Non-electrocardiography-gated dual-energy cardiac CT angiography for assessment of left atrial appendage thrombus

Objective:To explore the diagnosis value of a low dose,dual-energy cardiac computed tomography angiography(CTA)with non-electrocardiography-gated(non-ECG-gated)in detecting left atrial appendage(IAA)thrombus. Methods:Consecutive patients with atrial fibrillation who underwent cardiac CTA protocol(dual-energy scan for arterial phase and conventional scan for delayed phase)were prospectively enrolled.LAA lesions were proved by clinical comprehensive diagnosis,the final study included 18 cases with LAA thrombus and 48 cases with cir-culatory stasis.Quantitative parameters derived from dual-energy images were measured for the LAA lesions,including the conventional CT attenuation value(CT value),iodine concentration(IC),normalized iodine con-centration(NIC),effective atomic number values(Zeff)and energy spectrum curve slope(Slope).The differences between LAA thrombus group and circulatory stasis group were compared by independent sample t-test or Wilcoxon rank sum test regarding to the normality test.The diagnosis performance of the dual-energy parameters was assessed using receiver operating characteristic(ROC)curve analysis and area under curve(AUC). Results:All the dual-energy parameters were demonstrated significantly difference between LAA thrombus and circulatory stasis group(P＜0.05),and showed better diagnostic performance than the conventional CT value.ROC analysis revealed IC was the most predictive parameter with AUC equal to 0.836.The radiation dose in the arterial phase was(2.64±0.66)mSv. Conclusion:Dual-energy CTA scanning shows convincing diagnostic performance in detecting left atrial appendage thrombus with lower radiation dose,and may help reduce the need for delayed phase scan.