Verification Of Percentage Depth-Doses With Monte Carlo Simulation and Calculation Of Mass Attenuation Coefficients For Various Patient Tissues In Radiation Therapy

Abstract

Objective: First part of this work dedicated to the verification of the percentage depth dose curves that obtained experimentally for 6 MV and 18 MV x-ray photon beams via using Geant4 Monte Carlo simulation. Second part of this study compared the computed mass attenuation coefficients of various human tissues and water between MATLAB and XCOM. Material-Methods: The central-axis percentage depth doses of Varian Clinac IX linear accelerator were verified via Monte Carlo simulation (Geant4) with square field sizes (10x10 and 30x30 cm2) for 6 MV and 18 MV x-ray photon energies. In addition, mass attenuation coefficients of adipose tissue, blood, muscle, bone, skin and water were computed with MATLAB and were compared with the NIST XCOM data. Results: Results of the Geant4 modeling were in line with the experimental measurements for percentage depth dose curves. The consistency of Geant4 with experimental results was more explicit for 6 MV photons with the field size of 10x10 cm2. No statistical significant difference between MATLAB and XCOM were found for all mentioned human tissues, except for bone (p=0.039 for bone in both genders). The minimum median percentage difference were calculated for water and skin with a result of 1.23% and 2.19%, respectively. Conclusion: Geant4 can be used to predict percentage depth dose curves for medical linacs. Mass attenuation coefficients calculated with MATLAB yielded consistent results with previous studies, which means MATLAB can be used as an alternative simulation tool for estimating mass attenuation coefficients of various human tissues and water.