Detection of disease at the carotid bifurcation using ultrasound--including an imaging system

A two-stage approach is described for the detection of occlusive arterial disease at the carotid bifurcation using continuous wave Doppler-shift ultrasound with spectral analysis of backscattered signals from erythrocytes. The first stage involves analysis of Doppler-shift signals from the supraorbital and common carotid arteries. Abnormal signals from these arteries are frequently caused by the presence of atheroma at the carotid bifurcation and are used to indicate the necessity for imaging the bifurcation. This latter technique produces a physiological image of the arteries, as it depends on detecting erythrocyte velocities beneath a transducer which is guided over the surface of the neck. The investigation has advantages over arteriography in that it is noninvasive, has no attendant risk and may be repeated as often as required.In order to evaluate the accuracy of these methods the results have been compared with x-ray findings in patients undergoing carotid arteriography. In 20 comparisons there were no false positives and one false negative in which the arteriogram showed a small lesion. These results indicate that the two noninvasive methods may be used in sequence to demonstrate operable disease around the carotid junction.