冠状动脉CT血管成像评价临界狭窄准确性的体模研究

摘要

Objective To evaluate the accuracy of coronary computed tomography angiography (CTA) on the imaging of near-critical stenosis using a pulsatile phantom of coronary arteries. Methods A pulsating cardiac phantom with acrylic tubes provided by GE CT lab was used to simulate beating heart and coronary arteries of two diameters (4 and 3 mm) and four stenosis degrees (40% , 45% , 55% and 60% ) with plaques of two densities (800 Hu and 20 Hu simulating calcified plaque and soft plaque) at heart rate of 55 bpm. The contrast density was prepared to be 350 Hu inside the simulated vessels. The scans were performed with clinically typical parameters: 120 kV, 550 mA, 0.35 s/rotation, pitch 0.2. Based on the longitudinal images of the simulated coronary arteries, the stenosis rates were measured and compared with the actual values. In addition, the measured stenosis rates of different vessel sizes and plaque densities were compared. Results In the 4 mm vessels, all the stenosis parts were overestimated despite of density and stenosis degree. Even 40% stenosis could be overestimated as more than 50% . Measured stenosis rates with calcified plaques were higher than those with soft plaques (P < 0. 05). In the 3 mm vessels, only stenosis rate of 40% could be measured with calcified plaques, which was significantly overestimated. Stenosis caused by soft plaques were slightly overestimated in 3 mm vessels. Conclusion CTA tends to overestimate stenosis despite the composition of plaque, which may cause over-diagnose of coronary heart disease. Calcification can exaggerate the overestimation and cause trouble in stenosis determination.%目的 应用冠状动脉体模,评价冠状动脉CT血管成像(computed tomography angiography,CTA)显示冠状动脉临界狭窄的准确性.方法 应用搏动性心脏体模,其表面装置塑料管模拟冠状动脉.模拟冠状动脉管径分别为4 mm和3 mm,狭窄分别设置为40%、45%、55%和60%,斑块密度分别为800 Hu和20 Hu模拟钙化斑块和软斑块.体模心率设定为55 次/分.模拟冠状动脉腔内造影剂浓度设定为350Hu.扫描参数为:120 kV,550 mA,旋转速度每周0.35 s,pitch为0.2.基于模拟动脉的长轴位图像,对狭窄率进行测定并与实际值进行比较,同时对不同管径和斑块的密度情况下测定的狭窄率进行比较分析.结果在管径为4 mm的血管,狭窄程度均被高估,而无论其斑块密度和本身狭窄程度,即使40%狭窄也会被高估为50%以上.钙化斑块的测定狭窄程度显著高于软斑块(P<0.05).在3 mm血管,钙化斑块所致狭窄只有40%狭窄可以测定,并被显著高估.软斑块所致狭窄也被高估.结论 在临界狭窄的评价中,CTA趋于高估狭窄,而无论斑块成分,从而导致冠心病的过诊断.钙化会扩大高估的程度并可能使狭窄的评价难以进行.