ColorDoppler

ColorDoppler, or color Doppler imaging, is a Doppler ultrasound technique that overlays color on a grayscale two-dimensional image to display blood flow within vessels or chambers. It relies on the Doppler effect: ultrasound waves reflect off moving red blood cells, causing a frequency shift that is interpreted to indicate flow direction and velocity. Most systems use color to denote direction (typically red toward the transducer and blue away) and adjust hue or brightness with speed. Wall filters help reduce artifacts from tissue motion and wall movement.

Color Doppler is usually integrated with conventional B-mode ultrasound to provide qualitative visualization of flow patterns. For quantitative velocity measurements, spectral Doppler (pulsed-wave or continuous-wave) is used to generate time-velocity waveforms. Variants exist, including power Doppler, which increases sensitivity to low flow but does not convey direction, and three-dimensional color Doppler, which adds volumetric visualization.

Clinical applications are broad. In cardiology, it assesses valve function, stenosis, and regurgitation; in vascular imaging, it detects stenoses, occlusions, and aneurysms; in obstetrics, it evaluates fetal and placental perfusion; in abdominal imaging, it evaluates perfusion of organs such as the liver and kidneys; and it guides interventional procedures by visualizing vessels and movement of instruments or injected contrast.

Limitations include angle dependence, with best accuracy when the flow is parallel to the ultrasound beam; reduced sensitivity for very slow or very fast flows; susceptibility to motion and blooming artifacts; and reliance on qualified operators and adequate acoustic windows. ColorDoppler complements grayscale imaging but does not replace detailed hemodynamic assessment provided by spectral Doppler.