COLOUR-CODED CAROTID DOPPLER IMAGING: AN ANGIOGRAPHIC COMPARISON OF 324 BIFURCATIONS

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Abstract
The accuracy of a color-coded Doppler ultrasound imaging system in the assessment of the extracranial carotid tree is presented. A series of 162 consecutive patients (324 bifurcations) were assessed with angiographic control. Doppler frequency shifts of between 3600 and 5000 Hz, corresponding to yellow on the color code, detected carotid arteries that were stenosed .gtoreq. 50% with a sensitivity of 95%, a specificity of 72% and an overall accuracy of 81%. At frequency shifts of over 5000 Hz corresponding to the blue code, the sensitivity was 83%, specificity 90% and accuracy 87%. With highly stenosed lesions (90-99%), 24% were incorrectly diagnosed as occlusion by the imager. In those cases with a hemodynamically significant lesion on one side there is no evidence of a compensatory increase in velocity on the other side. The technique is readily learned but an awareness of its pitfalls is essential for accurate scanning and these are discussed. Carotid Doppler imaging has superseded phono-angiography and peri-orbital Doppler examination in the laboratory and is used with the oculoplethysmograph in the routine assessment of patients with suspected carotid bifurcation disease.