Quantitative evaluation of the dosimetric effects of balloon deformation and source position in high-dose rate mammosite breast brachytherapy.

Purpose: To investigate quantitatively the deformation of the mammosite balloon, eccentricity of the source position and their effects on the dose delivered to the tumor lumpectomy site and critical structures.

Materials And Methods: The distances of the brachytherapy source to the surface of the mammosite balloon were measured in using radiographic images for fractions 1 to 10 for twelve patients. The dose at the balloon surface (nearly 680cGy) and prescription dose of 340cGy at 1cm from the balloon surface were calculated for the different fractions and their dependence on the balloon volume and source position were investigated.