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PHY > instruments > Flashcards

instruments Flashcards

1
Q

a returning echo is what kind of wave?

A

mechanical wave

  • at the transducer, it is converted to an electrical wave
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2
Q

power ratio =??

A

gain (dB)

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3
Q

gain=?

A

output power/ input power

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4
Q

input electrical power is 20 W;
output electrical power is 200 W

What is the power ratio?

A

10x

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5
Q

what is amplification the opposite of?

A

attenuation

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6
Q

If you can calculate voltage ratio, you can find out power ratio. What is the ratio?

A

(VOLTAGE ratio)2 = (POWER ratio)

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7
Q

Amplifiers allow for? (2)

A
  • amplification (gain)

- compensation (TGC/LGC)

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8
Q

TGC= ?

A

time gain compensation

aka depth gain compensation

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9
Q

TGC ‘slope’ = ?

A

1 dB/cm∙MHz

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10
Q

aplification max?

A

100 dB

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11
Q

Lateral gain compensation is used for?

A

For adjacent structures that have different attenuation

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12
Q

Drawback to amplification?

A
  • amplifies noise
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13
Q

Summer function?

A
  • Signals added together as a ‘scan line’
  • Also involved in reception apodization
  • reducing the returning voltages on the peripheral of the transducer
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14
Q

If gain is 30 dB and output power is reduced by one half, the new gain is __________ dB.

A

27

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15
Q

reception channel of beam former function?

A

amplifies and combines the echo voltages from individual elements and sends them to signal processor

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16
Q

signal processor functions (3)

A
  • filtering
  • detection
  • compression
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17
Q

pulsed wave ultrasound produces a ________ of transmitted frequencies?

A

bandwidth

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18
Q

rage of frequencies contained in a pulse?

19
Q

signal processor- filtering?

A
  • passes range of frequencies

- rejects those above and below the bandwidth

20
Q

filtering is done with?

A

bandpass filters

21
Q

filtering is done with?

A

bandpass filters

22
Q

modification of the sinusoidal waveform as it propagates through the tissue is known as?

23
Q

filters in signal processor perform what function?

A

harmonics function

24
Q

at the signal processor what is filtered out?

A

fundamental frequency

  • happens when we press THI
25
Q

benifits of harmonics?

A
  • side lobes/grating lobes are eliminated
  • reduction of anterior reverberation
  • generated further into tissue- less chance for reverb
  • better detail resolution (lateral and elevational)
26
Q

anterior reverberation aka?

27
Q

what is anterior reverb?

A
  • reflections between transducer face and skin
  • can cause multiple horizontal lines of echoes to appear in near field
  • can happen at ribs
28
Q

benifits of harmonics?

29
Q

filtering drawbacks?

A
  • decreased penetration

- worse axial resolution

30
Q

filtering drawbacks?

A
  • decreased penetration

- worse axial resolution

31
Q

detection (demodulation)?

A

radio frequency form - video form/amplitude form

32
Q

2 steps to detection/demodulation?

A
  1. rectification

2. smoothing

33
Q

what is rectification?

A
  • turns negative voltages into postive voltages
34
Q

what is smoothing?

A
  • wraps an envelope around the signal to make it less bumpy
35
Q

power ratio of largest to smallest amplitude that system can handle is known as?

A

dynamic range

36
Q

what performs dynamic range function?

A

compression

37
Q

Power ratio = ?

A

voltage ratio ^2

38
Q

what is compresstion?

A

the process of decreasing the differences bwteen the smallest and largest echo amplitudes to a usable range

39
Q

Weaker signals are amplified ____ than the stronger ones

40
Q

compression reduces?

A

dynamic range with selective amplification

41
Q

compression affects?

A
  • affects contrast

- aperator controlled (DR button)

42
Q

decreased DR=?

43
Q

increased DR=

A

smoother image

PHY (5 decks)

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