Physics Chapter 5: Doppler

When doing color Doppler on an artery, no color flow is detected. What are some methods to ensure that slower blood flow is not missed? (3)

- decrease wall filter - decrease PRF -turn up gain

In conventional color Doppler imaging, black color represents: (2)

-no Doppler shift -90 degree angle

The amount of increase or decrease in reflected frequency is dependent on: (3)

-speed of reflector motion -angle between the wave propagation direction and the motion direction -frequency of the wave emitted by the source

the cosine of 90 degrees:

0

the cosine of 60 degrees:

0.5

the cosine of zero degrees:

1

A 5 MHz transducer is used to get Doppler shift at a segment of a vessel, and two Doppler angles are utilized: zero degrees and 60 degrees. Which Doppler angle would get a lower Doppler shift?

60 degrees

A 5 MHz transducer is used to get speed of flow at a segment of a vessel, and two Doppler angles are utilized: zero degrees and 60 degrees. Which Doppler angle would get a higher speed of flow?

60 degrees

To proceed from a measurement of Doppler shift frequency to a calculation of flow speed, what should be known?

Doppler angle

US Doppler shift is increased if ________ decreases

Doppler angle

T/F: in color Doppler, the presence of flow and direction can be detected.

True

formula for speed of blood flow:

V = (fD X C) / (2 X fO X cos)

Which of the following statements is false? a. aliasing does happen with color Doppler and power Doppler b. color Doppler and power Doppler are Doppler angle dependent to display the direction of flow c. both color and power Doppler could detect blood flow d. power Doppler is not limited by 90 degree Doppler angle

a. / b. a. aliasing happens with color Doppler and power Doppler b. color Doppler and power Doppler are Doppler angle-dependent to display the direction of flow

What is the duty factor of CW Doppler? a. 1 b. 100 c. 0.01 d. 1%

a. 1

Doppler shift is detected in: a. conventional color Doppler imaging b. Power Doppler imaging c. both A and B d. none of the above

a. conventional color Doppler imaging

If the reflector is moving toward the source, the reflected frequency is ________ than the incident frequency: a. higher b. lower c. the same d. none of the above

a. higher

If a 5 MHz ultrasound is reflected from a moving fetal heart at 100 cm/s toward the source, the Doppler shift is: a. positive Doppler shift b. negative Doppler shift c. equal to 5 MHz d. none of the above

a. positive Doppler shift

In conventional color doppler imaging, _______ is used to represent positive Doppler shift: a. red b. blue c. black d. none of the above

a. red

For blood flowing in the proximal renal artery with a plug flow profile, the Doppler shift is: a. the same across the proximal renal artery b. highest at the center

a. the same across the proximal renal artery

Negative Doppler shift occurs when: a. the transmitted frequency is greater than the received frequency b. the transmitted frequency is lesser than the received frequency c. the transmitted frequency is equal to received frequency d. none of the above

a. the transmitted frequency is greater than the received frequency

The signal processing technique used for color doppler imaging is called:

autocorrelation

What is the mathematical process or technique used in Power Doppler imaging?

autocorrelation

What is the mathematical process or technique used to detect Doppler shift in color Doppler instrument?

autocorrelation

Which type of Doppler examination relies on the strength of the Doppler shift? a. spectral Doppler b. power Doppler c. color Doppler d. all of the above

b / c power Doppler and color Doppler

In Power Doppler imaging, which of the following flow information is not provided?: a. presence of flow b. direction of flow c. speed of flow d. character of flow

b / c / d direction of flow / speed of flow / character of flow

Which one of the following able to detect slowest flow? a. conventional color Doppler imaging b. Power Doppler imaging

b. Power Doppler imaging

As the Doppler angle is increased from 30 to 60 degrees, the cosines of the Doppler angles would" a. increase b. decrease c. remains the same d. none of the above

b. decrease

Compared to gray scale imaging, color imaging will have ________ frame rate a. higher b. lower c. the same d. none of the above

b. lower

If the reflector is moving away from the source, the reflected frequency is ______ than the incident frequency: a. higher b. lower c. the same d. none of the above

b. lower

If a 10 MHz ultrasound is reflected from a moving fetal heart at 100 m/s away from the source, the Doppler shift is: a. positive Doppler shift b. Negative Doppler shift c. equal to 10 MHz d. none of the above

b. negative Doppler shift

If the blood vessel is situated 90 degrees to the sound beam when trying to detect blood flow, which of the following color Doppler imaging is better for this purpose? a. color Doppler imaging b. power Doppler imaging

b. power Doppler imaging

Which of the following is true of power Doppler imaging? a. able to obtain velocity information and direction of flow b. signal is obtained by detecting strength of Doppler shift c. it is prone to aliasing d. limited by perpendicular angle of incidence

b. signal is obtained by detecting strength of Foppler shift

Positive Doppler shift occurs when: a. the transmitted frequency is greater than the received frequency b. the transmitted frequency is lesser than the received frequency c. the transmitted frequency is equal to the received frequency d. none of the above

b. the transmitted frequency is lesser than the received frequency

When compared to gray scale imaging, which of the following statements regarding color Doppler is true? a. there is improved temporal resolution b. there is worse temporal resolution c. there are fewer pulses per scan line d. there is higher frame rate

b. there is worse temporal resolution

Which of the following will result in aliasing when doing color Doppler imaging? a. using lower operating frequency b. under-sampling of blood flow c. over-sampling of the blood flow d. none of the above

b. under-sampling of the blood flow

If the transmitted frequency is 2 MHz and the received frequency is also 2 MHz, then the Doppler shift is _________: a. positive Doppler shift b. Negative Doppler shift c. No Doppler shift d. none of the above

c. No Doppler shift

In color Doppler, _______ value of Doppler shift is presented: a. maximum b. minimum c. average d. none of the above

c. average

If the angle between sound direction and reflector motion is 90 degrees, and the incident frequency is 4 MHz, the propagation speed is 1540m/s, and the reflector speed is 250 cm/s moving toward the sound source, the reflected frequency is _________. a. greater than 4MHz b. less than 4 MHz c. equal to 4 MHz d. none of the above

c. equal to 4 MHz

What can be said about the ensemble length of color Doppler? a. it is less than 3 pulses per scan line b. it is more than 100 pulses per scan line c. it is about 10-20 pulses per scan line d. none of the above

c. it is about 10-20 pulses per scan line

If the reflector is stationary with respect to the source, the reflected frequency is _________ the incident frequency: a. higher b. lower c. the same d. none of the above

c. the same

When incident sound direction and reflector motion are not parallel, calculation of the reflected frequency involves the ___________ of the angle between these directions

cosine

Which Doppler angle yields the greatest Doppler shift? a. -90 b. 90 c. 45 d. 0

d. 0

Which one of the following is false regarding color Doppler imaging? a. aliasing could occur b. it obtains mean velocity measurements c. it uses autocorellation as its signal processing technique d. none of the above

d. none of the above

If the Doppler angle increases and other variables remain the same, the Doppler shift would ________

decrease

Based on the Doppler equation, if operating frequency is half and other variables remain the same, the Doppler shift is ____.

decreased

formula for the Doppler equation:

fD = (2 X fO X V X cos0) / C

T/F: Color Doppler imaging, just like B-mode imaging, is able to utilize multiple foci to display better color flow information

false

T/F: Flash artifact occurs more frequently in Color Doppler than power Doppler

false

T/F: Color Doppler technology is able to display the accurate velocity information of a blood flow

false (mean velocity only)

Motion of an echo-generating structure causes an echo to have a different ____________ from that of the emitted pulse

frequency

Doppler effect is a change in reflected ________ caused by reflector ______.

frequency / motion

As the Doppler angle increases, the speed of blood flow would ______________ if other variables remain the same.

increase

As the cosines of the Doppler angles decrease, the Doppler angles would _____.

increase

If the Doppler angle decreases, the cosines of that Doppler angle will _______

increase

If the source frequency increases and other variables remain the same, The Doppler shift will _______

increase

if the scatterer speed increases and other variables remain the same, the Doppler shift will ________

increase

if aliasing occurs when doing color Doppler examination, what should be done?

increase PRF

Based on the Doppler equation, if the Doppler angle is half and other variables remain the same, the Doppler shift is ____.

increased

Based on the Doppler equation, if the speed is doubled and other variables remain the same, the Doppler shift is ____.

increased

Yes/No: Does power Doppler detect Doppler shift?

no

Yes/No: Does power Doppler detect aliasing?

no

Yes/No: Does power Doppler detect character of flow?

no

Yes/No: Does power Doppler detect direction of flow?

no

Yes/No: Does power Doppler detect speed of flow?

no

Quantitative description of Doppler effect is provided by:

the Doppler equation

The Doppler shift is the difference between ______ and ______ frequencies

transmitted / received

T/F: The Doppler effect is used to detect and measure blood flow in vessels/

true

Yes/No: Does color Doppler detect Doppler shift?

yes

Yes/No: Does color Doppler detect aliasing?

yes

Yes/No: Does color Doppler detect character of flow (turbulent/laminar)

yes

Yes/No: Does color Doppler detect direction of flow?

yes

Yes/No: Does color Doppler detect presence of flow?

yes

Yes/No: Does color Doppler detect speed of flow?

yes

Yes/No: Does power Doppler detect presence of flow?

yes