June 1, 2005 — Pulmonary embolisms kill 60,000 people every year. Often, the clots form in the legs, break free and travel to the lungs, where they can cause sudden death. CAT scans can identify these clots in the lungs. Now, a study has shown that indirect CT venography, or CTV, can give doctors a better view of the smaller arteries that may provide evidence of the clots.
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Walking the long aisles of this warehouse isn't just part of Michael Leyva's job. It's good therapy for his legs and lungs. That's because mike has blood clots in the deep veins of his legs that nearly cost him his life.
"I was in cardiac ICU, and that's when they explained to me that I had blood clots that had broke away from being in my legs from a previous surgery a week before," Leyva says.
CT scans of the chest identify clots in the lungs. Now radiologists are taking the scans a step further -- scanning a patient's legs to spot clots before they travel.
"That's the major advantage of doing CT venography, because it allows us the chance to see the clot in the legs before it breaks off and goes to the lungs," Jeffrey Kline, Director of Emergency Medicine Research at Carolinas Medical Center in Charlotte, N.C., tells DBIS.
CT venography takes only three minutes more than a standard lung scan. But those three minutes can mean life or death.
Dr. Kline says, "It gives us an idea of the duration of treatment, what we have to do, and what we're gonna tell the patient to expect."
For Leyva, the additional scan showed more clots lurking in his legs. Doctors have him on a blood thinner to help dissolve the clots. "It's getting better, and hopefully in July they're gonna tell me, 'OK, you're off the Coumadin. You're off blood thinners,'" he says, a triumph over clots that, without CT venography, would have been a hidden -- and potentially deadly -- threat.
Dr. Kline says only about 20 percent of hospitals with the technology to perform CT venography are actually using the test. Other than a very small amount of extra radiation, there are no associated risks.
ABOUT PULMONARY EMBOLISM: Pulmonary embolism arises from thromboembolic disease, which causes blood clots to form in the blood vessels of the legs. Most pulmonary embolisms occur when a blood clot breaks free from an artery in the leg and travels to the lungs. More than 600,000 people in the U.S. suffer from pulmonary embolism every year, and 10 percent of those cases are fatal.
HOW CT SCANS WORK: CT scans use X-rays to image the body. X-rays can pass through most materials. It all depends on the size of the atoms that make up the material; larger atoms absorb X-ray photons, while smaller atoms do not, and the X-rays pass right through. For instance, the soft tissue in the body is composed of smaller atoms, so it doesn't absorb X-rays very well. But calcium atoms in the bones are much larger and do absorb X-rays. A camera on the other side of the patient records the patterns of X-ray light passing through the patient's body. In a CT scan, a series of X-ray beams is directed through the body from different angles. This creates cross-sections so scientists can get a better view of the body. The images are put together by computer into a stack of pictures that can be viewed rapidly, like flipping through a deck of cards.
THE STUDY: Researchers at New York Presbyterian Hospital in New York City studied more than 1,500 patients undergoing two different types of CT scanning techniques for suspected pulmonary embolism. CT pulmonary angiography (CTPA) scans the lungs to detect the presence of blood clots. But many of the clots in smaller arteries are not visible on this type of scan, so thromboembolic disease can do undiagnosed in some patients. Indirect CT venography (CTV) scans the leg and pelvic veins, giving doctors a more complete picture of what is happening in the body.
RESULTS: Combining CTPA and CTV scans increased the detection rate of thromboembolic disease by 20 percent. Adding indirect CTV following a CTPA exam requires no additional contrast material and takes only three minutes to perform. It also eliminates the need for a separate examination of the patient's lower extremities, which can delay diagnosis.
HOW CT SCANS WORK: CT scans use X-rays to image the body. X-rays can pass through most materials. It all depends on the size of the atoms that make up the material; larger atoms absorb X-ray photons, while smaller atoms do not, and the X-rays pass right through. For instance, the soft tissue in the body is composed of smaller atoms, so it doesn't absorb X-rays very well. But calcium atoms in the bones are much larger and do absorb X-rays. A camera on the other side of the patient records the patterns of X-ray light passing through the patient's body. In a CT scan, a series of X-ray beams is directed through the body from different angles. This creates cross-sections so scientists can get a better view of the body. The images are put together by computer into a stack of pictures that can be viewed rapidly, like flipping through a deck of cards.
THE STUDY: Researchers at New York Presbyterian Hospital in New York City studied more than 1,500 patients undergoing two different types of CT scanning techniques for suspected pulmonary embolism. CT pulmonary angiography (CTPA) scans the lungs to detect the presence of blood clots. But many of the clots in smaller arteries are not visible on this type of scan, so thromboembolic disease can do undiagnosed in some patients. Indirect CT venography (CTV) scans the leg and pelvic veins, giving doctors a more complete picture of what is happening in the body.
RESULTS: Combining CTPA and CTV scans increased the detection rate of thromboembolic disease by 20 percent. Adding indirect CTV following a CTPA exam requires no additional contrast material and takes only three minutes to perform. It also eliminates the need for a separate examination of the patient's lower extremities, which can delay diagnosis.
Note: This story and accompanying video were originally produced for the American Institute of Physics series Discoveries and Breakthroughs in Science by Ivanhoe Broadcast News and are protected by copyright law. All rights reserved.
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