Color flow doppler
This echocardiographic technique is based on the principles of pulsed wave Doppler echocardiography. Doppler color flow imaging works transmitting a pulse of ultrasound along each scan line that generates backscattered signals which are then received from each sample volume or gate along each scan line. Several bursts of pulses, also called burst length, are sued along each scan line to ascertain accurate velocity data. This process is done for every scan line across the image plane. Same with pulsed Doppler, the maximum depth of the Doppler signals determines the PRF.
The uniqueness of this techniques is that the velocities it detects are displayed with the use of a color scale. Red or orange indicates flow toward the transducer, while blue indicates flow away from it. Higher velocities within the Nyquist limit are designated lighter shades for better differentiation.
A color reversal represents aliasing at the Nyquist limit and at each its multiple. Varied blood velocities as well as directions usually signifies turbulent flow and the variance in velocities detected in this instances is represented by the color green.
The best use of color flow imaging can be found in the detection of regurgitant flows as well as in the assessment of pulmonary vein flow and intracardiac shunts in cases of ventricular and atrial septal defects. This technique also assists in continuous wave Doppler alignment in cases of tricuspid regurgitation velocities.