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Foundational Toolkit > Ultrasounds > Flashcards

Ultrasounds Flashcards

1
Q

What is ultrasound?

A

subtype of soundwave transmitted through air or soft tissues of patient - uses echolocation.

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2
Q

Why can’t we hear ultrasound?

A

frequency is above 20,000 Hz so it cannot be heard by the human ear

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3
Q

What is an echo?

A

sound that was reflected by a structure

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4
Q

What is the piezo electric effect?

A

the energy transfer that converts electric energy into mechanical energy - involves crystals and the production of soundwaves

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5
Q

What is transduction?

A

crystals become pressurized and this causes an energy change, which sends out a sound wave

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6
Q

What happens to the ultrasound pulse when the ultrasound frequency increases?

A

the higher the frequency, the shorter the pulse

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7
Q

Does ultrasound travel through different tissues at the same speed?

A

no

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8
Q

Does an ultrasound machine assume that ultrasound travels through all tissues at the same speed?

A

yes, it assumes 1540m/sec for soft tissue

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9
Q

What is the “time of flight?”

A

the time it takes for a signal to get from reflecting structure to receiver

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10
Q

What is specular reflection?

A

when the beam arrives at an interface which is smooth and or large dimension compared to ultrasound wavelength - part of beam is reflected, part is transmitted

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11
Q

What is ultrasound scattering?

A

multi-directional reflection that is produced either at an irregular interface between tissues or within a given tissue
- results from interaction between ultrasound and tiny reflecting objects that are comparable in size to or smaller than the ultrasound wavelength

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12
Q

What is ultrasound refraction?

A

change of direction by the beam due to an oblique angle that causes it to not return to the transducer

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13
Q

Does non-perpendicular reflection contribute to image formation?

A

no - it is a loss of signal

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14
Q

What contributes to the formation of the image of parenchyma?

A

multi-directional reflection caused by tiny objects that cause scattering

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15
Q

What contributes to the formation of the image of organ contours?

A

interface echoes due to specular reflection

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16
Q

When the difference in acoustic impedance between two tissues increases, what happens to the amount of reflection at the interface between these two tissues?

A

the proportion of ultrasound reflected is directly proportional to the difference in acousticimpedance(resistance), so reflection will increase

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17
Q

What is mostly responsible for attenuation of the ultrasound beam as it travels through tissues?

A

absorption is the dominant factor

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18
Q

When ultrasound frequency increases, what happens to attenuation?

A

the higher the frequency, the higher the attenuation

19
Q

What is B mode ultrasonography?

A

“brilliance” - most common type of display in diagnostic ultrasound, it is two dimensional

Represents a slice of a patient using a grey-scale display. It is called a tomographic technique

20
Q

What is M mode ultrasonography? What is its main area of application?

A

a single ultrasound line is studied continuously - continuous display of the variation in position and reflectivity of the structures along the line, as a function of time

main area of application: cardiology

21
Q

What is axial resolution?

A

resolution in the direction of the ultrasound beam
- discerning objects on top of eachother

22
Q

What happens to axial resolution when ultrasound frequency increases?

A

higher the frequency, higher the attenuation, so better axial resolution is achieved
- trade off: limited depth of exploration

23
Q

What is lateral resolution?

A

direction perpendicular to the ultrasound beam
- depends on width of beam
- discerning objects next to eachother

24
Q

Where is the lateral resolution the best along the path of the ultrasound beam?

A

the best resolution is where the ultrasound beam is the narrowest (focal distance)

25
Q

What is the focal zone?

A

distance where the beam is the narrowest

26
Q

What is the Doppler effect?

A

increase (or decrease) in frequency as sources move towards (or away from) each other
- if not moving, frequencies are equivalent
- sources are moving, so frequency plus delta F

Positive - moving towards transducer (red)
Negative - moving away from transducer (blue)

27
Q

What is Doppler ultrasonography used for?

A

hemodynamics

28
Q

What are the two principal types of Doppler display?

A
  1. Spectral doppler - analysis of flow is performed along a specific line of B-mode image
  2. Color-coded doppler - area of B-mode image is defined, and area is divided in multiple lines
29
Q

What effect does frequency have on depth of exploration?

A

as frequency increases, depth of exploration decreases

30
Q

What is the difference between a rectilinear, a curvilinear, and an annular-array transducer?

A

Rectilinear - a type of linear array transducer that consists of crystals aligned in a rectilinear fashion

Curvilinear - a type of linear array transducer that consists of crystals aligned in a curvilinear fashion

Annular array - consist of several crystals arranged in concentric circles

31
Q

What is the shape of the image produced by rectilinear, a curvilinear, and an annular-array transducer?

A

Rectilinear - rectangular

Curvilinear - cone

Annular array - cone

32
Q

Which of these three transducers is best suited to tendon ultrasonography?

A

Rectilinear array transducer

33
Q

Which transducer is the one most used for abdominal ultrasonography?

A

Curvilinear array transducer

34
Q

Which transducer is the one most used for echocardiography?

A

Annular array transducer

35
Q

What is the general gain?

A

regulates echo amplitude from all depths equally
- changes brightness of ultrasound image

36
Q

What is the TGC?

A

allows to amplify echoes depending on depth of reflector - provides an increasing amplification of the echoes with increasing depth to create a grey scale appearance through the image

37
Q

What does TGC correct for?

A

increases amplification of echoes with increasing depth

38
Q

What setting is used to make homogeneous organs like the liver look homogeneously bright on ultrasound?

A

TGC

39
Q

The spleen is hyperechoic to the renal cortex in normal dogs: what does that mean?

A

brighter

40
Q

Urine is anechoic in normal dogs: what does that mean?

A

echo-free, black

41
Q

What artifact can be associated with gas in intestinal loops?

A

reverberation - 2 parallel echogenic interfaces are located on the path of a beam, and some of the waves are trapped and bouncing back and forth by the interfaces

42
Q

What artifact can small gas bubbles create?

A

comet tail artifact - type of reverberation artifact

43
Q

What artifact can a bladder stone create?

A

acoustic shadowing - echoes coming back to transducer are weak due to absorption of incident beam, so they are not strong enough to generate reverberations

44
Q

What TWO artifacts can a normal gallbladder be associated with?

A
  1. edge shadowing - when beam reaches a border that separates two media, and a region deep to this does not receive any ultrasound, producing a shadow
  2. distal enhancement - when a fluid filled structure is encountered by beam

Foundational Toolkit (7 decks)

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