細胞S值與其微劑量分析之研究

Study of Cellular S Value and Its Microdosimetric Analysis

劉晉昇(Ching-Sheng Liu)

指導教授 ： 董傳中

國立清華大學/原子科學院/生醫工程與環境科學系/博士(2010年)

https://doi.org/10.6843/NTHU.2010.00024

摘要

本論文針對美國核子醫學學會MIRD委員會細胞S值報告及其應用上的限制，編寫一細胞劑量程式（Cellular Dosimetry Program, CDP），以蒙地卡羅方法計算細胞S值與線性能y值分布，並分析各輻射粒子之相對生物效應。
為了確保細胞S值計算的準確性。首先，將計算結果與MIRD委員會所發表的細胞S值比較，驗證其準確度與穩定性。對於單能量電子與阿伐粒子而言，誤差均少於1 %；放射性核種誤差大部份在2 %內，此方法的穩定度與可靠性在細胞微劑量學的運用是可以被信賴的。
線性能y值為另一項輻射指標，代表粒子在生物體內的游離能力，可視為輻射品質。輻射品質越高，其輻射生物效應越大。它同樣受輻射粒子種類、能量（射程）與細胞幾何關係等因子的影響。粒子射程對平均線性能 有很大影響力，當粒子射程與標靶大小相當時，其能量沉積最有效率，輻射品質也最高。
從較簡單的阿伐粒子，到具有能量歧離現象的電子，最後對整個放射性核種衰變能譜與硼中子捕獲治療中阿伐粒子與鋰-7重核粒子的劑量評估，將整個細胞S值與微劑量學參數做一有系統完整的研究。
本研究最主要的貢獻是完成細胞劑量計算平臺，同時提供微劑量學參數，適用於各種帶電粒子之細胞微劑量學研究。其次，是CDP程式將電子能量沉積計算的適用範圍擴展至低能量區域（為100 eV，相對於PENELOPE程式只適用於500 eV以上），並完成繁複的放射性核種細胞S值計算。第三項貢獻是評估THOR超熱中子束之有效RBE值。

關鍵字

細胞S值 ； 體內劑量 ； 醫用體內輻射劑量 ； 蒙地卡羅 ； 硼中子捕獲治療 ； 相對生物效應

並列摘要

ABSTRACT
In this dissertation, the cellular S value and lineal energy were evaluated for various charged particles, including alpha particles, electrons, and those from radionuclides and BNCT, with the MIRD cell model. To accomplish these calculations and analyze their relative biological effectiveness(RBE), Cellular Dosimetry Program (CDP) were developed with Monte Carlo simulation and the energy-range relations under the continuous slowing down approximation(CSDA).
Firstly, the calculated S values were compared with those results published in “MIRD Cellular S values” by Society of Nuclear Medicine(SNM), and their differences for alpha particles and electrons were within 1% and radionuclide mostly within 2 %, respectively.
Secondly, the lineal energy distribution were analyzed with respect to their energies, cell sizes or source-target configuration for the same situation. The S value refers to the radiation quantity within the target region. By contrast, the lineal energy was an index for radiation quality which definitely described ionizing ability within the biological system. In general, the charged particle whose range equivalent to target size possesses the most lineal energy and highest RBE within the target region.
Finally, the major contribution of this study is to build up the CDP system and carry out systematic research on cellular S values and microdosimetry for various charged particles. Especially, the radionuclides and BNCT were investigated, and the effective RBE of the THOR epithermal neutron beam was estimated for tumors and normal tissues of specified 10B concentrations.

並列關鍵字

Cellular S value ； Internal Dosimetry ； MIRD ； Monte Carlo ； BNCT ； RBE

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