Influence of Coronary Artery Diameter on Intracoronary Transluminal Attenuation Gradient During CT Angiography

OBJECTIVES The goal of this study was to assess the effect of coronary artery diameteronlluminal attenuation and the correlation between the transluminal attenuation gradient (TAG) and transluminal diameter gradient (TDG) on computed tomography (CT) coronary angiography. BACKGROUND Recent studies have reported promising results of TAG in detecting significant stenosis. However, because of the intrinsic nature of CT reconstruction algorithms, luminall attenuation may be affected by vessel diameter. METHODS In this 3-part study, phantom simulating vessels of various diameters immersed in different contrast mixtures were scanned, and lintraluminal attenuations were measured. In addition, dynamic volume CT scanning was performed in 3 mongrel dogs (untreated, a stenosis model, and an occlusion model) using 320-row area detector computed tomography and intraluminal attenuations, and TAGs were calculated at each temporal scan and compared. In a separate clinical study, TAGs and TD ryGs of 152 corona arteries from 62 patients who underwent 320-row area detector computed tomography coronary angiography and invasive angiography were measured and compared. RESULTS Intraluminal attenuation of phantom vessels gradually decreased along with a decrease in diameter. Animal studies revealed that the peak attenuation of distal smaller coronary arteries did not reach that of proximal larger coronary arteries: 55.2% to 78.1% peak attenuation of proximal coronary arteries. No differences in TAG were found between stenotic and normal Left circumflex arteries at temporal scans (all, p > 0.05). The clinical study demonstrated significant correlation between TAG and TDG (r = 0.580; p < 0.0001). CONCLUSIONS Intraluminal attenuation was shown to decrease with diminution of vessel diameters. In addition, TAG exhibited a significant correlation with TDG, implying that TAG may be a secondary result because of differences in diameters. (C) 2016 by the American College of Cardiology Foundation.