Doppler Effect Flashcards
What is the doppler effect?
the change in frequency of sound as the source and observer move towards (or away from) each other.
What does flow towards the transducer indicate?
Increased echo frequency
What does flow away from the transducer indicate?
Decreased echo frequency
What is the continuous doppler?
Continuously transmits and receives sound waves
What are the advantages of continuous wave doppler?
Detection of high velocity signals
Is there aliasing in continuous wave doppler?
No
Is there different or the same elements for the transmit/receive in continuous wave?
Different
What is pulsed doppler?
Sends out small pulses in short bursts
What is an advantage of pulsed doppler?
Collects info about velocities from well defined volume at a chosen depth
Is there the same or different elements for send/receive in pulse doppler?
Same
What is aliasing?
occurs when signal is not sampled at a sufficiently high sampling frequency and the signal frequencies are misrepresented
What is the nyquist sampling theorum?
A signal can be accurately reconstructed if the sampling frequency is at least twice the highest frequency component in the signal
List three types of spectral doppler
-pulsed
-continuous
-tissue doppler
What is spectral doppler?
Displays info on time, velocity and amplitude
What is spectral broadening?
occurs when sample volume is too large or too close to vessel wall/valve
