Abstract: ObjectiveTo compare the stenosis degree of mural coronary artery and myocardial bridge thickness of 128slice spiral coronary CTA with those of 256slice spiral coronary CTA，and to evaluate the difference of 128slice spiral CT and 256slice spiral CT.MethodsThe study collected 279 myocardial bridges at multicenter，totally 256 patients with the perfect form myocardial bridges，149 of them were male，115 of them were female， age from 27 to 87 years old. The analysis was made in the image of curved planar reformation(CPR）， multiplanar reformation (MPR)， maximum intensity projection(MIP)， the thickness and length of myocardial bridge， the pipe diameter of front and below and after the bridge section were measured，the degree of coronary artery stenosis was calculated. The stenosis degree of mural coronary artery and the thickness of myocardial bridge were calculated and measured. 128 and 256 slice spiral coronary were evaluated in the difference between the above indexes. ResultsThere was significant difference （P<0.01）  between the total myocardial bridge thickness with 128slice CT and 256slice CT， but in the thickness of myocardial bridge ≥3.2  mm，the two methods showed no significant difference（P>0.05）；There was no significant difference between the myocardial bridge length with 128slice CT and 256slice CT (P>0.05). There was significant difference between the stenosis degree of mural coronary artery between the two methods （P<0.01），but in the stenosis degree of mural coronary artery ≥13%， there was no significant difference between the two methods（P>0.05）. ConclusionWhen the thickness of myocardial bridge ≥3.2  mm or the stenosis degree of mural coronary artery ≥13%， 256slice CT is similar to  128slice CT， so 128silce CT can completely meet the clinical necessity.

Key words: coronary disease, myocardial bridge, tomomgraphy, Xray computer