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Objectives: We compared internal carotid artery Doppler peak systolic velocities (PSVs) measured with angle correction parallel to the artery wall (// wall) on grayscale images and parallel to the direction of blood flow (// flow) on color Doppler images. Methods: We studied 25 internal carotid lesions with PSVs higher than 125 cm/s. The PSVs were measured in the same imaging plane, at the stenosis orifice (0 cm) and at 0.5 and 1 cm downstream by both methods. Linear regression and correlation analyses were used to study the effects of the angle correction method on changes in PSVs as a function of the differences in angle adjustment and distance from the stenosis. Results: The 23 patients studied included 9 women and 14 men. There was a mean difference in absolute PSVs ± SD of −17.2 ± 29.5 cm/s (P < .008) between methods at the stenosis. The difference in the PSVs was associated with the angle difference between the flow jet and the artery wall (P < .01). At 1 cm from the stenosis, // flow PSVs were more strongly correlated with PSVs at the stenosis (r = 0.61; 95% confidence interval, 0.28, 0.82; P =.001) than // wall PSVs (r = 0.39; 95% confidence interval, –0.003, 0.68; P =.052). Conclusions: Blood flow velocity measurements made with angle correction parallel to the direction of the color Doppler blood flow lumen remain more consistent with the distance from the stenosis than blood flow velocity measurements made with angle correction parallel to the outer artery walls. [ABSTRACT FROM AUTHOR]