Word: ct
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Sharply detailed CT scans of the brain have been available for years, but it has taken much longer to get similar images of the heart. The reason is simple: the brain doesn't move. The heart does, of course, constantly, which means that conventional images are largely a blur. Some rather small (yet vitally important) blood vessels that lie on the surface of the heart compound the problem...
...latest CT scanners address both drawbacks by dividing the heart into 64 imaginary slices, compared with 16 slices in the most common older scanners. This higher number increases the resolution of the final image and decreases the amount of time needed to make it. It takes about eight heartbeats to get a complete picture, but sophisticated computer software makes it possible for images to be taken at precisely the same part of the cardiac cycle--ensuring that the heart is in the same position. The downside: people with irregular heartbeats aren't the best candidates for cardiac CT...
Under the right conditions, CT images of the heart are so sharp, however, that they can take a lot of the guesswork out of diagnosing heart disease. "There's a fairly large middle category of people where it's not clear how much heart disease they actually have," says Dr. David Bluemke at the Johns Hopkins Hospital in Baltimore, Md. "Their cholesterol is high. Their blood pressure is high. They have a few risk factors. That doesn't mean they need to go to the catheterization lab. But it sure would be nice to get a quantitative measure of their...
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...