirms the feasibility of radiochromic EBT film dosimetry in characterization of the TG-43 parameters for Ir-192 HDR source.