The challenge of coronary calcium on coronary computed tomographic angiography (CCTA) scans: effect on interpretation and possible solutions

Coronary calcium seen on coronary computed tomographic angiography (CCTA) scans is a common diagnostic challenge which can make interpretation difficult. It is the most common cause of false positive (FP) results from CCTA compared with invasive coronary angiography (ICA), and affects the positive predictive results. At the same time, coronary calcium can result in false negative (FN) results, and this again can affect the reported diagnostic accuracy of CCTA, as the high negative predictive value of CCTA compared to ICA is one of its strengths. This paper reviews the reasons that coronary calcium can cause FP and FN results, and the effects of the morphologies and sizes of the calcified plaques, with particular regard to their relationship with the visualization of the contrast-filled lumen of the coronary artery. Some possible solutions to overcome the limitations of reading CCTA scans with calcified plaques also are discussed, with a view to improving the accuracy of interpreting and reporting CCTA scans; these solutions include using the degree of residual visible contrast-filled lumen to help assess the likelihood of significant associated coronary stenosis, and applying newer technical developments such as dual-energy imaging and volume calcium subtraction.