Which one of the following is true about color map 1?
A. Red indicates flow toward the transducer
Which one of the following is true about color map 1?
D. Blue indicates flow away from the transducer
Which of the following is true about color map 2?
A. blue indicates flow away from the transducer
Which of the following is true about color map 2?
C. green indicates higher velocity flow toward the transducer
Which statement is true about color map 1?
E. red and yellow indicate flow toward the transducer
Which statement is true about color map 1?
A. green indicates turbulent flow away from the transducer
Which statement is best reason why color map 1 is a variance mode map?
B. blue and green indicate flow away from transducer
Which statement is true about color map 2?
C. dark blue indicates laminar flow away from transducer
Which statement is true about color map 2?
A. light blue indicates turbulent flow
In which direction does blood flow through the top of the vessel?
D. left to right
What does the black area in the center of both vessels represent?
D. zero Doppler shift
In which direction is blood flowing through the vessel?
C. right to left
The Doppler effect is presented as a ___________ when the sourse and the receiver are ___________.
frequency shift, in motion relative to each other
Starting from the same point, the sound source is moving toward the East at 12 miles/hour and the receiver is moving toward the West at 10 miles/hour. The Doppler shift is __________. (+ or -)
negative, because source and reciever are moving farther apart
Starting from the same point, the receiver is moving toward the West at 12 miles/hour and the source is moving toward the West at 10 miles/hour. The Doppler shift is __________. (+ or -)
negative, because the source and receiver are moving further apart
Doppler shift produces information about __________.
velocity
At what angle between the sound beam and the direction of motion will the Doppler shift be a maximum?
0 or 180 degrees (the sound beam and the direction of motion should be parallel)
At what angle between the sound beam and the direction of motion will the Doppler shift be a minimum?
90 degrees. no Doppler frequency exists becuase the cosine of 90 degrees is zero.
What is the difference between speed and velocity?
speed has only a magnitude. velocity has magnitude and direction
What is the current method of processing Doppler signals?
Fast Fourier Transform (FFT) method of spectral analysis is used for pulsed and CW. Autocorrelation is the method of spectral analysis for color flow Doppler.
What is the typical range of Doppler shift found in diagnostic imaging examinations?
between 20 Hz and 20 kHz (in the audible range)
The phenomenon where high velocities appear negative is called __________.
aliasing
The frequency at which aliasing occurs is called __________.
Nyquist limit
The are of interrogation in a pulsed Doppler exam is called __________.
sample volume
True or False.
The higher the emitted frequency, the more likely a pulsed wave signal is to alias.
True
True or False.
Shallower sample volumes result in more aliasing.
False
True or False.
Only pulsed wave Doppler exams have a sample volume.
True
An 8 MHz transducer with a pulse repetition frequency of 5,000 Hz is imaging to a depth of 7 cm. What is the Nyquist frequency?
C. 2.2 kHz
Nyquist limit is one-half of the pulse repetition frequency, 2.5 kHz or 2,500 Hz
An 8 MHz transducer with a PRF of 5000 Hz measures a Doppler shift of 7 kHz. The study is repeated with a 4 MHz transducer. What Doppler shift will be measured?
E. 3500 Hz
measured Doppler shift is directly related to transducer frequency
Which one of the following is true about color map 1?