低管电压结合迭代重建成像对冠状动脉支架评价的心脏体模研究

Evaluation of coronary artery stents using low tube voltage combined with iterative reconstruction:the phantom study

目的：利用心脏动态体模,评价低管电压结合迭代重建（IR）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%狭窄）,模拟心率58~62次/min,在固定对比剂CT值400 Hu下,用80 kV,100 kV,120 kV扫描,80 kV和100 kV采用IR成像,120 kV采用滤波反投影（FBP）成像。比较图像质量。与实际狭窄对照,比较诊断显著狭窄准确性,IR和FBP支架内径显示比较。比较辐射剂量和碘浓度。结果：图像质量主观评分差异无统计学意义（P〉0.05）。图像质量客观评价指标（支架内CT值、噪声、信噪比及对比噪声比）差异无统计学意义（P〉0.05）,与真实狭窄比较,三组支架内显著狭窄诊断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。IR与FBP支架内径值显示,差异有统计学意义（P﹤0.05）。IR支架内径平均显示率比FBP提高5.4%。80 kV组有效辐射剂量0.51 mSv,100kV组1.19 m Sv,120 kV组2.01 mSv。80 kV组碘浓度9 mg I/mL,100 kV组13.85 mg I/mL,120 kV组16.03 mg I/mL。结论：低管电压结合IR成像可以保证图像质量和诊断准确性,同时明显降低辐射剂量及碘浓度。IR重建可提高支架内径显示率。

Objective： To evaluate the feasibility and reliability of low tube voltage combined with iterative reconstruction（ IR） in coronary artery stent CT imagingusing 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 glass was inserted in each stent to simulate no stenosis,25%,50%,and 75%stenosis. At fixed CT value of 400 Hu,tube voltage of 80 kV,100 kV,and 120 kV were set during scanning,respectively. IR reconstruction was used at 80 kV and 100 kV and filtered back projection（ FBP） reconstructionwas used at 120 kV. 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 measuredandcomparedbetween IR and FBP reconstruction. The radiation dose and iodine concentration were compared. Results： Subjective image quality scores were not statistically different（ P〉0. 05） amongthree（ 80 kV,100 kV,120 kV） groups. There were no statistical difference in objective image quality including in-stent CT value,noise,signal noise ratio,contrast to noise ratio（ P〉0. 05）. Compared with reference standard,the sensitivityand negative predictive value（ NPV） for diagnosis of significant stenosis were 100%,specificity were from91. 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 statistical difference in stent diameter measurementfor IR and FBPreconstruction（ P〈0. 05）. The average diameter display rate of stents improved 5. 58% using IR reconstruction compared with FBP algorithm. The effective radiation dose was 0. 51 m Svin 80 kV group,1. 19 m Sv in 100 kV group,and 2. 01 mSv in 120 kV group. At fixed CT value,the iodine concentration was 9 mg /mlin 80 kV group,13. 85 mg / mL in 100 kV group,and 16. 03 mg I / mL in 120 kV group. Conclusion： Low tube voltage combined with iterative reconstruction can maintain the image quality while significantly reducing the radiationdoseand iodine load in coronary stent CT imaging. It is reliable to diagnose in-stent stenosis. The display rate of in-stent diameter can be improved by using IR reconstruction.