| Objective:1.To clarify the effects of contrast agent injection mode and bilateral arm placement position on image enhancement and image quality when using intelligent tracking technology with the bilateral internal jugular veins as the trigger region of interest in CT angiography of the superior vena cava.2.To clarify the effects of contrast agent dose and injection rate on image enhancement and image quality in patients undergoing CT angiography of the superior vena cava,using intelligent tracking technology with the bilateral internal jugular veins as the trigger region of interest,for both non-PICC and PICC groups.Methods:1.In the first part of the study,a total of 113 patients who underwent CT examination of the superior vena cava at the First Affiliated Hospital of Gannan Medical University from January 2021 to December 2021 were included in two study phases,with 53 patients in the first phase and 60 patients in the second phase.In the first phase,the effects of different contrast agent injection routes on image enhancement and image quality were discussed.The contrast agent injection route for the 53 patients was divided into three groups: left elbow vein,right elbow vein,and dorsal foot vein,with 20 patients in each of the left and right elbow vein injection groups,and 13 patients in the dorsal foot vein injection group.In the second phase,the effects of bilateral arm placement position on image enhancement and image quality during the examination were discussed.The60 patients were evenly divided into two groups based on the left or right elbow vein injection route,and then subdivided into two subgroups(with15 patients each)based on the different bilateral arm placement positions-arms extended over the head and arms placed flat on both sides of the body.All patients were randomly assigned to the study phase and study content according to the study design.2.In the second part of the study,a total of 120 patients who underwent CT examination of the superior vena cava at the First Affiliated Hospital of Gannan Medical University from December 2021 to December 2022 were included.The contrast agent injection route and body position were set based on the optimal results obtained from the first part of the study.The second part was divided into two study phases,with 60 patients in each phase.In the first phase,peripheral and superior vena cava catheters were not placed for any of the 60 patients.They were evenly divided into two groups.The first group was divided into three subgroups(with 10 patients each)based on different contrast agent doses(1.0 m L/kg,1.3 m L/kg,and1.5 m L/kg body weight,or 0.35 g I/kg,0.45 g I/kg,and 0.52 g I/kg),and the second group was divided into three subgroups(with 10 patients each)based on different contrast agent injection rates(3.0 m L/s,4.0 m L/s,and4.5 m L/s).The effects of contrast agent dose and injection rate on image enhancement and image quality were studied in patients without peripheral or superior vena cava catheters.In the second phase,all 60 patients had PICC catheters,and the contrast agent dose and injection rate groups,as well as the evaluation methods,were the same as those in the first phase.The effects of contrast agent dose and injection rate on image enhancement and image quality were studied in patients with PICC catheters.Finally,the scan delay time was summarized and compared in patients who met the diagnostic requirements.All patients were randomly assigned to the study phase and study content according to the study design.3.In each study phase,the images were reconstructed with a slice thickness and interval of 1.25 mm and sent to the post-processing workstation.The CT value of the cervical level 4 internal jugular vein,the superior vena cava at the level of the aortic arch,and the level of the aortic arch were measured,and the data were statistically analyzed.In addition,post-reconstruction analyses such as Maximum Intensity Projection(MIP),Volume Rendering(VR),Curved Planar Reformation(CPR),and MultiPlanar Reconstruction(MPR)were performed on the images.Two radiologists with qualifications higher than attending physicians independently conducted subjective evaluations of the overall quality of the images of the superior vena cava using the post-processing workstation.After the evaluation scores were checked for consistency,conflicting results were discussed,and a consensus was ultimately reached.The subjective evaluation criteria were divided into three levels: Level 3 was given when the CT value was above 200 HU,the contrast agent filling in the superior vena cava was uniform,the image enhancement was good,and there were no significant beam hardening or blood flow related artifacts,and the diagnosis was not limited.Level 2 was given when the CT value was between 150 HU and 200 HU,the contrast agent filling in the superior vena cava was relatively uniform,the image enhancement was lower than level 3,or there were mild beam hardening or blood flow related artifacts,and the diagnosis was slightly limited.Level 1 was given when the CT value was below 150 HU,the contrast agent filling in the superior vena cava was poor,the enhancement was poor,or there were significant beam hardening or blood flow related artifacts that affected the diagnosis greatly.Results:1.In the first phase of the study,there was no statistically significant difference in the CT values of the superior vena cava among the three contrast agent injection routes,i.e.dorsalis pedis vein,left cubital vein,and right cubital vein(P>0.05).However,the subjective evaluation of image quality of the superior vena cava showed that the dorsalis pedis vein injection group had lower ratings than the left and right cubital vein injection groups,and the difference was statistically significant(P<0.05).There was no statistically significant difference in the ratings between the left and right cubital vein injection groups(P>0.05).In the second phase of the study,when patients received contrast agent injections via the right cubital vein,there was no statistically significant difference in the CT values of the superior vena cava between the group with arms placed flat and the group with arms raised(P>0.05),and there was no statistically significant difference in the subjective evaluation of the image quality of the superior vena cava between the two groups(P>0.05).When patients received contrast agent injections via the left cubital vein,the group with arms placed flat had higher CT values of the superior vena cava than the group with arms raised,and the difference was statistically significant(P<0.05).Furthermore,the group with arms placed flat had higher ratings of the image quality of the superior vena cava,and the difference was statistically significant(P<0.05).2.Regarding contrast agent dose,in both the group without catheters and the group with PICC catheters,the CT values of the enhanced superior vena cava were lower in the 1.0 m L/kg contrast agent dose group than in the 1.3 m L/kg and 1.5 m L/kg groups,and the difference was statistically significant(P<0.05).There was no statistically significant difference in CT values between the 1.3 m L/kg and 1.5 m L/kg groups(P>0.05).When it comes to the subjective evaluation of image quality of the superior vena cava,the level of the 1.0 m L/kg group was lower than that of the 1.3 m L/kg group,and the difference was statistically significant(P<0.05).However,there was no statistically significant difference in image quality ratings between any other two groups(P>0.05).3.Regarding contrast agent injection rate,in both the group without catheters and the group with PICC catheters,the CT values of the enhanced superior vena cava were lower in the 3.0 m L/s group than in the 4.0 m L/s and 4.5 m L/s groups,and the difference was statistically significant(P<0.05).There was no statistically significant difference in CT values between the 4.0 m L/s and 4.5 m L/s groups(P>0.05).In the subjective evaluation of image quality of the superior vena cava,for the group without catheters,the ratings of the 4.0 m L/s group were higher than those of the3.0 m L/s group,and the difference was statistically significant(P<0.05),while there was no statistically significant difference in ratings between any other two groups(P>0.05).For the group with PICC catheters,both the4.0 m L/s and 4.5 m L/s groups had higher ratings than the 3.0 m L/s group,and the difference was statistically significant(P<0.05).However,there was no statistically significant difference in ratings between the 4.0 m L/s group and the 4.5 m L/s group(P>0.05).Conclusion:1.In the CT angiography examination of the superior vena cava,using intelligent tracking technology with bilateral internal jugular veins as the triggered region of interest for scanning under a reasonable technical scheme is a highly clinically valuable imaging method that better meets the personalized scanning needs of patients.2.For CT angiography of the superior vena cava using bilateral internal jugular veins as the triggered region of interest,it is recommended that the contrast agent injection route for patients should first use the right cubital vein and the body position should be with both arms placed flat on the sides of the body.If due to physical reasons the contrast agent needs to be injected using the left cubital vein,the same body position with both arms placed flat on the sides of the body can be used,as there is no difference in image quality compared to injection via the right cubital vein.3.For CT angiography of the superior vena cava using bilateral internal jugular veins as the triggered region of interest,it is recommended to use a contrast agent dose of 0.45 g I/kg and a contrast agent injection rate of 4.0 m L/s-4.5 m L/s for both group without catheters and group with PICC catheters,which can obtain high-quality images beneficial for postprocessing and diagnosis. |
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