Observed frequency change of reflected sound due to reflector movement relative to the source or the observer.
Continuous-wave Doppler (CW)
A Doppler instrument which emits an ultrasound beam without interruption. It is not range specific and so will detect flow at any depth of penetration governed by the frequency of the probe.
Pulsed wave Doppler
Single transducer system in which bursts of ultrasound are transmitted; reception of returning signals determined by gate which allows flow to be assessed at specific sites and depths.
Sample volume
Site of flow detection; size of sample volume determined by beam diameter and length of ultrasound burst.
Doppler angle
the angle at which the Doppler beam intersects blood flow.
Spectral analysis
A spectrum analyzer employs microprocessing to display and analyze the complete frequency range of the Doppler shift for more complete diagnostic information.
Peak systolic frequency
The peak frequency shift displayed on the spectral analysis created by the contraction of the left ventricle.
End diastolic frequency
The frequency shift displayed on the spectral analysis during the ventricular relaxation phase of the heart cycle.
Color flow imaging
Blood flow images produced using color Doppler.
Color Doppler
mean Doppler shift displayed as a specific color.
Color gain
Increases or decreases the sensitivity of the color Doppler signal displaying more or less color pizels.
Spectral gain
Increases or decreases the sensitivity of the spectral analysis displaying more or less brightness of the pixels.