The Clinical Application In The Disease Of The Lower Extremity By Combining Individualized Dosage Of Contrast Agent Scheme With Lower Tube Voltage

Objective:To investigate the refined classification of individualized dosage of contrast agent in computed tomography angiography(CTA)for lower extremity arterial disease by using surface(suf)and body mass index(BMI),and its value in reducing the dose of contrast agent and the dose of radiation as well as improving the efficiency of contrast agent and image quality combining with scanning using a low tube voltage(80 KV),and to analyze its specificity,sensitivity and total coincidence rate in the diagnosis of arterial occlusive disease of the lower extremity,so as to reduce patients'intake of contrast agent and meet the needs of clinical diagnosis to the maximum extent.Methods:A total of 60 volunteers with arterial occlusive disease of the lower extremity in the First Affiliated Hospital of Henan University of Traditional Chinese Medicine from March 2017 to March 2018 were selected,and divided into group A and B.The group A was treated with a dose of contrast agent of 1.0 ml/kg,normal saline of 50 ml,a flow rate of 4.5 ml/s and tube voltage of 120 KV.After examination,the relationships of the dose of contrast agent with suf and BMI were analyzed for patients with the enhancement peak of the abdominal aorta within 300-600 HU in the group A using a linear-regression analysis.The appropriate dose of contrast agent in the group B was selected based on the generated quantitative lookup table,combined with normal saline of 50 ml,a flow rate of 4.5 ml/s and tube voltage of 80 KV.BMI of all included patients was within 18.5-30 kg/m2.The dose of contrast agent,the value of arterial enhancement,the dose of radiation and image quality were analyzed in the 2 groups.Specificity,sensitivity and total coincidence rate in the group B were analyzed with digital subtraction angiography(DSA)as the gold standard.A Siemens SOMATOM Definition CT scanner with 64 slices and dual source(Germany,No.60320)was applied.In the supine position,the feet of the patients were entered firstly,with a scanning range from the inferior segment of the abdominal aorta(about the level of renal artery opening)to the pelma.Bolus injection was performed with closed venous indwelling needle in the antecubital vein,suspensory double-tube syringe as high pressure injector,iohexol(Omnipaque,350 mgl/ml)as contrast agent and flow rate of 4.5 ml/s.Then,50 ml normal saline was additionally injected with the same flow rate.At the start time of scanning,region of interest(ROI)was determined by bolus-tracking in the abdominal aorta(about the level of renal artery opening).Scanning was performed with threshold of 140 Hu,scanning time of 25-30 s,scanning thickness of 5 mm and reconstruction thickness of 1 mm.Results:1,Multiple regression analysis based on screening data of the group A showed that the partial regression coefficient of obtained Suf and BMI was 48.28 and 1.31,respectively and constant term bo =-53.62.Regression equation for individualized dose of contrast agent was as follows:the dose of contrast agent = 1.31 x BMI + 48.28 x Suf-53.62,deducing the lookup table of the relationships of the dose of contrast agent with Suf and BMI.2.The dose of contrast agent,abdominal aorta enhancement,bilateral common iliac artery enhancement,popliteal artery enhancement,image noise.CTDIvol and DLP showed statistically significant differences between the 2 groups(P<0.05).The dose of contrast agent reduced by 8.9%,peak of abdominal aorta enhancement reduced by 6.07%noise value increased by 36%CTDIvol decreased by 44.1%and DLP reduced by 17.5%in the group B compared with the group A.3.Image quality score was 3.3 ± 0.39 in the group A and 3.8 ± 0.23 in the group A.4.A total of 13 patients(195 segments of blood vessels)in the group B received DSA simultaneously.Among them,47 segments were normal in DSA,39segments showed mild stenosis,23segments presented moderate stenosis,24segments had severe stenosis and 62 segments had occlusion.A total of 187 segments were diagnosed consistently by CTA and DSA,lsegments were overestimated,and 3segment was underestimated.The specificity was 97.8%sensitivity was 97.9%and total coincidence rate was 98%in obstructive disease of the lower extremities(K-value:0.919).Conclusion:With Suf and BMI as standards of individualized refined classification can reduce the dose of contrast agent in examination.Combining with scanning using a low tube voltage(80 KV)can reduce radiation dose and improve image quality,providing a safer,less invasive and economical method for clinical examination.