What is the normal CT and MRI imaging appearance of the coronary arteries?
On unenhanced CT images, a normal coronary artery is a tubular structure demonstrating similar attenuation to the myocardium and blood pool. Due to the presence of surrounding fat, the coronary artery can usually be clearly identified on nonenhanced CT images; however, the lumen of the coronary artery is not distinguishable from the vessel wall. Coronary CTA, however, is able to highlight the lumen with the use of intravenous contrast material. The coronary artery is then identified as a tubular structure with similar attenuation to the ventricular cavity. The vessel wall is visible but to a much lesser degree.
Coronary MRA can be performed without or with intravenous contrast material. Unenhanced MR images of the coronary artery may be obtained by a dark blood technique with intermediate or T2-weighting, which is useful for depicting the vessel wall, or by bright blood technique, typically with the use of navigator respiratory gating technique. Contrast-enhanced coronary MRA may also be performed to improve the visualization of coronary artery anatomy and pathology. On dark blood images, the coronary arterial wall is visualized while the lumen of the vessel is dark. On bright blood images, the coronary artery lumen appears bright, similar to that on CTA images.