臨床光子射束之蒙地卡羅方法模擬研究

Monte Carlo Simulation of Clinical Photon Beams

林松彥(Sung-Yen Lin) ； 林招膨(Jao-Perng Lin) ； 劉幕台(Mu-Tai Liu) ； 張東浩(Tung-How Chang) ； 朱鐵吉(Tieh-Chi Chu)

《放射治療與腫瘤學》 7卷2期 (2000/06) Pp. 121-127

https://doi.org/10.6316/TRO/200007(2)121

摘要

目的：以蒙地卡羅方法模擬Siemens Primus直線加速器機頭，作為後續病人體內劑量計算之前驅步驟。
材料與方法：以EGS4為基礎的OMEGA/BEAM code為模擬計算之軟體，利用廠商提供之詳細加速器機頭構造模擬6與15 MV光子10 x 10 em2與20 x 20 em2照野。先於網鏡下設收集平面收集由加穿輪下之粒子訊息，再以此平面當作DOSXYZ之入射射源，計算在30 x 30 x 30 cm 3水假體中不同深度的劑量分佈與深度百分率劑量曲線，計算結果將與Wellhofer水假體系統量測結果比較。
結果與討論：6與15 MV模擬結果在照野內與照野外與量測結果契合良好，但於照野邊界處模擬結果略高於量測結果，但誤差皆在3 %以內。深度百分率劑量曲線6 MV模綴結果與量測結果各點誤差均在1.5 %以內. 15 MV則在1%以內。
結論：蒙地卡羅模凝結果與量測結果契合良好，因為模擬計算所需時間過長，目前不符臨床所需，可考慮以平行計算或模式化方法改善。

關鍵字

蒙地卡羅方法

並列摘要

Purpose: Monte Carlo simulation of the head of Siemens PRIMUS for the following step of patient dose calculation.
Material and Methods: EGS4 based user code, OMEGA/BEAM, was used in this study. With detailed, linac head structure, 6 and 15 MV of l0×10 cm2 and 20×20 cm2 fields were simulated. Particles were collected in scored plane, which is set under retied, and treat as phase space source in DOSXYZ. With simulating in 30 x 30 x 30 em3 water phantom via DOSXYZ, dose profiles at various depth and percent depth dose curve were gained. The simulation results will compare with Wellhofer scan system measurement.
Results and Discussion: The dose profiles of 6 and 15 MV in- and out- field fit quite well with measured data. However, simulation data encountered less than 3% larger than measured one at penumbra region. Percent depth dose curves were within 1.5% error of each point of simulation and measurement in 6 MY while within 1 %in 15 MV.
Conclusion: Monte Carlo simulation results fit quite well with Wellhofer scan data of dose profiles and percent depth dose curve. However, Monte Carlo simulation is time consuming and is not feasible for clinics so far. Parallel computing and modeling may considered for improvement.

並列關鍵字

Monte Carlo,EGS4,OMEGA/BEAM,DOSXYZ