We retrospectively reviewed clinical and imaging data of 87 patients with coronary artery calcification identified during either baseline or follow-up cardiac MDCT examinations.

Clinical cardiovascular risk factors were extracted by medical record review at the times of cardiac MDCT examinations. The 10-year CHD risk based on the Framingham risk score was calculated for each patient.

Image acquisition was performed using a Brilliance 64-slice CT scanner (Philips Medical Systems, Eindhoven, The Netherlands) or a dual source 128-slice CT (Somatom Definition FLASH; Siemens Healthcare, Forchheim, Germany).

64-Slice CT scanner

• Calcium score study: Prospective ECG-gating with a detector collimation of 40×0.625 mm, a tube voltage of 120 kVp and a tube current of 55 mAs.
• CCTA: Retrospective ECG-gating with a detector collimation of 64×0.625 mm, a tube voltage of 120 kV, and an effective tube current of 400–800 mAs with ECG modulation.

Dual source 128-slice CT scanner

• Calcium score study: Prospective ECG-gating with a detector collimation of 128×0.6 mm, a tube voltage of 120 kVp and a tube current of 80 mAs using CareDose 4D.
• CCTA: Retrospective ECG-gating with a detector collimation of 128×0.6 mm, a tube voltage of120 kV, and a target tube current of 300 mA with prospective tube current modulation technique and MinDose protocol (Siemens, Germany). 

Agatston calcium score (ACS) of each patients was calculated using semi-automated software (EBW; Philips Medical Systems) with identification of calcified plaque, which was defined as areas of at least 0.5 mm² with a density ≥ 130 HU (figure 1). Each calcium volume score was also calculated by multiplication of total calcium area by slice thickness (2.5 mm for 64-slice CT or 3 mm for dual source 128-slice CT).  

Epicardial fat was defined as the adipose tissue between the surface of myocardium and the visceral layer of the pericardium. The border of epicardium was semi-automatically traced (Superior boundary: center of the right pulmonary artery; Inferior boundary:  end of the pericardial sac). EFV was quantified by calculating the total volume of the tissue showing CT density of [−190 ~ −30 HU] within the epicardium. EFV was reported in forms of cubic centimeters (cm³) and was indexed (EFVi) as body surface-area (m²). The computer software (Aquarius, TeraRecon, San Mateo, CA, USA) automatically constructed three-dimensional image of the epicardial fat (Figure 2).  

Annual changes of each ACS, volume score and EFVi was obtained by multiplication of differences between baseline and follow-up study values with “12 (months) / Interval (months) between baseline and follow-up study”.

Regression analysis was used to assess the relationship between EFVi and the coronary calcium score Logistic regression analysis was used to determine whether baseline clinical variables and EFVi are predictive of rapid plaque progression which was defined as “highest tertile”.