Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biomedical Ultrasound > Acoustic Fundamentals > Flashcards

Acoustic Fundamentals Flashcards

1
Q

How does ultrasound imaging work?

A

Ultrasound pulses in (penetrates through skin with coupling gel)
Sound propagation and reflection (interaction with energy)
ultrasound out
image formation and display

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does an ultrasound machine contain?

A

display
controls
probes
electronics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What does the probe contain?

A

Individual elements which each produce their own A-line

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the frequency of the ultrasound pulses which are sent into the tissue?

A

a few MHz (3-15 MHz)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the wavelength of ultrasound in tissue?

A

0.1-0.5mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the ultrasound detected with when it is reflected?

A

By the same transducer that sent them in

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is ultrasound imaging used for?

A

cardiology
obstetrics
abdominal ultrasound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What type of wave is ultrasound?

A

A mechanical wave, a vibration of tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What can shock wave lithotripsy be used for?

A

To break up kidney stones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does a probe produce in the tissue?

A

Lines which each produce an A line

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is a propagating wave?

A

A mean by which energy can be transferred from one point to another without transfer of matter

Particles oscillate about their mean position

Periodic compression and expansion of an elastic medium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is a compressional (longitudinal) wave?

A

Particle motion is parallel to wave direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is a shear (transverse) wave?

A

Particle motion is perpendicular to wave direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What type of wave are ultrasound waves?

A

Longitudinal/compressional waves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the audible range?

A

> 20Hz
< 20kHz

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is infrasonic?

A

<20Hz

17
Q

What is ultrasonic?

A

> 20kHz

18
Q

What is tissue modelled as in ultrasound imaging?

A

A fluid (as significant fraction of human body is water)

19
Q

How does the piston transducer cause rarefactions and compressions?

A

It squashes tissue which is elastic and pushes back and expands
This causes the next tissue to also expand continue the process

20
Q

What causes rarefaction and compressions?

A

The change in potential and kinetic energy

21
Q

What is the continuum assumption?

A

The medium through which the ultrasound wave is travelling is continuous

(molecular level details can be ignored)

22
Q

When is the continuum assumption valid?

A

The acoustic wavelength&raquo_space; intermolecular distance

23
Q

Why is tissue not treated like a solid (shear wave)?

A

Shear wave speed is very low

Shear waves are not generated efficiently by ultrasound transducers

Shear wave attenuation can be quite high

24
Q

What is a wavelength?

A

The distance between successive points of equal phase

25
Q

What is the wave number/spatial frequency?

A

The characteristic spatial length of a wave (rad m^-1)

k = 2π/λ

26
Q

What is the equation of the speed of compression wave?

A

c = squareroot of bulk modulus/density

27
Q

What is the period?

A

The time between successive points of equal phase

28
Q

What is the frequency?

A

The characteristic temporal length of a wave

ω = 2πf = 2π/T

29
Q

What is particle displacement?

A

vector quantity
Variation of particles about mean position
(x,y,z)

30
Q

What is the total particle velocity?

A

u_T = u_0 + u
total = ambient + acoustic

31
Q

In a plane wave, are the acoustic particle and particle velocity in phase?

A

No out of phase

32
Q

What is the acoustic intensity?

A

The rate of acoustic energy flow per unit area per unit time

W m^-2

33
Q

What is the instantaneous acoustic intensity?

A

Pressure x particle velocity

(force per unit area) x distance per unit time

34
Q

What is the sound power?

A

The rate of acoustic energy flow across a specified closed surface S with a normal n

35
Q

What are decibels?

A

A ratio of two quantities with units of power

36
Q

What happens with an acoustic wave propagates?

A

The pressure, density, temperature and particle velocity all oscillate about their background values

Biomedical Ultrasound (2 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions