Problems of carotid Doppler scanning which can be overcome by using frequency analysis.

The value of the concomittant use of a real time frequency analyzer along with a continuous wave carotid Doppler scanner is demonstrated in this study of 118 cases. With a colour-coded Doppler scanner alone, internal carotid stenoses greater than 35% were diagnosed with a sensitivity of 95% and a specificity of 82%. With the addition of frequency analysis certain inherent problems with Doppler scanning were overcome and with the measurement of the peak Doppler frequency, the specificity was improved to 93%.