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題名 | 小照野劑量計算之準確模式化研究=Accurate Modeling of Small Field Dose Calculation Algorithm |
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作者 | 賴源淳; 劉幕台; 簡聿皇; 陳苑蓉; 王愛義; 張東浩; 謝忠志; | 書刊名 | 中華放射線技術學雜誌 |
卷期 | 28:2 民93.12 |
頁次 | 頁151-159 |
分類號 | 416.36 |
關鍵詞 | 光子刀; 蒙地卡羅模擬; 百分深度劑量; 劑量剖面; X-knife; Monte Carlo simulation; PDD; Dose profile; |
語文 | 中文(Chinese) |
中文摘要 | 由於光子刀射束照野小,因此在劑量特性的量測上有其困難度,現行並無最佳的量測系統可以提供適當的量測數據以供其建立該治療計畫系統劑量計算模式所需,而使用粒子追蹤的蒙地卡羅模擬方法可以準確的計算出小照野之劑量特性,因此本研究利用蒙地卡羅方法模擬小照野之劑量特性,期能作為治療計畫建立之參考。為保證模擬所得的數據具一定的準確度,我們將進行詳細的治療用直線加速器機頭模擬,並驗證其正確性,再使用所收集到的相空間資料模擬射束通過直徑分別為3.75 mm、7.5 mm、15 mm、20 mm及30 mm之準直錐後於水中所造成之百分深度劑量及不同深度之劑量剖面,探討其有效照野及半影區。結果顯示由於增建區範圍內側向電子非平衡效應隨照野減少而增加,而增建區範圍之外假體散射隨照野增加而增加,因此百分深度劑量隨著孔徑的增加而增加。直徑為20 mm、15 mm、7 mm及3.75 mm之準直錐於深度0.3 cm處之50%有效照野分別為30.4 mm、22.4 mm、11.4 mm及5.6 mm,半影區則隨著深度增加及準直錐孔徑的增加而有增加之趨勢。蒙地卡羅模擬可以避免一般方法量測光子刀射束參數時所面臨之問題,只要透過正確之模式化,並且使用足夠多之粒子數及歷程數,便可得出正確之射束資料,其限制是需要有功能夠強大之電腦硬體方可收省時及正確之效。 |
英文摘要 | Small radiation fields are used in X-knife and measuring the related characteristics of dose is considered to be difficult. Up to now, there's no best measurement system for X-knife that can be provide us adequate data to establish a dose calculation model needed for the radiation planning (RTP) system. Monte Carlo simulation, by tracing the events of particles, can precisely calculate the dose characteristics of small radiation fields. Hence, we use this method to simulate and hope it can make some contribution in establishing such a RTP system for small fields. To ensure the accuracy of simulation data, we first perform detailed simulation for head of the linear accelerator, and verify its accuracy. The beams with known phase space data pass through different cones and their percentage depth dose (PDD), dose profile, effective field size and penumbra are studied. Our results show the smaller the cones size the more the lateral electronic disequilibrium and the larger the field size the more the phantom scatter beyond the buildup area. Therefore, PDD increase with the increment of cone size. The 50% effective field sizes at 0.3 cm are 30.4 mm, 22.4 mm, 11.4 mm and 5.6 mm for 20 mm, 15 mm, 7 mm and 3.75 mm cones. Besides, the penumbra varies with depth and cone size. Monte Carlo simulation can solve the problems encountered during traditional measurement of photon beams. All we need to do is a proper modeling process with adequate particles and events collected then correct beam data will be obtained. For the time consuming issue, a powerful hardware is needed to overcome it. |
本系統之摘要資訊系依該期刊論文摘要之資訊為主。