利用田口方法找出256切CT解析度最佳化設定

Optimizing the Imaging Quality of 256-Slice CT Acquisition Protocol Using the Taguchi Analysis

陳欣妤(Hsin-Yu Chen) ； 李季達(Gi-Da Li) ； 陳啟昌(Chi-Chang Chen) ； 潘榕光(Lung-Kwang Pan)

《台灣應用輻射與同位素雜誌》 13卷1期 (2017/03) Pp. 1433-1440

摘要

本研究應用田口方法找尋腹部電腦斷層掃描中各項參數的最佳化組合，研究主要是以線對假體影像解析度配合專家評分系統進行。本實驗利用PMMA (Polymethylmethacrylate) line group 假體。根據田口方法，採用直交表設計，選定可能影響電腦斷層影像解析度作為研究因子，選定mAs、kV、thickness 和filter，各有兩個變動水準，Level 1: 200 mAs、100 kV、1 mm thickness 和filter smooth; Level 2: 250 mAs、120 kV、2 mm thickness 和filter sharp，掃描32 次，依據臨床上醫師判讀影像之標準，將每一組影像都重組成5 mm，且影像放大倍數為原始影像大小之兩倍，在機器端，讓三位臨床資歷五年之放射師進行評分，並進行分析驗證，取得最佳化調整參數。由評分資料分析與變異數分析(ANOVA)，最佳化調整參數為mAs: 200、kV: 120、thickness: 1mm、filter: sharp。本實驗中影響誤差之因素為將每一組影像都重組成5 mm，這也造成實驗誤差產生；但可藉由田口方式將評分結果找出各項參數之間的相互關係，以達到不同參數電腦斷層攝影影像最佳化之條件設計，以有效提升攝影影像之品質。將本實驗田口_8L SNR 大於49 以上、SD 最小之值，共有三組與臨床上用於患者的條件進行驗證。由此判定田口第三組(最佳化調整參數)為影像之最佳參數組合，進行驗證之結果，顯示其再現性佳，有效提升影像品質。

關鍵字

電腦斷層掃描儀 ； 田口最佳化方法 ； 變異數分析法

並列摘要

The CT scanning protocol for patients undergone abdomen examination was optimized according to Taguchi analysis and an indigenous line-paired flat phantom. The line-paired flat phantom was made by PMMA (Polymethylmethacrylate) and the major analytical method was setup according to Taguchi's recommendation. Accordingly, eight combinations of four factors were assigned in operating the CT scanning. The four factors were kVp, mAs, thickness and filter; furthermore, each was assigned 2 levels, respectively to scan the PMMA flat phantom in obtaining the optimal result. Each combination of the CT scan protocol was repeated four times to ensure the reproducibility that was also an essential data in running the ANOVA. The scanned imaging was scored by three well-trained radiologists to reduce the biased judgements. This is required for confirming the 95% confidence level of the optimal results. The optimal results was verified as 120 kVp, 200 mAs, 1 mm thickness and sharp filter for CT scanning of the abdomen region. The major uncertainty of the optimization process still came mostly from the staffs' subjective judgements in grading the imaging quality of CT scanning. However, the Taguchi's analysis was successfully in defining the correlation among individual factors and the cross interactions between any two factors. The optimal result was verified and compared to three conventional combination of CT abdomen scanning. The optimal combination of CT scanning protocol was proved to enhance the imaging quality of CT scanning.

並列關鍵字

Computer Tomography ； Taguchi Optimization Method ； Variance Analysis