Evaluation Of Coronary Artery Calcium Score Based On Virtual Non-Contrast Scan In Dual-Layer Spectral Detector CT

Objective:To evaluate the accuracy and feasibility of coronary artery calcium score（CACS）on virtual non-contrast scan（VNC）images obtained from coronary computed tomography angiography（CCTA）with dual-layer spectral detector computed tomography（SDCT）.Methods:The data of 197 patients who underwent CCTA scan in the Second Peoples Hospital of Hefei were analyzed retrospectively,and 88 patients with CACS>0 were further analyzed.Linear regression analysis of CACS and coronary artery calcium volume（CACV）of non-contrast enhanced（TNC）images and VNC images（CACS-TNC,CACS-VNC,CACV-TNC,CACV-VNC）was performed to obtain linear regression equation and correction coefficientsλ_1AVGandλ_2AVG..CACS-VNC and CACV-VNC were corrected by the corresponding regression equation and recorded as CCACS-VNC and CCACV-VNC,respectively.Spearman correlation coefficient was used for correlation analysis and Bland-Altman plot was used for consistency test.Wilcoxon signed rank sum test was used to compare the difference between CACS-TNC and CCACS-VNC,CACV-TNC and CCACV-VNC.The volume computed tomography dose index（CTDIvol）,dose length product（DLP）and effective radiation dose（ED）of each patient were recorded and divided into VNC group（CCTA scan）and routine group（TNC scan and CCTA scan）.The ED of the two groups were compared by Wilcoxon signed rank sum test.Cohen Kappa test was used to compare the consistency of cardiovascular disease risk stratification between CACS-TNC and CCACS-VNC.Results:For the overall coronary artery,there was a strong correlation between CACS-TNC and CACS-VNC(r_s=0.952,P<0.001,λ_1AVG=2.19),CACV-TNC and CACV-VNC(r_s=0.954,P<0.001,λ_2AVG=1.93).The results of Wilcoxon signed rank sum test showed that there was no significant difference between CACS-TNC and CCACS-VNC or between CACV-TNC and CCACV-VNC（P>0.05）,and the Bland-Altman plot showed good consistency between CACS-TNC and CCACS-VNC,CACV-TNC and CCACV-VNC.In terms of single coronary artery,there was a good correlation between calcium score in TNC and VNC images（r_s=0.782,r_s=0.878,r_s=0.875,r_s=0.848,P<0.001）.There was a good correlation between calcium volume in TNC and VNC images（r_s=0.730,r_s=0.890,r_s=0.888,r_s=0.814,P<0.001）.The Bland-Altman plot showed good consistency between CACS-TNC and CCACS-VNC,CACV-TNC and CCACV-VNC.The ED in the VNC group was significantly lower than that in the routine group,and the total radiation dose was reduced by 8.1%（0.69m Sv）,and the difference between the two groups was statistically significant（P<0.001）.The consistency between CACS-TNC and CCACS-VNC was good for cardiovascular disease risk stratification,with a Kappa value of 0.862.Conclusion:VNC images based on SDCT can accurately measure CACS and be used for cardiovascular risk classification,which is expected to replace TNC scan and reduce the radiation dose of patients.