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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.

The diagnostic accuracy of 5 MHz continuous-wave (C-W) Doppler with spectral analysis for detecting carotid bifurcation disease was evaluated. In a first phase of the study, normal confidence intervals for peak frequency data and spectrum width were established and Doppler spectrum abnormalities were separated into three types (spectral broadening with preserved window, spectral broadening without window, sequence of abnormalities including inverted Doppler spectrum). In a second phase the diagnostic accuracy of these variables was tested on 86 carotid arteries as independently compared with angiography. Whereas both peak frequency data and spectrum distribution findings were invariably abnormal in stenoses greater than or equal to 60%, spectrum distribution findings were more accurate in 30-59% stenosis. Using spectrum distribution criteria, sensitivity and specificity for stenosis greater than or equal to 30% were 94.6% and 90.7% respectively. All variables were insensitive for stenoses less than 30% lumen diameter reduction.