|Clinical image courtesy of Vital Images|
For years, conventional catheter-based angiograms have been the gold standard for imaging the coronary arteries and determining the presence and extent of cardiovascular disease. But now multislice CT technology is gaining a clinical foothold with users and earning believers as a new, noninvasive approach for studying the heart’s structure and its minute, vital arteries. The cardiovascular community is fighting a tough battle with America’s No. 1 killer, but the revolutionary capabilities of cardiac CT have the potential to offer earlier diagnosis and thus better cardiac patient management.
The cardiovascular community is committed to improving the diagnostic tools that can be used to evaluate and treat heart disease, utilizing imaging technologies such as nuclear medicine, stress echocardiography, catheter-based angiograms, cardiac MRI and cardiac CT. And in particular, volume acquisition, multislice technology, sub-second reconstruction of images and advanced visualization software is making CT an increasingly valuable tool in vessel assessment, particularly the coronary arteries.
“CT gives us that one more additional piece of information that we can feel comfortable in saying patients either do or do not have CVD,” says Peter Fail, MD, director of cardiac catheterization laboratories and interventional research for the Cardiovascular Institute of the South (CIS) in Louisiana. Advancements in CT technology are allowing cardiologists at CIS—and throughout the country—to reconstruct minute slices of the heart into three-dimensional images to better diagnose the presence and extent of disease.
CIS uses two Aquilion 64 CFX multislice systems from Toshiba America Medical Systems to image coronary and vascular arteries. “We do calcium scores, coronary artery angiography and peripheral angiography,” says Fail.
|A New Gold Standard Emerging|
In the past, ruling out—or determining the severity of arteriosclerosis in the coronary arteries—required interventional cardiologists to perform a diagnostic, catheter-based angiogram. CT angiography (CTA) is changing the diagnostic paradigm since it provides a means for contrast media to be administered intravenously and catheter insertion to be avoided completely. On the other hand, CTA images provide cardiologists a non-invasive look at the coronary arteries to determine whether either fatty deposits or calcium deposits exist.
According to Lenox Hill Hospital’s Harvey Hecht, MD, CTA could change the nature of the cardiac cath lab. “It could convert it from a diagnostic laboratory to one which is more and more devoted to interventions and those [patients] we already know by virtue of the CTA have significant [cardiac] disease,” explains Hecht.
Westside Medical Imaging’s Norman Lepor, MD, says, “I see CTA becoming the gold standard for coronary artery imaging. Therefore, doctors will only send their patients for conventional coronary angiographies either in the rare case of a non-diagnostic CT and there is an important clinical issue, or in anticipation of performing a percutaneous intervention.”
“We can look at physiology based on a perfusion scan or a stress echocardiogram, but we can not look at anatomy,” he continues. “The CT scan offers the opportunity to look at anatomy, which in correlation with physiology, helps put together the entire picture.”
The use of cardiac CT is evolving at Lenox Hill Heart & Vascular Institute, part of Lenox Hill Hospital, a 652-bed, acute-care hospital in Manhattan. “It is evolving fairly rapidly and we are using it for several purposes,” says Harvey Hecht, MD, director of cardiovascular CT. “We are using it to evaluate patients who have already had stress tests which are equivocal. Rather than take a patient directly to an invasive angiogram, we are doing coronary CT angiography [CTA]. Also, we are increasingly using it as a step before a stress test.”
The institute, an early adopter of multidetector CT, images cardiology patients on a Philips Medical Systems’ Brilliance CT 64-slice scanner. The system has 64 x 0.625 millimeter detector banks, giving total z-axis coverage of 40mm, and has a maximum gantry rotation speed of 0.4 seconds. “CT gets very high-quality pictures,” says Hecht. “With 64-slice scanners, the amount of artifact is much less and you can really see the entire coronary artery fairly well in most patients.”
The high sensitivity and specificity of CT imaging can assist in ruling out or determining