RESUMEN
Objective To study the role of monochromatic energy images from spectral CT in diagnosing X-ray negative biliary stones.Methods 32 patients who were diagnosed to have X-ray negative biliary stones were retrospectively studied.They were examined by spectral CT scanning and the spectral CT data were loaded into a spectrum analysis software.The optimal contrast-to-noise ratio (CNR) of the monochromatic energy images were exposed and the contrast ratio between the X-ray negative stones and bile on the optimal monochromatic and hybrid energy CT images were compared,respectively.The monochromatic and hybrid energy CT images for diagnosing X-ray negative biliary stones were validated by two senior radiologists based on postoperative histology.Results The corresponding KeV of optimal CNR for X-ray negative stones were not quite consistent.They were 140KeV in 19 patients,40KeV in 8 patients,53KeV,57KeV,62KeV,64KeV and 73KeV in one patient each.The contrast between the negative stones and the adjacent bile were (6.4 ±5.6) HU on hybrid energy CT images and (50.4 ±24.4) HU on optimal monochromatic energy CT images.The Eff-Z of negative stones and bile were 6.6 ± 0.6 and 7.9 ± 0.2,respectively.In our study,the diagnostic accuracy of hybrid energy CT images was 34.38％ and that of optimal monochromatic energy CT images was 78.13％.Conclusion The optimal monochromatic energy CT images were more valuable in diagnosing X-ray negative bile duct stones,which were obviously better than the hybrid energy images from traditional CT.