利用田口方法最佳化電腦斷層影像之品質特性

Optimizing Computed Tomography Image Quality Characteristics Using Taguchi Methodology

劉家昇(Jia-Sheng Liu)；謝栢滄(Bor-Tsung Hsieh)；廖兆旺(Zhao-Wang Liao)；葉治浩(Zhi-Hao Ye)；李政君(Zhen-Jun Li)

電腦斷層 ； 田口方法 ； 影像品質特性 ； 參考劑量限值 ； Computed Tomography ； Taquchi Methodology ； Image Quality Characteristics ； Reference Dose Limits

台灣應用輻射與同位素雜誌

11卷2期（2015 / 06 / 01）

1095 - 1106

繁體中文

現今電腦斷層已成為醫學診斷重要的檢查工具，影像品質與相關輻射劑量也更加受到重視，因此本研究目的是利用田口方法最佳化評估電腦斷層參數設定，使用電腦斷層專用校正假體，掃描對比細分元件，經由三位放射診斷專科醫師針對對比細分影像之解析度及影像品質評分，找出最佳化組合參數，並參照輻射醫療暴露品質保證標準及參考劑量限值，再找出最適化組合參數。數據結果經由變異分析後，顯示最佳化組合參數為管電壓140kVp、掃描厚度7mm、掃描照野25cm、管電流250mA、電腦斷層劑量指引CTDI 84.5mGy，最適化組合參數為管電壓120kVp、掃描厚度3mm、掃描照野35cm、管電流250mA、CTDI 26.7mGy，輻射劑量大幅降低68.5%。為避免專家評分方法因人為不客觀因素，導致研究結果的可信度降低，因此選擇再以電腦斷層影像處理軟體ROI（Region of Interest）測量對比細分CT值及壓克力背景CT值標準誤差，經由田口方法之操作窗型S／N（訊雜比）找出最佳化及最適化組合參數，來驗證專家評分方法的可信度，結果證明有相同的最佳化組合參數，兩種方法線性回歸分析的相關係數（R2）高達0.9672，驗證專家評分是可信賴的方法。

Computed Tomography(CT) has now become an important medical diagnostic checking tool, image quality and dose-related and more attention, so the purpose of this study is to optimize the CT parameter settings via the Taguchi method, using CT specific correction phantom, scanning contrast segments of image via three diagnostic radiology specialist for image resolution and contrast of the image segmentation quality scores, find the optimal combination of parameters, and with reference to the radiation exposure of medical quality assurance standards and reference dose limits, and then find the appropriate combination of parameters . Results data via ANOVA analysis, display the optimal combination of parameters for the tube voltage 140kVp, scanning the thickness of 7mm, scanning FOV (field of view) 25cm, tube current 250mA, CTDI (computed tomography dose index) 84.8mGy, the appropriate combination of parameters for the tube voltage 120kVp, scanning the thickness of 3mm, scan FOV 35cm, tube current 250mA, CTDI 26.7mGy, significantly reducing the radiation dose of 68.5%. To avoid Experts scores due to human factors is not objective, reducing the credibility of the results, so choose then computed tomographic image processing software circle ROI (Region of Interest) to measure CT number (Hu) of the contrast detail element and the standard error of the CT number of acrylic phantom background, via the Taguchi method of operating window type S/N (signal-noise ratio) to find the optimal and appropriate combination of the parameters to verify the credibility of the expert scoring method, the results show the same combination of optimal parameters, two methods via Linear regression analysis of the correlation coefficient (R2) up to 0.9673, Verification is reliable expert scoring method.