Cardiac CT
Cardiac CT is a heart-imaging test that
uses CT technology with or without intravenous (IV) contrast (dye) to
visualize the heart anatomy, coronary circulation, and great vessels
(which includes the aorta, pulmonary veins, and arteries).
- Calcium-score screening heart scan
- Coronary CT angiography (CTA)
- Total body CT scan
Calcium-Score Screening Heart Scan
The
calcium-score screening heart scan is a test used to detect calcium
deposits found in atherosclerotic plaque in the coronary arteries.
State-of-the-art computerized tomography methods, such as this one, are
the most effective way to detect early coronary calcification from
atherosclerosis (hardening of the arteries), before symptoms develop.
The amount of coronary calcium has been recognized as a powerful
independent predictor of future heart problems and is useful in making
lifestyle changes and guiding preventive care to reduce their risk.
Your doctor uses the calcium-score screening heart scan to evaluate risk for future coronary artery disease. If calcium is present, the computer will create a calcium "score" that estimates the extent of coronary artery disease based on the number and density of calcified coronary plaques in the coronary arteries.
Absence of calcium is considered a "negative" exam.
However, since there are certain forms of coronary disease, such as
"soft plaque" atherosclerosis, that escape detection during this CT
scan, it is important to remember that a negative test indicates a low
risk, but does not absolutely exclude the possibility of a future
cardiac event, such as a heart attack. The calcium-score screening heart scan takes only a few minutes to perform and does not require injection of intravenous iodine.
Coronary CT Angiography (CTA)
Coronary computed
tomography angiography (CTA) is a noninvasive heart imaging test
currently undergoing rapid development and advancement. High-resolution,
3-dimensional pictures of the moving heart and great vessels are
produced during a coronary CTA to determine if either fatty or calcium
deposits (plaques) have built up in the coronary arteries.
Before
the test, an iodine-containing contrast dye is injected into an IV in
the patient's arm to improve the quality of the images. A medication that slows or stabilizes the patient's heart rate may also be given through the IV to improve the imaging results.
During the test, which usually takes about 10 minutes, X-rays pass through the body and are picked up by special detectors in the scanner. The newer scanners produce clearer final images with less exposure to radiation than the older models. These new technologies are often referred to as "multidetector" or "multislice" CT scanning.
Another new technology, known as dual-source CT, uses two sources and two detectors at the same time. This technology provides full cardiac detail with about 50% less radiation exposure than traditional CT.
Since it's noninvasive, a coronary CTA can be performed much faster than a cardiac catheterization
(also called a "cardiac cath" or coronary angiogram), with potentially
less risk and discomfort to the patient, as well as less recovery time. Although
coronary CTA exams are growing in use, coronary angiograms remain the
"gold standard" for detecting coronary artery stenosis, which is a
significant narrowing of an artery that could require catheter-based
intervention (such as stenting) or surgery (such as bypassing) to treat
the narrowed area. However, coronary CTA has consistently shown the
ability to rule out significant narrowing of the major coronary
arteries. This new technology also can noninvasively detect "soft
plaque," or fatty matter, in the coronary artery walls that has not yet
hardened but that may lead to future problems without lifestyle changes
or medical treatment.
Coronary
CTA is most useful to determine whether symptoms of chest pain may be
caused by a coronary blockage, particularly in individuals that may be
at risk, such as those with a family history of cardiac events,
diabetes, high blood pressure, smokers, and/or those with elevated cholesterol. However, there is still much controversy as to when a coronary CTA should be used.
Total Body CT Scan (TBCT)
The total body CT
scan, or TBCT, is a diagnostic technique that uses computed tomography
to help identify potential problems or diseases before symptoms even
appear.
The TBCT scan -- which takes about 15
minutes to perform -- analyzes three major areas of the body: the lungs,
the heart, and the abdomen/pelvis.
In the heart, the
scan can detect aortic aneurysms and calcium deposits within plaque in
the coronary arteries. However, the presence of calcium deposits in the
coronary arteries does not necessarily mean that an artery is
dangerously narrowed by disease or that a severe health threat exists.
For example, calcium deposits are often found in older people as a
result of their age. In addition, the CT scan cannot give a precise
location of the diseased portion of the artery.
For
some high-risk individuals, the proposed benefit of having a TBCT scan
lies in the potential of early detection and treatment. But overall, its
use for early detection of heart disease is very controversial.
