Post processing: The Cardiac CT Angiography software (Philips, Cleveland, USA) allows extraction of the coronary tree from the heart and analysis of the arterial lumen. This application operates on the volume rendered image of the heart. After isolation of the coronary tree, the software enables the selection of an artery for quantitative analysis of its lumen. The obtained information includes presentation of the artery in panoramic views, visualization of the artery and adjacent vascular anatomy in Maximum Intensity Projection (MIP) mode for anatomical enhancement, and cross sectional views, perpendicular to the artery axis for free lumen/diameter analysis, thus providing a tool to estimate stenosis severity and dimensions. Using color mapping, plaque composition is delineated to distinguish calcified from soft plaque.