Purpose: To develop and validate the simulation of a breast treatment in a linear accelerator (LINAC) using the Monte Carlo Penetration and ENErgy LOss of Positrons and Electrons (PENELOPE) code. We implemented an experimental treatment using a breast-shaped acrylic phantom. To validate the radiation beam, we compared the experimental and simulated dose profile (DP) and depth dose percentage (DDP) values. The dose-volume histogram (DVH) and gamma index were calculated to determine the differences between the plannings.
Methods: PENELOPE modeled the exposure scenario, simulating the breast. Validation compared data obtained at Erasto Gaertner Hospital with experimental measurements. The geometry was irradiated with a Varian 600CD LINAC with a photon beam of nominal 6MV energy. Breast planning was performed without a dynamic filter, with two irradiation fields using the Eclipse® version 13.5 system. The dose distribution was qualitatively evaluated using a radiochromic film positioned within the phantom. A set of voxels was modeled to represent the radiation detectors along the central and axial axis.
Results: Differences between experimental and simulated dosimetric parameters were less than 2.5% for regions after accumulation, with an average error of 2.28%. PD at the maximum dose depth had errors less than 2.0% in the irradiation field region. It was not possible to correctly estimate the error for regions with high dose gradient due to boundary effects. The difference between the planned and simulated DVH is a root mean square error of 3.75. Manual co-registration and thresholding of dose distributions were performed to determine the gamma index, getting 98.68% of the points accepted with the pass criteria of 3%/3mm.
Conclusion: PENELOPE has allowed the simulation of breast radiotherapy planning, experimentally validated through the agreement between the dose distributions, with an acceptable gamma index. One of the limitations was the need for manual operations of correspondence between the distributions.
Not Applicable / None Entered.