Comparative Analysis of Percentage Depth Dose Calculations by Radiotherapy Treatment Planning System Algorithms in Non-Homogeneous Media

Abstract

This study aims to investigate the dose distributions produced by three treatment planning systems (TPSs) across various mediums by constructing a phantom that simulates a mediastinal environment. Materials and Methods: We utilized Computerized Tomography (CT) to scan a phantom with bone, PMMA, and lung blocks. It was subsequently moved to Eclipse™ TPS. In Eclipse TPS, we utilized a 6 MV photon beam with a Source Skin Distance of 100 cm and a field size of 20x20 cm2. We obtained the percentage depth doses (PDD) by recording the dose at 3 mm intervals from the center of each block to the desired depths. These processes were repeated for the other two TPSs. We observed that the PDD acquired from bone, PMMA, and lung blocks in Eclipse TPS using the PBC algorithm revealed a significant contrast in the bone block, which increased a s we move away from the build-up area. Subsequently PDD values from the lung medium are compared. Eclipse and Prowess TPS values were found to be similar, while Monaco TPS, utilizing the Monte Carlo Algorithm, demonstrated significant difference. Although Monaco TPS recorded higher PDD values compared to the other two TPSs both before and after the build -up region, it maintained a consistent level in the build-up region and yielded slightly lower doses than the other TPSs. The behaviors of TPSs employed in commercial radiotherapy planning should be calculated in different environments, and compared with the measured values. These differences should be taken into consideration when making treatment decisions.