Investigation of the dose distribution in the inhomogenous phantom simulated lung tumor

The scattering model of the electrons and photons of a radiation treatment planning system (RTPS) has been generally created in the water phantom with Monte Carlo (MC) simulation. The inhomogeneity correction has been made in each way of the RTPS using CT values. A phantom simulated a tumor in the lung tissue was used in the computational geometry of the inhomogenous region. We calculated the dose distributions of the RTPS and the MC simulation. The result by Pencil Beam Convolution (PBC) algorithm showed no re-build up in the different material. The dose differences of relative dose curves on the central axis between the RTPS result by the Convolution / Superposion (SP) and the MC simulation were within 1.2 % at the re-build up part of the tumor and was up to 3.5 % at the lung tissue located behind tumor. The result by the Anisotropic Analytical Algorithm (AAA) underestimated 2.4 % in average and up to 3.1% at the wide region of inhomogenous phantom.