以田口式最佳化探討腹部X光攝影之影像品質評估

Optimizing the X-ray Abdomen Imaging Quality Using Taguchi Analysis

林俊銘(Jiun-Ming Lin) ； 廖娸君(Chi-Chun Liao) ； 趙明政(Ming-Cheng Chao) ； 黃文進(Wen-Chin Haung) ； 林貞琬(Chen-Wan Lin) ； 黃華思(Hwa-Si Hwang) ； 鄭凱元(Kai-Yuan Cheng)

《中華放射線技術學雜誌》 39卷2期 (2015/06) Pp. 63-71

摘要

本研究利用田口式最佳化評估診斷用X光攝影參數對腹部X光影像對比解析度之影響。使用對比解析板，經由田口L_(18)直交表做參數組合的調整對模擬假體進行曝露，再由7位放射師對影像評分，依據評分的實驗數據做參數組合的最佳化之調整，找出最佳影像品質。應用田口法L_(18)直交表改變8個控制因子後，做出18組參數配對，8個因子為Grid ratio、Filter、FOV、SID、Air gap、kVp、mAs與Exposure Class（E. C）。模擬假體是由2公分厚的平板對比解析板上面置放20層1公分厚的固態水假體所組成，對比解析板上總共鑽有144個孔洞（12×12），其中最大的直徑為4 mm；最小為0.7 mm，深度最深為15 mm；最淺為0.5 mm。最佳化S/N比定義為S/N比越大影像對比解析度愈佳。10:1 grid ratio、none filter、FOV 43×43 cm^2、SID 85 cm、noneair gap、86 kVp、32 mAs、E. C 400為最佳設計組合並驗證其結果。重要因子是kVp、filter、grid ratio及SID，並經由ANOVA驗證。最佳參數組合的曝光指數值（the logarithm of the median exposure value of the rawhistogram, lgM）為2.13，與廠商建議的2.03～2.35最佳值範圍相吻合，並不會增加病人輻射劑量，同時可獲得更佳的影像品質。

關鍵字

影像品質 ； 對比解析度 ； 曝光指數值

並列摘要

This study optimized the quality characteristic of the abdomen X-ray imaging using the Taguchi analysis. The exposed images of the contrast-detail plate phantom was graded and analyzed by 7 well trained radiographers to optimize the imaging quality characteristics. Eight operative factors of diagnostic X-ray facility were organized into 18 various combinations according to the Taguchi's L_(18) recommendation. The 8 factors were grid ratio, filter, FOV, SID, gap, kVp, mAs, and exposure class. The plate phantom was assembled by 20 layers of 1-cm-thick solid water plates on top of a customized 2-cm-thick contrast detail plain plate. In addition, the contrast detail plain plate was drilled 144 (12×12) holes and each hole had unique depth (0.5-15 mm) and diameter (0.7-4 mm), respectively. The signal to noise ratio of the optimization process was thus defined as higher-the-better to imply the optimal contrast detail of phantom images. The optimal combination was verified as 10:1 grid ratio, none filter, FOV43×43 cm^2, SID85 cm, none air gap, 86 kVp, 32 mAs and E. C400. The dominant factors were kVp, filter, grid ratio and SID verified from the ANOVA. The accompanied exposure index (the logarithm of the median exposure value of the raw histogram, lgM) was limited to 2.13 for optimal combinations of the X-ray operative factors and still laid within the recommended range (2.03-2.35) to hold the exposed dose for patients.

並列關鍵字

Imaging quality ； Contrast detail ； Exposure index