Exam 1 - Spectral Doppler (PW & CW)

Wide Spectral Doppler Sample Volume

Narrow Spectral Doppler Sample Volume

Axises of Spectral Doppler

X = time

Y = velocity and direction

Z = amplitude/concentration

Pulsed Wave Doppler - PW

Detects flow by sending pulses within sample gate

Aliases with high velocities

Limited by sampling depth and speed of sound

Continuous Wave Doppler - CW

Continuously sends pulses along sample line

Accurately measures high velocities without aliasing

Positive Shifts in Spectral Doppler

Above baseline

Towards transducer

Negative Shifts in Spectral Doppler

Below baseline

Away from transducer

Spectral Window

Spectral Broadening

Spectral Doppler Scale/PRF

Max velocity detected

Set for waveform to occupy 2/3 of spectral display window

Set Spectral Doppler Scale/PRF Low for...

Slow/hard to find vessels

Set Spectral Doppler Scale/PRF High for...

Faster flow

Aliasing in Spectral Doppler

Wrap around display

How to correct aliasing in spectral Doppler?

Increase PRF/scale

Adjust baseline

Spectral Doppler Invert

Flips spectral tracing - scale is reversed

Wall Filter

Eliminates low frequency signals

Can clean-up signals, but can loose information

Sweep Speed

How fast spectral tracing moves/how many spectral tracings are on image

Slow Sweep Speed

More waveforms

Tighter configuration

High Sweep Speed

Less waveform

More spread out

Morphology assessment

Duplex Doppler

Most common

Color & 2D are frozen

Spectral Doppler is live

Best spectral signals

Triplex Doppler

Color, 2D, and spectral doppler are live simultaneously

Poor spectral signals, color, and frame rate