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Physic 2 > Basic Instrumentation > Flashcards

Basic Instrumentation Flashcards

1
Q

The machine will process stored voltages to do what

A

it will convert them and this will reconstruct the image from the reflectors in the body

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2
Q

Pulser

A

Sends the voltage pulse to the probe which will determine the: PRF,intensity and operating frequency

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3
Q

Range ambiguity is controlled by the?

A

Pulser

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4
Q

Pulse delays

A

Applies the delays ness art to accomplish focusing, beam steering and aperture size

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5
Q

Aperture size

A

How many crystals in a group that will be fired

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6
Q

Transmit/receive switch

A

Directs the pulse in the correct direction to protect the sensitive components from large voltage pulses

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7
Q

Transducer

A

What sends the pulse into the pulse when it receives it from the transmit receive switch

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8
Q

Amplifiers

A

Amplifies the weak pulses that return from the patient so that the pulses can make it through the entire circuit

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9
Q

ADC

A

Analog to digital converter

Pulses pass through this and are converted from analog to digital so they can be stored in the memory

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10
Q

Why is storing the voltages useful

A

Allows for manipulation of the image later on

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11
Q

Is the information lost in the process of analog to digital significant

A

No

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12
Q

Echo delays

A

Holds the first echo so all the other echos can catch up, so they are all in phase

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13
Q

Sum

A

Adds together the pulses from each element in the segment to form the resulting scan line

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14
Q

Why is digitation of the voltage crucial

A

Maintains the integrity of the data throughout the system

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15
Q

This process involves converting the voltage into a binary number

A

Digitization

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16
Q

Is a voltage or a binary number more stable

A

Binary number

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17
Q

When can digitization occur

A

Before or after the echo delay in the beam former

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18
Q

When is digitization preferred

A

Before the echo delay so the signal is stabilized early on

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19
Q

What are the two processes in signal processing

A

ADC

Receiver

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20
Q

What is the function of the receiver

A

Process the returned echoes as analog voltages in preparation for display

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21
Q

What are the five steps to the receiver

A 
Amplification 
Compensation
Compression
Rejection 
Demodulation
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22
Q

Amplification

A

Is the gain control
Amplifies weak return echos so they can complete the entire circuit
Can control the amount to brighten or darken the image

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23
Q

What is gain expressed in and what is the typical range

A

Decibels and it ranges from 60-100 dB

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24
Q

What does compensation do

A

It helps compensate for the attention of sound as it travels

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25
Q

Why is there a need for compensation

A

Similar signals from reflectors should have the same echogenisty regardless of the depth the reflector is imaged from

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26
Q

What control is related to compensation and how is it expressed as well as what is the range

A

TGC

Expressed in decibels and has a range of approx. 60dB

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27
Q

What’s another name for TGC

A

DGC-depth gain compensator

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28
Q

How does TGC operate and what does it correct for

A

Usually in one cm increments

Corrects for the main bang artifact and attention in the far field

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29
Q

Main bang artifact

A

As soon as the sound leaves the transducer it hits the skin of patient and sound energy is lost

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30
Q

What does compression do and how is it accomplished

A

Decreases the difference between the smallest and largest amplitudes
Accomplished by using a logarithmic amplification

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31
Q

Compression is also known as what

A

Dynamic range

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32
Q

How is compression expressed

A

In decibels

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33
Q

What is the reject level

A

Smallest amplitudes

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34
Q

What is the saturation level

A

Largest amplifications

35
Q

What is logarithmic amplification

A

The gain applied exponentially as a function of the input signal level and it results in the compression of the dynamic range

36
Q

Dynamic range

A

Reduces the number of shades of grey into range of shades that are more distinct from one another

37
Q

What does rejection do

A

Eliminates or suppresses low level echoes that may represent noise, improves the signal to noise ratio

38
Q

What does rejection help with and is it operator controlled

A

Reducing the dynamic range

May or may not be operator controlled

39
Q

What else is rejection known as

A

Threshold of suppression

40
Q

What is the demodulation process

A

Converts radio frequency signal into a video signal for monitor display

41
Q

What are the two stages of demodulation

A

Rectification and smoothing

42
Q

Rectification

A

Turns all negative portions of a single into positive portions

43
Q

Smoothing

A

Also called enveloping

Filters the signal to smooth out the bumps

44
Q

Scan conversion

A

Writes vertically acquires ultrasound data horizontally to the memory

45
Q

How does the analog scan converter differ from the CRT

A

Replaces the phosphor face with a dielectric matrix

46
Q

Dielectric matrix

A

A wafer of silicon

47
Q

What is the scan converter also known as

A

The memory

48
Q

electron beam moves across the dielectric matrix in what kind of format

A

raster

49
Q

what is pre-processing

A

any processing of the wave signal before it is transferred and stroed in the memory

50
Q

do different ultrasound machines use different processing

A

yes

51
Q

what are some pre-processing functions

A 
receiever functions
maps
interpolation
edge enhancement
write zoom
persistance
52
Q

what are maps

A

curves applied to the shades to accentuate different levels

53
Q

what is the purpose of maps

A

to enhance the visualization of certain aspects of the image

54
Q

what does interpolation do

A

averages pixel grey scal values and fills in the noexistant information

55
Q

what does interpolation improve and is there a trade off

A

improves the apperance but it creates the “what is real” question

56
Q

what can too much interpolation do

A

misrepresent the image

57
Q

what is edge enhancement

A

sharpens the boundaries of an image to make them more distinguishable making measurments more precise
improves the overall look of an image

58
Q

what is applied to an image to adchieve edge enhancement

A

a kernal

59
Q

what is write zoom

A

expands the image before storage in the memory

60
Q

what is another term for write zoom

A

regional expansion

61
Q

is the region of interst controlled by the sonographer

A

yes

62
Q

what is the advantage of the ROI

A

its rescanned and additional scan lines are added

63
Q

when additional scan lines are added what increases

A

spatial resoultion
detail
pixel ratio

64
Q

what is persistance

A

takes data from several frames and avearges them before displaying the image

65
Q

what does persistance improve

A

signal to noise ratio

66
Q

what will sampling over time do

A

will decreaser temporal resolution

67
Q

what must the be small so blurring does not occur

A

rate of movement

68
Q

when is persistance not used

A

obsetrical ad echocardiography

69
Q

what is post-processing

A

any processing that occurs after the information has been stored into the memory

70
Q

when is post processing applied

A

to a frozen image

71
Q

some post processing functions are

A 
measuring
annotations
post processing curves
read zoom 
colour doppler mapping
angle correct
b-colour
72
Q

curves can be applied to a frozen image in the assignment of what

A

display intensity to a digital scale

73
Q

is curves operator controlled and where is it accomplished in the machine

A

yes and in the DAC

74
Q

what is the most common curve used

A

linear

75
Q

what is the approx number of curves that eachmanufactor develops in accordance to their own hardware

A

~5-10

76
Q

what is read zoom

A

maginfies a frozen image by reassigning the pixel size

77
Q

what happens when read zoom is applied

A

a decrease in resolution

78
Q

what is the B-colour funtion

A

uses various colour schemes from oranges to purples to blues to be applied to each digital value instead of shades of grey

79
Q

Is the B-colour function operator controlled

A

yes

80
Q

what does the B-colour potentially improve

A

contrast resolution of the image

81
Q

what is the final step of image processing

A

the DAC reconverts the digital information into a voltage signal

82
Q

why is the information converted back into a voltage signal

A

because display systems will only accept a voltage

83
Q

what are the different voltages that a display system will accept

A

video

analog

Physic 2 (5 decks)

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