Two doctors at Froedtert Memorial Lutheran Hospital and the Medical College of Wisconsin are studying new medical technology that could revolutionize the way patients with heart disease symptoms are diagnosed.
The new machine, developed by GE Healthcare and called the LightSpeed volume computed tomography (VCT) scanner, takes digital photos of the interior of a patient’s body.
Although CT scanners have been used for decades, the LightSpeed scanner takes 64 cross-section "slices" per scan, compared with 16 or 32 "slices" with earlier CT devices.
Froedtert Hospital, located in Wauwatosa, recently became the first hospital in the United States to have the LightSpeed VCT scanner.
A team led by Dr. Dennis Foley, professor of radiology at the Medical College of Wisconsin and chief of digital imaging at Froedtert, and Dr. David Marks, an associate professor at the college and director of cardiac catheterization at Froedtert, is comparing the results of cardio catheterizations of 164 patients who had digital heart scans performed by the VCT.
In a cardio catheterization, or angiogram, a catheter is inserted into a blood vessel, and dye is injected, making blood vessels visible on X-rays. Angiograms take as long as 45 minutes.
For their study, both doctors are looking for patients who have been identified as being in need of cardio catheterization. That way, the physicians will be able to compare the results of LightSpeed scans and catheterizations, to determine how accurate the scans are. The patients in the study will effectively be their own controls.
"They need to be willing to have the CT scan before they have the (cardio) catheterization," Marks said. "That’s the reason it’s research – it’s not a substitution of care with CT. They will all get the best of both worlds. If we’re able to reduce the number of people who require catheterization, it will be a terrific thing for society."
If the VCT scan is able to gather the same type of data produced by a CT scan, it could be done for less money and with a less invasive procedure, the doctors said.
"The catheter is the gold standard," Marks said. "It is very safe, but it is invasive. You can take someone, numb their wrist and take the pictures with no trauma. However, for someone with bleeding problems, then it is a big deal. And non-invasive (procedures) would be lower risk. But if the VCT scan accuracy is not adequate for clinicians to make decisions, there’s no reason to do it."
Marks and Foley hope to begin their study within weeks.
The physicians plan to follow the participants for one year after their scans to track which of the patients develops later stage heart disease.
"We want to explore some of the new information we will derive from this, looking at plaque and disease differences," Marks said. "We hope we will get new information, differences on whose disease will progress and whose will stabilize."
The LightSpeed VCT scanner will quickly give information about the patient’s heart to physicians performing the study, Foley said. The scan of the heart takes about five seconds, although some medication is generally required to slow the heart beat of patients, so images can be taken while the heart is resting, he said.
If the study verifies the reliability of the data, both say there could be wide-reaching benefits for the medical community and those suffering from symptoms of heart disease.
"You’re looking at a major paradigm shift," Foley said. "(Heart disease) is the No. 1 killer in the country. And evaluation can be very invasive, and it can be quite expensive."
The LightSpeed scanner could also have applications in other areas of medicine, Foley said.
"This system provides unprecedented image quality almost instantaneously, which should provide significant impact on cardiovascular medicine and trauma," he said. "The LightSpeed VCT also should improve imaging in neurology, oncology and other fields."
From a patient’s point of view, the new scan will be easier, Marks said, because the patient will only need to be scanned for about 10 seconds after the machine is ready. However, computer processing of the images of the heart does take some time, he said.
The new LightSpeed scanner, with its 64-slice images, is a big step forward in technology, Marks said.
The LightSpeed scanner, Marks said, scans a block of tissue about four centimeters at a time. As the series of images is taken, the device spins around a patient’s body three to five times.
As the images are taken, they are timed to shoot when the heart is resting during its beat cycle.
"The trick is being able to take a 3-D structure like an artery, freeze it in time and space and resolve that artery with accuracy that is comparable to current technology," Marks said.
Previous CT scan technology was not of high enough resolution to be able to justify using it for making decisions about the heart, Marks said.
Both physicians predict they will have gathered data from their 164 patients in about six months.
"My sense is that there will be a large group (of patients) that this will be a terrific test for," Marks said. "(But) I’m not sure this will replace stress tests. The catheter rates may actually go up, because it will be easier to diagnose heart disease."
Regardless of the outcomes of the study, certain patients will not qualify for heart scans because of pre-existing medical conditions.
"It’s important to realize that the test isn’t for everyone," Marks said. "If someone has calcified arteries or a stent in place already, that makes a scan difficult."
April 15, 2005, Small Business Times, Milwaukee, WI
