Brainscape's Knowledge GenomeTM

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


See full index

CSH059 Imaging > Ultrasound > Flashcards

Ultrasound Flashcards

1
Q

PEI - Interface Depth Formula

A

d = vt/2

d = depth of reflector (m)
v = velocity of sound (1540 m.s)
t = roundtrip time of the pulse/echo

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

What is the Pulse Repetition Frequency?

A

Rate at which pulses are emitted from the transducer

Deeper the tissue imaged -> longer the transducer must wait for all echoes to return –> reduced PRF

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

Different Transducer Types and application

A

Curvilinear Probe -> Liver and deeper abdominal structures

Linear Array -> Cardiovascular, lens, retina, musculoskeletal (tendons)

Intracavity Probe -> Gynae, Uterus, Ovaries

Phased Array -> Used to squeeze between ribs and fan our prior to imaging heart

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

Examples of acoustic windows

A

Referring to a structure or anatomical configuration that allows deeper anatomy to be visualised by ultrasound (causes little attenuation of the beam)

Amniotic fluid (for developing foetus)

Aqueous and vitreous humor (eye structures, e.g., retina)

Full bladder when imaging pelvic organs (uterus, ovaries and prostate gland)

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

Effect of increasing Gain

A

Allows processing of more incoming echoes
-> brighter image, increase in noise and artefact
-> less contrast and less fine details

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

Effect of Decreasing Gain

A

Processing of less incoming echoes
–> darker image

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

B-Mode Control - Depth Function

A

Can be altered to instruct machine to wait longer for echoes to return

Penetration of US on a particular transducer can be altered by manipulating the frequency of the probe
-> reduce frequency —> pulse transmits further

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

B-Mode Control - Focus Function

A

Important to manually adjust the depth of the focus –> want target structure within the focal zone of the US beam

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

What is the focal zone

A

The narrowest part of the US beam
Provides the greatest lateral resolution during the scan

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

Effect of focus on the the US beam

A

Beam width is narrowest at the focal zone
Beam intensity is at its highest at the centre of the beam

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

B-Mode Control - Zoom function

A

Allows for the image size to be increased –> can result in improved resolution of structure

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

Y-Axis Movements (Longitudinal)

A

Slide
- slide transducer along patient

Rock
- rock transducer back and forth along y-axis
- used when imaging arteries -> improves doppler effect

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

Z-axis movements

A

Compression
- Used to push structures in and out (e.g., blood vessels)
- can be used to determine presence of blood clot

Rotation
- Rotate transducer from

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

What is the use of the QA phantom?

A

Assists in determining limits of axial and lateral resolution

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

Provide a definition for resolution and state the differing types

A

The degree of detail that structures can be seen on images

Spatial, temporal, contrast, colour

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

What is spatial resolution and the two types

A

ability to differentiate small structures on a B-mode image

axial and lateral

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

What is spatial resolution affected by

A

Beam characteristics
Line density
Resolution on the viewing monitor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is axial resolution

A

Closest distance two structures can be along the axis of the beam (up and down) and which can still be seen as different entities

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

Relationship between axial resolution and spatial pulse length

A

Axial resolution directly related to spatial pulse length

AR = 1/2SPL

SPL = no. of cycles x wavelength

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

What is the spatial pulse length affected by

A

frequency
- higher frequency = shorter wavelength = shorter SPL

transducer design
- better damping = fewer cycles = shorter SPL

20
Q

What is axial resolution affected by

A

Output power and gain

Increased output power/gain –> effective pulse length will increase

21
Q

How can you optimise axial resolution

A

using highest frequency possible
using low power / gain setting

22
Q

Is axial resolution affected by distance from transducer

A

It is not affected

23
Q

What is lateral resolution

A

Closest distance two structures can be at 90 degrees across the axis of the beam (left to right across the beam) at the same depth and still be seen as separate entities

Is related to and is approximately equal to the beam width

If entities are the same distance from each other as the beam width, they will appear as a single entity on the image (interfaces are not resolved)

24
Q

Beam focussing effect on lateral resolution

A

Beam focussing reduces beam width –> improves lateral resolution

25
Q

What is contrast resolution

A

ability to differentiate tissues of different echogenicity

no echoes (anechoic)
low (hypoechoic)
high (hyperechoic)

26
Q

What can affect the contrast resolution

A

Increase in background noise and backscatter interference in the image –> decrease in contrast resolution

Thin slices –> improve contrast resolution (minimises chance of tissue surrounding a lesion reducing contrast separation between the two)

27
Q

Why does backscatter interference occur

A

Echoes returning to transducer will interact with each other –> causes complex low intensity interference –> causes haze over the image

28
Q

What is temporal resolution

A

ability to resolve rapidly moving structures

29
Q

What is temporal resolution dependent on

A

high frame rate –> increased temporal resolution

30
Q

What is colour resolution

A

used to describe the spatial resolution of the colour display when defining moving substances (usually blood)

31
Q

Difference between red shift and blue shift

A

Red shift
- longer wavelength and lower frequency

Blue shift
- shorter wavelength and higher frequency

32
Q

What is the doppler effect

A

Assumed change in frequency that occurs due to relative motion between:
o Wave source
o Receiver
o Reflector of the wave

33
Q

When US beam is directed at target, what frequencies are detected by the wave source

A

transmit frequency

received frequency

34
Q

What is the doppler shift

A

Difference between received and transmitted frequencies due to motion of blood flow relative to the beam
o Change in f = Fr – Ft

35
Q

What is the doppler shift dependent on

A

Dependent on
o Transducer frequency
o Velocity of blood flow
o Intercept angle

36
Q

What is a colour doppler

A

Doppler overlay on the background b-mode picture

Doppler shift is coded to an area of interest -> a hue is allocated to represent to when a doppler is moving away or towards a transducer

Colour represents the average doppler shift.

37
Q

What is the colour doppler dependent on

A

blood velocity
doppler angle

38
Q

What are the 3 variables measured in a colour doppler

A

mean doppler shift
variance
doppler signal power

39
Q

what is the mean doppler shift in a colour doppler

A

Proportional to mean velocity

40
Q

What is the variance in a colour doppler

A
  • Measure of spectral broadening
  • Particularly important in detecting stenosis -> if present, area has large variance.
  • often green in image
41
Q

What is a pulsed weight doppler

A
  • Relies on the same ‘pulse echo principle’ as grey scale imaging.
  • Provides detailed information about a single sample volume.
42
Q

How is ultrasound used in RT

A

Clarity
Intrafraction motion estimation in breast and prostate
Ovary localisation, gynae application and placement of brachytherapy

43
Q

X axis movements

A

Sweep and fan

44
Q

B mode controls

A

Frequency, focal zone, gain controls, depth

45
Q

Frequency control

A

Displayed frequency is the median operating frequency that the system is set at
Lower frequency increases penetration into soft tissue but reduces resolution

46
Q

Effect of focus on the beam

A

Any given echo will give rise to a stronger echo when it lies within the focal zone because the beam is at its highest intensity at the centre of the beam
The beam width is also narrowest at focus and lateral resolution is improved

47
Q

TGC or DGC

A

Time gain compensation or depth gain compensation
Gain applied according to the depth or attenuation of the images as ultrasound travels through it

48
Q

Provide a definition for acoustic window

A

Referring to a structure or anatomical configuration that allows deeper anatomy to be visualised by ultrasound

CSH059 Imaging (8 decks)

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