輻射變色軟片在加馬刀劑量到量的應用

Study of Radiochromic Film Dosimetry on Gamma Knife

陳為立(Wei-Li Chen) ； 李秀文(Hsiu-Wen Lee) ； 林威廷(Uei-Tyng Lin) ； 李玉麟(Marshall Yl Lee) ； 顏上惠(Sang-Hue Yen) ； 任益民(Yee-Min Jen) ； 許世明(Shih-Ming Hsu)

《中華放射線醫學雜誌》 32卷1期 (2007/03) Pp. 9-15

摘要

探討輻射變色軟片偵測輻射之特性，包括軟片反應與時問關係、劑量線性度、能量依存度及角度依存度；並臨床應用於測量加馬刀之劑量輸出因子，亦與蒙地卡羅模擬計算結果進行分析比較。
本研究所使用的加馬刀為Leksell-B型(Leksell Gamma Knife Type B)、輻射變色軟片為MD-55,蒙地卡羅電腦模擬軟體則採用○MEGA/BEAM程式。利用核能研究所國家游離輻射標準實驗室(National Radiation Standard Laboratory)銫－137及X光機與陽明大學鈷－60作為本研究校正MD-55軟片之輻射源。使用蒙地卡羅法進行假體內劑量理諭計算，再以具有高度空間解析度的輻射變色軟片進行加馬刀輸出因子實際測量，驗證計算及治療計畫的正確度。
對於加馬刀準直頭盔孔徑為18、14及8mm的輸出因子，其輻射變色軟片劑量測定術及OMEGA/BEAM蒙地卡羅模擬程式與Elekta提供的數值皆在實驗誤差範圍內，但4mm輸出因子的量測值與Elekta提供的數值比較，低了2%。
研究結果顯示對於立體定位放射手術加馬刀的劑量品質確認和治療劑量的輸出，輻射變色軟片提供了精確的量測工具。

並列摘要

This article explored the properties of radiochromic films in monitoring radiation covering the relationships of time and film reaction, dosimetry linearity, energy dependency and angle dependency. The films were clinically applied in measuring the output dose factors of gamma knife; furthermore, the results were compared with those of the Monte Carlo simulations.
This experiment used the Leksell B (Leksell Gamma Knife Type B) gamma knife, MD-55 radiochromic films and the Monte Carlo OMEGA/BEAM simulation program. In this experiment, the Cs-137 radioactive source and the x-ray machine used were from the National Radiation Standard Laboratory (NRSL) and the Co-60 radioactive source was from the National Yang-Ming University. The Monte Carlo method was used to calculate the in-phantom dosimetry and then the measurements of gamma knife output factors were performed with the radiochromic films with high spatial resolutions to verify the accuracy of the calculations and treatment plans.
For the output factors of the 18, 14 and 8 mm gamma knife collimator helmet, the respective results from the radiochromic film measurements, Monte Carlo OMEGA/BEAM simulations and Elekta were all within experiment deviations, but for the 4 mm output factor, the measurement value was 2% lower compared with Elekta's value.
The results showed that the radiochromic films did make an explicit measurement instrument for the dosimetry quality verification and the treatment output of the 3-D positioning radiation surgery gamma knife.