64-MDCT coronary angiography: Phantom study of effects of vascular attenuation on detection of coronary stenosis

OBJECTIVE. The purpose of this study was to investigate the effects of vascular attenuation on the accuracy of stenosis evaluation with 64-MDCT coronary angiography. MATERIALS AND METHODS. A pulsating cardiac phantom was used to simulate the beating heart and coronary arteries of 5 and 3 mm in diameter with three degrees of stenosis (25%, 50%, and 75%) at a heart rate of 55 beats per minute. Coronary vascular enhancement had four attenuation levels: low, 200 H; moderately low, 300 H; moderately high, 350 H; and high, 500 H. Cardiac scans were obtained with 64-MDCT. Percentage stenosis, plaque area, and plaque density were measured on axial images. RESULTS. For 50% and 75% stenosis in 5-mm vessels, there were no significant differences among the four attenuation groups. For 50% and 75% stenosis in 3-mm vessels, significant underestimation of percentage stenosis occurred in the high-attenuation group compared with the moderate-and low-attenuation groups ( p < 0.05). For 25% stenosis in 5-mm vessels, low attenuation led to significant overestimation of degree of stenosis compared with the moderate and high attenuation levels ( p < 0.05). None of the instances of 25% stenosis in 3-mm vessels were detected in the high-attenuation group. Underestimation was found only for 3-mm vessels. For 75% stenosis, all plaques were detected irrespective of contrast attenuation and vessel size. CONCLUSION. Use of higher attenuation leads to a significant underestimation of stenosis in smaller vessels. Lower attenuation leads to slight and clinically acceptable overestimation of stenosis. The optimal vascular attenuation for stenosis detection in coronary 64-MDCT angiography is approximately 350 H.