Imaging the beating heart presents a significant challenge, and until recently, cardiac CT was a tenuous proposition at best. Although 16-slice scanners can perform the task adequately for some patients, its utility is far from universal. Enter the 64-slice scanner. CT's big gun is ideally suited to cardiac imaging and has thrust open the door to cardiac CT (and sales are going great guns, too!).
Cardiac CT is quickly convincing the clinical community of its capabilities. Michael Poon, MD, chief of cardiology at Cabrini Medical Center (New York City) and president-elect of the Society for Cardiovascular CT, explains, "CT is the only imaging modality to non-invasively view the lumen of the coronary arteries and provide information about vessel walls where plaque develops. Other cardiac modalities provide information at the end state of the disease process."
Jeffery Goldman, MD, director of cardiac CT and MR at Manhattan Diagnostic Radiology (New York City), adds, "Cardiac CT is ready for prime time. Sixty-four slice technology has the potential to completely change the way cardiac patients are managed."
A study in the May issue of the Journal of the American Medical Association supports cardiac CT aficionados. The study indicated multi-slice CT can provide high accuracy for coronary artery disease detection and may complement conventional coronary angiography. (See sidebar, "JAMA Study Supports Cardiac CT.")
Hospitals and independent practices are catching on. Ask anyone, especially facilities with a cardiac flare, about upcoming purchases. Chances are 64-slice CT is near the top of the list, and cardiac CT is one of the primary applications of the uber scanner. Sites that have taken the plunge into cardiac CT are deploying the scanner for coronary CT angiographies as well as studies of the carotids, aorta and pulmonary arteries and peripheral vascular scans.
But before joining the crowd, cardiac CT-wannabes need to understand appropriate applications as well as the benefits and challenges of implementing cardiac CT. This includes staff training, radiology-cardiology workload, technology to support cardiac CT and economics.
16 to 64
Washington Hospital Center (Washington, D.C.) is a typical cardiac CT site. The hospital has relied on a Philips Brilliance CT 16 Power for cardiac imaging and plans to upgrade to a 64-slice scanner in a few months. "Adequate coronary imaging can take place with a 16-slice scanner," asserts Guy Weigold, MD, director, cardiac CT program. Weigold says the 16-slice scanner is optimized for cardiac imaging with an x-ray tube and upgraded processing hardware to provide the horsepower and speed to facilitate cardiac CT. This is a good starting point for cardiac CT, says Weigold.
But Weigold foresees several advantages with the 64-slice scanner. The 20- to 30-second scan times with the 16-slice scanner will drop to 10 to 15 seconds, an easy, single breath-hold for most patients. And 64-slice is less prone to artifacts, resulting in better image quality. "We'll produce excellent quality scans in more patients," predicts Weigold.
Indeed the experience at Manhattan Diagnostic Radiology proves the point. "The problem with the 16-slice scanner is that at least one-third of studies are difficult to read because of motion artifacts. With the 16, we had to read a lot of cases without confidence," explains Craig Sherman, MD, managing partner. The practice upgraded to a Toshiba Aquilion 64 CFX scanner in March. "The improvement is greater than we expected. Almost all studies are diagnostic quality," continues Sherman.
Cabrini's Poon, who upgraded from a Siemens Sensation 16 to a SOMATOM Sensation Cardiac 64 in May, adds resolution to the list of 64-slice advantages. Siemens' 16-slice scanner has a resolution of 0.6 millimeters; the 64-slice upgrade drops resolution to 0.4. millimeters. "That's phenomenal compared to the gold standard of x-ray angiography, an invasive procedure with a resolution of 0.2 millimeters," claims Poon.
Cardiac applications: the short list
The Heart Center of Indiana in Indianapolis has relied on Siemens Medical Solutions SOMATOM Sensation Cardiac 64 as its cardiac powerhorse since early this year. "The primary benefit is that a 64-slice coronary study can replace a cardiac catheterization in a certain patient population," notes Ronald Razmi, MD, director of cardiovascular MR/CT. This includes patients with a low index of suspicion who don't have a lot of calcium in the