Cardiac CT scan overview

Cardiac CT is a noninvasive diagnostic imaging technique that employs x-rays to obtain images of the heart. During a cardiac CT scan, an x-ray source and opposing detector move continuously around the patient in a circular path while the patient table moves slowly through the scanner allowing imaging on many different planes. The x-rays passing through the patient’s tissues are captured by a receiver on the opposite side of the body and sent to a computer that reconstructs an image of the heart, viewable from different perspectives. Each unit on the reconstructed image appears as a shade of gray depending on the transmission of x-rays through that part of the body – a property known as attenuation, which is measured in Hounsfield (H) units. Bone, calcium, and metal, for example, have a high attenuation and appear as white. Water and fat have intermediate attenuation and appear as gray, and air has a low attenuation and appears as black. In some cases, an attenuating iodine-based contrast agent may be administered intravenously to highlight the blood vessels and inspect them for abnormalities, a technique commonly referred to as cardiac CT angiography (CTA). Scanning is relatively rapid and cardiac CT allows for a visual evaluation of the entire heart in less than 30 seconds.