OnlyAfterLongEnough. Atherosclerosis, known to start ~age 7 on average, & microcalcifications (within artery wall smooth muscle cells just outside the plaque) can be seen with a microscope & ca+2 stains within early years but are too small to see with any current ct machines. These may become visible by the best ct machines by early 30's, 2 decades later but typically a decade before obvious clinical events & symptoms.
See below. A ct can be done without or with contrast. As stated in the answer above a noncontrast study can evaluate calcium deposit in the coronary arteries. A contrast enhanced ct study can show the degree of stenosis as compared to the normal portions of the arteries.