| Objectives 1 To investigate the effects of different doses,flow rates,tube voltages and monitoring points in coronary CT angiography(CCTA)on image quality,patient radiation dose and Influence of contrast medium extravasation rate.2 To explore whether the optimal monitoring point combined with high-concentration contrast agent combined with low dose,low flow rate and low tube voltage can reduce the radiation dose received by patients on the basis of ensuring good image quality,and choose the optimal scheme for coronary CT angiography.Methods Prospectively selected patients from October 2020 to August 2021 who were admitted to our hospital due to suspected coronary artery disease.Coronary CTA was performed using GE Revolution 512-slice spiral CT machine,and high-concentration contrast agent was used as contrast agent.Classic Myron 400(400 mg I/mL).A total of three factors are included,namely monitoring point,injection scheme and tube voltage.Monitoring points include: descending aorta,ascending aorta,left atrium,and left ventricle.The injection scheme is the dose flow scheme,including group A(45ml;4.5ml/s),group B(40ml;4.0ml/s)and group C(35ml;3.5ml/s).Tube voltage includes 120 kVp,100 kVp,80 kVp.The grouping design was carried out with reference to the orthogonal table,and the patients were divided into 16 groups,and the patients in each group were randomly included.The images were evaluated subjectively and objectively,and SPSS 24.0 software was used for statistical analysis.The CT values of the aortic root,left main trunk,anterior descending branch,circumflex branch and right coronary middle segment,image noise,SNR of each target vessel,and CNR of contrast-to-noise ratio were compared by variance analysis,and Kruskal-Wallis rank sum test was applied.Compare image subjective ratings.Analysis of variance was used to compare the differences of radiation dose parameters CT volume dose index(CTDIvol),dose-length product(DLP)and effective dose(ED)in each group.The contrast medium extravasation in each group was recorded,and the chi-square test was used to compare the differences in the contrast medium extravasation rate.P <0.05 indicates a statistically significant difference between groups.Results A total of 208 patients were included,including 93 males and 115 females,and were divided into 16 groups with 13 cases in each group.1 There were statistically significant differences in the CT values of different cardiovascular sites in each group(all P<0.05).The CT value of each target vessel in group 4(descending aorta;45ml,4.5ml/s;80kVp)was the highest,which were(664.82±99.32)HU at the aortic root,(627.27±89.60)HU at the left main trunk,and near the anterior descending artery.Segment(575.40±92.17)HU,proximal circumflex branch(566.28±88.94)HU,and middle right coronary artery(598.22±72.10)HU.The CT value of each target artery in group 1(descending aorta;35ml,3.5ml/s;120kVp)was the lowest,which were(307.14±41.17)HU at the aortic root,(284.79±42.07)HU at the left main trunk,and near the anterior descending artery.Segment(286.37±44.87)HU,proximal circumflex branch(270.31±51.49)HU,middle right coronary artery(294.03±30.76)HU.The mean value of CT value of blood vessels in group1 failed to reach the best recommended diagnostic level of 325 HU,and the mean values of the other groups met the best diagnostic level.2 There were significant statistical differences in image noise,SNR and CNR values of each target blood vessel in each group(all P<0.05).Group 2(descending aorta;45ml,4.5ml/s;120kVp)had the lowest image noise at(19.29±4.71),and group 4 had the highest image noise at(28.45±3.64),which was32.2% lower in group 2 than in group 4 %.The CNR and SNR values of each target blood vessel in group 1 were the lowest,and the SNR and CNR of each target blood vessel in group 4 were the highest.3 The subjective image quality score was evaluated by two radiologists,and the consistency between the two was good(Kappa value=0.755>0.75).The average subjective image quality score of the 16 groups was 1.37 points,and the subjective image quality score among patients in each group was significant.Difference(χ~2=2.568,P=0.002<0.05).Group 10(left atrium;35ml,3.5ml/s;80kVp)and group 12(left atrium;45ml,4.5ml/s;100kVp)had the best mean subjective image quality score at1.08,and group 1 had the best mean subjective image quality score The worst was 2.00 points,and the average score of all groups reached the excellent level.4 There were significant differences in CTDIvol,DLP and ED in each group(all P<0.05).The radiation dose parameters of group 10 were the lowest,CTDIvol was(4.97±1.55)mGy,DLP was(59.98±19.12)mGy*cm,ED was(0.84±0.27)m Sv,and the radiation dose parameters of group 2 were all the same.was the highest,CTDIvol was(28.69±1.57)mGy,DLP was(362.00±38.04)mGy*cm,and ED was(5.07±0.53)m Sv.The highest radiation effective dose of group 2 was 6 times that of group 10,and group 10 was 83.4% lower than that of group 2.Among the 208 patients in this study,a total of 10 cases of contrast medium extravasation occurred,and the extravasation rate was 4.81%.There was no significant difference in the extravasation rate among the groups(χ~2=16.388,P=0.357>0.05),but there was a statistically significant difference in the extravasation rate among the groups by the injection regimen(χ~2=6.933,P=0.031<0.05).The extravasation rate in the high-dose,high-flow group was the highest(8.65%),and the extravasation rate in the low-dose,lowflow group was the lowest(0.00%).Conclusions 1 The high-concentration contrast agent can maintain the SNR and CNR of the image,and make the subjective and objective image evaluation of low tube voltage,low dose,and low flow rate meet the diagnostic needs.2 Reducing the tube voltage is the most important factor in reducing the radiation dose.3 The monitoring point was set in the left atrium,the injection scheme was(35ml;3.5ml/s),and the tube voltage was 80 kVp,which was an optimized scanning scheme for coronary CT angiography based on highconcentration contrast agents.Figure 3;Table 9;Reference 99... |
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