Research On Image Quality Improvement Of Using Spectral CT Monochromatic Imaging Based On Snapshot Freeze

BackgroundCoronary CTA is now increasingly used in the diagnosis of coronary artery disease.At present the temporal resolution,spatial resolution and image reconstruction algorithm continues to improve,But coronary CTA artifacts still exists and affects diagnosis,this problem should not be ignored.Motion artifacts that are more significant influence than the heart rate,the snapshot freeze,SSF is based on the hardware upgrade 64 row after the era of a new reconstruction algorithm,which USES adjacent cardiac cycle for the coronary artery by image information of the movement,thus correcting motion artifact to freeze the coronary arteries.ObjectiveTo assess the effect of a motion-correction algorithm(SSF)on image quality improvement at different CT value of using spectral CT monochromatic imaging on the fixed phrase of 65%.MethodsThe institutional ethical committee approved the trial in which patients were enrolled.Twenty-eight patients(mean age 56.3 ± 11.4;13males)underwent CCTA with a newly generation of spectral CT scanner(Discovery CT)and were randomly divided into 5 groups according to CT value: from 100 to 500 HU with increment of 100 HU.The CM volume was 200mgI/kg with injection rate was calculated as injection volume divided by 12(seconds).All images were reconstructed based on the fixed phase of 65% with 40% ASiR.Two independent readers evaluated coronary images according to a standard of 14 coronary arterial segments with a 5-point scale.Signal-to-noise ratio(SNR)and contrastto-noise ratio(CNR)of the ascending aortic root were compared with t test.Image quality of data set with and without SSF in different groups were assessed and compared with Wilcoxon test.ResultsThe SNR and CNR of 400HU(65keV)group were 16.8±2.5 and 21.9±3.2,which is higher than the other 4 groups.Image scores on a per-artery-segment level in different CT value groups without SSF were significantly lower than those with SSF algorithm(All p value <0.05).Image quality of LM,LAD-p,LAD-m,LAD-d,D1,D2,LCX-p,LCX-m,LCX-d,LMB,RCA-p,RCA-m,RCA-d,and PDA at 400HU(65keV)group with SSF(4.8±0.4,4.8±0.4,4.5±0.5,4.2±0.6,3.7±0.7,4.3±0.5,4.4±0.6,4.3±0.7,3.8±1,4.1±0.8,4.5±0.6,4.1±1,4.3±0.7,4.3±0.5)were better than without SSF(4.7±0.4,4.6±0.6,4.4±0.5,3.8±0.7,3.3±1,3.9±0.7,4.1±0.7,3.8±1,3.4±1,3.9±0.9,3.7±0.9,2±1,3.5±1,4.2±0.2).ConclusionsMotion-corrected reconstruction of SSF significantly improved image quality of the all segments of different CT value at the fixed phase of 65%.The optimal CT value was 400 HU.