In use at Hopkins since Feb. 21, the scanner is expected to replace many diagnostic angiograms, the current gold standard for diagnostic coronary imaging.
The upgraded Hopkins scanner is one of two identical systems currently operating in the United States, the other installed in Boston, Mass. Its use will be the subject of a continuing medical education seminar attended by more than 300 cardiologists on Saturday, March 5, immediately preceding the 2005 Annual Scientific Session of the American College of Cardiology (ACC) in Orlando, Fla.
"This added technology will dramatically alter the way we currently treat patients with suspected coronary disease and chest pain," says cardiologist João Lima, M.D., associate professor of medicine and radiology at The Johns Hopkins University School of Medicine and its Heart Institute.
"By immediately and very quickly checking for blocked arteries, we can sort out who is and is not at high risk of having a heart attack, and eliminate the need for unnecessary cardiac catheterization," he said. "And we no longer need to wait until a patient is stabilized before performing this critical diagnostic test."
The new scanner installed at Hopkins is an Aquilon 64 CFX multislice CT scanner, manufactured by Toshiba. Similar devices also are manufactured by Siemens and General Electric. Features include production of images at twice the speed and in greater detail than the 32-slice, and picture quality so good it decreases the need for invasive, more risky procedures, called angiograms or cardiac catheterization, to check for arterial blocks.
Cardiac catheterization requires threading a thin tube from the groin area to the heart's arteries, where a dye is released to produce contrast X-rays. The procedure also checks the function of heart valves and muscle, takes between 30 minutes and 45 minutes to perform, and requires almost an hour for recovery. Potential complications include infection, heart attack and stroke, but they are rare.
"This new generation of technology puts CT scanning among the first diagnostic tests performed, whereas it has been mostly performed until now only when necessary and if circumstances permitted," says cardiologist Eduardo Marbán, M.D., Ph.D., professor and chief of cardiology at Hopkins. Marbán is also director of the Hopkins Institute of Molecular Cardiobiology and the Michel Mirowski Professor in Cardiology. Indeed, Hopkins will be leading a multicenter clinical trial to compare the clinical effectiveness of cardiac catheterization to 64-slice CT imaging as the new standard for diagnosing cardiovascular disorders.
To produce a CT image, computer-driven machinery passes X-rays through the body, producing digitized signals that are detected and reconstructed. Each X-ray measurement lasts just a fraction of a second and represents a "slice" of an organ or tissue. The greater the number of detectors - the new device has a total of 64 - the better the resolution of the picture. A computer then uses these slices to reconstruct highly detailed, 3-D images of the heart and surrounding arteries. In some cases, a patient is injected with a contrast solution to increase the visual detail.
Each machine costs between $1.5 million and $2 million. A single test costs approximately $700.
Fellow cardiologist and Hopkins chief of medicine Myron L. Weisfeldt, M.D., a professor and past president of the American Heart Association, notes that the time between new generations of imaging technology has shrunk dramatically. "Within just the last few years, CT scanning technology has made incredible strides as a diagnostic tool," he says. Weisfeldt is also the William Osler Professor of Medicine at Hopkins. "As recently as 2003, the technical gold standard used to be 16-CT, in which a procedure would require a 20- to 30-second breath hold in the time it takes to perform the scan. This lengthy, more complicated test really restricted use of CT to experimental purposes."
Sample images are available for viewing (courtesy of Toshiba) at: http://www.