Image Quality And Its Influencing Factors Of 70kV Tube Voltage Prospectively ECG-triggered High-pitch CCTA With 30ml Iodine Contrast Agent

Objective:To evaluate the image quality and its influencing factors of 70 kV tube voltage prospectively ECG-triggered high-pitch CCTA with 30 ml iodine contrast agent in third-generation dual-source CT.Methods:544 consecutive patients with suspected coronary heart disease received high-pitch CCTA,grouped by heart rate,group A(heart rate<60 bpm)165 patients,group B(60 bpm≤heart rate<70 bpm)201 patients,group C(heart rate≥70 bpm)178patients.Using three generations of dual-source CT,the tube rotation speed is 250ms/rev,the scanning bed travel speed is 737 mm/s,the single-sector reconstruction time resolution is 66 ms,the detector collimation is 2 x 96 x 0.6 mm,the layer thickness is0.75 mm,and the layer spacing is 0.5 mm,pitch 3.2,matrix 512 x 512.For patients with a heart rate greater than or equal to 70 bpm,the CT data collection point is preset to35%of the ECG R-R interval;for patients with a heart rate less than 70 bpm,the CT data collection point is presetted to 65%of the ECG R-R interval.Using automatic tube voltage(select 70 kV)and automatic tube current regulation technology.Using Advanced modeled iterative reconstruction(ADMIRE)technology,the reconstruction intensity is 3 and the convolution kernel value is Bv40.The iodine contrast agent iopromide(300 mg I/ml,Bayer-Schering,Germany)was intravenously injected using a double barrel high pressure syringe at a flow rate of 6.0 ml/s.The iodine contrast agent tracking program was used to automatically trigger the technique.The region of interest(ROI)was placed in the ascending aortic lumen of the tracheal bifurcation level and the CT value was monitored.The threshold was set to 100 HU.When the CT value reaches the threshold,the CT delay 5 S automatically triggers the high-pitch CCTA scan.The original CT images were passed to a Syngo.via VB10(Siemens Healthcare,Forchheim,Germany)image post-processing workstation for analysis,Image quality was assessed subjectively with a 5-point scale.Heart rate,heart rate variability,body mass index(BMI),effective dose(ED),and iodine uptake were recorded.Results:(1)544 patients including 266 males and 278 females,aged 26-87(60.18±11.31)years old,BMI(23.34±2.23)kg/m~2,ED 0.13-0.61(0.31±0.05)mSv,and the input of iodine is 9 g.There were no significant differences in gender,age,BMI and ED among groups A,B and C(P>0.05).(2)Among all 6775 segments(544 patients),676,2729,2641,573,and 156 segments were 5,4,3,2,and 1 score respectively,with an average of 3.62±0.83 score.Among all 2069 segments(group A),289,1079,651,147and 3 segments were 5,4,3,2 and 1 score respectively,with an average of 3.77±0.45score;Among all 2517 segments(Group B),274,1058,971,177 and 37 segments were5,4,3,2 and 1 score respectively,with an average of 3.53±0.58 score;There were Among all 2189 segments(group C),113,592,1019,349 and 116 segments were 5,4,3,2 and 1 score respectively,with an average of 3.10±0.62 score;The difference among the three groups was statistically significant(P<0.05).(3)Among all 544 patients,the imaging diagnostic rates of patients,vascular branches and segments were 67.28%(366/544),85.12%(1384/1626)and 89.24%(6046/6775).In units of the patients,the diagnostic rates for groups A,B,and C were 89.09%(147/165),65.67%(132/201),and48.88%(87/178);In units of the vascular branchs,the diagnostic rates of groups A,B,and C were 96.96%(479/494),88.04%(530/602),and 70.75%(375/530);In units of the vascular segments,the diagnosis rate of group A,B and C was 97.58%(2019/2069),91.50%(2303/2517)and 78.76%(1724/2189);The difference among the three groups was statistically significant(P<0.05).(4)In 544 patients,the heart rate and heart rate variability were independent factors influencing the diagnosis of CCTA.When the heart rate was<68.5 bpm,the sensitivities and specificities of the images satisfying the diagnosis were 78.4%and 74.2%;When the heart rate variability was<7.04%,the sensitivities and specificities of the images satisfying the diagnosis were 78.4%and74.2%respectively.Conclusion:(1)With third-generation dual-source CT,70 kV tube voltage prospectively ECG-triggered high-pitch CCTA with 30 ml iodine contrast agent results in coronary image quality that meets diagnostic requirements in most patients with very low radiation dose(approximately 0.31 mSv)and iodine intake(9 g).(2)With third-generation dual-source CT,70 kV tube voltage prospectively ECG-triggered high-pitch CCTA with 30 ml iodine contrast agent is suitable to patients with suspected coronary heart disease whose heart rate is less than 68.5 bpm and heart rate variability is less than 7.04%respectively.