Evaluation of Calculation Errors of Treatment Planning System in Dose Distribution of Electron Beams inside the Lung in Three-Dimensional Conformal Radiation Therapy (3D-CRT)

Calculation of dose distribution of electron beams within in homogeneities may be complex for some of treatment planning systems (TPS). The aim of this study was to investigate the calculation errors of targeted image-guided radiation therapy (TiGRT) treatment planning systems for dose distribution of electron beams within lung.
The computed tomography (CT) images of an anthropomorphic Rando phantom were imported on the treatment planning systems (TiGRT, Lina Tech, China). The direct 10 MeV electron plan was performed by the TiGRT treatment planning systems. According to the plan, the phantom was irradiated using 10 MeV electrons of Siemens Primus linac. Dose measurements were done using LiF (TLD-100) inside the lung of this phantom. Finally, the calculation of the treatment planning systems was compared to the dose measurements.
Findings: The minimum (0.86%) and maximum (76.14%) calculation errors of the treatment planning systems were occurred on the chest wall-lung interface and at the end of lung, respectively.
It considerably seems that the treatment planning systems may not be able to perform some of essential corrections for dose distribution of electrons within in homogeneities. In this study, the in- homogeneities included ribs and lung with low electron density. The calculation errors may be resulted from production of secondary beams and multi scattering of electrons (when the electrons incident to ribs), and also X-ray contamination of electron beams at the end of its path. Therefore, the calculation of the treatment planning systems for dose distribution of electron beams within the lung is not comfortable.