氚(3H)在生物圈內是普遍存在的一種核種，因為氚可以藉由水循環來快速地傳遞到各個地方，加上氚可以經由許多的途徑進入人體內，例如：呼吸、喝水、飲食及皮膚吸收等等，所以必須要了解氚在人體內新陳代謝的途徑與分佈的情形，並進一步探討氚可能造成的生物效應，但因為跟其他核種相較下，氚由貝他衰變所釋放出來的能量(平均5.7 keV)是比較小的，因此很多輻射防護組織把氚歸類成最弱的核種內，可是隨著對氚的特性越來越了解，造成現在許多研究證據證明氚對人體造成的傷害是不可被輕視的。其中由於氚釋放的能量比較小，導致氚在人體內分佈與輻射敏感區之間的相互位置變得很重要，而氚值得注意的地方是它在人體內不論是以氚水(tritiated water)或者是以有機鍵結(organically bound tritium)的方式存在，都會進入到細胞核內並圍繞在 DNA的周圍，進而可能對人體造成嚴重的生物效應。本研究利用PENetration and Energy Loss of Positrons and Electrons(以下簡稱PENELOPE)，進行粒子遷移模擬。本研究主要為低能量電子模擬，模擬低能量電子均勻分布於細胞核(源區，Source region)內向外運動射出，爾後遷移至細胞核(靶區，Target region)內造成之能量沈積(或細胞質至細胞核或細胞膜至細胞核)，再據以求得、線性能量分布、頻率平均線性能量等，及細胞S值等微劑量學參數。本研究，主要模擬兩種不同大小的細胞，將源區與靶區分別各自定義為細胞核、細胞質、細胞膜、或整個細胞。在頻率平均線性能量的評估上，若初始能量的電子射程越接近靶區的大小時，數值越大。上述之研究結果，針對單能量電子與氚放射性核種，藉由這些計算，可做為核醫藥物與環境放射性核種用於生物效應評估依據，也可依不同細胞內源區與靶區之組合，評估最有效之核醫診斷與治療。

目錄
摘要………………………………………………………………………i
誌謝………………………………………………………………………ii
圖目錄 …………………………………………………………………v
表目錄………………………………………………………………….viii
第一章 緒論 ……………………………………………………………1
1.1 前言 ……………………………………………………………1
1.2 微劑量學之歷史…………………………………………………2
1.3 文獻探討…………………………………………………………4
1.4 研究動機與目的…………………………………………………6
第二章 微劑量學之理論基礎介紹 ……………………………………8
2.1 氚之基本特性……………………………………………………8
2.2 氚鍵結在DNA…………………………………………………11
2.3 微劑量學原理…………………………………………………12
2.4 微劑量學基本參數 ……………………………………………14
2.5 細胞劑量學 ……………………………………………………18
第三章 方法與材料 …………………………………………………23
3.1 蒙地卡羅方法 …………………………………………………22
3.2 混合演算法－PENELOPE程式………………………………23
3.2.1 模擬參數…………………………………………………23
3.3 模擬狀態 ………………………………………………………26
3.4 模擬流程………………………………………………………28
3.5 PENELOPE 主程式修改………………………………………32
3.5.1 射源均勻分佈在源區……………………………………32
3.5.2 計算不同區域下之平均步長……………………………35
3.5.3 能量沈積分布輸出檔……………………………………36
3.5.4 線性能量計算方式………………………………………36
第四章 結果與討論 …………………………………………………37
4.1 粒子數 versus 粒子俓跡………………………………………37
4.2 頻率線性能量…………………………………………………45
4.3 細胞S值………………………………………………………62
第五章 結論與建議 …………………………………………………65
參考文獻 ……………………………………………………………70
附錄……………………………………………………………………73

參考文獻
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