| Objectives 1 To explore the optimal scheme of combined optimization of the three factors of tube voltage,tube current and dosage of contrast agent in chest pain triad examination.2 To explore the main effect factors of tube voltage and tube current on radiation dose and whether there is interaction between these two factors.Methods A total of 80 patients admitted to the affiliated hospital of north China university of technology for chest pain underwent a 256-slice CT chest pain triad onestop combined scan.Depending on the voltage(120k V,100 k V),the different current(800 mas,the automatic current)and the different contrast dose(regular dose,low dose),randomly divided into eight groups of 10 each.Among them,group A used 120 k V tube voltage,800 m As tube current and conventional contrast dosage,B group used 120 k V tube voltage,800 m As tube current and low contrast agent dosage,C group used 120 k V tube voltage,automatic tube current and conventional contrast dosage,D group selected 120 k V tube voltage,automatic tube current and low contrast agent dosage,E group used 100 k V tubes,800 m As tube current and conventional contrast agent dosage,F group selected 100 k V tube voltage,800 m As tube current and low contrast agent dosage,G group selected 100 k V tube voltage,automatic tube current and conventional contrast agent dosage,H group selected 100 k V tube voltage,automatic tube current,low contrast agent dosage.The dosage of contrast agent should be no less than 75 ml and no more than 100 ml.By five points method,image quality records of 8 patients ascending aorta and aortic arch and descending aorta,left,right pulmonary artery and right coronary artery,left anterior descending coronary artery CT value and pattern noise(N),signal-to-noise ratio(SNR),contrast signal to noise ratio(CNR),the product of the length of the radiation dose(DLP)and the effective radiation dose(ED).Build Excel table,using SPSS17.0 software for statistical analysis,each of the patient’s general information(age,sex,body mass index)of the quantitative data using single factor analysis of variance,the qualitative data by chi-square test.Patients in each group of contrast agent,tube current,the CT value of each measurement point,image quality evaluation,image noise,SNR,contrast product of signal-to-noise ratio,the length of the radiation dose,scanning scope and effective radiation dose should be used in single factor analysis of variance,covariance analysis result was statistically significant using the LSD method are compared,and two effective radiation dose on impact pipe current and voltage using factorial analysis,analysis of the main effective doses of radiation effect and whether there is interaction,both with P < 0.05 for the difference was statistically significant.The image quality and radiation dose of 8 groups of patients were compared,and the effects of voltage,current and dosage of contrast agent on radiation dose were analyzed.Results There was no significant difference in age,gender and BMI between groups in 8 groups(P>0.05).Eight groups of contrast agent in patients with difference was statistically significant(P<0.05)and group B(88.10±4.01ml),D(85.30±6.17ml),F(84.80±7.10ml),H(83.00±6.98ml)four low contrast medium contrast agent dosage group was obviously lower A(93.40±7.76ml),C(95.10±5.43ml),E(95.50±6.31ml),G(93.30±7.99ml)four conventional contrast medium dosage group(P<0.05).Eight groups of patients with tube current comparison,the difference was statistically significant(P<0.05),the use of automatic tube current technology scan C(467.00±52.08 m As),D(443.00±46.68 m As),G(472.50±49.96 m As),H(462.00±41.58 m As)used by four groups significantly lower than the conventional tube circuit uses 800 m As tube current of each groups(P<0.05).The eight groups of patients were measured by the left and right pulmonary artery,ascending aorta and aortic arch and descending aorta and right coronary artery and the left anterior descending coronary artery CT value can be obtained,eight groups of patients with CT value of each measurement point were diagnosed can meet the requirements of CT value >200 HU,and between the CT value of each measurement point of difference was statistically significant(P<0.05).The image quality score of the patients in the 8 groups could be obtained,and there was no statistically significant difference in the score difference between the groups(P>0.05).The eight groups of patients,signal-to-noise ratio and contrast of image noise signal to noise ratio can be obtained,eight groups of patients,signal-to-noise ratio and contrast of image noise signal-to-noise differences had no statistical significance(P>0.05).The eight groups of scanning range of differences in patients with no statistical significance(P>0.05),eight groups of patients with DLP and ED difference was statistically significant(P<0.05),E,F,G,H four lower tube voltage group patients were significantly lower doses of radiation A,B,C,D four executives voltage group(P<0.05).Tube voltage and different tube current set of effective radiation dose of factorial analysis,the results can be concluded that tube voltage and tube current to the influence of radiation dose had statistical significance(P<0.05),to influence the main effect of the radiation dose;According to the results of factor analysis,there is an interaction between tube voltage and tube current(P<0.05).Conclusions 1 Using the 256-slice CT,a combination of low tube voltage,automatic tube current and low contrast agent can be used to obtain a lower radiation dose,which is worthy of clinical promotion,with the combination of low tube voltage,automatic tube current and low contrast agent.2 For the influence of radiation dose,tube voltage and tube current is the main effect factors,individual action can reduce the radiation dose;There is an interaction between the tube voltage and the tube current on the radiation dose,that is,the combined effect of the two is greater than the combined effect of the tube voltage and the tube current alone.In clinical work,the low-tube voltage combined with the automatic tube current can be used for the chest pain triad scanning,and the reasonable use of the contrast agent in combination with the patient’s body mass index,so as to optimize the scanning effect. |
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