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Computed Tomography
Angiography
(CTA)
Computed tomography angiography (CTA) is an examination that uses x-rays to
visualize blood flow in arterial vessels through the body, from arteries
serving the brain to those bringing blood to the lungs, kidneys, and the
arms and the legs. CT combines the use of x-rays with computerized analysis
of the images. Beams of x-rays are passed through 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 injection contrast material into an
artery, CTA is much less invasive and a more patient-friendly procedure.
Contrast material is injected into a vein rather than an artery. This exam
is used to screen individuals for arterial heart disease without having to
be admitted to the hospital.
CTA is commonly used to:
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Examine the pulmonary arteries in the lungs to rule out
pulmonary embolism.
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Visualize blood flow in the renal arteries, those supplying
the kidneys, in patients with hypertension and those suspected of having
kidney disorders. Narrowing of a renal artery is a cause of high blood
pressure in some patients, and can be corrected surgically. A special
computerized method of viewing the images makes CT renal angiography a very
accurate examination. It is also done in prospective kidney donors.
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Identify atherosclerotic disease, aneurysm, or dissection in
the body's main artery, the aorta and its major branches, the iliac
arteries.
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Detect atherosclerotic disease that has narrowed the arteries
to the legs.
Procedure
Before the actual exam begins, you will have a dose of 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. back |