Spectral and color Doppler artifacts.

Artifacts in spectral and color Doppler imaging can be confusing and lead to misinterpretation of flow information. The authors review these artifacts by considering three main causes: inappropriate equipment settings, anatomic factors, and physical and technical limitations of the modality. Incorrect gain, wall-filter, or velocity scale settings can cause loss of clinically important information or distortion of the tracing. Reflection of the Doppler signal from highly reflective surfaces can create a color Doppler mirror image. Vascular motion can introduce artifactual variation in velocity as the sample volume passes through different velocities in a laminar flow state. Unintentional motion can cause a generalized Doppler shift. Increasing the angle of Doppler interrogation degrades the quality of the tracing and gives the impression of spectral broadening. As angulation approaches 90 degrees, directional ambiguity can occur, suggesting bidirectional flow. Grating and side lobes can interrogate areas unrelated to the sample volume and introduce extraneous Doppler information to the apparent area of interrogation. Recognition of these artifacts is essential to proper interpretation of Doppler information and rendering a correct diagnosis.