Doppler examination of the carotid arteries. A comparative study with angiography.

The ability of Doppler ultrasound to detect extracranial carotid arterial disease was evaluated in 148 carotid arteries, examined also angiographically. A continuous wave, directional Doppler with zero-crossing meter was used. Doppler diagnosis was based on direct examination of the carotid bifurcation. Of four quantitative variables evaluated, only the end-diastolic ICA/CCA frequency ratio was found to be useful. In stenoses exceeding 75% a deranged Doppler recording was obtained. For stenoses greater than 50% or occlusion sensitivity was 98.3%, specificity 96.6% and over-all accuracy 97.3% with the direct examination technique. Corresponding figures for an indirect Doppler test (frontal artery flow) were 45.8%, 100% and 78.4%. Stenoses less than 50% could not be separated from normal vessels. Direct Doppler examination with a zero-crossing detector is reliable, provided that the limitations of the frequency analysis are considered.