Detection of Hemodynamically Significant Coronary Artery Stenosis With CT Enhancement Ratio: A Validation Study in a Porcine Model.

OBJECTIVE: Although numerous techniques that are based on CT number analysis have been proposed, the assessment of hemodynamically significant coronary artery stenosis remains a great challenge. The purpose of this study is to validate use of the CT enhancement ratio in the detection of hemodynamically significant coronary artery stenosis in a porcine model.

MATERIALS AND METHODS: Experiments involving eight closed-chest swine were performed. A balloon catheter was placed into the left anterior descending coronary artery to simulate different degrees of luminal stenosis. The myocardial blood flow (MBF) ratio was measured using the colored microsphere technique. The fractional flow reserve was measured using an invasive pressure wire. CT scans were performed during the first-pass phase, while the pigs were undergoing adenosine stress tests. The CT enhancement ratio and the CT attenuation ratio were calculated using data from the CT images obtained.

RESULTS: Results suggested that the CT enhancement ratio had a strong correlation (y = 0.07245 + 0.09963x; r(2) = 0.898; p < 0.001) with the MBF ratio measured using the microsphere technique, whereas only moderate correlation (y = -1.5508 + 2.2684x; r(2) = 0.498; p < 0.001) was noted between the CT attenuation ratio and the MBF ratio measured using the microsphere technique. In ROC curve analysis, the AUC values of the CT enhancement ratio and the CT attenuation ratio were 0.927 and 0.829, respectively, with regard to the detection of significant ischemia during adenosine stress tests, as defined by the fractional flow reserve.

CONCLUSION: The CT enhancement ratio provides a reliable prediction of the MBF ratio measured using the microsphere technique, indicating that this metric has good diagnostic performance in the detection of hemodynamically significant coronary artery stenosis. The CT enhancement ratio may have potential for use as an imaging biomarker for the relative quantitative assessment of myocardial perfusion.