A flattening filter for brachytherapy skin irradiation

Abstract

Radioactive sources in close contact offer an alternative to superficial radiation in the treatment of skin lesions. A flattening filter was designed for a lead surface applicator to improve the skin dose distribution of a high dose rate (HDR) brachytherapy unit (Nucletron). At three heights from the opening (10, 15 and 25 mm) of the cylindrical applicator, the 192Ir source can be driven into the centre of the applicator. Thin sheets of lead foil (0.2 mm) were cut into circular shapes and placed in the opening to build a cylindrical cone that acts as a flattening filter. The shape of the cone was optimized in an iterative process using a spreadsheet and the resulting dose distribution under ..