This single-centre retrospective study included 400 consecutive unenhanced non-ECG-gated chest CT examinations of patients between the ages of 40 and 69 years over a period of three months. Exclusion criteria included previous cardiac intervention (coronary stent, coronary artery bypass graft or valve replacement) and repeat scans in this time period. All scans were performed using volumetric acquisitions with slice thickness of 1mm on a multislice CT scanner. The kV median and interquartile range (IQR) was 120 [120-130] and mA adjusted according to patient factors. The mediastinum window [WW: 400, WL: 40] was used for analysis. 

Coronary artery and aortic valve calcification was quantified using the Ordinal method and the Agatston score. The Ordinal method was determined by assigning a value of 1, 2 or 3 for <1/3rd artery length affected, up to 2/3rds affected and >2/3rds affected to each of the four main coronary arteries respectively. The final score represented the sum of the per-vessel values and was categorised as mild (<4), moderate (4-8) and severe (>8) disease^[5]. Aortic valve calcification was described as mild (one leaflet/punctate calcifications), moderate (two leaflets affected) and severe (three leaflets affected). Using the Agatston score, three severity groups were defined: 1-100 mild; 101-400 moderate; >400 severe disease for CAC, and <150 mild, 150-500 moderate and >500: severe for aortic valve calcification.

Data analysis included the comparison of visual score results of the Ordinal method determined by one observer and the Agatston score calculated with syngo.via (Siemens Helthineers, UK) software by a second observer. Both were blinded to the results of the other method. Spearman rank correlation coefficient was calculated to describe the relationship between these two methods of calcium score assessment.