A Comparision Of Coronary CTA Between Diastolic And Systolic Images In Patients With 65-75bpm:Using High-pitch Mode

Objective:To investigate the image quality and radiation dose of Force CT coronary angiography using the high-pitch Turbo Flash spiral scanning mode with different acquisition phases(diastolic and systolic)in patients with 65-75bpm heart rate.Methods:A total of sixty patients who underwent computed tomography angiography of Force CT were analyzed.Among of the patients,25 females and 35 males had an average age of 63.02±9.33 years,with the age range of 41-82 years.All the patients were known or suspected to have coronary artery disease.All cases of CTA image data included a complete examination of ECG data and dose statistics report.According to the different phases of the CTA acquisition triggering,the cases were divided into two groups:30 patients in group A,the high-pitch Turbo Flash spiral scanning mode with diastolic acquisition phase was used,and the scanning phase was set at 65%R-R interval.30 patients in group B,the high-pitch Turbo Flash spiral scanning mode with systolic acquisition phase was used,and the scanning phase was set at 30%R-R interval.1.CT Scan Protocol and Image ReconstructionAll cases were scanned using Force CT.Scan parameters:using the high-pitch Turbo Flash ECG trigger spiral scanning mode and tube current automatic adjustment(CARE Dose 4D,Siemens)technology,and the reference tube voltage was 100kV.After the scan,the original data was uploaded to the syngo.via workstation,and a rich experiences of cardiovascular radiologist performed image processing,including VR,CPR and so on.2.Image Quality AnalysisSubjective image quality analysis was performed using a 17 segmented coronary artery model recommended by the American Heart Association.In order to avoid potential bias,the image quality of coronary artery segments were evaluated by two radiologists in unknown all the information,and the Likert scoring method was used.Using the CT value of coronary artery,image noise and other parameters were calculated for the signal to noise ratio and the contrast noise ratio to evaluate the objective image quality.3.Estimation of Radiation DoseThe scan dose reports were obtained by the Force CT system,included the number of X-ray exposure,volume CT dose index,scan times and dose length product.The effective dose was defined as the product of the weight factor ratio and the dose length product,the weight factor ratio was selected as the chest K=0.014mSv/mGy·cm.4.Statistical AnalysisStatistical software SPSS version 22.0 was used for data analysis.The Student's t-Test was used to compare the gender,the BMI index,the ED value,the signal to noise ratio and the CNR value in the two groups.Inter-observer variability between the two radiologists of subjective image quality assessments were evaluated with K statistics.The P values less than 0.05 were considered to be statistically significant.Results:1.Image Quality of Coronary Artery SegmentsOf the sixty patients there were 779 coronary segments(392 cases in group A and 387 cases in group B)in this study were evaluated.According to the assessments of group A,the highest image quality was recorded for segment of OM2 branch(score 1.00),and followed by LM(score 1.15);the lowest image quality was for the middle branch of RCA(score 2.33).In group B,the highest image quality was recorded for segment of OM2(score 1.00),and followed by LM(score 1.35);the lowest image quality was for the distal branch of LCX(score 2.33).In group A,there were 9 segments(n=9,2.3%)with a score of 4,appeared in the middle segment of RCA(n=5),the distal segment of the RCA(n=3)and the PDA(n=1).There were 19 segments(n=19,4.9%)with a score of 4 in group B,appeared in the proximal segment of RCA(n=3),the middle segment of RCA(n=2),the distal segment of RCA(n=2),the posterior descending branch(n=2),the posterior branch of left ventricle(n=2),the LM(1 times),the proximal segment of LAD(n=1),the middle segment of LAD(n=1),the first diagonal branch(n=1),the proximal segment of LCX(n=1),the first obtuse marginal artery(n=2)and the middle segment of LCX(n=1).Compared the results in the two groups,the image quality of the first diagonal branch,the first obtuse marginal artery,the proximal and middle segment of LCX in group A was significantly better than that in group B,and the other coronary segments showed no statistically significant difference.The image quality results of two radiologists were analyzed by Kappa,the results showed good consistency by the score(Kappa=0.816).Comparison of the measurements of CT value,image noise,SNR in the root of ascending aorta,the right and left coronary artery in the two groups,the results showed no significant difference(P>0.05).2.Radiation DoseThe mean values of CTDIvol,DLP and ED in group A were 3.53,59.82 and 0.84.The mean values of CTDIvol,DLP and ED in group B were 3.21,54.78 and 0.77.The comparison of the various parameters between the two groups showed no difference(P>0.05).Conclusion:1.The Turbo Flash mode of Force CT using low tube voltage(100kV)and low contrast-medium dose(40ml)combined with the ADMIRE iterative reconstruction,can meet the requirements of clinical imaging diagnosis,and the effective dose is less than 1mSv.2.When the patients with a heart rate of 65-75 bpm underwent coronary artery CTA,the use of high-pitch diastolic acquisition mode has a slight advantage,and the image quality of LCX is better.