Oneself comparison study of CTPA imaging qulity with different iodine concentrations at tube voltage of 80 kVp / 实用放射学杂志

ABSTRACT

Objective To investigate the lowest concentration of iodine contast medium which can ensure CT pulmonary angiography (CTPA) imaging quality at tube voltage of 80 kVp.Methods Ten New Zealand rabbits underwent CTPA four times every three days with the iodine concentrations of contrast medium at each time were 350,300,270 and 250 mg I/mL respectively.The attenuation values of trunk pulmonary artery and air around the body on the same level,as well as right and left pulmonary arteries,and the pulmonary artery branches were compared among different groups.Meanwhile,image noise (N),contrasvto-noise ratio (CNR) and signal-to-noise ratio (SNR) were calculated.All those data were analyzed with One way classification ANOVA test.When multiple samples compared,Dunnett-t test was employed.The pulmonary arteries were divided into large and small arteries and assessed by multiple sample Kruskal-Wallis H test and analyzed with LSD-t test when multiple samples compared.When the attenuation of trunk pulmonary artery of different viewers or the different times of the same viewer compared,paired t test was employed.Wilcoxon signed rank testing was employed for comparing the scores of pulmonary arteries among different groups.Results All the images of CTPA could demonstrate sixthorder branches of pulmonary artery.The attenuation of pulmonary arteries of the 300-group was the highest,however no statistical difference was found between 270 and 300-group [major pulmonary arteries(687.17±167.83) HU,(848.68±185.03) HU,t=-161.52,P =0.097].The CNR (6.3±1.30) and SNR (10.9±2.01) of the 270-group were the highest (t=-45.99,P=0.008;t=3.73,P=0.088),and N (62.84±6.05) was the lowest (t=-11.09,P=0.016).No statistical difference was found between 270-group and other 3 groups.And for the subjective scores of large arteries,no statistical differences (from 350-group to 250 group,3.91±0.35,3.90±0.38,3.90±0.42 and 3.86±0.42,H=6.588,P=0.086) were found.The scores of small arteries of 270-group were lower than those of 350 and 300 group,but the image quality of 270-group (3.34±0.51) met the diagnostic requirements.Conclusion When the tube voltage being 80 kVp,the contrast medium of 270 mg I/mL is more suitable for rabbits' CTPA.Thus,the iodine dose per unit can decrease effectively.