ESTRO 2024 - Abstract Book

S384

Beachytherapy - Physics

ESTRO 2024

Monte Carlo simulations were performed with the EGSnrc code. 2 The simulation geometry (see Fig. 1) comprised bench-marked models 1 of the MatriXX Evolution (IBA Dosimetry, Schwarzenbruck, Germany) array and a single dwell position of the Flexisource 192 Ir HDR source, as well as a PMMA phantom previously employed in the literature. 3 The latter incorporates air and teflon inhomogeneities to resemble patient attenuation and scatter conditions. The 2D dose distribution registered by the array was scored in different simulations for the source centered with respect to the array, as well as positioned 1 mm along the catheter (towards +y) and 0.5 mm across the catheter (towards +z), respectively.

Results:

Assuming typical source strength, dose values registered by the array were found at least an order of magnitude greater than its nominal threshold dose rate of 0.5 mGy/min, validating its efficiency in clinical scenarios.

A clear pattern of differences (see ratios in Fig. 2) was observed between the dose distributions for the source centered and the source with 1 mm offset along the catheter. On the contrary, corresponding differences for the 0.5 mm source offset across the catheter were within uncertainties, as expected.