With the constant deepening of the reform in the health system and the further development of community healthcare services in China, the status and functions of outpatient emergency treatment in hospitals have been put under challenge. Judging from the actual conditions of current China, outpatient emergency treatment in hospitals still occupies a decisive position. It is imperative to transform its functions, enhance pre hospital emergency treatment, supervision of critical cases and healthcare of the general population, broaden programs of medical services, expand channels of economic benefits, and actively adapt to the development in the reform of community healthcare services.

Objective:To evaluate the feasibility of coronary artery calcium (CAC) detection, quantification and risk classification using ultra-low-dose chest CT (ULD-CT) combined with a calcium-aware algorithm.Methods:A total of 115 patients were prospectively enrolled from April to October 2022 at Zhejiang Provincial People′s Hospital, who underwent a standard calcium scoring CT (CACS-CT) scan followed by an additional ULD-CT scan. CACS-CT adopted a prospective ECG-triggered sequence scan with a tube voltage of 120 kVp, and the reconstruction algorithm with Qr36 (group CACS-CT Qr). ULD-CT adopted non-ECG-triggered high-pitch scan with a tube voltage of Sn 100 kVp, and the standard algorithm Qr36 (group ULD-CT Qr) and calcium-aware algorithm Sa36 (group ULD-CT Sa) were respectively used to reconstruct two groups of images. Taking the CAC detection of CACS-CT as a reference, the accuracy of ULD-CT for detecting CAC was calculated, and kappa was used to evaluate the agreement of CAC detection between scanning protocols. The agreement of CACS quantification between scanning protocols was assessed using intraclass correlation coefficients (ICC) and Bland-Altman plots, and the agreement of risk classification between scanning protocols was assessed using weighted kappa. Results:The CAC was found in 66.96% (77/115) of patients in CACS-CT Qr. Taking the CAC detection in CACS-CT Qr as a reference, the sensitivity of CAC detection in ULD-CT Qr and ULD-CT Sa was 96.1% and 97.4%, respectively, and the specificity was 94.73% (k= 0.902, 0.921). The CACS for ULD-CT Qr and ULD-CT Sa was lower than that for CACS-CT Qr (3.6, 6.2 vs. 8.5; P< 0.001), but strongly correlated with CACS for CACS-CT Qr ( r= 0.983, P< 0.001). The mean difference in CACS for ULD-CT Sa and CACS-CT Qr was smaller (12.33), and the agreement was better (ICC= 0.992). The agreement of risk classifications between ULD-CT Sa and CACS-CT Qr was relatively high (weighted k= 0.936), and the reclassification rate (6.08%) was relatively low. The effective radiation dose for ULD-CT was reduced by approximately 77.22% compared with that for CACS-CT. Conclusions:It is feasible to evaluate CACS using Non-ECG-triggered ULD-CT combined with a calcium-aware algorithm.