| Objective: To evaluate the accuracy of the second generation dual-source computed tomography(DSCT)in diagnosis of coronary stent restenosis which the dimmer was ≤3 mm compared with invasive coronary angiography, exploring the value of measuring and analysis the CT values of the in-stent and two sides of the stent in diagnosis of coronary stent occlusion.Methods: A total of 70 patients confirmed or suspected with coronary artery in-stent restenosis after implantation were underwent both coronary CT angiography(CCTA)and invasive coronary angiography(ICA) examination from October 2011 to December2014. There were 52 males and 18 females, and age was 43-85(65.6 ± 9.4)years old.This group of patients underwent coronary stent implantation before the CCTA 4-168(57.76 ± 40.10) months due to coronary artery stenoses(a total of 132 stents). The interval between CCTA and ICA was 1-18(7.56 ± 3.93) days. CCTA using retrospective ECG-gated spiral scan mode or prospective-ECG triggered sequential scan mode on a second generation DSCT system. Acquisition parameters were as follows: 280 ms gantry rotation time, 2×64×0.6 mm detector collimation, 2×128×0.6 mm Z-flying focal spot technique. 75 ms time resolution of reconstruction. Parameters for image reconstruction include time resolution of 75 ms, a slice thickness of 0.75 mm, increment of 0.7 mm. The tube voltage was set as 120 k V and the tube current was 350-400 m As every round. Images were reconstructed with filtered back projection(FBP) and a medium soft convolution kernel(B26f). Contrast medium enhancement was achieved by injecting 50-60 ml of iodinated contrast material and injected at 5-6 ml/s followed by 30-50 ml of saline through an 18-G intravenous antecubital catheter by using a dual-syringe injector. A test bolus was first injected and the region of interest was placed within the ascending aorta to determine the required delayed time, which was defined as6 s when the CT value of interest of the ascending aorta was over 100 HU.Cross-sectional images reconstructed at multiple phases of the cardiac cycle window,curved planar reformation(CPR) and maximum intensity projection(MIP) were reconstructed, and selected the best DSCT image for assessment. The image quality of stent was assessed. The CCTA results were double-blind comparison with the ICA,evaluating the accuracy by the unit of stent, vascular branch and patient independently.Evaluate the accuracy of CCTA in diagnosis of coronary stent restenosis for different types of diameter. Comparing the CT values of the two sides and inside of stents without restenosis. Comparing the CT value difference of two sides of the stent between the stents without restenosis, restenosis stents and occluded stents.Results:(1)The CT images of 70 patients with 129 coronary stents were qualified for assessment. The sensity, specificity, positive predictive value and negative predictive value were 86.4%-88.9%, 90.6%-93.3%, 82.6%-93.3% and 87.5%-93.3% by the unit of stent, vascular branch and patient for the detection of coronary artery stent restenosis by CCTA. The sensity, specificity, positive predictive value and negative predictive value was 73.3%, 89.5%, 84.6% and 81.0% of CCTA for diagnosing the coronary artery stent restenosis of which is < 2.75 mm in diameter. The sensity, specificity, positive predictive value and negative predictive value was 95.0%, 85.7%, 79.2% and 96.8% of CCTA for diagnosing the coronary artery stent restenosis of which is ≥ 2.75 mm and ≤ 3mm in diameter. The sensity, specificity, positive predictive value and negative predictive value was 93.1%, 90.9%, 81.8% and 96.8% of CCTA for diagnosing the coronary artery stent restenosis of which is ≥ 2.75 mm in diameter. The sensity,specificity, positive predictive value and negative predictive value was 88.9%, 96.8%,88.9% and 96.8% of CCTA for diagnosing the coronary artery stent restenosis of which is > 3 mm in diameter.(2) The inner CT values of stents without restenosis was significant higher than the two sides of the stent( 149.59 ± 27.40 HU and 96.89 ± 24.94 HU, P < 0.01; 149.59 ± 27.40 HU and 87.83 ± 23.39 HU, P < 0.01). The CT value difference between proximal and distal of occluded stents was significant higher than that of the stents without restenosis( 41.74 ± 30.58 HU and 9.06 ± 11.13 HU,P < 0.01); The CT value difference between proximal and distal of occluded stents was significant higher than that of the stents with restenosis( 41.74 ± 30.58 HU and 16.21± 15.77 HU, P < 0.05); The CT value difference between proximal and distal of stents without restenosis and the stents with restenosis was no significant difference( 9.06 ±11.13 HU and 16.21 ± 15.77 HU, P > 0.05).Conclusion:(1)The second generation DSCT has a high diagnostic efficiency in the diagnosis of stent restenosis which is ≥ 2.75 mm in diameter. There is high sensitivity and negative predictive value in the diagnosis of stent restenosis with the second generation DSCT in which is ≥ 2.75 mm or ≤ 3 mm in diameter, it shows that it can be used for the diagnosis of coronary stent restenosis which is 2.75 mm and 3 mm in diameter.(2) There is a limit of the second generation DSCT in diagnosis of coronary artery stent restenosis which is < 2.75 mm in diameter because of the low accuracy of diagnosis.(3) For the stent without restenosis, beam hardening artifacts and / or partial volume effects lead to the high CT value of stent lumen, interfere with the evaluation of the stent lumen.(4) It may be helpful by measuring and analysis the CT values of the in-stent and two sides of the stent, and calculating the difference between them to identify the occluded stent from stent restenosis. |
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