| Objective:To evaluate the image quality of coronary computed tomography angiography with low concentration of contrast agent and low radiation dose and compare with retrospectively/prospectively ECG-triggered CCTA,to explore the clinical feasibility of prospectively electrocardiogram(ECG)-triggered high-pitch in third-generation dual-source computed tomography with low-voltage and low-contrast..Methods:641 consecutive patients who had suspected coronary artery disease underwent coronary CTA were divided into two groups randomly,341 patients in group A underwent prospectively ECG-triggered high-pitch CCTA,these patients were divided into two groups according to their HR,185 cases of heart rate<70bmp patients with group A1,and 156 patients with heart rate>70bmp with group A2.300 patients in group B underwent conventional retrospectively/prospectively ECG-triggered CCTA.Using the third generation dual source CT for CCTA inspection,rack rotation time:0.25s/r,detector collimation:2×96 ×0.6 mm,reconstruction time resolution:66ms;layer thickness:0.75mm,layer spacing:0.7mm;Patients in group Ai were scanned with prospectively triggered at 75%and patients in group A2 were scanned with prospectively triggered at 35%of the R-R%interval respectively.Exposuring with automatic tube voltage and tube current.Patients in group B using a retrospectively/prospectively ECG-triggered.Prospective ECG-triggered sequential acquisition were performed in patients with final heart rate<70bpm,retrospective ECG-triggered sequential acquisition was performed in patients with final heart rate>70 bpm.The tube voltage and current modulation were determined according to individual body habitus.Image reconstruction algorithm:iterative reconstruction(IR)technique(ADMIRE,Siemens),smooth kernel(Bv40,strength 3).Contrast agent concentration:30ml?35ml(group A),70ml?75ml(group B).The region of interest(RQI)was set up on the level of tracheal bifurcation in the ascending aorta by using iodine contrast agent tracer.The triggering threshold with group A and group B were>80HU and>100HU respectively,after reaching the threshold delay 5s automatically start the heart scan.The image was then reconstructed and analyzed by Syngo.via VB10(Siemens Healthcare,Forchheim,Germany).The average CT value and noise(SD)in ascending aortic root(AA),right coronary artery(RCA),left main coronary artery(LM),left anterior descending(LAD),left circumflex artery(LCX)proximal lumen and apex adipose tissue were calculated,and the signal to noise ratio(SNR)and contrast to noise ratio(CNR)of each part were calculated.Evaluated the image quality independently and compared the image quality of group A1 and group A2 with group B respectively.Results:? There was no significant difference in the general information between group A and group B.The effective radiation dose and contrast agent dose in group A was significantly lower than those in group B(P<0.01).? Heart rate and heart rate variability are the independent factors influencing the diagnosis of high pitch images.When the heart rate is<69.5bmp,the sensitivity and specificity of the images satisfying the diagnosis were 80.0%and 69.7%,respectively;When the heart rate variability is?5.5bmp,the sensitivities and specificities of the images satisfying the diagnosis were 61.8%and 68.2%.? The CCTA image score>3 was defined as the image quality to meet the diagnosis.Based on the number of patients,the imageable rates of the group A1,group A2,and group B were 87.56%,69.87%,92.00%respectively;Based on the number of blood vessel segments,the imageable rates of the group A1,group A2,and group B were 5.76%,90.10%,96.15%respectively.There was significant difference between group Ai and group A2,group A2 and group B(P1=0.000/0.000,P3=0.000/0.000),but there was no significant difference between group A1 and group B(P1=0.109/0.404).?The CT value and noise of group A were significantly higher than those of group B(P<0.05),and there was no significant difference in SNR and CNR among these three groups.? The image quality scores of the group Ai,group A2 and group B were 3.63±0.77,3.36±0.84,3.68±0.80.There were significant differences between group Ai and group A2,group A2 and group B(P1=0.000,P2=0.000),but there was no significant difference in image quality between group Ai and group B(P3=0.112).Conclusion:? Using the third-generation dual-source CT high pitch with low-voltage and low-contrast for coronary CCTA,patients with low heart rate(?69.5bmp)and low heart variability(?5.5bmp)have a high diagnostic ability and excellent image quality,and the radiation dose and iodine contrast agent decreased significantly;?There showed no significant difference in CT value,noise,CNR,SNR between patients with high heart rate(>69.5bmp)and low heart rate(?69.5 beats/min),but the image quality scores and evaluate rates in former subjective is low,and its clinical application may be limited. |
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