Dosimetric Accuracy of an HDR Brachytherapy Treatment Planning System for Different Irradiation Lengths with Monte Carlo Simulation

Abstract

OBJECTIVEThe purpose of the present study was to verify calculated dose rate profiles of Ir-192 for four differentirradiation lengths and various numbers of dwell positions by using treatment planning system (TPS)calculations and Monte Carlo (MC) simulations.METHODSDose rate profiles per air-kerma strength in μGy m2/h (abbreviated as U) were calculated on transverseaxis for irradiation lengths of 2, 3, 4, and 5 cm by Nucletron Oncentra TPS. The same irradiation scenarios were simulated with Monte Carlo N-Particle (MCNP) Transport Code. The MC and TPS calculateddose rate profiles were compared for all settings.RESULTSThe difference between the calculated dose rate profiles by MC and TPS was found within 2% at aninterval of 2 mm–8 cm away from the source for all irradiation lengths. The largest discrepancy of 5.2%was computed at a distance of 10 cm from the source for 5 cm irradiation length.CONCLUSIONThere is a good consistency between the calculated dose rate profiles by MCNP and Oncentra TPS. Thedeviation between the calculated dose rate values slightly increases as the distance from the source center increases >5 cm from the source, and its quantity depends on the number of dwell positions.