These researchers are developing a measurement apparatus to obtain detailed 3D spatial distributions of absorbed dose in the vicinity of small high Z metals. Monte Carlo simulations allow the study of how radiation interacts with matter and transport in a medium in realistic geometry. This project uses a free Monte Carlo particle simulation code, the EGS (Electron Gamma Shower) code system, to study the characteristics of photon and electron transport in water-equivalent media containing solid materials of high atomic numbers (Zs). The main goal of the Monte Carlo study is to validate the measurements by comparing the measured data with the Monte Carlo simulation results. This comparison study will provide a necessary confidence of the new measurement tool which can be used to study experimental setups with different geometries and materials for clinical applications. High-performance computing capability is needed for the proposed study for the following reasons. First, the spatial dimension being analyzed is in the range of 1 mm to 50 mm and the required special resolution of the dose calculation is 0.1 mm in 3D. Secondly, the high-Z metals easily attenuate radiation (or photons and electrons), so the number of particles transporting through the medium decreases rapidly, leading a situation very difficult to simulate accurately by a Monte Carlo method. These factors consequently demand higher computing power to achieve a reasonable precision of estimated radiation doses within a reasonable computing time.