| Objective To assess the image quality, radiation dose, and diagnostic accuracy of Revolution CT under the tube voltage 80 KVp and low concentration and volume of contrast material for normal body mass index patients. and to investigate the radiation dose and iodine load.Material and methodsObject of study: In our hospital internal Medicine-Cardiovascular Department,60 patients who were suspected to have coronary artery diseases and BMI between 18~25kg/m2 were collected. After the CCTA examination, all the patients were received the coronary angiography(CAG) in one week. according to the number of table were randomly divided into A,B groups,each group had 30 patients. Before the CCTA examination, the heart rate of each patient was controlled in 90 times per minute with a sinus rhythm. And all the patients were signed the informed consent. This study obtained the approval of ethics committee of YanCheng Third People’s Hospital.CCTA protocol: The CCTA examinations were performed using GE Revolution CT.The parameters of scan were as follows, tube voltage: 80kVp(group A) and120kVp(group B), tube current automatic, FOV 23 cm, scan thickness 0.625 mm, rotation time 280 ms and Matrix 512×512.group A:low concentration of contrast medium iodixanol270 mg I/ml, the total weight 0.6ml/kg, flow rate was 5ml/s. group B:high concentration of contrast medium iodixanol 350 mg I/ml, the total weight 1.0ml/kg, flow rate was 5ml/s.After injection of contrast agent, two group were injected 30 ml saline by the same rate.The CM automatic bolus-tracking was used.Using axial scan model The patients were supine on the examination bed as foot go into firstly, using prospective ECG gating to scan.The scanning range is from 10 mm below the bifurcation of tracheal to 10 mm below the diaphragmatic surface. According to the patients were scanned prior to recording of ECG automatic selection of scanning phase, coronary artery enhanced scan. The original data were used iterative reconstruction such as ASIR-V.CAG protocol: DSA images was getted form GE angiography machine. Coronary angiography was achieved according to routine Judkin’s method by experiencedphysicians of cardiology who has the interventional qualification. Coronary angiography was accomplished using conventional percutaneous cradial artery. The left main artery(LM), the left circumflex artery(LCX), left anterior descending artery(LAD) and the right coronary artery(RCA) were displayed respectively. The coronary angiography images were observed by two cardiovascular specialis.Image analysis: After scanning recording scan length, dose length product and CT volume dose index,calculating the effective radiation dose.To objectively evaluate the attenuation(in HU)and standard deviation(in HU)of the descending thoracic aorta,and the attenuation(in HU) of the three territories(right coronary artery, left circumflex coronary artery, left anterior descending and perivasculartissue of each of the arteries).Then determined SNR and CNR of RCA,LCX,LAD.The CT data analysis was performed by two radiologists who had more than 8 years of experience in cardiovascular radiology respectively.Statistical analysis: All the data were analyzed by SPSS20.0 software. The normal distribution test and homogeneity of variance test were imposed in the weight, age, height,heart rate, BMI, CTDIvol, DLP, ED and the attenuation(HU) of the descending thoracic aorta, RCA,LAD,LCX. While all of them were compared by independent samples t-test.There is statistically significant difference when P<0.05. The sensitivity, specificity,positive predictive value and negative predictive value for in-stent restenosis of the two groups were calculated respectively by using CAG as the gold standard. Then the consistency between CCTA and CAG was examinated by Kappa test.Results:(1)The attenuation(in HU) and image noise in the two groups were statistically different(P < 0.05). The A group was less than B group, but there were no significant difference between two groups of SNR and CNR.(2)The ED of A Group was0.67 mSv and B group was 1.61 mSv, there were statistically significant differences between them, Group A were less than B group.(3)The amount of iodine in group A was10.8gI, and the amount of iodine in group B was 23.10 gI, the difference between the two groups was statistically significant.(4)For Coronary artery stenosis, the diagnostic sensitivity and specificity of group A with CCTA were 92.8% and 87.5%, while that of group B with CCTA were 80.0% and 93.4%. The positive predictive value and negative predictive value of group A with CCTA were 86.7% and 93.3%, while that of group B with CCTA were 92.3% and 88.2%. There were good agreement in consistency between CCTAand CAG, as the Kappa value between group A and CAG was 0.800 and that between group B and CAG was 0.795.Conclusion: For the normal heart rate in patients with normal body mass index, the use of low concentration and low amount of contrast agent in the low tube voltage 80 KVp coronary artery CTA examination, the image quality does not affect the diagnosis of coronary artery disease, and can effectively reduce the radiation dose and iodine load. |
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