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研究生:紀金輝
研究生(外文):Jin-Huei Ji
論文名稱:蒙地卡羅方法於臨床光子射束劑量分佈研究
論文名稱(外文):A Monte Carlo Study of Dose Distributions in Clinical Photon Beam
指導教授:趙敏趙敏引用關係楊世能楊世能引用關係
指導教授(外文):Min ZhaoShi-Neng Yang
學位類別:碩士
校院名稱:中臺科技大學
系所名稱:放射科學研究所
學門:醫藥衛生學門
學類:醫學技術及檢驗學類
論文種類:學術論文
論文出版年:2007
畢業學年度:95
語文別:中文
論文頁數:79
中文關鍵詞:OMEGA/BEAM程式劑量計算蒙地卡羅模擬
外文關鍵詞:OMEGA/BEAM programdose calculationMonte Carlo simulation
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中文摘要
近年來,蒙地卡羅方法廣泛地用於放射治療相關之劑量計算,作為評估一般商業化治療計畫系統劑量計算準確性之工具。本研究為應用OMEGA/BEAM程式所建構,適用於醫用直線加速器的蒙地卡羅系統,其中需要有正確的直線加速器治療機頭之幾何結構參數與入射電子射束參數後才能成功建構,因此取得機頭幾何結構參數後,入射電子射束參數的調整便顯得相當重要。本研究分析不同入射電子射束能量與入射電子射束寬度於射出之光子射束劑量分佈之表現,訂定其入射電子射束參數最佳化設定流程,以找出最佳入射電子射束參數,並驗證其產生射束之分佈。再者,利用此蒙地卡羅系統與治療計畫系統評估臨床頭頸部病患之劑量分佈情形,尤其比較兩者於空腔界面處之劑量差異,並分析其結果。
Abstract
The Monte Carlo method has been widely used for modeling linear accelerators in medical physics currently. The Monte Carlo simulation can provide a more accurate dose calculation than those form TPS especially for heterogeneous media and/on interface. Establishment of the linac Varian Clinac 21EX component module has been setup by the code OMEGA/BEAM. Two important parameters, beam energy and spot sizes of incident electrons which will affect dramatically the dose distribution were decided firstly in this study. We have proposed a method to derive these two parameters by comparing the dose distribution between the results form Monte Carlo method and IC-10 ion chamber. Subsequently, we have also used Monte Carlo method to simulate/calculate the dose distribution for a head and neck cancer patient and compared the results form the TPS.
目錄 頁次
中文摘要................................................................................................................I
Abstract................................................................................................................II
目錄 ...................................................................................................................III
圖目錄 ................................................................................................................V
表目錄..................................................................................................................X
第一章 前言.......................................................................................................1
1.1 研究背景................................................................................................1
1.2 研究目的................................................................................................2
1.3 論文架構................................................................................................2
第二章 文獻回顧.................................................................................................3
2.1 OMEGA/BEAM程式建構直線加速器模擬系統.................................3
2.2 臨床光子射束之表現............................................................................4
第三章 材料與方法.............................................................................................7
3.1蒙地卡羅方法.........................................................................................7
3.1-1亂數..............................................................................................9
3.1-2蒙地卡羅演算法基本原理.........................................................9
3.2 OMAGE/BEAM程式介紹...................................................................12
3.2-1 BEAMnrc程式介紹...................................................................14
3.2-2 BEAMDP程式介紹...................................................................25
IV
3.2-3 DOSXYZnrc程式介紹..............................................................27
3.2-4變異縮減技巧...........................................................................33
3.3直線加速器治療機頭的模擬...............................................................37
3.3-1治療機頭構造簡介...................................................................37
3.3-2治療機頭的模擬.......................................................................40
3.3-3理想模擬參數之設定...............................................................44
3.4 驗證臨床劑量之差異..........................................................................48
3.4-1 CT影像轉至DOSXYZnrc程式假體之設定.............................48
3.4-2臨床劑量之模擬.......................................................................49
第四章 結果與討論...........................................................................................51
4.1 理想模擬參數設定之結果..................................................................51
4.2 直線加速器模擬與產生射束之驗證結果..........................................56
4.3 治療計畫系統與蒙地卡羅法之劑量驗證結果..................................71
第五章 結論.......................................................................................................74
參考文獻.............................................................................................................76
V
圖目錄 頁次
圖3-1 蒙地卡羅法與一般實驗方法之比較示意圖..........................................8
圖3-2 蒙地卡羅方法示意圖..............................................................................8
圖3-3 蒙地卡羅演算法之輻射粒子遷移流程圖............................................11
圖3-4 EGSnrc程式流程圖[23]..........................................................................13
圖3-5 BEAMnrc程式之圖形操作介面.............................................................17
圖3-6 BEAMnrc程式流程圖.............................................................................17
圖3-7 治療機頭元件模組之選擇....................................................................18
圖3-8 SLABS模組幾何意示圖.........................................................................18
圖3-9 CONS3R模組幾何意示圖......................................................................19
圖3-10 FLATFILT模組幾何意示圖..................................................................19
圖3-11 CHAMBER模組幾何意示圖................................................................20
圖3-12 MIRROR模組幾何意示圖....................................................................20
圖3-13 JAWS模組幾何意示圖.........................................................................21
圖3-14 選擇作用截面示意圖..........................................................................21
圖3-15 直線加速器機頭元件的幾何結構參數輸入圖;以靶為例..............23
圖3-16 BEAMnrc之模擬加速器機頭運跑參數輸入圖...................................23
圖3-17 射源參數設定輸入圖,如選用徑向強度為高斯分布之單能量射束,能量為6.1MeV、入射電子射束為0.15cm,朝z軸方向射入........24
VI
圖3-18 建立編譯執行檔..................................................................................24
圖3-19 BEAMDP程式之圖形操作介面,可分析phase space檔案的各項資訊..............................................................................................................26
圖3-20 DOSXYZnrc程式流程示意圖..............................................................29
圖3-21 DOSXYZnrc程式之圖形操作介面......................................................29
圖3-22 DOSXYZnrc程式主要運跑參數設定圖..............................................31
圖3-23 DOSXYZnrc程式採用dsurround參數,減少模擬計算時間的幾何切割示意圖[27]...........................................................................................31
圖3-24 一般自定假體的參數輸入圖..............................................................32
圖3-25 入射射束參數設定圖,以phase space檔案為入射射源為例,如XYZ軸各中心點座標為0,0,0、射源至中心點的距離為0公分............32
圖3-26 醫用直線加速器構造圖......................................................................39
圖3-27 治療機頭結構意示圖..........................................................................39
圖3-28 模擬直線加速器機頭與其產生之射束驗證之流程圖......................47
圖3-29 穿透劑量模擬流程圖..........................................................................50
圖4-1 使用入射電子射束能量6.1MeV,入射電子射束寬度為0.03公分與0.21公分之模擬計算40×40 cm2照野之百分深度劑量曲線圖.......53
圖4-2 模擬不同能量於10公分深度之百分深度曲線值,虛線為實際量測值..............................................................................................................53
VII
圖4-3模擬不同入射電子射束寬度參數於1.5公分深度之劑量分佈剖面圖..............................................................................................................54
圖4-4 模擬計算不同入射電子射束能量之劑量分佈剖面圖,其FHWM固定為0.15公分........................................................................................54
圖4-5 不同入射電子射束寬度參數模擬計算劑量分佈剖面之評分統計圖55
圖4-6 6MV光子於10×10 cm2照野於水假體內之模擬計算與實際測量值之百分深度劑量比較圖.............................................................................58
圖4-7 6MV光子於10×10 cm2照野之增建區之百分深度劑量曲線圖,可看出蒙地卡羅之模擬計算值與markus 平板型游離腔之測量值相當符合..............................................................................................................58
圖4-8 6MV光子於20×20 cm2照野於水假體內之模擬計算與實際測量值之百分深度劑量比較圖.............................................................................59
圖4-9 6MV光子於20×20 cm2照野之增建區之百分深度劑量曲線圖,可看出蒙地卡羅之模擬計算值與markus 平板型游離腔之測量值相當符合..............................................................................................................59
圖4-10 6MV光子於40×40 cm2照野於水假體內之模擬計算與實際測量值之百分深度劑量比較圖.........................................................................60
圖4-11 6MV光子於40×40 cm2照野之增建區之百分深度劑量曲線圖,可看出蒙地卡羅之模擬計算值與markus 平板型游離腔之測量值相當符合..........................................................................................................60
VIII
圖4-12 6MV光子於10×10 cm2照野之深度1.5公分處之模擬計算與實際測量之比較結果.........................................................................................61
圖4-13 6MV光子於10×10 cm2照野之深度5公分處之模擬計算與實際測量之比較結果.........................................................................................62
圖4-14 6MV光子於10×10 cm2照野之深度10公分處之模擬計算與實際測量之比較結果.........................................................................................62
圖4-15 6MV光子於10×10 cm2照野之深度20公分處之模擬計算與實際測量之比較結果.........................................................................................63
圖4-16 6MV光子於10×10 cm2照野之深度30公分處之模擬計算與實際測量之比較結果.........................................................................................63
圖4-17 6MV光子於20×20 cm2照野之深度1.5公分處之模擬計算與實際測量之比較結果.........................................................................................64
圖4-18 6MV光子於20×20 cm2照野之深度5公分處之模擬計算與實際測量之比較結果.........................................................................................65
圖4-19 6MV光子於20×20 cm2照野之深度10公分處之模擬計算與實際測量之比較結果.........................................................................................65
圖4-20 6MV光子於20×20 cm2照野之深度20公分處之模擬計算與實際測量之比較結果.........................................................................................66
圖4-21 6MV光子於20×20 cm2照野之深度30公分處之模擬計算與實際測量之比較結果.........................................................................................66
IX
圖4-22 6MV光子於40×40 cm2照野之深度1.5公分處之模擬計算與實際測量之比較結果.........................................................................................67
圖4-23 6MV光子於40×40 cm2照野之深度5公分處之模擬計算與實際測量之比較結果.........................................................................................68
圖4-24 6MV光子於40×40 cm2照野之深度10公分處之模擬計算與實際測量之比較結果.........................................................................................68
圖4-25 6MV光子於40×40 cm2照野之深度20公分處之模擬計算與實際測量之比較結果.........................................................................................69
圖4-26 6MV光子於40×40 cm2照野之深度30公分處之模擬計算與實際測量之比較結果.........................................................................................69
圖 4-27 蒙地卡羅模擬與商業用治療計畫系統及實際量測於固態水假體中劑量分佈曲線.....................................................................................73
圖 4-28 單一開放照野之等劑量曲線分佈圖,右圖為蒙地卡羅模擬,左圖為治療計畫系統.....................................................................................73
X
表目錄 頁次
表3-1 OMEGA/BEAM主要程式及簡介..........................................................13
表3-2模擬治療機頭之各元件模組列表.........................................................43
表3-3模擬相關運跑參數之設定[28]...............................................................43
表3-4蒙地卡羅模擬CT假體中CT number對應之相對物理密度..................50
表4-1百分深度劑量於蒙地卡羅模擬與實測值之百分誤差.........................61
表4-2 6MV光子於10×10 cm2照野之不同深度的劑量曲線之百分誤差與差異度............................................................................................................64
表4-3 6MV光子於20×20 cm2照野之不同深度的劑量曲線之百分誤差與差異度............................................................................................................67
表4-4 6MV光子於40×40 cm2照野之不同深度的劑量曲線之百分誤差與差異度........................................................................................................70
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