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Week 7 - 12 > Ultrasound 1 > Flashcards

Ultrasound 1 Flashcards

1
Q

What is sound?

A

The result of mechanical energy producing compression and rarefaction in the form of a wave

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2
Q

What’s the unit of frequency?

A

Hertz - one cycle per second

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3
Q

Why does ultrasound differ from normal sound?

A

> 20 kHz

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4
Q

Frequencies of diagnostic sonography:

A

1 - 20 MHz

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5
Q

What did Tom Brown do?

A

Converted the idea of medical purposes of ultrasound scanning into a practical proposition

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6
Q

How does diagnostic ultrasound work?

A

Short sound pulses are transmitted into the body

Reflection, scattering and absorption result in attenuation in the intensity of sound pulses through matter

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7
Q

What does attenuation do?

A

Limits depth of ultrasound imaging

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8
Q

Advantages of ultrasound:

A

Safe

No ionising radiation

Portable, compact and inexpensive equipment

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9
Q

Disadvantages of ultrasound:

A

Highly operator dependent

Organs obscured by gas (e.g. lung) and structures surrounded by bone do not give clinically useful images

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10
Q

What is the ultrasound machine like?

A

Monitor

US unit

Control panel

Transducers

Data storage device

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11
Q

What does the US unit do on ultrasound machine?

A

Processes signals

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12
Q

What do ultrasound transducers do?

A

Sends an ultrasound

Detects sound and converts it into an electrical signal for diagnosis

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13
Q

What are piezoelectric crystals?

A

Ceramic crystals

Become distorted when echoes return to transducer - generates electric pulse processed into an image

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14
Q

What do high-amplitude echoes produce?

A

Greater crystal deformation - generate larger electronic voltage

Result in brighter pixels on image

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15
Q

What images are used because of the significance of high-amplitude echoes?

A

2D grey-scale images

A.K.A. B-mode images

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16
Q

What are linear-array transducers like?

A

Linear array has a flat superficial surface

Only high-frequency probes used for superficial structures as don’t penetrate deeply

Letter L on image

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17
Q

What are curved-array transducers like?

A

Linear array has a curved convex surface

Letter C on image

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18
Q

What’s a phased-array transducer like?

A

Every element in array participates in formation of each pulse

Smaller - used between ribs

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19
Q

What are intraluminal probes like?

A

Small - various body lumens

Positioned close to organ - allows use of higher frequencies

Higher quality images produced

20
Q

Disadvantages of intraluminal probes:

A

Limited imaging depth

21
Q

What is A-mode imaging also called?

A

Amplitude-mode

22
Q

What is A-mode imaging?

A

Displays echoes acquired in 1 dimension

Echo amplitude displayed along 1 perpendicular axis

23
Q

What is B-mode imaging also called?

A

Brightness or 2D mode

24
Q

What is B-Mode imaging?

A

Spike is converted into a dot

Brightness of dot = amplitude of returning signal

Position of dot = depth of returning signal

2D image produced

25
Q

Black images:

A

Anechoic

E.g. fluid, pus

26
Q

Dark grey images:

A

Hypoechoic

E.g. bone, gall stones, metal

27
Q

What does isoechoic mean?

A

Structure same shade of grey as surrounding tissue

28
Q

What colour images are solid organs usually?

A

Grey with black inside (where vessels are)

29
Q

What’s colour doppler?

A

Measures direction and magnitude of Doppler frequency shifts that occur in moving RBCs

Produces grey-scale image

30
Q

What’s Power colour Doppler?

A

Depicts amplitude, or power, of Doppler signals

31
Q

Significance of Power colour Doppler:

A

Better sensitivity for visualisation of small vessels

32
Q

What’s Pulsed Doppler?

A

Positions sampling volume (or gate) in a vessel on grey-scale image

Displays spectrum of range of blood velocities within gate

33
Q

What is M-mode also called?

A

Motion mode

34
Q

What is M-mode?

A

Analyses tissue motion

35
Q

What is 3D ultrasound imaging?

A

Uses 2D scanner and stack of parallel cross sections

3D images displayed in varying formats

36
Q

What does the gain control do?

A

Adjusts amplification of returning acoustic signals

Optimises US image

37
Q

What does reduced gain produce?

A

Dark image

Detail is masked

38
Q

What does too much gain produce?

A

White image

Detail saturated

39
Q

Why must the US image be properly oriented?

A

To identify anatomic relations of various structures on the monitor

Groove on transducer = orientation marker

40
Q

What is enhancement?

A

Brighter area in image due to sound passing more easily through a structure

41
Q

What are the US probe manipulation manoeuvres?

A

Pressure

Alignment

Rotation

Tilt

42
Q

Tilting the probe:

A

90 degrees to structure of interest

43
Q

What is anistropy?

A

An artefact encountered - may result in incorrect diagnosis

44
Q

What is the anisotropic effect dependent on?

A

Angle of ultrasound beam

45
Q

What may the dots on right side of screen correspond to?

A

1cm intervals on patient - give estimate of depth

Week 7 - 12 (38 decks)

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