A Comparative Study Of Iterative Reconstruction Technique In CT Coronary Dual-Low Scan Stent Imaging With Different Convolution Kernel

Objective: Percutaneous coronary intervention(PCI)has become one of the main treatment of coronary heart disease,however,coronary in-stent restenosis(ISR)is the more serious complications,to some extent,limits the widespread use of PCI,studies show that even if the IRS drug-eluting stents incidence is still around 10%,thus postoperative follow-up evaluation is necessary.Coronary computed tomography angiography(CCTA)has been widely used in the follow-up of stents.However,patients after PCI stent implantation are affected by stent image artifacts and image noise.CCTA still faces great challenges in the follow-up evaluation after PCI.Previous studies have shown that adjusting the convolution kernel can improve the display of the stent lumen and improve the detection rate of stent restenosis after PCI.At present,only commonly used cardiac convolution kernel(B26f,B46 f,I26f,I46f)are used in the study,while more convolution kernel,such as I50 f,have not been reported yet.There is still a lot of research space and prospect in the evaluation of coronary stent images by iterative reconstruction combined with convolution kernel.The purpose of this study was to evaluate the improvement of Safire iterative reconstruction technique in CT coronary stent imaging with different convolution kernel,and to assess the influence of convolution kernel(I50f)image on coronary stent display,and to explore ways to improve coronary stent imaging and provide higher quality imaging data for clinical use.Methods: 42 patients with 84 coronary stents were examined by dual-source coronary computed tomography angiography(CCTA).Scanning plan was made according to the patients with BMI to choose suitable tube voltage and scanning contrast medium dose.Images were reconstructed at convolution kernel of I26 f,I46f and I50 f with Safire iterative reconstruction technique.Safire iteration strength is 3,reconstruction of thickness is 0.5 mm.Two-dimensional and three-dimensional comprehensive observation of the reconstructed image is carried out by post-processing software.The three groups of images are evaluated and analyzed subjectively and objectively.Image noise was scored and stent was scored as subjective image evaluation,and objective evaluation including the aortic root CT value and stent lumen measurement noise.The differences in image noise and stent display between the three groups were compared.SPSS20.0 software was used for statistical analysis.Quantitative variables were expressed as mean ± standard deviation.Inter observer agreement for image quality was calculated using kappa(?)statistic.The subjective scores were analyzed by Friedman analysis and Wilcoxon test.Objective indicators for evaluating the three groups of continuous variables were analyzed by variance.P < 0.05 was considered statistically significant.Results: The image quality evaluation results of three groups of different convolution kernel reconstruction showed good consistency of the two physicians' scores.The subjective evaluation analysis of the three groups of images showed that images of I50 f group was rated best for clearly showing the details of the stents and its lumen showed the highest score of 4.07±0.32,and the score in the I26 f group was the lowest 3.39±0.42.The difference in the quality of the three groups of images was statistically significant(P=0.000).In the subjective analysis,with the convolution kernel value growing,the noise of the image increased.The noise score in the I26 f group is the highest(2.44±0.15)and the I50 f group is the lowest(2.02±0.09).Statistical significance could be found among the three groups(P=0.000).The objective evaluation showed that the noise of in-stent lumen among the three groups were not significant different(P>0.05).It shows that the three groups of image noise have little effect on the display of stent.Conclusion: Safire technology can effectively reduce noise and improve image quality,meanwhile it combined with the convolution kernel of I50 f is the best evaluation for stent display in this study,which can improve the display of stent wall and lumen,reduce image noise,and provide higher quality images for clinical use.