Dosimetric evaluati̇on of air cavity effect on dose distribution in brachytherapy

The data which are used for Brachytherapy are obtained at homogenous density conditions. Nevertheless, when radiation that is applied to patient pass through such as medium like lipid, bone, muscle, lung and air layer in the human body, it behaves differently according to homogeneous condition because of inhomogeneous structure of human body. The aim of this project is to evaluate the effect of air cavity that are inside of human body to dose distribution from special designed mechanism with different volume type air filled apparatus by using gafchoromic EBT3 films. In this study ,empty (without air) cylindrical apparatus which are made of polypropylene are prepared with fixing proper junctions and adding inside polystyrene foam so as to in each case which size of 20x30 cm and divided 13,18 and 22 mm portions separately. A catheter which has 2mm diameter is located far 1 cm laterally from exterior surface of apparatus parallelly for using the source of Ir-192 Brachytherapy. Afterwards 3 films are irradiated for each apparatus to evaluate the effect of air cavity that have different volume to dose distribution. For each air cavity, means of different volume for 13, 18 and 22mm diameters are measured respectively 1,69, 2,97 and 2,22 by calculating differences between tissue equivalent medium and percentage dose values with different distance. As a result, percentage dose value shows increase depend on volume of air cavity which are located treatment areas with similar distance according to tissue medium in Brachytherapy applications. Considering the effect of air cavity that have different volume to dose distribution is recommended to sensitive dose estimation.