Duplex ultrasound scanning of the carotid arteries with velocity spectrum analysis.

Duplex ultrasound examination of the carotid arteries using high-resolution realtime imaging and pulsed Doppler flow measurements with velocity spectrum analysis was performed on a series of 50 consecutive patients (100 vessels), and findings were compared with findings of conventional carotid arteriography. The criteria for an abnormal duplex examination included: a velocity ratio of 1.5 or more (ratio of the maximum internal carotid artery ICA flow velocity to the maximum common carotid artery flow velocity); turbulence, as indicated by an ICA velocity spectral width of 40 cm per second or more; visible plaque that produced an ICA stenosis of 50% or more; a maximum ICA velocity of 100 cm per second or more; and inability to detect ICA flow. A flow-limiting stenosis was defined arteriographically as a 50% or greater stenosis of the diameter of the arterial lumen. The velocity ratio was the best single duplex criterion, with an overall accuracy of 88%. The sensitivity or specificity of the duplex examination was as high as 97%, depending on the number of duplex criteria that were abnormal.