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WorksheetsUltrasound Physics chapter 19
Total questions: 72
Worksheet time: 54mins
What is the Doppler effect?
The change in frequency and wavelength caused by motion of the sound source
The change in amplitude of a wave due to the observer's position
The change in speed of sound in different mediums
The change in pitch of a sound due to the temperature of the environment
What is another factor that can cause the Doppler effect besides the sound source and the receiver?
The reflector
The angle of incidence
The harmonic series
The decibel level
What happens to the wavelength and frequency of a sound when the source or reflector moves towards the receiver?
Wavelength increases, frequency decreases
Wavelength decreases, frequency increases
Wavelength and frequency both increase
Wavelength and frequency both decrease
What is the term used to describe the change in frequency due to motion?
Sonic boom
Resonance
Doppler shift
Frequency modulation
What happens to the frequency of a wave when an object is moving towards the receiver, causing a positive Doppler shift?
The frequency remains the same.
The frequency is less than transmitted.
The frequency is greater than transmitted.
The frequency becomes zero.
What is observed when there is a negative Doppler shift?
The object is stationary relative to the receiver.
The object is moving towards the receiver.
The object is moving away from the receiver.
The received frequency is greater than transmitted.
What happens to the frequency of the reflected sound when red blood cells are moving toward the transducer?
The frequency remains the same
The frequency becomes unpredictable
The frequency is reflected at higher frequencies than what the transducer is producing
The frequency is reflected at lower frequencies than what the transducer is producing
What happens to the frequency of the reflected sound when red blood cells are moving away from the transducer?
The frequency is reflected at higher frequencies than what the transducer is producing
The frequency remains the same
The frequency becomes unpredictable
The frequency is reflected at lower frequencies than what the transducer is producing
What is the operating frequency of a 5 MHz transducer?
5,000 Hz
500,000 Hz
5,000,000 Hz
50,000,000 Hz
If the transducer transmits a frequency of 5,000,000 Hz and the received frequency is 5,003,000 Hz, what is the Doppler shift?
3,000 Hz
300 Hz
30,000 Hz
3 Hz
What is the Doppler shift (Hz) formula?
Doppler shift (Hz) = frequency t - frequency r
Doppler shift (Hz) = frequency r + frequency t
Doppler shift (Hz) = frequency r / frequency t
Doppler shift (Hz) = frequency r - frequency t
If a 5 MHz transducer transmits a frequency of 5,000,000 Hz and receives a frequency of 4,997,000 Hz, what is the Doppler shift?
3000 Hz
-3000 Hz
5000 Hz
-5000 Hz
What is the purpose of the demodulator when using the Doppler?
To amplify the reflected frequency
To demodulate or identify small frequency shifts and extract them for further processing
To convert the ultrasound frequencies into visible light
To increase the range of frequencies received by the machine
What is the unit for Doppler shift?
Decibels
Watts
Hertz
Meters per second
What is the typical range of Doppler shifts detected by ultrasound?
0 Hz - 10 Hz
20 Hz - 20,000 Hz
100 Hz - 10,000 Hz
50 Hz - 5,000 Hz
What is the definition of speed?
The direction of an object
The distance that an object moves in a specific direction
The distance that an object moves in a period of time
The time it takes for an object to move in a specific direction
What is the difference between speed and velocity?
Speed is a vector quantity (magnitude and direction), while velocity is not
Speed is a scalar quantity (magnitude), while velocity is a vector quantity (magnitude and direction)
There is no difference; they are the same
Velocity indicates distance, while speed does not
Which units could be used to measure speed?
MHz
N (Newtons)
cm/s
kg (Kilograms)
Which variable represents the operating frequency in the Doppler shift equation?
Velocity
Propagation speed
FrequencyO
Cosθ
What must one know how to do with the Doppler equation according to the learning material?
Rearrange the equation to solve for velocity
Rearrange the equation to solve for propagation speed
Rearrange the equation to solve for frequency
Rearrange the equation to solve for angle θ
What does the constant "2" in the Doppler equation represent?
The speed of sound in the medium
The frequency of the transmitted beam
The fact that there will be a Doppler shift when the transmitted beam strikes the RBC and another when the RBC reflects the sound
The angle between the sound beam and the direction of blood flow
What is the unit of the operating frequency fO used in the Doppler equation?
kHz
Hz
MHz
m/s
What does the variable "v" in the Doppler equation denote?
The speed of the transducer
The frequency shift
The velocity of the moving object
The angle of the moving object
What does the variable fD represent in the Doppler equation?
The angle of blood flow to the direction of the sound beam
The modifier to the velocity
The direction of the sound beam
The Doppler frequency shift
What is the role of the angle θ in the Doppler equation?
It represents the speed of sound in the medium
It is the angle of blood flow to the direction of the sound beam
It is the initial frequency of the emitted sound wave
It is the velocity of the moving reflector
What does the term cosθ in the Doppler equation modify?
The initial frequency of the emitted sound wave
The speed of sound in the medium
The velocity of the moving reflector
The angle of the sound beam
What is the significance of the angle of flow in relation to the sound beam when calculating direction in the Doppler equation?
It determines the speed of sound in the medium
It is used to calculate the modifier to the velocity
It is irrelevant to the calculation of direction
It is used to determine the frequency of the emitted sound wave
What is the angle Θ when the flow is toward the transducer and the beam is parallel to the flow?
30°
60°
0°
180°
At what angle Θ does the flow provide the most accurate and greatest Doppler shifts?
45°
0° or 180°
30° or 150°
60° or 120°
Why should the angle Θ never exceed 60° (or 120°) in ultrasound measurements?
It is the most accurate angle for velocity measurement
It provides the least Doppler shift
It is the threshold of inaccuracy that we allow in ultrasound
It is the angle at which the flow is away from the transducer
At what angle θ can no Doppler shift (or velocity) be detected?
0°
45°
90°
180°
Why should Doppler never be attempted when the sound beam is perpendicular to the flow of blood?
Because it can damage the transducer
Because it can cause an inaccurate reading of flow direction
Because it can overestimate the velocity of blood flow
Because the machine cannot tell if blood is flowing towards or away from the transducer
What happens when the Doppler angle is 0° according to the diagram?
Maximum Doppler shift is detected
No Doppler shift is detected
The machine can tell the direction of blood flow
The machine cannot tell the direction of blood flow
What is the cosine of 0 degrees?
0
0.5
1
-1
What is the cosine of 90 degrees?
1
0
-0.5
0.5
What is the cosine of 180 degrees?
0
1
-0.87
-1
What is the cosine of 60 degrees?
0.87
0.7
0.5
-0.5
What is the cosine of 150 degrees?
-1
-0.87
0
0.87
What is the propagation speed of soft tissue used in the Doppler equation?
1540 m/s
154,000 m/s
1540 cm/s
154,000 km/s
From an ultrasound perspective, what is considered a constant in the Doppler equation?
The frequency of the moving reflector
The propagation speed of the medium
The angle of incidence
The velocity of the moving reflector
What happens to the Doppler shift if the sonographer switches from a 4 MHz transducer to an 8 MHz transducer, given that the Doppler shift with a 4 MHz transducer is 3,000 Hz?
The Doppler shift decreases to 1,500 Hz
The Doppler shift remains the same
The Doppler shift increases to 6,000 Hz
The Doppler shift increases to 9,000 Hz
What happens to the Doppler shift if the frequency of the transducer is doubled?
A) The Doppler shift remains the same
B) The Doppler shift is halved
C) The Doppler shift is doubled
D) The Doppler shift is quadrupled
If the velocity of blood is tripled, what happens to the Doppler shift?
It remains the same
It is halved
It is doubled
It is tripled
By changing the Doppler angle from 60° to 0°, and knowing that the cosine of 60° is 0.5 and the cosine of 0° is 1, what happens to the Doppler shift?
The Doppler shift remains the same
The Doppler shift is halved
The Doppler shift is doubled
The Doppler shift is quadrupled
How can the velocity (v) in cm/s be calculated from the Doppler frequency (f_D) and the original frequency (f_o)?
v (cm/s) = f_D(kHz) x c (cm/s) / (2 x f_o (kHz) x cosθ)
v (cm/s) = (2 x f_o (kHz) x cosθ) / (f_D(kHz) x c (cm/s)
v (cm/s) = f_D(kHz) / (2 x f_o (kHz) x cosθ)
v (cm/s) = (f_D(kHz) x c (cm/s)) / (2 x f_o (kHz))
How are Doppler shift and velocity related according to the velocity relationships?
They are inversely related
They are not related
They are directly related
The relationship varies
What is the relationship between operating frequency and velocity?
They are directly related
They are inversely related
They are not related
The relationship is inconsistent
According to the velocity relationships, how are Cosθ and velocity related?
They are directly related
They are inversely related
They are not related
The relationship is proportional
If the Doppler shift doubles, what happens to velocity?
It halves
It remains the same
It doubles
It quadruples
What happens to velocity when the Doppler angle changes from 0° to 60°?
It increases
It decreases
It remains the same
It becomes zero
When is the velocity measurement most accurate in Doppler ultrasound?
A) When the sound beam is at a 90° angle to the flow
B) When the sound beam is perpendicular to the flow
C) When the sound beam is parallel with the flow
D) When the sound beam is at a 45° angle to the flow
Up to what angle is it acceptable to perform Doppler ultrasound for accurate measurements?
A) 45°
B) 60°
C) 90°
D) 120°
Why is an angle of 90° considered the worst for Doppler ultrasound measurements?
A) It is the most accurate angle
B) It is too shallow for any measurements
C) It is too steep for any measurements
D) It is too inaccurate for diagnostic ultrasound
What allows the machines to recognize flow moving towards or away from the transducer?
Color flow mapping
Phase quadrature or quadrature detection
PW ultrasound
CW ultrasound
What do spectral Doppler signals produce?
A static image of the organ being examined
A graph showing the velocities of blood cells as they pass through the ultrasound beam
A color map indicating the direction of blood flow
A single velocity measurement of the blood flow
How many crystals do CW transducers have?
1
2
3
4
Which of the following is a characteristic of CW transducers?
Have a high Q factor
Have a low Q factor
Have a wide bandwidth
Are not very sensitive
In CW Doppler, what is the region where both the transmit and receive beams overlap called?
The sample volume
The imaging guide
The measurement zone
The reflection area
What is one advantage of continuous wave Doppler?
It can measure low velocities inaccurately
It has a high degree of aliasing
It can accurately measure very high velocities
It cannot determine the exact location of moving blood cells
What is the disadvantage of CW Doppler?
Ability to accurately measure very high velocities
No aliasing
Range ambiguity
Reflections from deeper cells have a higher amplitude
What color would indicate a small negative Doppler shift?
Yellow
Red
Blue
Green
What does the variable "c" represent in the Doppler equation?
The speed of sound in the medium
The frequency of the emitted sound wave
The velocity of the moving object
The angle between the ultrasound beam and the direction of motion
What color would indicate a large positive Doppler shift?
Yellow
Red
Blue
Green
What color would indicate a laminar positive Doppler shift?
(a)
Circle the area that indicates a positive turbulent Doppler shift.
What type of artifact is demonstrated in this image?
Clutter
Crosstalk
Ghosting artifact
Aliasing
What type of artifact is observed in this image?
Crosstalk
Clutter
Aliasing
Ghost artifact
What artifact is the large white arrow indicating in this image?
Clutter
Crosstalk
Ghosting artifact
Aliasing
What is the main advantage of power color Doppler?
Very sensitive to slow flow
Angle dependent
Indicates the direction of flow
Indicates turbulent flow
Multiple ultrasound pulses are required to accurately determine red blood cell velocities. What term describes these pulses?
Frequency packets
Doppler packets
Doppler shifts
Power Doppler
This mathematical process yields Doppler shift information for each sample time following pulse emission.
(a)
Fast Fourier transform is used to process both pulsed and continuous wave Doppler signals. What are the two advantages?
lower frame rates than conventional color flow Doppler
Exceedingly accurate
Displays all individual velocity components that make up the complex reflected signal
No aliasing, since the velocity information is ignored
