Clinical Application Of Right Atrium Triggering Technique Under Calm Breathing In Pulmonary Artery CTA "Double Low" Scan

ObjectiveThe purpose of this study was to explore the clinical value of the right atrium triggering technique under calm breathing in pulmonary CTA "double low" scanning through a controlled study.MethodsThis study was a prospective,controlled study,in which 80 patients in our hospital who were clinically suspected of pulmonary embolism from January 2018 to March 2019 were enrolled for pulmonary CTA imaging.According to the principle of random grouping,all the patients were divided into groups A and B,with 40 patients in each group.Scanning parameters of group A:the tube voltage was set to 100kV(BMI?25kg/m2)or 120kV(BMI>25kg/m2),the dose of contrast agent was 1ml/kg,the method of breath holding scanning was adopted with the pulmonary trunk as the region of interest(ROI),the trigger threshold was 100Hu,and the delay time after automatic trigger was 6s.Scanning parameters of group B:the tube voltage was 80kV(BMI<25kg/m2)or 100kV(BMI>25kg/m2),the dose of contrast agent was 0.7ml/kg,the right superior atrial vena cava injection was adopted as the area of interest(ROI)for calm breathing scanning,the trigger threshold was 80Hu,and the delay time after automatic trigger was 4s.Both groups used CARE Dose 4D automatic tube current modulation technology,and the contrast injection rate was 4.0 ml/s.The original data were transmitted to Philips workstation,and the CT values of the main pulmonary artery(MPA),the right superior pulmonary artery(RULA),the posterior basilar segment artery(RLPA),the right superior pulmonary vein(RUPV)and the right inferior pulmonary vein(RLPV)were measured in the two groups.Measure the signal-to-noise ratio(SNR)and contrast-noise ratio(CNR)of the pulmonary artery image,and subjectively evaluate the image quality.Two senior radiologists used double-blind method to evaluate the quality of the images.The corresponding effective radiation dose(ED)was calculated according to the dose parameters automatically output by the machine.SPSS19.0 medical statistical software was used for data analysis.Paired t test was used for CT value,SNR,CNR and other count data between groups,and ?2/rank sum test was used for rate comparison and grade data.P<0.05 was considered statistically significant.ResultsExamination results:in this study,there were 40 patients in group A and group B,and the image quality in both groups reached the diagnostic standard.Among them,3 patients were diagnosed with PE in group A and 4 patients were diagnosed in group B.Results of subjective evaluation of image quality:there was no statistical significance in the image quality score of the two groups(P>0.05),and the kappa value of consistency evaluation of the two CT physicians was 0.901,with good consistency.The average score of image quality in the two groups was(4.60±0.58)and(4.40 ± 0.88),respectively,with no statistically significant difference(t=1.061,P>0.05).Objective evaluation results of image quality:There was no statistically significant difference in MPA,RULA and RLPA CT values between the two groups(t=0.334,1.924,1.714,P>0.05).RUPV and RLPV CT values in group B were(116.92 ±29.85)Hu and(132.74±55.72)Hu,respectively,which were significantly lower than those in group A(294.32±39.87)Hu and(284.61±42.87)Hu,and the differences were statistically significant(t=22.352,18.957,P<0.05).The mean SNR and CNR of pulmonary artery images in group A were(10.81±1.42)and(9.95±1.79),respectively,while those in group B were(9.22±1.92)and(8.26±1.82),with no statistically significant difference(t=1.824,1.774,P>0.05).CT radiation dose results:CTDlvol,DLP and ED in group B were(2.65 ± 0.19)mGy?(123.06±12.69)mGy·cm?(2.09±0.26)mSv,respectively,significantly lower than those in group A(3.76±0.28)mGy?(196.94±16.08)mGy·cm?(3.35±0.36)mSv,with statistically significant differences(t=5.036,32.715,3.857,P<0.05).ConclusionsThe multi-slice spiral CT right atrium trigger technique under calm breathing combined with "double low" scanning technique can effectively reduce the radiation dose,at the same time,increase the degree of pulmonary artery enhancement,reduce the pollution of pulmonary vein,and obtain image quality satisfying clinical needs.