双源CT双能量虚拟平扫在上腹部不同扫描时期的应用研究

Application study of different periods of dual- source CT dual- energy virtual non- contrast in the upper abdomen

目的评价双源CT上腹部动脉期、门静脉期双能量虚拟平扫(VNC)的图像质量和辐射剂量。方法对200例患者行上腹部CT平扫加增强扫描,常规平扫(CNC)采用单能模式,动脉期与门静脉期采用双能模式,选择Liver VNC应用程序,获得动脉期和门静脉期两期虚拟平扫图像,对比分析CNC、VNC图像质量评分、平均CT值、信噪比(SNR)、病灶检出率及辐射剂量。结果 VNC图像质量评分低于CNC,两期VNC图像质量评分无统计学差异。VNC图像中除了脾脏及腹膜后脂肪的CT值、SNR及胆囊的SNR与CNC无统计学差异,其他感兴趣区(ROI)的CT值、SNR均与CNC有统计学差异(P<0.05);动脉期VNC肾脏CT值低于门静脉期VNC,动脉期VNC腹主动脉CT值高于门静脉期VNC,其余两组感兴趣区的CT值、SNR无统计学差异。CNC、两期VNC图像的病灶检出率差异无统计学意义(P>0.05),门静脉期VNC对病灶检出率高于动脉期VNC。双能量增强扫描的辐射剂量低于常规平扫(P<0.05),动脉期、门静脉期之间无差异;如减少常规平扫,受检者接受的有效辐射剂量可减少38.73%。结论上腹部VNC不仅能够满足影像诊断的需要,同时减少了辐射剂量,门静脉期VNC的图像质量评分及病灶检出率更接近于CNC。

Objective To estimate the image quality and radiation dose of arterial and portal phase of dual- energy virtual non- contrast（ VNC） in the upper abdomen. Methods Abdominal CT conventional and enhanced scans were performed in 200 patients with suspected abdominal lesions by using dual- source CT. The single energy mode was performed on the conventional non- contrast（ CNC）,while dual- energy mode was performed on arterial and portal phase. The liver VNC software was used to reformat the virtual non – contrast CT with at arterial and portal phase. The image quality score,mean CT value,signal to noise ratio（ SNR） and radiation dose for arterial phase VNC,portal phase VNC and CNC imaging were compared resepectively. Results The image quality score of VNC was lower than that of CNC. No significant differences were observed between arterial phase VNC and portal phase VNC. There are no significant difference in CT value,SNR for spleen,fat and gallbladder SNR,while the result was significantly opposite in other regions of interest（ ROI）. A significant difference was also observed in CT value between arterial phase VNC and portal phase VNC and in SNR of the kidney and aorta（ P〈 0. 05）. No significantly difference was observed in the lesion detection rate between VNC and CNC（ P〈 0. 05）. Radiation dose was significantly lower in single enhanced scan than in CNC（ P〈 0. 05）. No significantly was found in the radiation dose between arterial phase VNC and portal phase VNC. The radiation dose could reduce 38. 73% without CNC. Conclusion VNC scanning can meet the needs of clinical diagnosis and reduce radiation dose. And the portal phase VNC image quality score and detection rate of lesions are closer to CNC.