Doppler

Question 1

What is Doppler

Answer 1

broad category which includes spectral Doppler, waveform Doppler, audio Doppler, color flow imaging

Question 2

Doppler Effect

Answer 2

Shift in frequency

Question 3

what is Doppler effect used for

Answer 3

The mechanism by which blood flow is detected, measured, and monitored noninvasively within the body

Question 4

how is the doppler effect exemplified?

Answer 4

change in pitch that occurs as a high-speed train or car approaches and then speeds past

Question 5

what is the apparent shift in frequency the result of?

Answer 5

changes that occur to the wavelength because of the relative motion

Question 6

If the object is moving towards the observer

Answer 6

The wavelength will be shorter

Question 7

If the object is moving away from the observer

Answer 7

The wavelength will be longer

Question 8

Therefore, since a shorter wavelength produces a higher frequency

Answer 8

The motion towards the observer produces a higher frequency than the original wave

Question 9

Motion away from the observer

Answer 9

Produces a lower frequency than the frequency of eh transmitted wave

Question 10

Doppler shift is proportional to what

Answer 10

The relative velocity

Question 11

The doppler shift increases as what increases?

Answer 11

velocity increases

Question 12

Doppler shift is also affected by what?

Answer 12

Parameters that affect the wavelength

Question 13

when the distance between the source and the observer is increasing

Answer 13

Relative motion is away

Decompression occurs

Question 14

When the distance between the source and observer is decreasing

Answer 14

Relative motion is towards

compression occurs

Question 15

Compression leads to what?

Answer 15

Higher frequency and a positive frequency shift

Question 16

Decompression

Answer 16

Lower frequency and a negative frequency shift

Question 17

Shift can be what?

Answer 17

Positive or negative

Question 18

A greater shift only tells what?

Answer 18

only amount, not direction

Question 19

Unless we know what, we cannot tell if the shift was positive or negative

Answer 19

Must know the relative motion

Question 20

If the relative motion is towards

Answer 20

the greater shift implies an increasing higher frequency

Question 21

If the relative motion is away

Answer 21

greater shift implies an increasing lower frequency

Question 22

what is the doppler shift

Answer 22

Relative difference between the detected frequency and transmitted frequency

Question 23

when the detected frequency is higher than the transmitted frequency

Answer 23

Doppler shift is positive

Question 24

If the velocity of the train doubles, the frequency shift A) Halves
B) Doubles
C) Cannot be determined because direction is not known

Answer 24

B) If the velocity of a train doubles, the frequency shift doubles

Question 25

If the velocity of the train doubles, the positive frequency shift A) Halves B) Doubles C) Cannot be determined because direction is not known

Answer 25

C) Cannot because determined because direction is not known

Question 26

Which represents a greater Doppler shift, +2kHz or -3 kHz A) 2 KHz B) 3kHz C) cannot be determined

Answer 26

B) -3kHz

Question 27

As the relative motion increases

Answer 27

Doppler Effect also increases

Question 28

wavelength and operating frequency have what kind of relationship

Answer 28

Inverse proportional

Question 29

As operating frequency increases

Answer 29

Doppler shift also increases

Question 30

As propagation velocity increases

Answer 30

Doppler shift decreases

Question 31

Roundtrip effect

Answer 31

Measurement is not made by the observer but rather by measuring the reflected frequency back to the transducer

Question 32

As the wave travels to the moving structure

Answer 32

there is an associated shift

Question 33

why is there a doubling effect?

Answer 33

Structure acts as the source of the reflected wave | The structure is moving as it reflects the wave back to the transducer

Question 34

The doppler shift

Answer 34

Can be both positive or negative depending on the direction of motion relative to the observer

Question 35

Simplified Doppler Equation

Answer 35

Doppler shift frequency=2transmit frequency velocity of the target through medium/speed of interrogating beam through medium

Question 36

Doppler shift frequency is proportional to

Answer 36

Velocity

Question 37

Doppler shift frequency is proportional to

Answer 37

transmit frequency

Question 38

Doppler shift frequency is inversely proportional to

Answer 38

speed of interrogating beam through medium

Question 39

For a given interrogating frequency, if the velocity triples, what happens to the doppler shift frequency?

Answer 39

Doppler shift is proportional to the velocity therefore a tripling of the velocity implies a tripling of the Doppler shift

Question 40

If the transmit frequency is changed from 2MHz to 10 MHz, what happens to Doppler shift frequency

Answer 40

Doppler shift is proportional to operating frequency an increase in the operating frequency by a factor of 5 implies an increase in the Doppler shift by a factor of 5

Question 41

What is the usual target in diagnostic ultrasound

Answer 41

Red blood cells

Question 42

What is the usual observer in diagnostic ultrasound

Answer 42

transducer

Question 43

what is the simplified equation for velocity

Answer 43

v=c*fdop/2f0

Question 44

The _______ ________ is a shift in frequency caused by relative motion between the observer and target

Answer 44

Doppler Effect

Question 45

A positive shift is caused by motion _____________the observer

Answer 45

Towards

Question 46

A __________shift is caused by motion away from the observer

Answer 46

negative

Question 47

A Doppler shift will ______if both the target and observer are moving away from each other faster

Answer 47

Increase

Question 48

A Doppler shift will _____if both the target and observer are moving towards each other faster

Answer 48

Decrease

Question 49

The _______the target moves, the higher the Doppler shift

Answer 49

faster

Question 50

The Doppler shift is to the operating frequency

Answer 50

Proportional

Question 51

The Dopplere shift is _______to the propagation velocity

Answer 51

inversely proportional

Question 52

Because the Doppler effect is based on motion relative to an observer

Answer 52

The angle between the observer and the motion affects the Doppler Effect

Question 53

what is the optimal transmit frequency for red blood cells deeper than 3cm?

Answer 53

Below 3MHz

Question 54

At shallower depths, high frequencies produce what?

Answer 54

Stronger Doppler signals because of increased reflectivity

Question 55

At deeper depths, lower frequencies produce what?

Answer 55

Stronger Doppler signals because of the increased absorption that occurs with higher transmit frequencies

Question 56

red blood cells produce what kind of scattering?

Answer 56

Rayleigh scattering

Question 57

The amount of scattering increases with....

Answer 57

Increased frequency

Question 58

how is Rayleigh scattering related to the frequency

Answer 58

Non-linearly

Question 59

What is the problem with increasing frequency

Answer 59

Increasing the frequency increases reflectivity but also results in significantly increased attenuation

Question 60

what is spontaneous contrast

Answer 60

rouleau formation which allows for the visualization in blood in 2D

Question 61

Spontaneous contrast

Answer 61

Can indicate a pathology/hemodynamic problem

Question 62

what is the Doppler Angle

Answer 62

The angle that is formed between the observer's line of sight and the direction of the target object

Question 63

what is the doppler angle also referred to as?

Answer 63

Insonification angle or angle of insonification (measured between the beam steering direction and the direction of flow)

Question 64

why is the correct insonification angle important

Answer 64

1. Ability to determine flow direction 2) Ability to measure doppler measurement accurately 3) Ability to minimize Doppler Error sources 4) Ability to assess the likelihood of artifact related issues (spectral broadening)