以兩種輻射變色軟片(Gafchromic EBT film、EBT2 film)評估肺癌病人在臨床治療計畫上,所接收之劑量是否超過AAPM或ICRU的5%誤差範圍,並驗證IMRT技術。實驗分二部分:(1)以田口方法(Taguchi method)找出掃描器的最佳掃描參數,提高掃描機對於底片劑量計的能量鑑別度。以不同劑量照射EBT film和EBT2 film,以原點直線式 設計掃描器參數,再利用Photoshop、Matlab,導出劑量校正曲線,以最大斜率的那一組為最佳掃描參數。(2)治療計畫的擬定。在70公斤的壓克力假體(PMMA Phantom)和藍道假體(Rando Phantom)中模擬大約長10㎝,寬4㎝的肺癌腫瘤。比較臨床肺癌治療劑量和EBT film和EBT2 film之等劑量曲線是否吻合。比較輻射變色軟片在均質(固態水假體)和不均質假體之間的變化。結果發現最佳掃描參數EBT film:(A)resolution 96、(B)exposure -2、(C)Gamma 0.83、(D)shadow 45。EBT2 film:(A)resolution 72、(B)exposure 2(C)Gamma 0.5、(D)shadow 45。EBT film和EBT2 film在等劑量曲線中的高劑量區皆會高估約20 cGy,在低劑量區50 cGy以下之劑量不穩定,故捨棄不用,此方法使臨床肺癌治療劑量和EBT2 film劑量誤差在10 %,為容許值範圍之內。因實驗最主要就是壓克力假體的應用,EBT film和EBT2 film兩者比較之下,以EBT2 film等劑量曲線和治療計畫吻合度為高,EBT film有高估的現象,超過容許值。建議使用壓克力假體在放射治療上,以EBT2 film為劑量計較為適合。
This study evaluated the absorbed dose of lung cancer patient underwent Intensity Modulated Radiation Therapy (IMRT) using the Gafchromic EBT film and EBT2 film technique. A reliable and convincible film dose evaluation system was essential to reduce the uncertainty below 5 % according to the AAPM and ICRU recommendation. This study was accomplished two major parts (1) optimization the film scanner operating factors by Taguchi method. The optimal result was defined by a dynamic robust designation to have the largest linearity of film count verse dose curve. (2) confirmation of the dose given by the treatment planning of IMRT. In doing so, the EBT film and EBT2 film was inserted inside an indigenous PMMA phantom and Rando phantom that was made to stand for a 70 kg adult. The optimal result for the scanner parameter of EBT film was:(A) resolution set as 50, (B) exposure set as -2, (C) Gamma set as 0.83, (D) shadow set as 30. The optimal result for the scanner parameter of EBT2 film was: (A) resolution set as 72, (B) exposure set as 2, (C) Gamma set as 0.5, (D) shadow set as 45. The derived integrated error was below 10 % in comparing the IMRT given dose and the EBT film derived dose. The EBT2 film was superior to the EBT film. Therefore, the EBT film dose system can provide convincible result in verifying the IMRT treatment planning with PMMA phantom.