Angiography CT

Overview

Computer tomography angiography (CTA) is an examination that uses x-rays to visualize blood flow in arterial vessels throughout the body, from arteries serving the brain to those bringing blood to the lungs, kidneys, and the arms and legs. CT combines the use of x-rays with computerized analysis of the images. Beams of x-rays are passed from a rotating device through the area of interest in the patient's body from several different angles so as to create cross-sectional images, which then are assembled by computer into a three-dimensional picture of the area being studied. Compared to catheter angiography, which involves placement of a catheter and injecting contrast material into an artery, CTA is a much less invasive and a more patient-friendly procedure; contrast material is injected into a peripheral vein rather than an artery. This exam has been used to screen large numbers of individuals for arterial disease. Most patients have a CT angiography without being admitted to a Hospital.

Patient Prep

Consume only clear liquids four hours prior to your study. You will be asked whether you have asthma or any allergies to foods or drugs, and what medications you are currently taking. If you are pregnant, you should inform the technologist before the procedure.

Test Procedure

Before the actual exam begins, you will have contrast material injected into a vein to make the blood vessels stand out. An automatic injector machine is used that controls the timing and rate of injection, which may continue during part of the time images are recorded. During the examination, the rotating device spins around the patient, creating a fan-shaped beam of x-rays, and the detector takes snapshots of the beam after it passes through the patient. As many as one thousand of these pictures may be recorded in one turn of the detector. The real work of CTA comes after the images are acquired, when powerful computer programs process the images and make it possible to display them in different ways, for instance, in cross-sectional slices or as three-dimensional "casts" of the blood vessels.

Test Uses

CTA is commonly used to:

• Examine the pulmonary arteries in the lungs to rule out pulmonary embolism , a serious but treatable condition.
• Visualize blood flow in the renal arteries (those supplying the kidneys) in patients with high blood pressure and those suspected of having kidney disorders. Narrowing (stenosis) of a renal artery is a cause of high blood pressure in some patients, and can be corrected. A special computerized method of viewing the images makes CT renal angiography a very accurate examination.
• Identify aneurysms in the aorta or in other major blood vessels. Aneurysms are diseased areas of a weakened blood vessel wall that bulges out—like a bulge in a tire. Aneurysms are life-threatening because they can rupture.
• Identify dissection in the aorta or its major branches. Dissection means that the layers of the artery wall peel away from each other—like the layers of an onion. Dissection can cause pain and can be life-threatening.
• Identify a small aneurysm or arteriovenous malformation inside the brain which can be life-threatening.
• Detect atherosclerotic disease that has narrowed the arteries to the legs.

Test Results

Typically the results of CTA are available within 24 hours, although in complicated cases special computer analysis may take somewhat longer. The radiologist will report the findings to your physician, who in turn will discuss them with you.