Scanner provides non-invasive diagnosis
Image of a patients heart taken with the 64-slice CT scanner
The new Somatom Sensation 64-slice computerized tomography system, one of the first five in the nation, gives doctors a view of the coronary arteries not previously possible without the more invasive procedure.
“MUSC is one of the first facilities in the nation to have the new scanner, and we have been using it for more than a month,” said Philip Costello, M.D., chairman of the MUSC Department of Radiology, who participated in the development of this pioneering technology from its infancy. The only other centers in the U.S. that took delivery of this new technology at the same time as MUSC are the Mayo Clinic, Johns Hopkins, UCLA and the Cleveland Clinic.
The scanner is located in MUSC’s Heart & Vascular Center, and the initial use of the equipment is in the area of cardiovascular medicine. MUSC will be at the forefront of this new technology and will be instrumental in doing comparative studies to determine if the scanner provides just as useful information as catheterization. Costello said that it is appropriate for an academic medical center to work with this highly sophisticated technology and develop protocols for optimal usage.
“Imagine the blurry image of a moving race car you would get if you attempted to photograph the moving car with a slow shutter speed,” said Christopher D. Nielsen, M.D., director of MUSC adult catheterization laboratories. “Compare this with the clarity that could be obtained with an ultra-fast shutter speed.”
It is this superior image clarity that helps doctors decide if a patient presenting with chest pains requires medical intervention, treatment with a stent or balloon, or perhaps bypass surgery.
A cardiac catheterization involves the insertion of a small tube into an artery, usually in the groin, and threading it up into the arteries of the heart. A dye is then injected into the coronary arteries, and X-rays reveal the locations and extent of blockages. Nielsen said that the procedure is invasive and involves some risks. “The risks are very rare, but they are real,” he said. “The day of complete elimination of diagnostic cardiac catheterization is not here yet, but I anticipate that this day will come in the next few years as a result of this new advanced technology.” For the present, the new diagnostic procedure will be performed on low-risk patients and those for whom catheterization poses a higher than normal risk.
MUSC physicians and researchers plan to use the scanner to follow the results of therapy—whether it is stents, laser or surgery—to see if patients are responding to therapy or having recurrences of the initial blockages. Also, lipid-lowering drugs have been shown to decrease plaque in the coronary arteries. This scanner is a means of non-invasively following patients on these drugs to see if the drugs are producing the desired effect.
In addition to providing greater clarity, the new system is more comfortable for the patient. With the older 16-slice CT scanners, patients having their hearts scanned would have to hold their breath for 20 seconds. The 64-slice system scans the heart in only 10 seconds with superior resolution. In addition, for patients with rapid heartbeats, using the older scanner meant having to slow down the heartbeat with drugs. But the most serious limitation of the older scanner is that it only allows visualization of the first two thirds of the coronary artery. As the artery becomes smaller, there is more motion and the image becomes fuzzier. The 64-slice scanner permits visualization of the entire artery.
The speed and high-resolution of the 64-slice system will be especially advantageous for use in children who can be difficult to examine, said radiologist U. Joseph Schoepf, M.D. “In six seconds we can scan a child’s entire chest and abdomen, looking for congenital deformity of the aorta,” he said. The faster scan means a child would less likely have to be sedated.
Another advantage of the 64-slice scanner is in the area of safety, according to Schoepf. The machine has an automatic adjustment mechanism that gauges the density of tissue it penetrates and then automatically adjusts to take the image of using a minimal amount of radiation.
The Catalyst Online
December 10, 2005
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