Martin J. Willemink
• The presence or absence of coronary artery calcium in asymptomatic individuals is a robust measure of subclinical atherosclerosis, allowing for risk reclassification for the primary prevention of atherosclerotic cardiovascular events.
• Coronary artery calcium scoring is recommended in asymptomatic adults at intermediate cardiovascular risk. In select cases of adults with low-to-intermediate risk coronary artery calcium may be used to further evaluate risk.
Coronary artery calcium has shown to be a strong predictor of the long-term risk for atherosclerotic cardiovascular disease in asymptomatic individuals. Coronary artery calcium can be quantified with a non-contrast CT scan. Coronary artery calcium can be used to reclassify asymptomatic individuals at intermediate cardiovascular risk. The absence of coronary artery calcium on a CT scan is a strong marker for identification of individuals at very low 10-year risk. Elevated coronary artery calcium scores indicate that the individual is likely to benefit from treatment.
• Reducing the tube potential to 100 kVp results in a substantial radiation dose reduction. However, low-voltage acquisition is not routinely performed because it changes the calcium scores. This can be partially corrected by adjustment of the Hounsfield unit (HU) threshold.
• In general, convolution kernels with medium sharpness are used for calcium scoring, to compromise between noise and blooming of calcifications. The selection of convolutional kernel depends on the vendor.
• Besides dedicated ECG-triggered CT scans, the calcium burden can be semi-quantified on non-gated chest CT exams. Visual interpretation (as discussed later) may be used to quantify coronary calcium on these exams, but Agatston scores cannot be calculated on non-gated chest CT.
See also Chapter 1.5.
Volume and mass scores
• Calcium mass (mg) is calculated by multiplying the mean attenuation of each calcified plaque by the plaque volume. A correction factor based on the attenuation of water is used to calculate the mass.