Determination of a beam quality conversion factor from 60Co to 192Ir

Publication date: Available online 29 March 2018 Source:Journal of Radiation Research and Applied Sciences Author(s): Luciana Tourinho Campos, Luis Alexandre Gonçalves Magalhães, Carlos Eduardo Veloso de Almeida Radiation dosimetry is an integral part of the radiation therapy process. The ultimate goal of radiation dosimetry is to determine the dose delivered to the tumor and to the normal tissues in a patient undergoing radiotherapy. The importance of HDR 192Ir brachytherapy as the main mode of treatment calls for an accurate dosimetry standard. A dosimetry standard for the direct measurement of absolute dose to water in 192Ir sources is not available. The AAPM TG-43, along with its update, constitutes the accepted protocol for dose to water determination based on an air kerma strength Sk,air measurement. The air kerma strength of the radioactive source is converted to dose to water via dose rate constant Λ (a calculated absolute quantify) and several relative correction factors accounting for scatter attenuation and anisotropy of the dose distribution among other effects. In this work, we proposed an absorbed dose conversion by determination of a beam quality factor (k Q ) with an ionization chamber. Ideally, the k Q should be measured directly for each chamber at the same quality as the user beam. However, this is not achievable in most standards laboratories. When no experimental data are available, or it is difficult to measure k Q directly to realistic beams, in...
Source: Journal of Radiation Research and Applied Sciences - Category: Physics Source Type: research