Objective: To compare the accuracy of the main Doppler methods for quantifying the degree of carotid stenoses in 133 patients.
Method: seven parameters were measured: maximum velocity (V.max) inside the stenosis (by pulsed wave [PW]), grade and index of spectral disturbance (STI) at the outlet of the stenosis (by PW and continuous wave [CW]), ratio of velocities I(IC/CC) in the internal and common carotid (by PW), and ratio of vessel cross-section and residual lumen area (%Color) inside the stenosis (color Doppler). The reference methods were the grades of spectral disturbance and the STI (by CW), already validated against endarterectomy specimens.
Conclusion: For poststenosis measurements, a high correlation was found between the grades or STI measured by PW and CW (reference method). The measurement of these parameters was easier in PW mode. For intrastenotic velocity, the increase in V.max was not proportional to the degree of stenosis, and V.max showed large fluctuations for the same degree of stenosis. I(IC/CC) also showed large fluctuations for the same degree of stenosis. The correlation was poor for these two parameters, which could only be used for detecting two groups of stenosis: >75% or >90% in area. Color Doppler (conventional and power) routinely overestimated the degree of stenosis by 10%-15% but correlated better with the reference method and was more accurate and reproducible than V.max. A special procedure can be used to avoid this overestimation and improve the accuracy of the color Doppler.