利用田口方法探討腹部X光攝影條件之最佳化

Optimizing Photographic Conditions for Abdominal X-rays Via the Taguchi Methodology

目的：現今放射領域中，一般X光影像已經成為診斷不可或缺的輔助工具，影像品質及相關劑量越來越受重視，因此本研究的目的是利用田口方法L9（34）模擬腹部X光影像品質最佳化的條件。方法：本研究使用壓克力雙假體並量測其圓球假體及空心圓柱假體來模擬類似腹部空氣與軟組織，應用望大公式（Larger the better）訊雜比（signal to noise ratio）越大越好之特性，找出最佳化參數組合後再分析是否因條件的改變會影響原本廠商所設定的條件。結果：由變異數分析及驗證實驗結果，顯示最佳化參數組合是管電壓（kVp）為70，管電流（mAs）為30，照野大小（FOV）為14×17（in2），放射源與影像接收器的距離（SID）為80cm。結論：本研究運用田口方法，不僅可節省實驗耗費時間及次數，又可達到最佳化設定的結果，藉著調整影像後處理的功能來加強空氣與軟組織的影像對比，對照原本廠商所給的條件，結果發現不僅真正可以降低病人管電流（mAs）的劑量高達33％，也符合ALARA精神，至於射源與影像接收器的距離（SID）方面也減少了20％，可以減少影像失真又增加影像的品質，此最佳化參數組合不但降低原本廠商設定條件的輻射劑量，相對地影像品質也符合我們的要求。

Purposes: General radiologic images are an essential technique in diagnostic radiology. Image quality and the relative dose of general radiologic images are thus areas of interest. Methods: This study used Taguchi method L9(34) to optimize the operative parameters in abdominal X-rays to achieve better images from a practical viewpoint. An acrylic dual phantom was adopted in this work because the pellet prosthesis and hollow cylindrical phantom had similar responses to air and tissues in the actual examination and a higher SNR; the conditions changed and affected the results because the hospital had set the conditions. Results: Based on ANOVA, the experimental results showed that the optimal parameter settings were as follows: kVp, 70; mAs, 30; FOV, 14 inches x 17 inches; and SID, 80. The reconstruction filter for smooth and ring artifact suppression was weak and verified based on ANOVA. Conclusions: The optimal setting had a superior SNR or a lower dose to the original setting. Using Taguchi method L9(34) not only minimized the experimental frequencies, but also lowered the exposed dose in the actual examination.