Metoprolol (100 mg, Selokeen, AstraZeneca, London, UK) was administered orally 1 h before CT in patients with heart rates >65 beats per minute. A 64-slice single source CT system (Sensation 64; Siemens, Forchheim, Germany) with a gantry rotation time of 330 ms, acquisition time of 165 ms and voxel size of 0.4 mm3 was used to acquire standard spiral low-dose and ECG-gated coronary calcium CT images. CT parameters were 32 × 2 slices per rotation, individual detector width of 0.6 mm, 3.8-mm/rotation table feed, 120-kV tube voltage, 150-mAs tube current, with activated prospective x-ray tube modulation. Overlapping slices were reconstructed at 65% of the R–R interval using the B35f convolution kernel. Reconstructed slice thickness was 3.0 mm with an increment of 1.5 mm. The radiation exposure, estimated using dedicated software (ImPACT, version 0.99x, St. George’s Hospital, Tooting, London, UK), was 1.4 mSv in men and 1.8 mSv in women. One observer (with more than 3 years’ experience), who was blinded to the CCA and clinical data, measured the coronary calcium.