Clinical Application Of 256-slice CT Combined With Adaptive Iterative Reconstruction In Reducing Radiation Dose Of Coronary CTA

Objective:The radiation dose,contrast agent dosage and image quality of patients undergoing coronary CTA examination were studied by using 256-slice CT combined with adaptive iterative reconstruction technique,in order to explore the better scanning scheme,adaptive iterative reconstruction weight and contrast agent use scheme.Methods:A total of 180 patients who underwent coronary CTA with GE Revolution CT between September 2019 and September 2020 were enrolled in this study.All patients were aged between 18 and 80 years old and were treated with iodinated contrast medium 370mgI/ml.The injection rate was the dosage of contrast medium/duration of continuous injection(duration of continuous injection was 13 seconds),and the patients were divided into three groups according to the scanning method,with 60 people in each group.In the first group(100kV group),the tube voltage was 100kV,the dosage of contrast medium was 0.8ml/kg,and 50%ASiR-V was used for iterative reconstruction.The tube voltage of the second group(kV Assist group)was automatically set by kV Assist,and the dosage of contrast medium was 1.0ml/kg(fatless weight was used in this group,and the calculation formula of fatless weight was male=1.00×weight-128×(weight/height)2;Female=1.07×weight-148×(weight/height)2),50%ASiR-V iterative reconstruction;The voltage of the third group was 120kV,the contrast medium was 1.0ml/kg,and iterative reconstruction was not adopted.All the three groups were treated with prospective ECG gating and SSF.The contrast medium was stimulated at 200HU with a delay of two seconds,and automatic tube current scanning was performed.The scanned images were sent to the workstation for post-processing,and the coronary tree extraction and curve planar reformation(CPR)were performed.,and volume rendering(VR)of the heart and coronary vessels.The corresponding dose length product(DLP)and CT dose index volume(CTDIvol)were recorded,and the effective radiation dose(Efective dose,ED)=DLP×k[k=0.014mSv/(mGy·cm)].Two physicians with more than three years of experience in imaging diagnosis separately used the five-point method for subjective evaluation of the images.When the results were inconsistent,senior cardiovascular imaging diagnostic physicians were asked to discuss and determine the final score.CT values of aortic root,left main coronary artery,proximal,middle and distal segments of left anterior descending,proximal and distal segments of circumflex,and proximal,middle and distal segments of right coronary artery were measured,and objective evaluation indexes such as image noise,contrast-to-noise ratio and signal-to-noise ratio were recorded.All data were analyzed using SPSS 22.Results:(1)The subjective score of coronary artery CTA image quality in the three groups was more than 2 points,which met the diagnostic requirements.There were differences in subjective quality score,signal-to-noise ratio and contrast-to-noise ratio among the three groups,and the kV Assist group was the best.The kV Assist group also had better image quality for patients with different BMI.(2)The ED and dosage of contrast medium in the 100kV group were not statistically different from those in the kV Assist group,and both were lower than those in the 120kV group.The ED and dosage of contrast medium in the 100kV group were 30%and 19%lower than those in the 120kV group,and,in the kV Assist group,the decrease was 20%and 23%compared with the 120kV group.(3)In the kV Assist scanning condition,the image quality increased with the increase of the ASiR-V iteration ratio.Conclusion:(1)Compared with the 120kV group,the scanning and iterative reconstruction scheme of the kV Assist group and the 100kV group could obtain better image quality and reduce the amount of contrast medium and ED.(2)Among patients with different BMI,the image quality was better in the kV Assist group when the same or lower dosage of contrast medium was used than in the 100kV group.(3)Under the scanning condition of kV Assist,the image quality increases with the increase of ASiR-V iteration ratio,and a higher iterative reconstruction ratio can be selected to obtain better image quality.