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

  • Dr. Santhosh VS Assistant Professor, Department of Radiation Physics Government Medical College, Thiruvananthapuram, Kerala, India
  • Dr. Anand RK Assistant Professor, Department of Radiation Physics Government Medical College, Thiruvananthapuram, Kerala, India
Keywords: Tissue inhomogeneity, Monte carlo Methods, Percentage Depth Dose, Radiotherapy



Introduction; The central axis radiation beam parameters are used for the dose calculations in radiotherapy and usually measured in a homogeneous medium. Human body is not homogeneous in nature and the incident beam has to travel through different medium such as bone tissue air etc to reach the tumor. The presence of such Inhomogeneity perturb the central axis beam parameters.The experimental measurements of dose variation in the presence such Inhomogeneity is seldom possible and Monte Carlo methods can be used to study in cases.

Objective: The objective of the present work is to study the effects of tissue Inhomogeneity on central axis beam parameter such as Percentage Depth Dose using Monte Carlo Methods

Materials and Methods:The Monte Carlo simulation is a virtual experiment and can be conducted with the  Monte Carlo software tool installed in a PC .Input files are written as per the specification of the Monte Carlo code. Two radiation beams beams commonly used for radiation treatment such as Cobalt 60 and 6MV X ray were used for the simulation.  The study conducted for a homogeneous tissue medium,and two Inhomogeneity situations such as tissue air tissue and tissue bone tissue medium. Percentage Depth Dose(PDD) curves were generated from the simulated results.

Results: Depth Dose characteristics in homogeneous tissue medium for Cobalt60 and 6MV X rays beams were studied and is consistent with the published experimental values.In the second case, at the interface between tissue and bone the PDD pattern changed as reported by the previous works. And the absorbed dose at bone layer is higher than the dose value predicated in a homogeneous condition. In the next simulation we conducted the simulation for a tissue air tissue medium. It was observed that as the beam passes through the tissue air interface the distribution changes drastically. The dose deposition in air become very small and the PDD values at other points in the air medium show large variation than the homogeneous condition. Interestingly It is also observed that a buildup condition occur at the second air tissue interface.

Conclusion: The Monte Carlo Our studies clearly demonstrate the perturbation effects caused by the presence of Inhomogeneity when a radiation beam is transporting through the human tissues.For the accurate estimation of absorbed dose the Inhomogeneity effects must be considered in actual clinical practice and the Monte Carlo study can be used to estimate the Inhomogeneity correction factors that have to be incorporated for dose calculations.The present study clearly demonstrate that Monte Carlo methods simulation can be used as a tool for estimation of dose in tissue Inhomogeneity where measurements are seldom possible.


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DOI: 10.17511/ijmrr.2020.i05.03
Published: 2020-10-29
How to Cite
Dr. Santhosh VS, Dr. Anand RK. Study of Tissue Inhomogeneity Effects on Central Axis Radiation Beam Parameters using Monte Carlo Methods. Int J Med Res Rev [Internet]. 2020Oct.29 [cited 2020Dec.5];8(5):352-6. Available from:
Original Article