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RUSVM Diagnostic Imaging > Intro To US > Flashcards

Intro To US Flashcards

1
Q

How does an ultrasound produce an image?

A

High-freq sound waves 1-30MHz

Sound in to tissues and return as echo

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2
Q

What is the propagation velocity of US wave?

A

1540m/sec

For US purposes, a constant velocity of sound is assumed within soft tissues even though differences do exist

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3
Q

What is acoustic impedance?

A

Property of tissue on how much resistance there is to ultrasound waves

=velocity x tissue density

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4
Q

What is wavelength ?

A

Distance between one peak or trough and the next

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5
Q

What is the frequency of an US?

A

Cycles per second (hertz)

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6
Q

If you have small wavelength and high frequency US, how does this impact your resolution and penetration?

A

Better resolution.

Poor penetration

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7
Q

If you have a low frequency, long wavelength US, how does this impact resolution and penetration

A

Poor resolution

Better penetration

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8
Q

What are the types of attenuation that can occur when US waves interact with tissue?

A

Reflection (acoustic impedance)
Refraction
Absorption

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9
Q

T/F: attenuation increases with increased distance from the transducer and lower frequency transducer

A

False

Attenuation increases with increased distances from the transducer and HIGHER frequency

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10
Q

What is acoustic impedance?

A

Characteristic of propagation medium

A rejected sound wave is generated at the interface of an impedance mismatch (eg air and bone)

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11
Q

T/F: there is no acoustic impedance in a homogenous medium

A

True

There is no propagation mismatch —> no reflections occur

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12
Q

The more difference between two mediums, the more wave is reflected back, this will appear how on the US?

A

Reflection will appear bright white

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13
Q

The amount of sound reflected in US depends on ______________

A

Acoustic impedance

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14
Q

What assumptions does a US make when generating an image?

A

Speed of sound in all body tissues is 1540m/s

Beam only travels in a straight long with constant rate of attenuation

The beam is infinitely think with all echos originating form its central axis

The depth of a reflector is accurately determined by the time taken for sound to travel from transducer to reflector and back

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15
Q

What is acoustic shadowing?

A

Distal to highly reflective objects
Eg -air and bone

Interface absorbs or reflects entire sounds resulting in anechoic area

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16
Q

Clean acoustic shadowing occurs at the __________________ interface

A

Tissue-bone

Complete absence of reverberation artifacts

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17
Q

Dirty acoustic shadowing occurs at the ______________ interface

A

Tissue-gas

99% of the soundwave gets reflected

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18
Q

What is acoustic enhancemt?

A

Fluid of homogenous acoustic impedance attenuated less sound than the surrounding tissue

-> machine overcompensates and results in a HYPERechoic area distal to the structure

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19
Q

What is edge shadowing?

A

Reflection and refraction around the edges of a round structure

No sound returned -> HYPOechoic area

**useful to identify small round structures

20
Q

What is slice thickness artifact?

A

On round surfaces, US assumes flat and averages acoustic impedance between the round edge and area within that edge—> grey average

-can mimic sediment

21
Q

What type of US artifact produces a false image on the other side of a reflector?

A

Mirror image artifact

At highly reflective interface (air/fluid) beam is reflected onto a structure, but US assumes image is in straight line —> appears on other side of reflector

22
Q

How can you determine a mirror image artifact vs a true image?

A

The false image is more grey and less defined because it is a reflection

23
Q

What frequency would be best to penetrate a small dog/cat

A. 10MHz
B. 5MHz
C. 2MHz

A

A 10 MHz

-> higher frequency, smaller wavelength has less penetration

24
Q

What frequency would be best to penetrate large animals?

A. 10MHz
B. 5MHz
C. 2MHz

A

C. 2 MHz

Lower frequency, larger wavelength -> deeper penetration

25
Q

What frequency would be best to penetrate tendons and small parts like the eye?

A. 10MHz
B. 5MHz
C. 2MHz

A

10 MHz

High frequency, small wavelength -> superficial penetration

26
Q

What is power vs gain?

A

Power is the strength of the signal going into the tissue

Gain is the amount of signal coming back to the transducer

27
Q

What is time-gain compensation?

A

Can selectively choose areas to suppress or enhance so you can have a homogenously gray image

Eg if you increase gain in deep tissues -> increase gray in that area so tissue doesnt appear hypoechoic

28
Q

T/F: structures should be viewed at edges, away from the focal point of the US beam

A

False!

Investigate structures near the focal point

29
Q

M-mode is for??

A

Motion

30
Q

Doppler is for ?

A

Determine direction of flow

31
Q

How should you prep an animal for an abdominal US?

A 
12h fasting 
Free water access 
Avoid stress 
Shave fur 
Dorsal recumbancy 
US on left side with dog head in direction of machine

Acoustic coupling gel!

32
Q

Each organ should be examined in how many planes?

A

Two

Eg sagital/dorsal/transverse

33
Q

If you are taking a sagital plane, the transducer should be oriented __________

A

Cranially

34
Q

Is you are scanning in a transverse plane, the transducer should be oriented toward ??

A

Left (towards the examiner)

35
Q

What “echo”-signs are we looking for?

A 
Size 
Shape 
Number
Location 
Margination 
Echogenicity
36
Q

What do you call an area of an US that is homogenously black?

A

Anechoic

37
Q

An area that is lighter in intensity in an US is called?

A

Hypoechoic

38
Q

If two structures have the same echogenicity, they are ________

A

Isoechoic

39
Q

A structure that has high echogenicity and is bright white is called?

A

Hyperechoic

40
Q

Put the following tissues from anechogenic to most hyperechogenic

Air 
Bone 
Fat 
Kidney
Liver 
Prostate 
Spleen 
Urine
A

Urine < kidney < liver < spleen < prostate < fat < bone/air

41
Q

T/F: you can compare echogenicities of different tissues that are at different depths

A

False

42
Q

The earliest accumulation of free abdominal fluid occurs where?

A

Apex of the bladder and between liver lobes

43
Q

Can you assess any tissues distal to fluid

A

Nope - acoustic enhancement

44
Q

Transudate will appear ________ on US

A

Anechoic

45
Q

Exudate, blood, or chyle will appear ___________ on US

A

More echogenic (speckled)

46
Q

T/F: When doing a fine needle aspirate you should see the see the whole length of the needle with US

A

True

RUSVM Diagnostic Imaging (5 decks)

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