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NMSK > Ultrasound > Flashcards

Ultrasound Flashcards

1
Q

What frequencies does ultrasound use

A

Sound waves with higher frequency than we can hear
Between 1-15MHZ

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2
Q

What are sound waves like?

A

It is a longitudinal wave with compressions and rarefactions of the molecules it is travelling through.

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3
Q

How is an ultrasound Image obtained?

A

When ultrasound passes through the body it will hit boundaries and beam is split into four:
- transmitted beam
- reflected beam
- refracted beams
- scattered beam

Reflected beam back to its source gives the image

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4
Q

How does the ultrasound transducer produce an image?

A

In the ultrasound transducer, or probe, crystals emit packets of sound and then wait and “listen” for any returning echoes. The machine then constructs the image based on the loudness of the echo and the time it takes to return to the probe.

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5
Q

What is ultrasound machine measuring

A

the amount of reflection at a particular boundary.

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6
Q

What is acoustic impedence and how does it vary

A

describes how much resistance an ultrasound beam encounters as it passes through a tissue

the physical density of the tissue (d, in kg/m3) the velocity of the soundwave

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7
Q

How is acoustic impedence linked to reflection

A

Larger difference in acoustic impedence means greater amount of reflectiom

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8
Q

What tissue has the highest/ lowest acoustic impedence

A

Highest- bone
Lowest- air

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9
Q

What colour is fluid on an ultrasound

A

Black (no sound is reflected)

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10
Q

What colour is bone on an ultrasound and why?

A

White because lots of sound is reflected back

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11
Q

What colour are things on ultrasounds

A

Fluid- black
Tissue- grey (denser the tissue the whiter it’ll be)

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12
Q

What are the important things to consider when setting up an ultrasound?

A

Frequency of wave
Gain applied to returning echo (amplification of the ultrasound signals your transducer records.)
Where the ultrasound is focused

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13
Q

What are the pros/ cons of low frequency for ultrasound

A

Good penetration but poor resolution

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14
Q

What are the pros and cons of high frequency for ultrasound?

A

Poor depth of penetration but good resolution

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15
Q

What does gain have to compensate for/

A

The further the sound has to travel, the quieter the returning echo will be

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16
Q

When is gain turned up and why?

A

For deeper tissues to give a balanced image

17
Q

What are the different types of transducers?

A

Sector transducers
Phased array
Linear array
Curved array

18
Q

What are the pros, cons and uses of sector transducers?

A

Pros; small contact area, but divergent beam so can get a wide field of vision

Cons; they do not give good detail in the near field and also the fact that the beam diverges means the sound is more spread out in the far field, so does not have optimal resolution. You also need to warm them up by turning them on a few minutes before use due to the mechanical movement

Uses: intraabdominal regiosn, echocardiograms

19
Q

What are the pros, cons and uses of phased array transducers?

A

Pros; diverging Beam, so good resolution
Cons: reduced near field divisions

Uses:echocardiogram

20
Q

What are the pros, cons and uses of linear array transducers?

A

Pros: good near field resolution, and as the beam does not diverge, they give good far field resolution too but with a limited field of view

Cons: large contact area, so can only really be used for areas with easy access

Uses: abdomen or limbs

21
Q

What are the pros, cons and uses of curved array transducers?

A

Pros; with a diverging beam to give a wider field of view in the deeper tissues.
Cons: large contact area

Uses; abdominal organs

22
Q

How is frequency linked to resolution

A

Higher frequency means higher resolution

23
Q

Why are stand off pads used?

A

If probe is too close to tissue then no image is shown

Increases distance between probe and superficial tissue

24
Q

What is the mediolateral position?

A

Proximal aspect at the top
Cranial aspect at left

25
Q

What are the pros of using ultrasound

A

Good for soft tissue
Good for small scale/ details
Real time motion can help see how organs function

26
Q

What are cons of using ultrasound?

A

Requires good practice and skill to obtain good image
Difficult to interpret images unless in real time
Difficult to assess how structures are related spatially to each other due to narrow field of vision

27
Q

What is anechoic structures?

A

Produce no echo
All sound passes through the tissue and none is reflected back
Appears black on ultrasound image
Usually blood, fluid

28
Q

What are hypoechoic structures

A

Produce little echo
Most of the sound passes through the tissue but some is reflected back
Appears dark grey
Tissues with high water content (cartilage, muscle, renal medulla)

29
Q

What are medium echogenicity structures?

A

A medium amount of sound is passed through
A medium amount of sound is reflected back
Appear lighter grey
Liver. Spleen, Prostate, testes

30
Q

What is hyperechoic structures?

A

Produces much echo
Little sound passes through the echo
Large amount reflects back
Appears white on ultrasound
Gas, bones dense connective tissue

31
Q

What are homogenous tossues

A

They have the same/ similar appearance throughout

32
Q

What are heterogenous tissues?

A

Have a mixed or regular pattern

33
Q

What effects does increasing the ultrasound frequency have on the properties of the beam

A

Decreased tissue penetration
Increased image resolution

34
Q

What environment is it best to perform an ultrasound in?

A

Quiet, calm, Dark/lights off, comfortable seat for scanner and restrained. Bed for the patient to lie on

35
Q

What patient preparation would you need to do

A

Clip over the site to be scanned
Clean the skin with alcohol/surgical spirit to remove grease and dirt.
Apply a generous amount of coupling gel to the skin and rub in.

36
Q

Why do you need to add a gel to the patient and the transducer for ultrasound work

A

The acoustic impedance of transducer head, air and tissue is very different and so unless the gel is put on the transducer to allow free passage of ultrasound across the air gap between transducer and tissue, all the ultrasound is reflected back before it has even entered the body. Therefore, no image would be possible.

37
Q

Why do you need to adjust the contrast and brightness on the ultrasound machines?

A

These settings optimize the screen settings for viewing NOT CREATING the image, taking into account the environment you are viewing the screen in

38
Q

What Frequencies are commonly used in Veterinary Ultrasound?

A

Most small animal ultrasound is done at a range of 4-10 MHz
Large animal ultrasound may use a range between 2-18MHz

39
Q

What is echogenicity?

A

the brightness of an image caused by the reflection of soundwaves

NMSK (47 decks)

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