Word: cardiac
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Some doctors in emergency rooms are already starting to count on cardiac CT for what they call a "triple rule-out." Here's a typical situation: a middle-age woman walks in complaining of chest pains but otherwise seems fine. The biggest concerns are that she might be having a heart attack, that her aorta may have developed a tear or that she has a major clot in the blood vessels of the lungs. Any of these could swiftly be deadly. Her electrocardiogram comes back normal, and blood tests indicate no cardiac damage. With no compelling reason to suspect...
...least that's the idea. Cardiac CT is not foolproof. Unlike catheterization, it doesn't yet produce clear enough pictures of some of the smaller arteries of the heart. And any arterial plaques that contain calcium deposits, which typically appear in older people, show up like white blobs, so that the blockage could be partial or total (see box). Then there's the issue of radiation. A typical cardiac CT scan exposes a patient to 50 to 80 times the amount of radiation in a series of full-mouth dental X rays. Researchers hope to figure out ways to decrease...
Before 64-slice CT appeared on the scene, many physicians thought the future of cardiac scans belonged to a completely different technology: magnetic resonance imaging. Instead of X rays, MRI uses powerful electromagnets that are tuned to detect the hydrogen found in water--which in turn is present in most of the body's soft tissues. An MRI machine can produce astonishingly detailed images of the heart. Just as important, it can also determine how healthy the cardiac tissue is. For example, in a heart-attack patient, an MRI can pick out precisely which sections of the cardiac muscle...
...issue. "Right now many heart patients have to undergo a combination of tests that add up to more than the expense of one MRI scan," says Dr. Andrew Arai, a researcher at the National Heart, Lung and Blood Institute in Bethesda, Md., who is studying the use of cardiac MRI in the emergency room. If a single MRI could replace the need for lots of echocardiograms, cardiac catheterizations and nuclear perfusion scans, it might be worth the price...
...make all these imaging technologies work together. One approach combines the anatomical accuracy of CT imaging with the functional information provided by a type of nuclear scan called positron-emission tomography (PET). Still in its early days in the clinic, PET/CT could help doctors see how much of the cardiac muscle is still alive after a heart attack and whether a bypass operation, balloon angioplasty or stent surgery would help damaged areas recover...