Calcium scoring is a technique where the extent of calcification in the coronary arteries is measured and scored. It has been around for many years and was initially performed using EBCT (electron beam CT), but is now increasingly performed using mult-slice CT. As a rule, the faster the scanner, the more accurate is the calcium scoring.
There is a direct correlation between the extent of calcium in the coronary arteries and the risk of a future cardiac event. For example, a calcium score of more than 400 is considered severe and it would be necessary to take steps to prevent further advancement of atherosclerosis and plaque formation. The higher the calcium score, more likely is there a chance of severe stenosis as well.
A calcium score of 0 does not rule of soft plaques, but statistically rules out significant coronary artery disease. Though the calcium score does not show soft plaques (which however are best seen on a CT angiogram), the higher the calcium score, the more is it likely that there are soft plaques as well. Rupture of a soft plaque is the commonest cause of an acute coronary syndrome (i.e. a heart attack).
Calcium scoring is offered as a separate stand-alone test, but
more and more, since we are reliably able to assess the coronary
arteries themselves, it is being performed an an initial part
of the entire cardiac CT examination.