Flash CT Speeds Diagnosis with Less Radiation

Adenosine stress 128-slice dual source computed tomography perfusion imaging (CTP) with a high pitch factor appears to provide faster, more accurate heart scans for both viewing blood vessels in the heart and measuring blood supply to the heart muscle - while exposing patients to less radiation, researchers report in Circulation: Cardiovascular Imaging, a journal of the American Heart Association.

In preliminary tests from a small trial of 39 patients with an average age of 64, “Flash” CT, as this form of CTP is called, captured quicker images of the entire heart, allowing doctors to better see artery blockages and reduced blood flow through the heart. The scans, which were augmented by a contrast agent and vasodialator, involved just one-tenth of the radiation of current CT scans, the standard test for diagnosing and pinpointing the location of heart disease.

The new technology captures images of the entire heart in less than 0.3 seconds - within one heart beat - as compared to six seconds and several heartbeats for conventional CT scans.
The new technology answers two questions with one scan, the researchers said: whether the blood vessels of the heart are narrowed and whether there is reduced blood flow. That could open the door for better clinical efficiency and cost savings, they added.

“The new exam is faster and more convenient for the patient,” said Gudrun M. Feuchtner, MD, a study co-author and radiologist at Innsbruck Medical University in Austria.

For accuracy, the new scan was compared to cardiac MRI images as well as an invasive angiograms, which involved snaking a catheter through an artery in the groin or arm to the heart. Compared to cardiac MRI, 78 percent to 95 percent of the time the new CT correctly identified restricted blood flow; Flash CT correctly ruled it out 84 percent to 94 percent of the time.

Compared to invasive angiography, the new CT had 90 percent accuracy in detecting significant blockages. The new CT’s accuracy improved to 95 percent when added to CT perfusion - a scan taken after using contrast dye.

The scan proved particularly useful in patients with advanced heart disease or diabetic patients who reported no symptoms, but were found to have areas of poor coronary blood flow, Feuchtner said. Because people with diabetes may have nerve damage, they may not always experience the chest pains that typically accompany reduced blood flow to the heart.

Larger studies are needed before the new technology is widely used, researchers said.