Optimization Study Of Spectral Computed Tomography Venography On Mesenteric Vein

[Objective]The purpose of this study is to optimize the energy spectrum CT enhanced scanning technology of the mesenteric vein.Based on the energy spectrum CT scan,to study which contrast injection rate and delay time can achieve the best mesenteric vein image quality.It provides a theoretical basis for the formulation of delay time and contrast agent injection rate when using energy spectrum CT for mesenteric vein enhanced scanning in clinical practice.[Methods]Prospectively enrolled 280 patients who underwent abdominal enhancement examination from December 2019 to December 2020 in the First Affiliated Hospital of Kunming Medical University.The 280 patients were divided into 8 groups according to the scanning method,injection rate,and delay time after the arterial phase.There were 50 cases in the scanning group and the energy spectrum scanning group,and the remaining 180 cases were divided into 6 groups with 30 cases in each group.The research is carried out in the following three phases:the first phase is to study the difference in the image quality of the mesenteric vein between conventional scanning and the energy spectrum scan;the second phase is to study the effect of using different contrast agent injection rates to enhance the image quality of the mesenteric vein scanned by energy spectrum,and the contrast agent rates are respectively It is 3.0ml/s,3.5ml/s,4.0ml/s;the third phase is to study the influence of venous phase delay time after different arterial phase on mesenteric vein imaging.The delay time is 15s,20s,25s after arterial phase,respectively.The energy spectrum scan is set to a single energy value of 60keV,and 50%ASIR algorithm reconstruction.The objective evaluation of image quality mainly includes measuring the CT value and noise of the superior mesenteric vein,erector spinae and subcutaneous fat tissue at the same level in each group of images,and calculating the contrast-to-noise ratio of each group of images.The subjective score of image quality is the volume rendering(VR),maximum intensity projection(MIP)and thin-slap MIP of each subject by 2 experienced imaging physicians,TSMIP)The reconstructed image was scored by a 5-point scoring method,and the mesenteric vein classification was evaluated by the 5-point scoring method.The two independent sample t test was used to compare the image quality between the routine and the energy spectrum group.The image quality of different injection rate groups was compared by analysis of variance,and if there were differences,the LSD method was used for pairwise comparison.The image quality of different delay time groups in the arterial phase and the venous phase were compared by analysis of variance,and the pairwise comparison was by LSD.The P value is less than 0.05,which is statistically significant.[Results]1.The effect of routine and energy spectrum scanning on the image quality of mesenteric veinsObjective score:The CT value and image noise of the superior mesenteric vein in the energy spectrum scan group were higher than those in the conventional group,and the difference was statistically significant(P<0.05).There was no significant difference in the CT value and CNR of erector spinae between the energy spectrum group and the routine group(P>0.05).The classification of mesenteric veins in the energy spectrum group was higher than that in the conventional group,and the difference was statistically significant(P<0.05).Subjective score:The scores of the 2 diagnostic imaging physicians were all tested by independent samples,and the difference was statistically significant(P<0.05).2.The influence of different injection rates of energy spectrum scan on the image quality of mesenteric veinObjective score:The difference in CT value of superior mesenteric vein,erector spinae muscle,image noise and contrast noise in 3.0ml/s,3.5ml/s and 4.0ml/s groups was not statistically significant(P>0.05).Subjective score:The scores of the two diagnostic imaging physicians were analyzed by variance analysis,and the difference was not statistically significant(P>0.05)3.The effect of the delay time of the venous phase after different arterial phases on the image quality of mesenteric veinsObjective score:The difference in CT value,image noise,and contrast-to-noise ratio of the superior mesenteric vein in the 15s,20s,and 25s lag time groups was statistically significant(P<0.05).Among them,the 15s group and the 20s group had statistically significant differences in CT value,image noise,and contrast-to-noise ratio(P values were 0.009,0.024,0.007);the 15s group and the 25s group had statistically significant differences in the contrast noise ratio(P<0.05);The image noise of the 20s group and the 25s group was statistically significant(P<0.05).The scores of the two diagnostic imaging physicians were analyzed by variance analysis.The scores of the 15s group and the 20s and 25s groups were significantly different(P<0.05).There was no statistically significant difference between the 20s group and the 25s group in the delay time(P>0.05).[Conclusions]1.Energy spectrum parameter scanning and its image post-processing function can significantly improve the image quality of mesenteric veins,and better display the small branches of mesenteric veins.2.Under the premise of keeping the total iodine content relatively constant,the injection rate(3.0 ml/s,3.5 ml/s,4.0 ml/s)has no significant effect on the image quality of the mesenteric vein.3.When the venous phase delay time after the arterial phase is setto 20s-25s,the quality of the obtained mesenteric vein image is better.