Reproducibility of carotid artery Doppler frequency measurements

Doppler sonography of 29 extracranial carotid arteries was performed twice within three days or less. Angiography revealed stenoses with from 10 to 95% diameter reduction in 25 internal carotid arteries whereas four vessels were found to be normal. The systolic peak frequency of the internal carotid artery read from the Doppler spectrum (n = 29) could be reproduced very well. This was shown by a linear regression nearest the line of identical values with a coefficient of correlation r = 0.97 (p less than 0.001). Other values derived from the spectral analysis of the Doppler shift signal were not so well reproduced including the peak frequency ratio (systolic peak frequency of the internal carotid artery/systolic peak of the common carotid artery) (n = 22; r = 0.81; p less than 0.001). The mean frequencies read from the zero-crossing detector recordings (n = 20) could not be reproduced as demonstrated by a linear regression far away from the line of identical measurements with a coefficient of correlation r = 0.43 (p less than 0.05).