Brainscape's Knowledge GenomeTM

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


See full index

RA6007 Advanced Medical Radiation Science > Ultrasound > Flashcards

Ultrasound Flashcards

1
Q

describe a sound wave

A

Sound is a longitudinal wave that requires a medium for propagation.

This wave consists of a series of compressions and rarefactions.

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

What happens to medium particles with the soundwaves?

A

The particles in the medium simply oscillate back and forth as the sound wave propagates through the tissue

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

The range of ultrasound frequnecies

A

2 - 10 MHz

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

What does the higher the frequency mean?

A

the more superficial the wavelength travels into soft tissue

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

What is acoustic impedance?

A

It is a measure of how “easy” it is for sound to pass through a medium

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

Why is acoustic impedance important?

A

as differences in acoustic impedance between tissues cause sound wave reflection, which allows the transducer to detect echoes and form images.

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

What effect will a big difference in acoustic impedance e.g., tissue and air?

A

It will result in strong reflection of the soundwave

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

Ultrasound is a wave motion. True or False?

A

True

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

How are US images constructed?

A

By computing the time it takes for the beam to travel and reflect back to the transducer.

This provides depth data.

The magnitude of the echo modulates the brightness of the display

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

How does refraction of ultrasound obey similar laws to light?

A

Sound changes
velocity in going from one medium to another (wavelength changes).

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

What does refraction result in?

A

The beam bends as it passes from one medium to another
Beam axis no longer lies beneath transducer axis. Usually does not cause significant artefact

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

What is diffraction?

A

the bending of the ultrasound beam into the shadow of a
strong absorber
It occurs at the absorber edge e.g. gall stone
Can cause minor artefact

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

What is the basis of ultrasound

A

Images are constructed by computing the time it takes for the beam to
travel from the transducer and return from a reflecting surface.

This gives us our depth data (based on the velocity of sound in tissue)

The magnitude of the echo modulates the brightness of the display

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

What is a transducer?

A

A device which converts one form of energy to another form

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

What is used for the ultrasound transducer?

A

Piezoelectric crystal

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

How does this crystal work for the transducer?

A

By applying a voltage across the crystal the molecular dipoles
change orientation, changing the shape of the crystal.

The reciprocal effect also happens. By mechanically altering the
shape of the crystal a small voltage is generated across the crystal.
Thus the piezoelectric crystal can be used to generate and detect an ultrasound signal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What two modes can the transducer have?

A
  1. Transmit more
  2. Receive mode
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What occurs in transmit mode?

A

a high pulsed voltage is applied to the transducer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What occurs in receive mode?

A

the small voltage generated by deformation of the crystal
is detected and amplified

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What mode is the transducer in 99.9% of the time?

A

Receive mode

21
Q

What is the function of backing block of of the transducer?

A

dampens reverberations in the crystal and absorbs backward transmission of the ultrasound pulse

22
Q

Why is there a plastic matching layer positioned between the crystal and the skin in the transducer?

A

As there is a huge difference in acoustic impedance between the transducer crystal and the tissues, it improves sound transmission

23
Q

The crystal thickness is ____ the wavelength of the US beam

A

Half

24
Q

What is the use of the acoustic insulator in the transducer?

A

An acoustic insulator such as rubberized cork separates the crystal and backing block from the casing. This prevents artefacts due to casing vibrations

25
Q

Why is ultrasound gel used?

A

to make good contact between the probe and the skin by eliminating the air layer. If we did not use ultrasound gel one would get almost 100% reflection

26
Q

What kind of wave is used in ultrasound in modern days?

A

Pulse wave

27
Q

How many wavelengths should an ultrasound pulse have?

A

Ideally, 2-3 wavelengths

28
Q

“The deeper the area of interest in ultrasound, the ____ the spatial resolution is”

A

Worse

29
Q

What is pulse repetition frequency?

A

This is the number of pulses per second.
It is set by a master clock in the ultrasound unit.

30
Q

What drives the transducer?

A

an electrical pulse generator

31
Q

By increasing the PRF we increase ____ but shortens ____

A

Image information rate (Echoes received), shortens the receive time

32
Q

What determines spatial resolution in ultrasound?

A

Spatial Pulse Length (SPL)

33
Q

What is SPL?

A

the lenght of the pulse (mm)

34
Q

“an increase in SPL results in a _____ of spatial resolution”

A

decrease

35
Q

What determines the maximum depth which can be imaged?

A

PRF

36
Q

The range of frequencies within a pulse is called…

A

a Bandwidth

37
Q

By increasing the SPL we _______ the bandwith

A

Decrease

38
Q

What is specular reflection?

A

occurs when the boundary between two structures is smooth. It is responsible for generating the echoes that define organ boundaries

39
Q

Nonspecular reflection

A

occurs when the surface irregularities are similar in size
to the beam’s wavelength. echoes are must smaller than in specular reflection

40
Q

How does scatter occur in ultrasound?

A

When sound waves encounter structures that are much smaller than their wavelength they are scattered more or less equally in all directions.

The scattered echoes interfere and produce a” Speckle” appearance which is characteristic of the tissue structure, could be mistook for pathology

41
Q

What is an important artefact in ultrasound?

A

Mirror artefact

42
Q

What is mirror artefact?

A

When the reflecting surface meets the beam at a large angle of incidence (e.g. diaphragm)

Part of the beam is not reflected directly back to the transducer. This can result in a mirror image of a structure

43
Q

Fresnel zone

A

Near field

44
Q

Frauenhoffer zone

A

Far field

45
Q

Which is more superior, Axial or Lateral reolution?

A

Axial

46
Q

Axial resolution is…

A

The ability to distinguish two structures parallel to the US beam. It depends on the SPL (ie., shorter pulses improve resolution)

47
Q

Lateral resolution is…

A

the ability to distinguish 2 structure perpendicular to the US beam. It is determined by the beam width (ie., narrower beam improves resolution)

48
Q

What is Time Gain Control?

A

it amplifies the signal proportional to the time delay between transmission and detection of the echo

It allows us to see all signals at once, rather than just looking at the signal most recently received.

49
Q

What is the Doppler effect?

A

a change in the perceived frequency of sound emitted by a moving source (eg blood flow)

RA6007 Advanced Medical Radiation Science (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions