Application of CTA with monoenergetic imaging combined with iterative reconstruction using a sharp convolution kernel in the evaluation of in-stent restenosis

Abstract:

Objective：To study the practical value of computed tomography angiography（CTA） with monoenergetic imaging combined with iterative reconstruction using a medium-sharp convolution kernel（B60f，SAFIRE） in the diagnosis of in-stent restenosis（ISR） of the lower extremities. Methods：CTA of the lower extremity arteries was performed in 72 patients（37 males and 35 females） with a stent implanted in the femoral artery. Among the above patients，25 underwent dual-energy scanning combined with iterative recon－struction using a medium-sharp convolution kernel（B60f，SAFIRE） and were subdivided into two monoenergetic imaging groups（70 keVsharp and 80 keVsharp）；47 underwent 100-kV scanning and were subdivided into 100 kVstandard group（23 cases，using adaptive statistical iterative reconstruction[50% ASIR]） and 100 kVsharp group（24 cases，using iterative reconstruction with a medium-sharp convolution kernel[B60f，SAFIRE]）. These groups were com－pared for image noise（standard deviation[SD]），signal-to-noise ratio（SNR），contrast-to-noise ratio（CNR），stent-vessel deviation（SVD），and measured-actual deviation（MAD）；the diagnostic accuracy for ISR was evaluated by taking into ac－count the results of vascular ultrasound or digital subtraction angiography. Results：In groups of the same energy level and processed with different reconstruction methods，the image noise（SD） was significantly lower in the 100 kVstandard group than in the 100 kVsharp group；there were no significant differences between groups in SNR or CNR（P>0.05）. Between groups of different energy levels and processed with the same reconstruction method，there were significant differences in image noise（SD）（70 keVsharp<80 keVsharp<100 kVsharp，P<0.05） and intraluminal SNR and CNR（100 kV sharp<70 keVsharp<80 keVsharp，P<0.05）. There were significant differences between groups in SVD（70 keVsharp<80 keVsharp<100 kVsharp<100 kVstandard，P<0.05），MAD（80 keVsharp<100 kVsharp<70 keVsharp<100 kVstandard，P<0.05），subjective image quality score（70 keVsharp<100 kVs－tandard<100 kVsharp<80 keVsharp，P<0.05），and diagnostic accuracy for ISR（70 keVsharp（71.04%）<100 kVstandard（86.19%）<100 kVsharp（91.27%）<80 keVsharp（95.8%），（ χ2=9.95，P=0.019），κ=0.743，P<0.05）. Conclusion：Monoenergetic imaging combined with iterative reconstruc－tion using a medium-sharp convolution kernel（B60f，SAFIRE） in the 80 keVsharp group can help optimize the image quality of CTA for stent-implanted vessels and improve the diagnostic accuracy for ISR.