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Sound Beam & Flow Direction
Define Me
Transducers & Doppler
Artifacts
100
The sound beam must be _____ to RBCs in order to achieve the most accurate blood velocity measurement.
What is Parallel
100
The change in frequency due to relative motion between the sound source and the receiver.
What is Doppler Frequency / Doppler Shift
100
This transducer has two crystals--one that transmits, the other receives. Anatomic imaging is absent.
What is A dedicated continuous wave transducer
100
Color Flow artifact that displays very small Doppler shifts that are made from moving anatomy.
What is Ghosting
200
The angle at which the Cosine (theta) is 0.87
What is 30 degrees?
200
The process of extracting the Doppler shift from the returning frequency.
What is Demodulation
200
This Doppler has the greatest advantage of accurately measuring higher velocities but suffer from range ambiguity.
What is a Continuous Wave Doppler
200
Used to eliminate low frequency doppler shifts caused by moving anatomy.
What is a Wall Filter
300
What is the Cosine (theta) at 90 degrees?
0
300
It is a magnitude--indicates a distance traveled within a certain distance in a certain direction.
What is Velocity
300
This Doppler requires only one PZT and uses a gate to sample velocities without range ambiguity.
What is Pulsed Wave Doppler
300
"Mirror Image" artifact that only arises from spectral Doppler and appears on both parts of the baseline identically.
What is Crosstalk
400
The true velocity of a measured Main Portal Vein is 25 cm/s. If sampled at a 90 degree angle, what will the measured velocity be?
What is 0 cm/s.
400
Simultaneous anatomic imaging and Doppler (is called?)
What is Duplex imaging
400
"non-coherent" is associated with which form of Doppler?
What is Nondirectional Doppler
400
Exists only with pulsed Doppler, peaks wrap around to the opposite side of the baseline if the velocity is too high.
What is Aliasing
500
Sampling a velocity of 8 cm/s at 60 degrees--What speed are the RBCs moving at?
What is 16 cm/s
500
Within this speed limit, aliasing will not occur.
What is Nyquist Limit?
500
This form of Doppler reports direction, anatomic imaging, average velocities, and is subject to aliasing.
What is Color Flow Doppler
500
Out of the 5 ways to fix aliasing, this one has the last amount of disadvantages.
What is selection of a shallower sample volume