Arterial Phase CTA Replacement By A Virtual Arterial Phase Reconstruction In Preschool Children

Objective: To study the feasibility of the reconstruction of virtual arterial phase instead of real arterial phase from GSI chest images of preschoolers.Materials and methods: A total of 30 children who needed to undergo chest energy spectral enhanced CT scan to further exclude pulmonary vascular were collected,with ages ranging from 3 to 6years old,including the youngest 3.1 years old and the oldest 5.8 years old,with an average age of(4.1±0.7)years old.There were 17 males and13 females.All the children were scanned under GE Revolution256-slice CT.Conventional enhanced arterial scanning was performed,and GSI venous scanning was performed after 35 s delay.Monochromatic images of 40 Ke V ～ 70 Ke V venous phase were reconstructed at 2 Ke V intervals.CT values and standard deviations of pulmonary artery,left pulmonary artery,left inferior pulmonary artery,thoracic aorta and erection spinal muscle were measured in monochromatic images of venous phase and mixed energy images of arterial phase.Signal noise ratio(SNR)and contrast noise ratio(CNR)were calculated according to the formula.The quality of each group of single images was scored subjectively.Results:(1)In the 16 groups of 40 Ke V～70Ke V monochromatic images,the CT value,SCN value,CNR value of pulmonary artery,left pulmonary artery,left inferior pulmonary artery,thoracic aorta and image background noise gradually decreased with the increase of Ke V,and the difference was statistically significant(P < 0.05).The subjective scores of the two doctors were consistent,and the Kappa value was 0.719.(2)The monochromatic image quality subjective score first gradually increased with the increase of Ke V,reached the peak at 50 Ke V,and then gradually decreased with the increase of Ke V,and the difference was statistically significant(P <0.05).(3)There were no significant differences in CT values,SCN values,CNR values and average background noise of all levels of pulmonary arteries and thoracic aorta between the venous phase 50 Ke V image and mixed energy image in arteries phase(P >0.05).(4)There were statistically significant differences in CT values,CNR valuesf all levels of pulmonary arteries and thoracic aorta and the average background noise of images between the two groups(P <0.05),while there were no significant differences in SCN values of main pulmonary artery and left pulmonary artery between the two groups(P>0.05).The SNR values of left inferior pulmonary artery and thoracic aorta were significantly different the two groups(P <0.05).(5)There were significant differences in the CT values of pulmonary artery,left pulmonary artery,left inferior pulmonary artery and thoracic aorta between the venous 40 Ke V image and mixed energy image in arteries phase,as well as the background noise between the two groups(P <0.05).The mean SNR and CNR values of pulmonary artery,left pulmonary artery,left inferior pulmonary artery and thoracic aorta were not significantly different between the two groups(P >0.05).(6)There was no significant differences in radiation dose between energy spectral scan and conventional scan(P >0.05).Conclusion: CT can be improved by changing the energy level of monochromatic imaging CNR and SNR of the image and increase vascular contrast with the surrounding tissue.In this study,the Optimal monochromatic image for chest vasculargraphy CT in preschool children was 50 Ke V.The SNR and CNR of the virtual arterial phase images can be reconstructed by using CT energy spectral imaging.When the energy level is in the range of 40 to 50 Ke V,the SNR and CNR values of the virtual arterial phase images are similar to those of the conventional arterial phase images.