Study of Tissue Inhomogeneity Effects on Central Axis Radiation Beam Parameters using Monte Carlo Methods

Introduction: The central axis radiation beam parameters are used for the dose calculations inradiotherapy and usually measured in a homogeneous medium. Human body is not homogeneous innature and the incident beam has to travel through different medium such as bone tissue air etc toreach the tumor. Objective: The objective of the present work is to study the effects of tissueInhomogeneity on central axis beam parameter such as percentage Depth Dose using Monte CarloMethods Materials and Methods: The Monte Carlo simulation is a virtual experiment and can beconducted with the Monte Carlo software tool installed in a PC. Input files are written as per thespecification of the Monte Carlo code. Two radiation beams beans commonly used for radiationtreatment such as Cobalt 60 and 6MV X ray were used for the simulation. Results: Depth Dosecharacteristics in homogeneous tissue medium for Cobalt60 and 6MV X rays beams were studied andis consistent with the published experimental values.In the second case, at the interface betweentissue and bone the PDD pattern changed as reported by the previous works. And the absorbed doseat bone layer is higher than the dose value predicated in a homogeneous condition. In the nextsimulation we conducted the simulation for a tissue air tissue medium. Conclusion: The presentstudy clearly demonstrate that Monte Carlo methods simulation can be used as a tool for estimationof dose in tissue Inhomogeneity where measurements are seldom possible.