Mirror image artifacts of color Doppler images causing misinterpretation in carotid artery stenoses.

A knowledge of mirror image artifacts in color-coded duplex sonography is important as they can lead to diagnostic problems in the morphologic evaluation of stenoses and plaques. Mirror image artifacts were detectable in stenosed vessels when strongly reflecting plaques on the wall of the vessel distant from the transducer head were insonated obliquely. The artifacts were revealed in regions that were hypoechoic or anechoic on B-mode scans. Depending on the angle of insonation and the surface structure of the plaque, the mirror image artifact could be linked with the vessel lumen and thus imitate ulcerations or branches. The artifact appeared in both the longitudinal and the transverse projections and also occurred in the power Doppler and in pulsed Doppler sonographic modes. Mirror image artifacts with linkages to the vessel lumen that could result in a misinterpretation were seen in 2.5% of the stenosed vessels.