利用電腦斷層掃描NIPAM凝膠劑量分布

Investigating Dose Distributions for N-Isopropylacryl-Amide Gel by Using X-Ray Computed Tomography Scanning

10.6316/TRO/201522(1)41

趙璽雅(His-Ya Chao)；謝栢滄(Bor-Tsung Hsieh)；張志嘉(Chih-Chia Chang)；曾玉華(Yuk-Wah Tsang)

聚合物凝膠 ； 電腦斷層掃描儀 ； γ測試 ； Polymer gel ； Computed tomography ； Gamma test

放射治療與腫瘤學

22卷1期（2015 / 03 / 01）

41 - 50

繁體中文

目的：利用電腦斷層掃描凝膠劑量分布臨床實用性。材料與方法：使用直線加速器（Varian Clinic iX，美國）作為射源，照射NIPAM聚合物凝膠劑量計，凝膠聚合反應完成後使用 X-ray電腦斷層掃描儀（HiSpeed GE，美國）擷取切面凝膠影像，利用Matlab（The MathWorks, Natick, MA, USA）軟體分析凝膠之切面影像，比較治療計畫與NIPAM凝膠劑量計之γ測試。結果：結果呈現使用多張CT image計算影像平均CT值，可以大幅降低CT雜訊，搭配利用聚合物凝膠未照射當背景影像（Background image）減贅後，第一次實驗結果環狀假影消失γ測試由68.40%提升至 95.02%通過率。第二次實驗結果得到與TPS更為相近凝膠劑量分布，γ測試的分析結果為97.57%通過率。結論與討論：該結果表明X-ray電腦斷層掃描儀是可以應用於臨床聚合物凝膠劑量驗證計讀工具上。

Objectives: Using computed tomography (CT) scanning to evaluate the clinical applicability of intensity modulated gel dosimeter based on the dose distribution. Materials and Approaches: A Clinac iX linear accelerator (Varian, USA) was adopted as the radiation source to irradiate an N-isopropylacrylamide (NIPAM) polymer gel dosimetry. After the polymerization reaction, the gel was scanned using a HiSpeed CT scanner (GE, USA), and sliced images of the gel were analyzed using Matlab (MathWorks, Natick, MA, USA). Next, the gamma test obtained for the treatment plan and the NIPAM polymer gel were compared. Results: The results indicated that using numerous CT images to calculate the mean CT numbers of the images can substantially reduce CT noise. In addition, when the polymer gel was unilluminated and background subtraction occurred, the ring artifacts produced in the first experiment disappeared. Furthermore, the gamma test increased from 68.40% to 95.02% pass rate. The gel dose distribution yielded in the second experiment was similar to that of the treatment plan system, and the obtained gamma test was 97.57% pass rate. Discussion and Conclusion: The results showed that X-ray CT scanning can be applied to clinical polymer gel dosimeters.