Week 8 Flashcards

1
Q

B-Mode in Duplex ultrasound visualizes an _________, and is used to study __________.

A

Image, Anatomy

2
Q

Doppler in Duplex ultrasound visualizes __________, and is used to study ____________.

A

Velocity, Physiology

3
Q

Define the Doppler Effect

A

A change in Frequency when a reflector or source of sound is moving

4
Q

The difference between the frequency sent vs the frequency received is the ____________________.

A

Doppler Frequency Shift

5
Q

Doppler echoes are evaluated for what three things?

A

Timing (depth), Strength (amplitude), Frequencies

6
Q

What is the Doppler Equation?

A

∆ƒ = [2 v ƒo (cos ø)] / C

7
Q

Relation. Frequency shift and Cosine of the doppler angle.

A

Directly

8
Q

Relation. Frequency shift and Velocity.

A

Directly

9
Q

Relation. Speed of Sound and Frequency Shift

A

Indirectly

10
Q

Relation. Initial Frequency and Frequency Shift.

A

Directly

11
Q

The initial frequency is changed when it encounters what?

A

Moving reflectors

12
Q

What is an example of a moving reflector that Doppler would encounter?

A

RBCs

13
Q

The speed of blood is heard as _________ and is measured by _____________.

A

pitch, frequency

14
Q

The number of blood cells is heard as __________ and is measured by _____________.

A

loudness, amplitude

15
Q

Rearrange the Doppler Equation to solve for Velocity.

A

V = [∆ƒ C] / [2 ƒo (cos ø)]

16
Q

If there is a positive frequency shift, that means the reflector is moving (TOWARDS/AWAY) from the beam.

A

TOWARDS

17
Q

If there is a decrease in frequency, that means the reflector is moving (TOWARDS/AWAY) from the beam.

A

AWAY

18
Q
```If a 10 MHz Doppler beam creates an echo read by the equipment at 10.005 MHz, what is the frequency shift?
A. 10 MHz
B. 5 MHz
C. 5 kHz
D. 10.005 Hz```
A

C. 5 kHz

19
Q
```If a + 3 kHz frequency shift was created by a reflector, the flow direction was \_\_\_\_\_\_\_\_\_\_\_.
A. Away from the Doppler Beam
D. Toward the Doppler Beam```
A

D. Toward the Doppler Beam

20
Q
```If a 2 MHz probe results in an echo of 1.998 MHz, what is the frequency shift?
A. + 2 kHz
B. -2 MHz
C. -2 kHz
D. + .998 MHz```
A

C. -2 kHz

21
Q

Why is there a “2” in the Doppler Equation?

A

Because there are actually 2 doppler shifts in ultrasound.

1) when the moving RBC meets the sound beam
2) as it sends the echo back

22
Q

What does the velocity (or how it changes) tell us?

A

how tight a narrowing is in an artery

23
Q

What is the average speed of sound in soft tissue (C)?

A

1540 m/s

24
Q

What does ø measure?

A

the angle between the doppler beam and the flow direction

25
Q

ø must be (,or =) 90˚?

A
26
Q

cos 45˚ = ______.

A

0.71

27
Q

cos 30˚ = ______.

A

0.87

28
Q

cos 90˚ = ______.

A

0

29
Q

cos 60˚ = _______.

A

0.5

30
Q

cos 0˚ = _______.

A

1.0

31
Q

What is the Doppler angle?

A

the angle between the Doppler beam and the flow direction

32
Q

A decrease in angle = ____ cos, _____ frequency shift, ________ velocity

A

increase, increase, decrease

33
Q

What would the equation look like for calculating frequency shift using a 5 MHz probe, 100 cm/s velocity, and 60 degrees?

A

Frequency shift = 2 (5000 kHz) (1 m/s) (0.5) / 1540 m/s

34
Q

For the Doppler equation, frequencies should be measured in what unit? What unit should velocities be measured?

A

kHz, m/s

35
Q

If solving for velocity, what unit should your final answer be in?

A

cm/s

36
Q

What part of Duplex is used to see an image and study anatomy?

A

B-Mode

37
Q

What part of Duplex is used to visualize velocity and study physiology?

A

Doppler

38
Q

Define Doppler frequency shift.

A

The difference between the frequency sent vs the frequency received

39
Q

What does a moving reflector do?

A

Change the initial frequency

40
Q

0.5 = ______

A

cos 60

41
Q

0.87 = ______

A

cos 30

42
Q

1.0 = __________

A

cos 0

43
Q

0.71 = _________

A

cos 45

44
Q

0 = _______

A

cos 90

45
Q

The process of extracting the low Doppler frequency from the transducer’s carrier frequency is called __________.

A

Demodulation

46
Q

Doppler shift = __________ - ____________

A

reflected frequency - transmitted frequency

47
Q

Velocity is defined by what?

A

magnitude AND direction

48
Q

When an angle exists between the direction of flow and the sound beam, the measured velocity is _______ than the true velocity.

A

Less