不同碘浓度CT成像对冠状动脉支架评价的研究

CT evaluation of coronary artery stents using different iodine concentrations

目的：利用心脏动态体模,评价低碘浓度CT成像对冠状动脉支架评价的可行性及可靠性。方法：利用体外心脏动态模型及带支架模拟冠状动脉12条（每条支架内分别放置阶梯状有机玻璃以模拟无狭窄及25%,50%,75%的狭窄）,模拟心率58-62次/min,在管电压100 k V下,保持5种CT值（250 Hu、300 Hu、350Hu、400 Hu、及450±5 Hu）不变的情况下扫描,将图像进行迭代算法（IR）重建。比较组间图像质量（包括主观评分及支架内CT值、噪声、信噪比及对比噪声比）,与真实狭窄对照,比较组间诊断显著狭窄准确性,比较支架内径显示率,比较各组碘浓度。结果：图像质量主观评分组间差异无统计学意义（P〉0.05）。图像质量客观指标显示：支架内CT值、信噪比、对比噪声比均差异有统计学意义（P〈0.05）;图像噪声差异无统计学意义（P〉0.05）,与真实狭窄比较,五组支架内显著狭窄诊断的敏感度及阴性预测值均为100%,特异度91.67%-95.83%,阳性预测值92.31%-96.00%,总符合率95.83%-97.92%,Kappa=0.91-0.95。不同碘浓度对支架内径值及内径显示率比较无明显差异。通过五种碘浓度比较,从250 Hu到450 Hu,碘浓度由8.2 mg I/m L升至14.75 mg I/m L,碘含量增加了79.88%。结论：低碘浓度成像可以保证图像质量,诊断支架内狭窄具有可靠性,同时可明显降低碘负荷,支架内径显示率不降低。

Objective：To evaluate the feasibility and reliability of low iodine concentrationCT imaging ofcoronary artery stentsusing the dynamic cardiac phantom. Methods：The dynamic cardiac phantom （heart rates of 58-62 bpm were simulated）and 12 simulated coronary arteries were used. Ladder-shaped organic glasswere inserted in each stent to simulate no stenosis,25%, 50%, and 75% stenosis. Tube voltage was set at 100 kV, CT values were set to 250 Hu, 300Hu, 350 Hu, 400 Hu, and 450 Hu, respectively. IR reconstruction was used. Image quality, including subjective scores and objectiveimage quality （in-stent CT value, noise, signal noise ratio, contrast to noise ratio）were compared. The diagnostic accuracyof in-stent stenosis was evaluated with real stenosis as the reference standard. The average diameter display rateof stents was measuredandcompared. The iodine concentrations were compared. Results：Subjective image quality scores were not statistically different （ P 〉 0. 05 ） among five groups. There were statistical difference in objective image quality including in-stent CT value, signal noise ratio, and contrast to noise ratio（ P 〈 0. 05 ）. There were no statistical difference in noise（ P 〉 0. 05 ）. Compared with reference standard, the sensitivity and negative predictive value （NPV） for diagnosis of significant stenosis were 100% , specificity were from 91.67 % to 95.83 % , positive predictive value （PPV） were from 92. 31% to 96. 00%. The consistent rate was from 95.83% to 97. 92%. Kappa =0. 91 -0. 95. There was no significant difference in stent diameter measurement and the average diameter display ratefor IR recon- struction among different iodine concentrations. By comparing 5 kinds of diluted contrast-medium with CT value from 250 Hu to 450 Hu, iodine concentration increased from 8. 2 mgI/mL to 14. 75 mgl/mL, the increase rate was 79. 88%. Conclusion：Low iodine concentration imaging can maintain the image quality. It is reliable to diagnose in-stent stenosis,while significantly reducing the iodine load. The display rate of in-stent diameter isn＇t decreased.