Study On The Clinical Application In CT Pulmonary Angiography With Lower Radiation Dose And Lower Contrast Medium

Purpose:To explore the feasibility of lower radiation dose and lower contrast medium in CT pulmonary angiography,by comparing the effects of different tube voltage,different concentrations of contrast medium,different contrast medium volume and the influence of rate on the image quality of CT pulmonary angiography.Methods:1.90 cases of patients whose station of illness need them to conduct CT pulmonary angiography.They were divided into three groups,each group was 30 cases,using the 120 KV,100 KV and 80 KV tube voltage,and coordinating with automatic tube current modulation technique(range 100-400 m A,NI=11)and 50% adaptive statistical iterative reconstruction(ASIR).Contrast medium using 370 mg I/ml,the volume of contrast medium was 45 ml,injection rate with 5 ml/s,after contrast medium injection using the same rate of 30 ml saline.Comparing each image CT value,noise and effective dose and the quality of image.2.The �group 80KV� in Part one was considerd as the �group 370� in Part two;another 60 cases of patients were collected randomly,and they were divided into �group 320� and �group 300�,each group was 30 cases.Using 320 mg I/ml and 300 mg I/ml contrast medium respectively in �group 320 �and �group 300�,other parameters are the same as Part one.Compared each image CT value,noise and the quality of image.3.The �group 300� in Part two was considerd as the control group in Part three;another 30 cases of patients were collected randomly,and they were divided into Individualized group.Using the same concentration of contrast medium,9s as injection time with the volume of contrast medium according to the body weight(0.6 ml/kg),and the injection rate was limited for 3 ml/s ~ 5 ml/s,after contrast medium injection using the same rate injected 30 ml of saline,other parameters are the same as the control group.Compared each image CT value,noise and the quality of image.Results:1.The radiation dose decreased with the decreasing of tube voltage,the difference between the three groups was statistically significant(P<0.05),the effective dose of group 80 KV decreased by 42.18% compared with group 120 KV.The mean CT value of pulmonary artery increased with the decreasing of tube voltage,the difference between the three groups was statistically significant(F=4.968,P=0.009).The standard deviation(SD)increased with the decreasing of tube voltage,the difference was statistically significant(F=5.582,P=0.004).The signal-to-noise ratio(SNR)and contrast noise ratio(CNR)were not statistically significant(P>0.05).The score of each image was not less than 3,and the score of each group was not statistically significant(F=1.219,P=0.301).2.The mean CT value of pulmonary artery decreased with the decreasing concentration of contrast medium,the difference between the three groups was statistically significant(F=11.192,P=0.000).There was no significant difference in pulmonary arterial standard deviation(SD)between the three groups(F=1.198,P=0.307).Signal-to-noise ratio(SNR),contrast to noise ratio(CNR)have significant statistical significance difference(P < 0.01),but each image can be well displayed blood vessels,the score of each image was not less than 3,the score of each group was not statistically significant(F = 0.502,P = 0.607).3.In Individualized group,the volume of each patient was 37.5ml,which was 16.67% lower than the control group,and the injection rate was 4.16ml/s,which was 9.56% slower than the control group.The mean CT value of pulmonary artery,SD,SNR and CNR were not statistically significant between both groups.Both groups of images showed better blood vessels,with no less than 3 scores,and no statistically significant difference in subjective scores of each group(F=0.123,P=0.727).Conclusions:1.With low tube voltage combined with ATCM technology and ASIR reconstruction,the radiation dose of CTPA was significantly reduced,and the image quality could meet the diagnostic requirements.2.The CT value of the pulmonary artery increased significantly with the decreasing of tube voltage.In the group of low tube voltage(80KV)combined with ASIR reconstruction,with 300 mg I/ml contrast medium,and CT value remained at a relatively high level.3.According to the body-weight based individualized contrast medium injection,the decrease of CT value in the blood vessels was not obvious,and the image can meet the diagnostic requirements.4.CTPA in 256-slice helical CT,using low voltage tube(80KV),and the ATCM technology combined with low concentration of contrast medium(300mg I/ml),according to the body-weight based individualized contrast medium injection,with the 50% of ASIR image reconstruction,image quality can satisfy the requirements of clinical diagnosis,and the radiation dose and the volume of contrast medium were greatly reduced.