Reproduction of a left-breast 3DCRT field-in-field radiation therapy planning in an anthropomorphic and anthropometric phantom

Abstract

The proposal of this study was to reproduce the dosimetry established by a treatment planning system (TPS) following a 3D conformational radiation therapy (3DCRT) protocol of two parallel-opposite fields applied to the left-breast in a thorax phantom, with the complementary use of the field-in-field technique. The computed tomography (CT) images of the thorax phantom were transferred to the XiO version-5 for the elaboration of the breast teletherapeutic planning with 2 Gy per day, in 25 fractions, with prescribed dose of 50 Gy. A set of ten EBT2 radiochromic films were irradiated at doses gradually. The values of RGB (Red, Green, Blue) of the films were obtained by scanning and data transformed in optical density (OD), whose values were used to construct the calibration curve. Radiochromic films were positioned outside and inside of the thorax phantom. After phantom radiation at the linear accelerator 6 MV Elekta Precise were measured the intensities of the films in RGB by software ImageJ, transformed in OD and converted in bidimensional dose distributions, applying the calibration curve. In addition, graphics and dose-volume histograms (DVH) were developed. The dose measurements in the glandular-TE in breast did not present statistically significant differences in relation to values at equivalent positions generated in the TPS. The organs at risk received doses below the reference values, according to TPS. It was possible to reproduce the dosimetry prescribed in TPS into the thorax phantom exposed to a breast conformational teletherapy. The use of the radiochromic films in dosimetry proves to be increasingly useful and shall become routine in radiotherapy services.

Keywords

• breast teletherapy
• breast phantom
• dosimetry.