Dosimetry of MammoSite® applicator: Comparison between Monte Carlo simulation, measurements, and treatment planning calculation

Abstract

To investigate the dosimetric characteristics of accelerated partial breast irradiation technique by MammoSite® applicator using thermoluminescent dosimeter (TLD) and Monte Carlo simulation to comparing them with treatment planning system calculation for planning target volume (PTV) and organs at risk such as skin, lung and chest wall. The Monte Carlo MCNP-5 code was used to simulate dose rate in the PTV that is a MammoSite® balloon with 1 cm margin around it. Experimental dosimetry was carried out within a female-equivalent chest phantom with TLD dosimeter after insertion of 192 Ir source into the MammoSite® applicator. Three dimensional planning (TP) was done for dose delivery to the specific points within the phantom by means of FlexiPlan software. Statistical comparisons were done between TP calculation, Monte Carlo simulation and TLD. Our results showed good agreement for surface doses between simulation and measurement. The mean skin dose for the simulation and TLD result was 61.7% and 56.8% of prescription dose, respectively. The maximum dose to the chest wall for Monte Carlo and TLD were 114.4% and 111.8% of prescription dose, respectively. The maximum dose to the lung for Monte Carlo and TLD results were 28.4% and 27.3% of prescription dose, respectively. Using Monte Carlo simulation and an average female chest phantom, it was possible to demonstrate the accuracy on the calculated dose rate in the PTV of a MammoSite® dose delivery system with 192 Ir HDR sources. The results showed acceptable agreement between simulation, treatment planning, and experimental dosimetry results.