Improving Image Quality Of Off-peak Cardiocerebrovascular CTA Using DE-CT Non-linear Blending Technique

Objectives:To investigate the application of dual energy non-linear blending on CCTA、CTPA and head CTA which the subjective image quality are not more than 3 score,and investigate the optimization selection of non-linear blending coefficients for the image of head CTA.Methods:1.56 CCTA patients,64 CTPA patients,and 53 head CTA patients underwent contrast-enhanced DSCT scan which LB subjective image quality that are not more than 3 score,and all have NLB.2.CCTA images were divided into 4 groups,including 100kV group,140kV group,linear blending(LB)group and non-linear blending(NLB)group.Contrast image quality,CT value,SD,SNR and CNR of 4 groups were measured and calculated respectively.ROI(region of interesting)selected on 4 coronary arteries(the far segment of RCA,LM,the far segment of LAD,and the far segment of CX)left heart normal myocardium,infarcted myocardium and normal myocardium at the same level,evaluated the CT value,SD,SNR,CNR and subjective image quality of 4 groups.CTPA images were divided:into 2 groups,including linear blending(LB)group and non-linear blending(NLB)group.Contrast image quality,CT value,SD,SNR and CNR were measured and calculated respectively in the 2 groups.ROI(region of linteresting)selected on 7 pulmonary arteries(pulmonary artery trunk,right pulmonary artery,left pulmonary artery,left upper lobe artery,left lower lobe pulmonary artery,right upper lobe pulmonary artery and right lower lobe artery),embolus and back muscles,evaluated the CT value,SD,SNR,CNR and subjective image quality of 2 groups.3.Each head DECT NLB data was post-processed with 8 different settings:NLB1-4:BW was fixed to 200HU and BC were set to 0,80,150,250 HU;NLB5-8:BC was fixed to 150HU and BW were set to 0,100,200,300 HU.All NLB data sets were compared with linear blending images(M=0.4)in subjective image quality,CT value,image noise,signal noise ratio(SNR),contrast to noise ratios(CNR)at various anatomy regions:internal carotid artery,middle cerebral artery,basilar artery,brain stem.4.The subjective image quality score of CCTA uses 4 points scale,4 point is high quality image,and 2 point could meet the diagnostic requirements.The subjective image quality score of CTPA and head CTA use 5 points scale,5 point and 4 point were high quality images,and 3 points could meet the diagnostic requirements.1-2 points to 3 points was defined as image quality improvement,which could avoid re-scanning,and 3 point increase to 4 point or more was defined as image quality improvement.Results:1.For the CT value.SNR and CNR of the 8 ROIs of coronary arteries,100kV group was highest CT value,NLB group was better than LB group,the difference had statistically significance(P<0.05).For SNR,NLB group is higher than 100kV group and 140kV group(P<0.05).And the CNR of NLB group was better than other three groups(P<0.05).For the mean CT value and air noise of normal myocardium,there were no statistically significant differences between NLB group and LB group(P>0.05).Contrast the CT values of infarcted myocardium,and the difference between normal myocardium and infarcted myocardium,the nfarcted myocardium of NLB group was lower than that of LB group,and the CNR of NLB is higher than that of LB group.After NBL,the CCTA subjective image quality score had improved than before,which had significant difference(P<0.05).NBL had increased the subjective scroe based grading of vascular 0.50 score.1-2 score improved 8.93%,3 score improved 30.36%.2.For the CT value.SNR and CNR of the 7 pulmonary arteries,NLB group was better than LB group,the difference had statistically significance(P<0.05).Contrast the CT value of embolus,NLB group was lower than LB group,and the enbolus CNR of NLB group were higher than LB group(P<0.05).For the mean CT value of back muscles,there were no statistically significant differences between NLB group and LB group(P>0.05).The subjective image score of NLB group increased 0.53 score,which was higher than LB group(P<0.05).3.After NBL,the subjective image quality score had improved than before,which had significant difference(P<0.05).Subjective scroe based grading of vascular increased 0.51 score.including 1-2 score 7/16(43.38%),3 score 20/37(54.05%).the CT value,SNR and CNR of NLB were higher than LB(P.<0.01),and NLB groups had lower background noise than LB(P<0.05).For the CT value,80kV group was highest,and NLB group was batter than LB group(P all<0.05).The CT value and CNR of NLB 1-3 were higher than NLB4 in the three arteries,NLB 1 and NLB5 had highest CT value,CNR in NBL1-4 and NLB5-8(P<0.05).But there were no statistically significant difference in SD and SNR in NLB 1-8(P<0.05).For subjective scoring,NLB 1 improved 0.47,which was higher than NLB4(P<0.05),and NLB5 improved 0.37,which was higher than NLB8(P<0.05).Conclusion(s):The NBL takes obvious advantages in improving the image quality of CCTA,CTPA,and head CTA,and increases the diagnosable rate and excellent rate.The NBL could enhance the contrast of coronary plaque and artery,the contrast of infarcted myocardium and normal myocardium,the contrast of pulmonary embolus.and BC(0-80HU)and BW(0-100HU)could obtain optimal CT value and CNR in head CTA.