能谱CT单能量成像诊断胆道系统X线阴性结石

Monochromatic energy images from spectral CT in diagnosing X-ray negative biliary stones

目的探讨能谱cT单能量成像对胆道系统x线阴性结石的诊断价值。方法回顾性分析解放军第117医院收治的32例已确诊的x线检查阴性的胆道系统结石患者能谱CT扫描图像。应用能谱图像后处理软件获得阴性结石的最佳对比噪声比（CNR）对应的单能量图。分别测量单能量图与混合能量图中结石与周围胆汁的对比度，并进行比较分析。由2位资深医师回顾性分析每例患者的混合能量图和单能量图，并与手术结果作对比。结果本组患者阴性结石的最佳CNR对应的KeV并不完全相同，其中140KeV患者为19例，40KeV为8例，53KeV、57KeV、62KeV、64KEY和73KeV各为1例。混合能量图和最佳单能量图中阴性结石与胆汁的对比度分别为（6．4±5．6）HU和（50．4±24．4）HU。阴性结石和胆汁的有效原子序数（Eff-Z）分别为6．6±0．6和7．9±0．2。本组混合能量图组的诊断准确率为34．4％，最佳单能量图的诊断准确性为78．1％。结论单能量图在诊断X线阴性结石方面具有较高的价值，明显优于传统CT的混合能量图。

Objective To study the role of monochromatic energy images from spectral CT in diag- nosing X-ray negative biliary stones. Methods 32 patients who were diagnosed to have X-ray negative bili- ary stones were retrospectively studied. They were examined by spectral CT scanning and the spectral CT da- ta were loaded into a spectrum analysis software. The optimal contrast-to-noise ratio （CNR） of the mono- chromatic 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 radio- logists 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 va- luable in diagnosing X-ray negative bile duct stones, which were obviously better than the hybrid energy ima- ges from traditional CT.