Dosimetria Fricke gel na caracterização dos feixes de elétrons para radioterapia intraoperatória (IOERT) da mama

Abstract

Intraoperative electron beam radiotherapy (IOERT) is one of the most modern radiotherapeutic techniques that allows the delivery of high doses of ionizing radiation to the tumor volume, which requires new methods to control the quality of the procedures performed. For the three-dimensional verification of these dose distributions there is still no consolidated dosimeter in the clinical routine. In this context, the dosimetry gel stands out for the three-dimensional dosimetry and characterization of the clinical bundles. In this work, the electron beams were characterized with energies of 7, 8, 10 and 12 MeV used in intraoperative radiotherapy of the breast. The measuring instruments used were phantoms containing Fricke gel based on polyvinyl alcohol (PVA) and glutaraldehyde (GTA). For this work was chosen the treatment of breast cancer because it is currently one of the most common types of cancer among women. In the context of the dosimetry gel, in order to obtain the volumetric information an image technique is required, in the present case the dosimeters reading was made by magnetic resonance imaging (MRI), which proved to be a powerful technique in the acquisition of images. From these images it is possible to determine the dose distributions, the dose-in-depth (PDP) curves and field profiles, processing them in the ImageJ software, and then comparing the results obtained with the data in the literature qualitatively and quantitatively. The results obtained with the gel dosimetry presented some significant differences in relation to the literature data obtained with the ionization chamber and Monte Carlo simulation. These differences should be investigated in the future, but it is possible to affirm that the methodology defined in this work through Fricke gel can be used to obtain three-dimensional doses in the IOERT services.