双源CT双能量虚拟平扫技术在胆系疾病诊断中的价值

目的探讨第二代双源CT（DSCT）双能量虚拟平扫技术在胆系疾病诊断中的应用价值。方法回顾性分析58例病理或临床治疗证实的胆系结石、息肉或肿瘤患者的DSCT影像资料。所有患者行DSCT腹部常规平扫、动脉期双能量扫描、门静脉期及延迟期常规增强扫描后，利用LiverVNC软件处理得到动脉期虚拟平扫图像，比较虚拟平扫和常规平扫的图像质量、病灶检出率、平均CT值、信噪比（SNR）及辐射剂量。结果虚拟平扫图像质量有所下降（P〈0．05），但对于病灶的显示仍能满足临床诊断要求；尤其对于阴性胆结石（病理提示为胆固醇结石或混合性结石）的显示，反而明显优于常规平扫。虚拟平扫图像的噪声低于常规平扫，SNR明显高于常规平扫（P〈0．05）；在阳性结石、息肉和肿瘤等病变检出中，结合增强扫描，二者的检出率无明显差异（分别为100％、88．9％、90．9％），在胆系阴性结石中，虚拟平扫的检出率明显高于常规平扫（分别为94．7％、52．6％）；虚拟平扫的总CT容积剂量指数（CTDIv01）和总剂量长度乘积（DLP）均低于常规平扫（P〈0．05），分别降低了39．4％、34．3％。结论DSCT动脉期虚拟平扫具有良好的图像质量，对病变的检出率高，尤其对阴性胆结石的显示有特殊优势，并且降低了辐射剂量，有望取代常规平扫。

Objective To assess the value of the virtual non-contrast （ VNC ） of the second-generation dual-source computed tomo-graphy （ DSCT ） in the diagnosis of biliary tract disease. Methods The image data of 58 patients proved biliary tract disease by pathology or clinical treatment were analyzed in the study. The true non-contrast CT （ TNC ） , the venous phase and the delay phase were scanned in a single-energy acquisition mode and the arterial phase was scanned in a dual-energy acquisition mode.The VNC images were derived from the arterial phase data by the liver virtual non-contrast software.The image quality, the lesion detection sensitivity, the mean CT values, the signal noise ratio, the radiation dose of volume CT dose index （ CTDIvol ） and the dose length product （ DLP ） were compared between the TNC and VNC. Results Compared with the TNC, the image quality scores of VNC was poorer, which could meet the diagnostic requirements in clinical. The VNC image had the higher sensitivity for the detection of cholesterol gallstone to our surprise. The image noise of VNC was lower than TNC, and the SNR of VNC was higher than TNC （ P〈0.05 ） .The TNC and VNC image had the same sensitivity for the detection of cholochrome cholelith, polyp of gallbladder and biliary tract tumor （ 100%, 88.9%, 90.9%, respectively ） , but the VNC image was more sensitive for the detection of cholesterol gallstone than TNC （ 94.7%, 52.6%, respectively ） . The total radiation dose of VNC was lower than TNC （ P〈0.05 ） . Compared with TNC, the value of total CTDIvol and DLP in VNC were significantly reduced by 39.4% and 34.3%, respectively. Conclusion The VNC images derived from the arterial phase has the advantages of good image quality, high detection sensitivity, and low scanning dose, which may replace the TNC in the future.