CT Revs Up the Slices

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Sixteen-slice CT is proving to be sweet with blossoming applications in cardiac and vascular imaging in addition to classic CT studies in the liver, pancreas and kidney. And 32-, 40- and 64-slice are promising even more punch for cardiac imaging as well as perfusion imaging and trauma.

The multislice CT era has dawned, and in the slice-wars, sixteen-slice technology is proving to be a tremendous hit. Elliot Fishman, MD, professor of radiology at Johns Hopkins University (Baltimore), contends, "CT will be the physical examination of the 21st century." Take for example the ER patient with abdominal pain. A surgeon could be called in to examine the patient and detect the probable etiology of the pain. Or the patient could undergo a 10 to 20 second CT scan to pinpoint the exact condition. But the latest and greatest scanners are extending the boundaries of CT far beyond routine abdominal studies and making cardiac CT reality. Fishman estimates that CT volume at Johns Hopkins has increased nearly 20 percent since deploying its 16-slice scanners two years ago.

Sixteen-slice CT scanners have been available for about two years, and many sites are finding that sixteen is the CT scanning sweet spot. Scott Lipson, MD, associate director of cardiac imaging at Long Beach Memorial Medical Center (Long Beach, Calif.), opines, "Going forward over the next five years, I think 16 will be the dominant technology. There are clear advantages of 16 over four- and eight-slice technology, and most single-slice scanners will be phased out and replaced with 16-slice scanners."

What is it that makes 16-slice so sweet? "It's the best of both worlds," according to Fishman. "We can do everything we did before on a four-slice scanner better and there are new applications [made possible by the 16-slice scanner's increased speed and improved resolution.]"


Johns Hopkins' radiology department relies on four Sensation 16 CT scanners from Siemens Medical Solutions (Malvern, Pa.) as its departmental workhorses. The scanners are used for classic CT applications-liver, pancreas and kidney studies-with better results than a four-slice scanner. The ultra-fast acquisition and sub-millimeter thin slices yield a high-resolution dataset for these bread-and-butter CT scans. For example, the 16-slice scanner can be used to create a vascular map of the liver with additional fine detail.

Lipson says the Aquilion 16 CFX scanner from Toshiba America Medical Systems (Tustin, Calif.) has made a tremendous difference for his practice. The practice realized increased CT utilization and improved patient care since upgrading from a four-slice scanner. One of the primary 16-slice applications is CT angiography, which is doable, but barely, on a four-slice scanner.

Lawrence Tanenbaum, section chief of MRI, CT and Neuroradiology at Edison Radiology Group (Edison, N.J.), says CT angiography is a prime example of how the GE Healthcare LightSpeed 16 makes a difference in clinical care. CT angiography provides better visualization than conventional angiography for conditions such as a leak in an aortic stent. What's more, because CT angiography replaces the conventional invasive procedure, it's possible for radiologists to diagnose patients who aren't candidates for an invasive procedure.

Other new applications made possible by 16-slice scanners include coronary artery studies and virtual colonoscopy. Coronary CT is the only way to visualize soft plaque, which is thought to play a role in half of heart attacks deaths-those that occur without evidence of an obstruction. And like CT angiography, virtual colonoscopy serves as a replacement for a conventional invasive procedure for many patients.

Sixteen-slice scanners enhance clinical care in other ways as well. For starters, the higher resolution means that radiologists are able to see things to make diagnoses that weren't possible before. "We can make more accurate diagnoses with the scanner," Tanenbaum explains. "Axial interpretation can be confusing at times. Adding the coronal and sagittal plane makes an enormous difference in the radiologist's ability to see subtle details." Lipson adds, "We're obtaining isotropic thin sections and multi-planar reconstruction on all patients, which has changed how we interpret studies."

The new, volume-based world does require a change in mindset and workflow. "You need a good PACS and 3D workstations to take advantage of what 16-slice scanners have to offer," Lipson explains.