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New Scanner Creates a Virtual Heart in Just a Few Beats
Oct 2, 2007 6:00 PM
In a few heart beats -- a five- to ten-second breath hold -- the Definition Dual Source Computed Tomography (CT) scanner can capture a three-dimensional image of the heart.
"We've been looking for something that would allow earlier detection of cardiovascular disease and that is also quicker, more accurate, and safer than previous methods," explains cardiologist Sheldon Litwin, M.D., who went through six-weeks of intensive training to learn how to manipulate and read the images. Patients of University Health Care Cardiovascular Center will benefit from the region's newest cardiac imaging technology -- the fastest scanner in the Intermountain West. While older scanners detect artery problems only when they are 70 percent blocked; this new scanner will find blockages at 30 percent or less.
The Cardiovascular Center's newly acquired technology is also safer than the previous generation of scanners not only because it is noninvasive, but its speed minimizes exposure to radiation -- some 50 percent less. Additionally, patients no longer have to take beta-blockers to slow down the heart rate. This allows the scans to be performed with less delay. Within minutes of getting off the table, patients know about the blockage and can begin changing their lifestyles to lower risk.
According to the American Heart Association, one in three adults experience some type of cardiovascular disease. Early detection of heart disease can be lifesaving, yet most people are asymptomatic. For 25 percent of them, a heart attack will be their first symptom. Conventional stress tests will only find severe blockages. Past methods of non-invasive testing included the "treadmill" test and one using nuclear agents. "These don't pick up on early changes, which is important since a heart attack may be caused by a 30-40 percent blockage that suddenly is completely occluded by a clot," points out Litwin. This new CT scanner detects heart matters earlier than any other procedure.
A Virtual HeartIn a room of its own, the turbo-sized inner portion of the scanner spins continuously around the patient at a rapid speed without a need to stop to "rewind." While the patient moves through the scanner, it creates spiral images that are reconstructed by a computer to create high-resolution 3-D imagery.
In another room on a screen, the images can be rotated and viewed at a variety of different angles revealing a virtual heart that hides little. Viewing images of the heart beating can reveal how well the heart muscle (ejection fraction) and the heart valves are functioning. These beats also allow the cardiologist to choose which phase of the cardiac cycle will provide the best image of the arteries. Images can be manipulated to allow the viewer to follow each branch of the heart arteries, revealing any areas of narrowing. "Because different tissues react differently to varied X-ray energy levels, we can process the scan data to look at just the blood vessels and not the heart tissue, or just the heart and not the vessels," explains Steve Stevens, M.D., professor and chair of the radiology department.
The CT scanner has strengthened University Hospital's emergency response as well. "In a matter of 15 seconds we can scan the entire body of a trauma patient, allowing for a very fast diagnosis," says Stevens. Other patients who benefit from the new CT scanner are those who don't need the full power of the scanner to get a high resolution image, so their exposure to radiation is halved.
Why Not An MRI?
While an MRI is good for visualizing the heart muscles, it is not yet as good as a CT for assessing coronary artery anatomy. An MRI also takes more time, requiring a patient to repeatedly hold their breath throughout a 45-minute period, which can be difficult for a sick patient. Litwin recalls that 15 years ago the MRI was thought to be the ideal tool for coronary detection. Now with the CT scanners "slip ring" technology and multiple-image capabilities, it has surpassed the MRI. The cost for CT scanning is on par with an MRI: $1,000-$1,500.
Educating the public and referring doctors about the CT scanner is a top priority for the U's Cardiovascular Center. This includes assisting physicians in deciding what would be the most cost-effective and health-effective test for their patients. "It's about using the best test, to get the most information, with the least risk," says Litwin.
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