| Summary: | 碩士 === 長庚大學 === 醫學物理暨影像科學研究所 === 97 === The main purpose of this thesis is to apply a newly developed Monte Carlo DNA damage simulation program, MCDS1, to evaluate the ionization radiation induced DNA damage yields including single strand break (SSB) and double strand break (DSB) in a simulated cell culture dish setting. The nanoparticles often used in current small animal model experiments are considered in the simulation to investigate their future potential clinical impact. BEAMnrc, a Monte Carlo simulation system for modeling radiotherapy sources, was used to model a single layer of cell and culture medium in a cell culture dish. The simulated cell culture dish was irradiated by the primary mono-energetic x-ray photons and the secondary electron particle spectrum was generated from the phase space file. Then the secondary electron particles were treated as the primary electron particles and used in the MCDS program to estimate the DNA damage yields. The energy levels of x-ray photons selected in this work are 30, 50, 100, 300, 500, and 1000 keV. For further understanding the biological consequences of the nanoparticle impact in the fundamental level of physics, we calculated the absolute radiation dose absorbed in the simulated cell culture dishes to check the correlation between the DNA damage yields and dose enhancement. The scatter-to-primary ratios (SPRs) were also computed to characterize the nanoparticle properties in the cell culture simulation. Among other numerous biomedical and molecular imaging related applications, these nanoparticles considered in this work have been developed as an excellent x-ray imaging contrast agent for small animal model study. Our DNA damage simulation results could serve as the prior indication of radiobiological consequences in the foreseeable future.
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