Feasibility of high concentrated contrast media combined with monochromatic images to improve image quality with double low scanning in dual-layer spectral coronary CT angiography / 中华放射学杂志

ABSTRACT

Objective:To evaluate the feasibility of high concentrated contrast media combined with monochromatic images to improve image quality with double low scanning in dual-layer spectral coronary CT angiography.Methods:Fifty-six patients with suspected coronary artery disease were enrolled and randomly separated into two groups. All patients were scanned at 120 kVp in step-and-shoot mode using a dual-layer detector CT (IQon spectral CT). Patients were either injected with 18 ml high concentration contrast medium(400 mgl/ml) at 2 ml/s (group A) or 45 ml contrast medium (370 mgl/ml) at 4 ml/s (group B). Forty to 80 keV monoenergetic images with 10 keV increment and conventional image (group A2) were reconstructed for group A, conventional poly-energetic image was reconstructed for group B. Region of interest was placed on aorta root (AO), middle segment of left anterior descending (LAD), left circumflex (LCX) and right coronary artery (RCA) to measure the attenuation and noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). Image quality was assessed by two reviewers independently with a 4-point scale on image quality (1-undiagnostic,4-excellent). The objective and subjective image evaluation were compared using the Kruskal-Wallis test. The Steel Dwass was used for multiple comparisons between monoenergetic images in Group A and conventional images in Group B, after the Kruskal-Wallis test.Results:There were significant differences among the attenuation, noise, SNR and CNR of group B, group A2, and monoenergetic images(all P<0.001).The CT value in the aortic root was significantly higher at 40-50 keV monoenergetic images than that in group B(all P<0.05), and similarly, the CT value in LAD,LCX and RCA at 40 keV were superior than that in group B(all P<0.001). There was no significant difference in the noise of the aortic root among 40 keV image, group A2 and group B(all P>0.05),while the noise in the 50-80 keV monoenergetic images were significantly lower than that in Group B(all P<0.001). The SNR and CNR in the aortic root were significantly higher at 40-60 keV monoenergetic images than that in group B(all P<0.001).The SNR in LAD and RCA at 40，50 keV and the CNR in LAD and RCA at 40-60 keV were higher than that in group B(all P<0.01).The SNR at 40-60 keV and CNR at 40-70 keV in LCX were superior than that in group B(all P<0.05). There were significant differences among the subjective image quality score of group B, group A2, and monoenergetic images(all P<0.001).The subjective image quality score of 40，50 keV images were not significantly different from that in group B (all P>0.05),while the score in 60-80 keV image and group A2 were lower than that of Group B(all P<0.001). Conclusion:40，50 keV low monochromatic images derived from dual-layer spectral detect CT combined with high concentrated contrast media can provide comparable or superior image quality with double low scanning in CCTA study.