Abstract: Objective:To study chronic lower limb intravenous contrast-enhanced spiral CT examination of optimal scanning parameters so that the intravenous contrast agent reached by upper limbs lower limbs of intravenous contrast-enhanced spiral CT diagnosis of image effects. Materials and methods:a collection of 400 patients with chronic diseases CT enhanced check information. Which 200 cases experimental group due to long-term upper limb intravenous caused vein vascular injury serious chronic disease people, in for enhanced CT check work in the, take by lower limb vein (feet, and ankle Department vein vascular mainly) injection contrast agent spiral CT enhanced check, injection rate to 2.5~3.3 mL/s, non-ion type contrast agent 70~100 mL, artery period and the vein period under organization organ are more upper limb intravenous contrast agent extended delay time 8~15 seconds, Spiral CT scans include checks organ range, lesions and sweep the thin layer; control group of 200 patients with intravenous contrast-enhanced CT examination of the elbow chronic diseases of upper limb, depending on the tissues and organs of different injection rate, non-ionic contrast dose and spiral CT scanning method and experimental groups are the same, arterial and venous injection contrast set the delay time for the period according to the tissues and organs. Two sets of normal tissue CT image analysis of measurement and pathological tissue CT value and scan curves, and for statistical analysis. The result:Experimental group of 200 cases of lower limb vein (foot, ankle, vein) injection of contrast-enhanced spiral CT examination of cases linked to the control group of 200 cases of intravenous contrast-enhanced CT examination of the elbow in the upper limbs chronic enhanced check image quality similar to the statistical analysis. Upper and lower limbs arterial CT value arterial CT value is matching, the statistics analysis t value is 4.371, P=0.000, think that the two groups there exist significant differences, have a statistics meaning, that is, upper and lower limbs arterial CT value arterial CT value in different ways. Upper limbs vein phase CT value and venous phase CT value matching comparison, t value is 1.664, P=0.103>0.05, think it's the difference between them was not statistically significant, no significant difference, that is, upper limbs vein phase CT value and venous phase CT value difference was not statistically significant, believe that the difference does not exist. Conclusion:Long-term serious chronic diseases caused by intravenous injection of vein injury of upper limbs after intravenous contrast-enhanced scan of lower extremity take appropriate scans can increase latency time achieved quality of intravenous contrast-enhanced spiral CT scan of upper extremity.