Which of the following is/are true with respect to assessment of the carotid circulation?

a. The external carotid artery flow pattern resembles those obtained from peripheral arteries

b. The internal carotid artery maintains forward flow throughout the cardiac cycle

d. An end diastolic velocity greater than 120 cm/sec suggests a stenosis greater than 80%

The brain is a low resistance vascular bed and internal carotid artery blood flow is positive throughout the cardiac cycle. The external carotid artery which supplies the muscles of the face and neck resembles peripheral arteries. A great deal of attention has focused on determining criteria for estimating stenosis severity. A peak systolic velocity exceeding 130 cm/sec suggests a stenosis of greater than 50% and end diastolic velocity greater than 120 cm/sec suggests a stenosis greater than 80%. An internal carotid/common carotid peak systolic velocity ratio of 4.0 or more and an end diastolic velocity of 100 cm/sec have been proposed as criteria for identifying diameter stenosis of 70%.