Combined analysis of coronary CT angiography (CTA) and stress dual-energy CT (DECT) myocardial perfusion reduces the number of false-positives in a high-risk population for coronary artery disease (CAD) and outperforms coronary CTA alone for the detection of morphologically and hemodynamically significant CAD, according to a study published in the July issue of the American Journal of Roentgenology.

Myocardial perfusion DECT has the ability to recognize perfusion defects and late enhancement and could be useful in combination with coronary CTA because the performance of CTA is affected by the pretest risk of CAD. “In particular, the specificity of coronary CTA can be limited by extensive coronary calcification, which can cause artifacts that may lead to false-positive findings,” wrote the study’s lead author, Carlo Nicola De Cecco, MD, of the Medical University of South Carolina in Charleston, and colleagues. The researchers believed that combining the two modalities could be useful in reducing the number of patients who are needlessly referred to catheter angiography because of false-positive coronary CTA findings.

In order to determine the value of adding adenosine stress DECT myocardial perfusion imaging to coronary CTA for CAD assessment in a high-risk population, De Cecco et al utilized SPECT and catheter angiography as the reference standards in 29 patients. The members of the study’s population were referred for cardiac SPECT exams for known or suspected CAD and were also to undergo pharmacologic stress cardiac DECT.

In 25 patients, cardiac catheterization was available as the reference standard for morphologically significant stenosis. Calculations of sensitivity, specificity and area under the curve values were used to assess the performance of coronary CTA alone, DECT myocardial perfusion alone and the combination of both.

The study’s results revealed that for morphologically significant stenosis, coronary CTA alone and myocardial DECT assessment alone has 95 percent sensitivity and 50 percent specificity. The combined approach produced a sensitivity of 100 percent and specificity of 33 percent if either was positive. If both were positive, sensitivity was 90 percent and specificity was 67 percent. The area under the curve was highest at 0.78 if both were positive.

For hemodynamically significant lesions, coronary CTA alone had 91 percent sensitivity and 38 percent specificity. DECT alone had 95 percent sensitivity and 75 percent specificity. The combined approach yielded 100 percent specificity and 38 percent specificity if either was positive and 75 percent specificity if both were positive. The area under the curve values were highest for DECT alone at 0.85 and the "both positive" evaluation at 0.80.

“The rest DECT acquisition can be performed at the same radiation dose as a standard coronary CTA study,” wrote the study’s authors. “For this reason, the rest DECT acquisition does not have disadvantages for the patient in comparison with a conventional coronary CTA study, while providing additional information on the myocardial blood pool distribution.” The researchers suggest the pairing outperforms coronary CTA alone for CAD detection and reduces the number of false-positives in a high-risk population.