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Ultrasound Physics > Pulsed Echo Instrumentation > Flashcards

Pulsed Echo Instrumentation Flashcards

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1
Q

highly sophisticated machine that creates and receives sound pulses to present audio and visual information for interpretation

A

ultrasound machine

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2
Q

6 major components of an ultrasound machine

A 
transducer
pulser and beam former
receiver
display
storage
master synchronizer
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3
Q

what creates and controls the electrical signals sent to the transducer that generate sound pulses

A

pulser and beam former

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4
Q

what does the pulser determine

A

amplitude, PRP, PRF

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5
Q

what does the pulser do

A

excites the crystal and creates the sound beam

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6
Q

does the pulser operate during transmission or reception

A

transmission

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7
Q

can we adjust the pulser voltage?

A

yes, by changing the output power

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8
Q

attempts to standardize output have resulted in these two measurements on modern systems

A

thermal and mechanical index

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9
Q

thermal index

A
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10
Q

mechanical index

A
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11
Q

what determines firing delay patterns for phased array systems

A

beam former

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12
Q

is the beam former part of transmission or reception

A

considered part of transmitter but functions during both

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13
Q

what does the beam former do

A

coordinates electrical signals to optimize the sound beam being transmitted
adjusts electrical spike voltages to reduce lobe artifacts
establishes correct time delays used for dynamic receive focusing in reception
controls dynamic aperture by varying the number of PZT crystals used during reception and transmission

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14
Q

what are the advantages of using a modern, digital beam former

A

has system updates, software updates, rapid product improvement, rapid development, stable (no mechanical parts to wear out), and versatile because they can use transducers of wide frequencies

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15
Q

what is the beam former switch

A

a transmit/receive switch that protects receiver components from powerful signals during transmission
also directs signals from transducer to appropriate electronic processing components within the US system

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16
Q

function of the receiver

A

to transform electrical signals from transducer into a form suitable for display

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17
Q

order of operations of a receiver

A 
amplification 
compensation
compression
demodulation
reject
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18
Q

what is the process of improving quality of signal before it is amplified

A

preamplification

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19
Q

what are the 2 parts of demodulation and their purpose

A

rectification - convert negative voltages to positive ones

smoothing / enveloping - smoothing line around bumps

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20
Q

purpose of US display

A

to display data

21
Q

storage devices

A

hard drive, CD, DVD, videotape, magneto-optical discs, paper printouts, photos, USB drive

22
Q

what is the purpose of the master synchronizer

A

to maintain and organize proper timing and interaction of system components

23
Q

random disturbance that reduces a signal’s clarity and contaminates an image

A

noise

24
Q

comparison of signal to noise

A

signal to noise ratio

25
Q

when the signal to noise ratio is high, the signal is (higher or lower) than the noise

A

higher

26
Q

signal to noise ratio has what relationship with power

A

direct

27
Q

what is another name for PRP

A

depth of view

28
Q

the time between a voltage spike and the next (or time from the start of one pulse to the start of the next pulse)

A

PRP

29
Q

can we adjust the PRP?

A

yes, by changing the depth

DIRECTLY related to depth

30
Q

what is the number of pulses that an US system transmits per second

A

PRF

31
Q

can we adjust the PRF?

A

yes, by adjusting the depth of view

INVERSELY related to depth

32
Q

what is a channel made of

A

made of a single PZT element, beam former / pulser, and the wire connecting them

33
Q

amplification

A

also called receiver gain,
treats all signals identically
amplitude brightens the entire image
we CAN adjust it

34
Q

compensation

TGC, DGC, swept gain

A

treats all signals differently based on depth because of attenuation
uniformly bright, with proper compensation images become increasingly darker with depth
we can adjust it

35
Q

compression

log compression, dynamic range

A

signals treated differently based on strength
changes in grayscale mapping, strong signals appear bright white
we CAN adjust

36
Q

demodulation

A

prepares electrical signals to be suitable for display

we CANNOT adjust this

37
Q

reject

threshold, suppression

A

only weak signals affected
weak echoes appear or are eliminated from image
we CAN adjust

38
Q

near gain

A

constant amount of compensation

39
Q

delay

A

varying compensation

40
Q

slope

A

compensation corrects for attenuation

41
Q

knee

A

reflections are at max compensation

42
Q

far gain

A

max compensation that receiver can provide

43
Q

if a TGC curve attenuates at a shallow depth, it has a (high or low frequency)

A

high

44
Q

dynamic frequency tuning

A

dampening of high frequency pulses to create a good axial resolution

45
Q

ALARA

A

as low as reasonable achievable

used to minimize bio effects on patient

46
Q

what do output power and receiver gain have in common

A

they both change the brightness of the entire image

47
Q

output power

A 
changes brightness of entire image
alters signal to noise ratio
alters bio effects 
bioeffect concerns
decrease this FIRST if image is too bright
48
Q

receiver gain

A 
changes brightness of entire image
does not alter signal to noise ratio
no exposure
no bioeffect concerns
increase first if image is too dark

Ultrasound Physics (24 decks)

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