臺灣博碩士論文加值系統

穿透式X光管其薄靶與結構的獨特性，相較於一般傳統的反射式X光管得以輸出更高比例的特性輻射，而透過該特性輻射與相應原子序物質的作用將有助於鄂惹電子的產生。本研究的目的既是探討穿透式X光管所釋出的特性輻射與碘-127作用後所產生的鄂惹電子對於細胞劑量上的貢獻。其中本研究除了透過對穿透式X光管與鈷-60治療機之能譜與百分深度劑量的模擬，確認兩者之射源結構的正確性外，亦透過對穿透式X光管之滲漏輻射進行量測，以確保其所產生的滲漏輻射並不影響本研究細胞劑量的模擬結果。
對於穿透式X光管之滲漏輻射的量測，任何位置之滲漏輻射皆位在實驗場所背景值之範圍中，因此可判定其符合IEC 60601-2-8與SGS的報告規定，但對於輻射輸出面如F1至F4的量測位置仍具有滲漏輻射的產生。
穿透式X光管與鈷-60治療機，其能譜與百分深度劑量的Geant4蒙地卡羅模擬，其結果與實際量測值相近，並與EGS4nrc蒙地卡羅所模擬的結果以及參考文獻具有良好的一致性與準確性。因此這亦驗證了Geant4所模擬的穿透式X光管與鈷-60治療機之射源結構的正確性。此外，研究亦發現透過Geant4對能譜的模擬將可得出更優良的能量解析度。
對於細胞模型的Geant4蒙地卡羅模擬，相較於鈷-60治療機，透過穿透式X光管所釋出的特性輻射與碘-127作用後，將能產生近40倍的劑量增強效果。此外，本研究亦發現鄂惹電子對於細胞更是提供了34-42 %的劑量貢獻，因此這亦驗證了透過穿透式X光管所釋出的高比例特性輻射與碘-127作用後所產生的鄂惹電子應用於放射治療的可行性。

Since transmission X-ray tube’s thin target and unique structures, the output proportion of characteristic radiation is higher than conventional reflective X-ray tube. More Auger electron production is through the interaction between this characteristic radiation and corresponding atomic materials.
The aim of this study is to investigate the absorbed dose of Auger electron from the effect of characteristic radiation emitted by transmission X-ray tube and iodine-127 on the cellular dose. In addition, the simulation study of spectrum and percentage depth dose of the transmission X-ray tube and cobalt-60 therapy source were used to verify the correctness of geometry structures of this two sources. The measurements of leakage radiation from the transmission X-ray tube were also used to ensure that the leakage radiation generated from the transmission X-ray tube did not affect the results of cellular dose simulation.
The leakage radiation from the transmission X-ray tube at any position was located within the background value of the site, indicating that it conformed to IEC 60601-2-8 and SGS report, but for the radiation output region, such as F1 to F4 measurement positions still had leakage radiation provided.
For the Geant4 Monte Carlo simulation of spectrum and percentage depth dose of the transmission X-ray tube and cobalt-60 therapy source, the results had an excellent consistency and accuracy when compared with the results of measurements, EGS4nrc Monte Carlo simulation and the references, so there were verified that the correctness of geometry structures of the transmission X-ray tube and cobalt-60 therapy source simulated by Geant4 Monte Carlo. In addition, the study also found that the Geant4 Monte Carlo simulation of spectrum would be able to provide an excellent energy resolution.
Regards the Geant4 Monte Carlo simulated cell model, the interaction between characteristic radiation released from the transmission X-ray tube and iodine-127 would be able to produce nearly 40 times of the dose enhancement effect. In addition, the Auger electron provided a proportion of 34-42 % dose contribution to the cell, which represent the role of Auger electron in the feasibility of radiotherapy is through the interaction between the high proportions of characteristic radiation released from transmission X-ray tube and iodine-127.

致謝...i
摘要...ii
Abstract...iv
目錄...vi
表目錄...x
圖目錄...xi
第一章緒論
1.1 研究目的...1
1.2 實驗流程架構...4
1.3 研究假説...5
第二章文獻回顧
2.1X光的發現...6
2.2反射式與穿透式X光管之基本原理與差異...7
2.3鈷-60射源之基本特性與應用...11
2.4鄂惹電子(Auger electron)之發現...13
2.4.1光電效應(Photoelectric process)與共振激發(Resonant excitation) ...13
2.4.2電子捕獲(Electron capture, EC)...16
2.4.3 内轉換(Internal conversion, IC) ...17
2.5鄂惹電子之特性...18
2.6 鄂惹電子之相關研究...21
2.6.1 奈米金粒子之細胞生物研究...22
2.6.2 奈米金粒子之蒙地卡羅研究...28
第三章材料與方法
3.1 研究設備...32
3.1.1 穿透式X光管...32
3.1.2滲漏輻射(Leakage radiation)量測系統...32
3.1.2.1 平板形游離腔與電量計讀儀...32
3.1.2.2水平儀...33
3.2 穿透式X光管之滲漏輻射量測...33
3.2.1實驗場所背景值之量測...34
3.2.2X光管在進行治療時，由X光管裝配(X-ray tube assembly)所產生的滲漏輻射之限制(201.10.1.2.101)...35
3.2.2.1 對於70kVp以下（含）的操作管電壓...35
3.2.2.2對於150 kVp以下（含）的操作管電壓...37
3.2.3除X光管治療期間外，X光管裝配所產生的滲漏輻射以及不需要的輻射(Unwanted radiation)之限制(201.10.1.2.102)...38
3.2.3.1 對於70 kVp以下（含）的操作管電壓...38
3.2.3.2對於150 kVp以下（含）的操作管電壓...39
3.2.4裝有射束限制裝置(Beam limiting devices)或射束裝療器(Beam applicators)的X光管裝配，其不需要的輻射之限制(201.10.1.2.103)...40
3.2.5除X光管裝配以外的裝置所產生的輻射之限制(201.10.1.2.104)...42
3.2.6 穿透式X光管之滲漏輻射量測條件之總結...43
3.3蒙地卡羅(Monte Carlo)模擬法...45
3.3.1 Geant4蒙地卡羅模擬法...46
3.3.2模擬參數最適化...47
3.3.3穿透式X光管之幾何結構模擬...48
3.3.4鈷-60治療機之幾何結構模擬...49
3.3.5能譜模擬...51
3.3.5.1 穿透式X光管之能譜...51
3.3.5.2鈷-60治療機之能譜...51
3.3.6水假體劑量分佈模擬...52
3.3.6.1 穿透式X光管之百分深度劑量...52
3.3.6.2 鈷-60治療機之百分深度劑量...53
3.3.7細胞模型之幾何結構模擬...54
3.3.8 蒙地卡羅模擬參數之總結...56
第四章結果與討論
4.1穿透式X光管之滲漏輻射量測...58
4.1.1實驗場所背景值之量測...58
4.1.2X光管在進行治療時，由X光管裝配所產生的滲漏輻射之限制(201.10.1.2.101)...58
4.1.3除X光管治療期間外，X光管裝配所產生的滲漏輻射以及不需要的輻射之限制(201.10.1.2.102)...60
4.1.4裝有射束限制裝置或射束裝療器的X光管裝配，其不需要的輻射之限制(201.10.1.2.103)...60
4.1.5除X光管裝配以外的裝置所產生的輻射之限制(201.10.1.2.104)...62
4.2Geant4蒙地卡羅模擬...65
4.2.1 能譜模擬...65
4.2.2水假體劑量分佈模擬...73
4.2.3細胞模型之劑量模擬...75
第五章結論...78
第六章未來展望...79
參考文獻...81
 
表目錄

表一、治療型放射性核種的一般特性。...19
表二、能量為80 kVp與 6MV的光子對奈米金粒子層貼附於細胞核表面的細胞進行照射後所產生的劑量增強比。其中Total表示所有細胞結構的總劑量，且其所使用的Physics list為Geant4-DNA與Livermore所結合的物理模式。...31
表三、本研究於實驗場所背景值與穿透式X光管滲漏輻射之量測，所使用的部分條件設定。...44
表四、MCNP6，PENELOPE與Geant4蒙地卡羅模擬程式應用於微劑量學研究之差異。...47
表五、本研究於蒙地卡羅模擬所使用的部分參數設定。...57
表六、穿透式X光管鑭靶特性輻射之比較，其中皆利用Geant4所模擬的結果與J. A.Bearden的文獻數據，實際量測值與EGS4nrc所模擬的結果進行該特性輻射能量位置的比較。...66 

圖目錄

圖一、德國科學家侖琴與其妻子左手的X光影像。...6
圖二、反射式X光管之固定式陽極。...8
圖三、反射式X光管之内部結構與焦斑有效面積。(a)旋轉式陽極。 (b) 焦斑與電子之撞擊面積。...9
圖四、穿透式X光管之内部結構。...10
圖五、鈷-60的衰變能階圖。...11
圖六、光電效應與鄂惹效應。(a) 游離輻射將作用靶原子的内層軌道電子擊出。 (b) 鄂惹電子的產生。...14
圖七、重原子核的光電效應與共振激發之示意圖。(a) 當K層電子被游離後，重原子核的外層軌道將出現許多的電子空洞。 (b) 共振激發的偶極向上激發遷移。...15
圖八、電子捕獲之原理。(a)原子核外的電子被原子核所捕獲。 (b) 鈹-7的衰變能階圖。...16
圖九、内轉換之原理。(a) 進行β-衰變的母核。(b) 子核所釋出的加馬光子使原子核外的電子被擊出。...17
圖十、金-198的衰變能階圖與其β-粒子的能譜。...18
圖十一、鄂熱電子在水中的射程與線性能量轉移係數之對應曲線，其中亦説明不同放射性核種的電子射程與LET的對應關係。...19
圖十二、沿著β-粒子，鄂惹電子與α粒子的徑跡所產生的局部游離，其中的*號表示該位置的游離粒子。...20
圖十三、金、骨頭與軟組織質量衰減係數之比較。...21
圖十四、奈米金粒子研究之發表。...22
圖十五、奈米金粒子直徑的大小對輻射敏感性之影響。(a)細胞存活分率間的差異，其中(■)表示不具有任何的奈米金粒子；而(▼)、(●)與(▲)則分別表示具有14nm、50 nm與74 nm直徑大小的奈米金粒子。(b) 不同直徑大小的奈米金粒子之輻射敏感增強因子。...23
圖十六、細胞攝取奈米金粒子與細胞對輻射敏感性之研究。(a) 細胞對奈米金粒子的攝取，其中(▲)、(■)與(●)分別表示直徑大小為14 nm、50 nm與74 nm的奈米金粒子。 (b) 對於不同直徑大小的奈米金粒子，細胞對輻射的敏感性與細胞攝取奈米金粒子的數目(□)以及細胞中奈米金粒子的總重量(○)成一函數關係。...24
圖十七、介質中奈米金粒子的濃度與細胞存活分率成一函數關係。其中(●)、(▲)與(■)分別表示濃度為1 x 109、1 x 108與1 x 107 gold nanoparticles/ml的奈米金粒子，而圖中的插圖則表示細胞對奈米金粒子的攝取與介質中奈米金粒子的濃度成一函數關係。...25
圖十八、各能量的光子對細胞存活分率的影響。其中(●)表示直徑為50nm的奈米金粒子，而(■)則表示不具有任何的奈米金粒子。...26
圖十九、經治療後小鼠腫瘤的平均體積變化。其中(▲)表示未進行任何的治療；(◆)表示僅注射奈米金粒子；(●)表示僅照射250kVp的X光；(■)表示尾靜脈注射1.35 gAu/kg濃度的奈米金粒子後再利用250kVp的X光進行照射。...27
圖二十、經治療後小鼠的存活曲線。其中(●)表示未進行任何的治療，且僅注射1.35 gAu/kg濃度的奈米金粒子者無法與未進行任何治療者進行區分；(▲)表示僅照射250 kVp的X光；而(■)與(◆)分別表示尾靜脈注射1.35 gAu/kg與2.7 gAu/kg濃度的奈米金粒子後再利用250 kVp的X光進行照射。...27
圖二十一、腫瘤受照射的幾何設置説明圖，其中腫瘤内含有850個細胞並漂浮於水的懸浮液介質中。...28
圖二十二、兩種不同幾何形態的奈米金粒子在細胞中的結構。 (a) 400 nm的奈米金粒子群隨機地分佈於細胞質中。 (b) 一層厚度為300 nm的奈米金粒子層貼附於細胞核的表面上。...29
圖二十三、能量為80 kVp的單一光子在細胞各結構中所造成的總能量沉積。(a) 所使用的Physics list為Livermore的物理模式。 (b) 所使用的Physics list為 Geant4-DNA與Livermore所結合的物理模式。圖中所示的*號表示為與Control組具有統計的顯著意義。...30
圖二十四、直徑與厚度各為2 cm與0.2 cm的鉛塊。...35
圖二十五、射束限制裝置末端輻射照野之1.1與1.5倍側面尺寸的鉛塊，且兩者厚度皆為0.2 cm。...40
圖二十六、射束限制裝置，其厚度為0.1 cm。...41
圖二十七、本研究於鉛塊邊緣26 mm的位置上進行滲漏輻射的量測，其中藍色圓圈表示為PTW Markus 23343平板形游離腔，而A1-A4分別表示該游離腔的量測位置。...42
圖二十八、Eldorado 6鈷-60治療機内部構造的模擬示意圖。...50
圖二十九、鈷-60射源内部構造的模擬示意圖。...50
圖三十、穿透式X光管百分深度劑量之水假體幾何架構的模擬示意圖。...53
圖三十一、鈷-60治療機百分深度劑量之水假體幾何架構的模擬示意圖。...54
圖三十二、MDA-MB-468乳癌細胞。 (a) 實際MDA-MB-468乳癌細胞的影像，其中細胞質與細胞核分別利用了綠色與藍色的熒光染劑進行染色。(b) 蒙地卡羅之MDA-MB-468乳癌細胞的模擬結構，其中含有一層厚度為300 nm的碘-127。...55
圖三十三、對於70 kVp以下（含）的操作管電壓，X光管在進行治療時，由X光管裝配所產生的滲漏輻射之量測結果。...59
圖三十四、對於70 kVp以下（含）的操作管電壓，除X光管治療期間外，X光管裝配所產生的滲漏輻射以及不需要的輻射之量測結果，其中的插圖已將y軸的刻度進行闊大。...61
圖三十五、裝有射束限制裝置或射束裝療器的X光管裝配，其不需要的輻射之量測結果，其中的插圖已將y軸的刻度進行闊大。...62
圖三十六、除X光管裝配以外的裝置所產生的輻射之量測結果。...63
圖三十七、射束限制裝置與壓克力照射架的散射輻射對於滲漏輻射的劑量貢獻。...64
圖三十八、穿透式X光管之能譜。...68
圖三十九、穿透式X光管能譜之特定能量範圍擴展。(a) 20-30 keV之能量範圍。 (b) 30-40 keV之能量範圍。...68
圖四十、鈷-60治療機之能譜。(a) 計數面大小為2 x 2 cm2。 (b) 計數面大小為60 x 60 cm2。...71
圖四十一、G. M. Mora等人以及N. Chofor等人的鈷-60治療機能譜。 (a) G. M. Mora等人利用BEAM-EGS4蒙地卡羅所模擬的鈷-60治療機能譜，其中所使用的計數面大小為2 x 2 cm2，且其所使用的能量頻道寬度為10 keV。 (b) N. Chofor等人利用BEAM-EGS4蒙地卡羅所模擬的鈷-60治療機能譜，其中所使用的能量頻道寬度為13.3 keV。...72
圖四十二、穿透式X光管之百分深度劑量。...74
圖四十三、鈷-60治療機之百分深度劑量。...74

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