- 學位論文
使用蒙地卡羅模擬外部X光誘發I-127產生鄂惹電子的劑量討論
Analysis of radiation dosage of Auger electrons from I-127 induced by external X-ray : a Monte Carlo simulation
摘要
使用放射性標誌藥物治療腫瘤已是一種研究趨勢，而目前臨床上甲狀腺疾病相關的病人也日益增多，現階段口服131I用β粒子來殺死癌細胞為大宗。近年來也有許多文章提到用鄂惹電子方式治療，所以本研究主要透過Monte Carlo Method，來模擬外部X光誘發穩定的127I及其他放射性碘元素(123I、125I、131I)產生的Auger eletrons累積劑量作探討。 本篇主要用蒙地卡羅GATE/Geant4此套程式，設定一組35keV到130keV的光子射束，在10-120公分的不同間距中，針對一個均勻填充不同碘核種的仿甲狀腺假體分別做誘發，並依序計算其沉積的鄂惹電子能量與S值。研究結果顯示，穩定元素127I會隨著X-ray能量增加而使假體內A-J的劑量也增多，而另外幾個放射性碘元素則是在X-ray略高於碘的K層電子束縛能時會有較高的沉積能量，接著數值便下降直到約100 keV左右時才又漸升，我們也發現X光誘發的距離並不會影響鄂惹電子總量的多寡。 從此次實驗成果可得知，使用光子射束誘發127I是可以在甲狀腺假體內造成不錯的鄂惹電子能量，若於模擬階段可行，未來則能進一步做實體試驗來證明，並與常用的大劑量原子碘方式相互比較優劣差異之處，這在未來臨床上或許會多一項更適切的治療新選擇。
並列摘要
As the clinical prevalence of thyroid-related diseases increase, radioactive targeted therapy in cancer treatment is becoming a trending topic. Utilization of 131I-emitted β particles after oral ingestion is one of the more commonly adopted methods today.This study explored the efficacy and efficiency of Auger electrons in treatment with Monte Carlo simulation. The radiation dosage of Auger electron emission from 127I and other iodine nuclides following photoelectric absorption of external X-rays were evaluated. This study was performed using the GATE/Geant4 simulation platform. A series of photon beams (energy range 35 keV to 130 keV, distance range 10 cm to 120 cm) was focused to induce excitation in a thyroid-emulating phantom homogenously filled with iodine nuclides, the energy and S-value of the induced Auger electrons were calculated. The results showed the stable nuclide 127I produced increased accumulated dose within the phantom with increased external photon energy, while other iodine nuclides produced higher accumulated dose when the external photon energy is slightly above the nuclide’s K-shell binding energy, then reduced until rebounding when the energy is near 100 keV. The relation between the distance of the inducing X-ray and the total amount of Auger electrons was also found to be not significant. This study concluded the stimulation of stable 127I nuclide with X-rays of specific energy levels can effectively create a high accumulation of Auger electrons in a localized area. After proving to be feasible in simulations, biological experiments should be performed to replicate and confirm the efficacy. When compared with other current treatment regimens such as high dose 131I treatments, this may provide a new and more appropriate choice for cancer treatment in the future.
參考文獻
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