How Scans Replace Catheters
One of the goals in medicine’s advance is to reduce the risks of procedures— even tiny risks—by using new tools that can perform non-invasively procedures that were once invasive. That’s why the SPECT /CT —a single-photon emission computed tomography combined with a computed tomography scanner—is a vital new addition to the medical toolbox at Westchester Medical Center, which is the only hospital in the region to feature it.
Its name is a mouthful, and its operation is complex. But what’s important to understand about the SPECT /CT is that it can be used to determine noninvasively whether or not coronary arteries are blocked, in many cases making catheterization unnecessary. Cardiac catheterization, a technique first developed back in the 1950s and ’60s, involves the introduction of a thin tube into the body—usually through an opening in the groin—that travels through the arterial system to the heart. It can be employed to open blocked arteries as well as to assess them, and over the years it has greatly reduced recovery times, hospital stays and pain as an alternative to surgery.
Catheterization remains an important tool, but while it’s a low-risk procedure, it isn’t risk-free, says Diwakar Jain, M.D., Director of Nuclear Cardiology at the Medical Center. So an opportunity to replace it in some instances with a non-invasive test is an important advance in safety. “All invasive procedures carry some risk,” says Dr. Jain. “With catheterization, you do have to insert a catheter into the arterial system and inject a dye into the body. There is a very small chance of complications.”
For this reason, he says, catheterization should be performed “only in patients with a very high probability of coronary artery disease. If we are just looking to rule out or confirm a blocked artery, it’s better to do simple, non-invasive tests, and nuclear imaging of the heart is one of those tests.” If the imaging reveals a blockage, he explains, the patient can undergo cardiac catheterization to open the affected artery.
The new scanner detects gamma rays that come from the patient after a radiotracer is injected into his or her body. It produces three-dimensional images of the heart. “While the technology isn’t brand new, with this camera the manufacturer has addressed some of the issues that were associated with earlier models,” says Dr. Jain. “It produces images that are more accurate and more reliable.”
The test actually requires two separate images, each of which takes about 10 to 15 minutes to complete. The first is taken while the patient is at rest, lying on a table. “The camera rotates around the patient’s body to take pictures from all different angles, and the results are processed by the computer to create a 3-D image,” the doctor says. Then, about 60 minutes later, a “stress test” image is taken after the patient undergoes a treadmill exercise. Stress tests compare blood circulation while the patient is at rest with the same patient’s circulation during maximum physical exertion. Comparing the two images will reveal differences in what’s called “stress perfusion”—the amount of blood that flows through the heart’s arteries. “If the heart is normal, the two images will appear very similar,” Dr. Jain says. “If there is a blockage, they will look different.”
For patients who cannot exercise on a treadmill for reasons of age, infirmity or other medical conditions, Dr. Jain can inject a chemical that mimics exercise stress, he says. The scanner is also used for followup surveillance with heart-transplant patients. One of the possible side effects of antirejection medications is an arterial blockage, Dr. Jain explains. So it makes sense to use the SPECT/CT scanner to look for blockages as part of the regular post-transplant follow-up routine, he says.
The new SPECT/CT scanner is “among the most sophisticated gamma cameras in the region,” Dr. Jain says. “Westchester Medical Center was visionary in opting for this camera. It helps us meet our goal of providing the best possible care to patients in the region.”
Related Read: A Gentler Way to the Heart