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Clinical > Ultrasound > Flashcards

Ultrasound Flashcards

1
Q

What is sound?

A

A result of mechanical energy producing alternating compression and rarefaction of the conducting medium

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2
Q

What is the unit of frequency?

A

Hertz (Hz)

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3
Q

What range of frequencies can humans hear?

A

20 Hz to 20 kHz

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4
Q

What is the frequency of ultrasound waves?

A

Greater than 20kHz

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5
Q

How do diagnostic ultrasound machines work?

A

Uses short sound pulses that are transmitted into the body
These can be reflected, scattered, refracted or absorbed
The combine effects of this causes attenuation in the intensity of the sound pulse as it travels
This allows the machine to distinguish between different tissues and create an image

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6
Q

What are the advantages of ultrasound?

A

Ultrasound is safe
No ionizing radiation
Equipment is portable and inexpensive

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7
Q

What are the disadvantaged of ultrasound?

A

Highly operator dependent
Structures around bone do not give clinically useful images
The attenuation of the ultrasound signal at air/tissue boundaries means it is unsuitable for imaging structures obscured by gas

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8
Q

What are the different components of an ultrasound machine?

A 
Monitor
US unit- signals are processed
Control panel
Transducers
Data storage device
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9
Q

What are the main parts of the transducer?

A 
Electrodes applying an alternating potential difference
Piezoelectric crystal
Plastic nose
Backing block
Acoustic insulator
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10
Q

What are piezoelectric crystals?

A

Ceramic crystals that deform and vibrate when they are electronically stimulated

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11
Q

How do piezoelectric crystals work?

A

Echoes distort the crystals and generate an electric pulse to create an image

High-amplitude echoes produce greater crystal deformation and generate a larger electronic voltage

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12
Q

What are the different types of transducers?

A

Convex array
Micro-convex array
Linear array
Endovaginal and rectal array

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13
Q

Describe linear-array transducers

A

Images obtained with linear arrays always have a flat superficial surface

Often very high frequency so can only be used for superficial tissues

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14
Q

Describe curved-array transducers

A

The surface is curved creating a convex shape

Those with short radi can be used for endoluminal scanning

Those with larger radi can be used for abdomen scanning

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15
Q

Describe phased-array transducers

A

Every element in the array participates in the formation of the pulse

Because the sound beams are steered at varying angles from one side to the other, sector images are produced

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16
Q

Describe intraluminal probes

A

Small transducers that can be placed within body lumens

Can be positioned closer to the organ so a higher resolution image can be obtained

Very small transducers have been added to flexible endoscopes to scan and guide biopsies in the gastrointestinal tract

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17
Q

What is A-mode imaging?

A

A method of displaying echoes acquired in 1 dimension.

Depth is represented along 1 axis and the echo amplitude is displayed along a perpendicular axis

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18
Q

What is B-mode imaging?

A

Brightness is the most commonly US mode

The brightness of the dot represents the amplitude of the returning signal

The position of the dot represents the depth from which the signal is returning and depends on the round-trip time of the US signal

Multiple scan lines across a plane are combined to produce a 2D image

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19
Q

What do the colours black, white and grey represent in a B-mode US?

A

Black- anechoic fluid
Dark grey- pus in an abscess
White-bone
Grey- organs and tissue

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20
Q

What are the different types of Doppler US?

A

Colour
Power colour
Pulsed

21
Q

Describe colour doppler US

A

Measures and colour codes the direction and magnitude of the mean doppler frequency shifts that occur in moving red blood cells and superimposes a colour depiction of these data on the gray-scale image

22
Q

Describe power colour doppler US

A

Depicts the amplitude or power of the doppler signals. This allows better sensitivity for the visualisation of small vessels, but at the expense of directional information

23
Q

Describe pulsed doppler US

A

Allows a sampling volume to be positioned in a vessel visualised on the gray-scale image and displays a spectrum of the full range of blood velocities within the gate plotted as a function of time

24
Q

Describe M-mode US

A

Designed to document and analyze tissue motion

Uses a line from the 2D scan- reflections from this line are displayed in a graphic form

Motion on vertical axis, time on the horizontal axis

Important for studying cardiac valve

25
Q

Describe 3D US

A

Data is accquired as a stack of parallel cross sections with the use of 2D scanner

Can be displayed as multiplanar reformatting, surface rendering, volume rendering and virtual endoscopy

26
Q

What frequency setting is resolution?

A

Highest

27
Q

What frequency setting is penetration?

A

Lowest

28
Q

What frequency setting is general?

A

Intermediate frequency

29
Q

What is the gain control?

A

Adjusts amplification of the returning acoustic signals

Too little produces a dark image

Too much produces a white image

30
Q

What sort of presets would be present on a US machine?

A

Vascular, breast, nerve, muscoskeletal

31
Q

Describe acoustic enhancment

A

Only a small amount of energy will be absorbed by some fluids, meaning the tissues behind will be shown in a greater depth

32
Q

What are the 4 manipulation manoeuvers?

A

Pressure
Alignment
Rotation
Tilt

33
Q

What angle would you position the transducer?

A

At 90 degrees to the structure of interest

34
Q

What is ansiotropy?

A

An artefact encountered when the US incorrectly diagnoses a tendon tear

35
Q

How does ansiotropy happen?

A

Changing the angle when examining the tendon will change the colour from hyperechoic to hypoechoic. When seeing hypoechoic it is easy to misdiagnose tendinosis

36
Q

What is lithotripsy?

A

Stones present in the urinary system are crushed by the vibrating impulses of the ultrasound machine

37
Q

What is cavitation?

A

When the US produces small pockets of gas in the tissue

38
Q

What are the Thermal index (TI) and Mechanical Index (TI) used for?

A

Provides operator with an indication of the potential for ultrasound induced bio-effects

39
Q

What is the acronym ALARA?

A

As Low As Reasonably Achievable

40
Q

What value should you keep the TI and MI under?

A

1

41
Q

What is point-of-care ultrasound (POCUS)?

A

Defined as a goal-directed, bedside US examination to answer a specific diagnostic question or to guide performance of an invasive procedure

42
Q

How does US help vascular access?

A

Guides the needle/cannular allowing the health professional to see the object enter the patients vein, in both transverse and cranial planes

43
Q

How does the angle of incidence effect the resolution of the image?

A

If perpendicular more waves will be reflected back to the transducer resulting in a better image

If the wave are more parallel the waves will be scattered and create a worse image

44
Q

How can you assess the hip stability of newborns?

A

A transverse scan of the hip while in flexion

45
Q

Describe a benign breast lump

A 
Oval shaped
Wider than deep
SMooth
Variable to hyperechogenicity
Uniform homogeneity of internal echoes
46
Q

Describe a malignant breast lump

A 
Variable in shape
Deeper than wide
Irregular or spiculated
Low-level echotexture
Absent lateral shadowing
Attentuation with obscured posterior margin
Calcification
Microlobulation
Intraductal extension
Infliltration across tissue planes
47
Q

What does the acronym FAST stand for?

A

Focused Assessment with Sonography in Trauma

48
Q

What is FAST used for?

A

Performed in the emergency department to assess patients admitted with blunt abdominal trauma

Clinical (6 decks)

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