Spectral Doppler Flashcards
In spectral doppler display, what is on the X and Y axes?
X - time
Y - velocity
What spectral doppler application “emits pulses and receives echoes using a SINGLE transducer element”?
PW
What separates forward and reverse doppler shift voltages to determine if it will be either a positive or negative doppler shift?
Phase quadrature detector
What is the technique used to separate a spectrum of doppler shifts into individual frequency bins? hint: a bin is a narrow range of frequency shifts that are converted into a velocity
FFT - it determines the # of RBC’s travelling together at a certain velocity in a certain direction
What is known as a vertical thickening of the spectral trace?
Spectral broadening
What types of flow produce spectral broadening?
Turbulent
Disturbed
What artifact can be produced in the spectral window when gains are too high and may mimic spectral broadening?
Blossoming artifact - can look like spectral broadening
In spectral doppler, the beam former sends out pulses via the pulser that has pulse lengths of how many cycles ?
5-30
PW can determine where the echoes are coming from at a certain depth known as?
Sample volume or range gating
What is the MOST COMMON artifact encountered in doppler ultrasound?
Aliasing
How do you unwrap the signal in aliasing?
- Increase the scale
- Shift baseline
What “rejects frequencies below an adjustable value”?
Wall filters - eliminates clutter
Wall filters reduce signals with:
a) low DS, low amplitude
b) low DS, high amplitude
c) high DS, high amplitude
d) high DS, low amplitude
B - reduces signals with low DS, and high amplitude (clutter)
Why does CW doppler have the inability to sample at specific locations like PW?
Because we are continuously transmitting and receiving - NO pulses of sound per scan line (PRF)
Doppler shifts are detected via?
Phase quadrature
