Objective:To evaluate the optimal scan delay time of 64 rows spiral CT cerebral angiography by the comparative study of high and low dose test bolus.Methods:Select 69 adult voluntaty patients

take test bolus with 20ml and 60ml contrast medium respectively

then getting 2 peak time of test bolus with high and low dose

calculate the difference of 2 peak time.Results:The arterial peak time difference between high and low dose test bolus of 69 cases

57(83%) cases are 10 seconds

while the venous peak time difference of the same 69 cases

59(85.5%) cases are 8 seconds.Conclusion:The scan delay time of 64 rows spiral CT cerebral angiography could be set by using a peak time of low dose test bolus

plus 8(seconds Median 10 seconds reduce 2 seconds scan time which are taken from the start slice to interest slice)

so as to guarantee the satisfactory image quality and ensuring success of the examination.