Abstract: Objective: To evaluate the thoracico-abdominal aorta imaging effect on 64-slice MSCT with different dosage of contrast medium(CM)according to different weights.Methods: 60 suspecting aortic-diseases patients informed consented were divided into three groups averagely:In group A,20 patients with the weight over 75 kg were injected 75 mL contrast medium and 25 mL physiological saline;in group B,20 patients with the weight between 60-70 kg were injected 60 mL contrast medium and 40 mL physiological saline;in group C,20 patients with weight under 60 kg were injected 50 mL contrast medium and 50 mL physiological saline.All groups were injected at the same injection rate.Before CT scanning,Patients'weight,height,blood pressure and heart rate were measured then received real-time monitoring and triggering scan to measure diameter of the intersecting surface of the blood vessel,the CT values of aorta ascending,thoracic aorta(T7),lumbar arteries(L2)aorta descending and the crotch of the artery.Two professional radiology diagramming doctors evaluated the recombined images of the aorta and branched blood vessels,and statistically analyzed the intensified extent of the blood vessels,diameter of the intersecting surface of the blood vessels,weight,height blood pressure and heart rate.Results: Of three groups,the average CT values of aorta ascending,thoracic aorta(T7),lumbar arteries(L2) aorta descending and the crotch of the artery are 317.08 Hu,320.27 Hu,317.61 Hu respectively.The diameters of the blood vessels are 26.45 mm,23.91 mm,21.57 mm,the average weights are 79.98 kg,68.60 kg,49.50 kg,the average heights are 180.81 cm,171.70 cm,152.50 cm,the systolic blood pressure are 126/78 mmHg,130/78 mmHg,124/80 mmHg,the heart rates are 74.8,76.5,74.5 beat/min,the delayed scan time 7.3 s,6.7 s,6.1 s.The intensified CT values as well as clarity of the recombined blood vessels and display of crotch of the artery are of no statistical significance(P>0.05),The average scan time and diameters of the blood vessels are meaningful statistically(P<0.05).Blood pressure and heart rate are of no statistical significant in three groups.Conclusions: In 64 slices MSCTA,the dosage of contrast medium should be provided according to different weight,and clear images can be obtained to meet with the diagnosis requirement and the potential CIN risk can be lowered.