The Preliminary Study On The Application Of CCTA Under Double-low-dose In The Follow-up Of Patients With Prior Coronary Stents Implantation

Objective To estimate the image quality, radiation dose, and diagnostic accuracy of double-low-dose coronary CT angiography(CCTA). And to investigate the clinical value of double-low-dose CCTA in the follow-up of patients who have received the surgery of coronary stents implantation.Material and methodsObject of study: From June 2014 to January 2015, 40 patients who were implanted coronary stents were collected. There were 25 male and 15 female, aged from 49 to 72 years old with an average age of 62.±7.1 years old. All patients were divided into A or B group by random as 20 patients in each group. Group A were examed with 270 mg I/ml iodixanol and a tube voltage of 100 k V, while group B were scanned with 350 mg I/ml iohexol and a tube voltage of 120 k V. The body mass index(BMI) of each patient was caculated through the height and weight before the CCTA examination. 83 stents were implanted in all the 40 patients, with an average of 2 stents in each patient. Before the CCTA examination, the heart rate of each patient was controlled in 50 ~ 70 times per minute with a sinus rhythm. And all the patients were signed the informed consent. After the CCTA examination, all the patients were received the coronary angiography(CAG)anytime soon. This study obtained the approval of ethics committee of Yan Cheng Third People’s Hospital.CCTA protocol: The CCTA examinations were performed using Gemstone-CT(GE Discovery 750 HD). Patients with heart rate higher than 70 times per minute before the examination were taken 25 to 50 mg metoprolol to control heart rate. All the patients were trained breathing and taken 0.25 mg nitroglycerin by sublingual to expansion coronary artery at 5 minutes before the examination. The patients were supine on the examination bed as foot go into firstly, using prospective ECG gating HD model to scan. The scanning range is from 10 mm below the bifurcation of tracheal to 10 mm below the diaphragmaticsurface. Before the enhancement scanning of coronary artery, the calcium score of coronary artery was scanned firstly. The parameters of scan were as follows, tube voltage:100k V(group A) or 120 k V(group B), tube current 600 m A, FOV 23 cm, scan thickness0.625 mm, rotation time 350 ms and Matrix 512×512.CAG protocol: DSA images was getted form GE angiography machine. Coronary angiography was achieved according to routine Judkin’s method by experienced physicians 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: The original and reconstruction data were transported to AW4.6workstation,then the CT data were analyzed with double blind method by two radiologists who was worked in cardiovascular radiology more than three years. The the attenuation(HU) of the descending thoracic aorta, RCA, LAD, LCX were measured in each patient. While the scan length(L), volume CT dose index(CTDIvol) and dose length product(DLP) were recorded. Finally, the effective dose(ED) of radiation was calculated.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: The differences of weight, age, height,, heart rate, BMI, CTDIvol, DLP.and the attenuation(HU) of the descending thoracic aorta, RCA, LAD, LCX have no statistically significant between the two groups. The ED of A Group was 1.19 m Sv and B group was 1.93 m Sv, there were statistically significant differences between them. For in stent restenosis, the diagnostic sensitivity and specificity of group A with CCTA were83.3% and 96.7%, while that of group B with CCTA were 90.0% and 93.5%. The positive predictive value and negative predictive value of group A with CCTA were 90.9% and93.5%, while that of group B with CCTA were 81.8% and 96.7%. There were good agreement in consistency between CCTA and CAG, as the Kappa value between group A and CAG was 0.822 and that between group B and CAG was 0.809.Conclusion: The CCTA examination with double-low-dose technology can be applied in the follow-up of patients who recieved coronary stents implantation. It can significantly reduce the radiation dose on the premise of ensuring the image quality. The CCTA examination with double-low-dose technology has highly diagnostic accuracy in the diagnosis of stent restenosis.