Low-Energy Electron Interactions with Liquid Water and Energy Depositions in Nanometric Volumes

• Main Authors: Wen-Tung Chan, 詹文棟
• Other Authors: Chuan-Jong Tung
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/28990995583324082479

碩士 === 國立清華大學 === 生醫工程與環境科學系 === 95 === The investigation of targeted therapy is extensively conducted in recent years. One popular topic of them is Anti-gene radiotherapy. Anti-gene radiotherapy uses the property of Auger electrons that will deposit abundant energy in the range of nanometer to achieve the purpose of cure. Besides biological experiment, Monte Carlo simulation can also be used to estimate the biological effect caused by binding Auger emitter to DNA strands. There are four major portions in a Monte Carlo simulation code: cross section data, algorithm, geometry, and analysis. The accuracy of cross section data and algorithm can be crucial to the reliability of the simulation results. In this research, interactions of low-energy electrons with medium were investigated by theoretical method. Extended Drude dielectric model and reconstruction of sum-rule-constrained Classical-binary-collision model were used to calculate the inelastic cross section of valence band and inner shells of liquid water and DNA, respectively. Apply these cross section data to a developed Monte Carlo code-NMC, which provides an estimate of the damage caused by low-energy electrons in a simplified DNA model. This model consisted of two parallel cylinders of 0.5 nm in diameter, 16 nm in height. Any energy deposition greater than 17.6 eV in the cylinder was assumed to cause a single strand break (ssb) by direct action. An energy deposition of 12.6 eV or greater within 0.5 nm of the cylinder surface was assumed to induce an OH radical which had a probability of 0.13 to produce a ssb by indirect action. When two ssbs occurred on opposite strands separated by 10 or fewer base pairs, a double strand break (dsd) was assumed. The algorithm and analysis of NMC were improved to simulate more accuracy. Source position and energy were changed to find out the most effective way of Anti-gene radiotherapy