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Phys 254 > Module 2: Basic Instrumentation > Flashcards

Module 2: Basic Instrumentation Flashcards

1
Q

The Ultrasound systems converts the mechanical sound waves from the patient and converts them to what?

A

Electrical information

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2
Q

The converted voltages are processed by the machine to do what?

A

Reconstruct an image from the reflectors in the body

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3
Q

Once the voltages are processed by the machines to reconstruct an image from the reflectors in the body. What happens?

A

The voltages are stored and converted once again into the image we see on the monitor

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4
Q

What is the process for basic instrumentation?

A
  1. Tech
  2. Beam former
  3. Signal processor
  4. Image processor
  5. Display
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5
Q

What is the process for beam formers?

A
  1. Tech
  2. Transducer
  3. Amplifier
  4. ADC’s
  5. Echo delays
  6. Sum
  7. Signal processors
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6
Q

What is the other alternative process for beam former?

A
  1. Pulsed
  2. Pulse delay
  3. T/R
  4. Amplifiers
  5. ADC
  6. Echo delays
  7. Sum
  8. To signal processors
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7
Q

Digitizations of the voltage is crucial to maintain what?

A

The integrity of the data through the system

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8
Q

The process of digitizations involves what?

A

Converting the voltage into a binary number which is more stable

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9
Q

Digitizations can occur before or after what?

A

The echo delay in the beam former but the preferences is before to stabilize the signal early on

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10
Q

Signal processing involves what two steps?

A
  1. ADC
  2. The receiver
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11
Q

What is the function of the receiver?

A

It’s function is to process the returned echoes as analog voltages in preparation for display

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12
Q

There are five separate steps for the receiver preparing images for display. What are they?

A
  1. Amplification
  2. Compensation
  3. Compression
  4. Rejection
  5. Demodulation (includes rectification and smoothing)

Rac cd

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13
Q

Why must we use amplification for images?

A

Returning echos are weak and must be amplified if they are to make it through the circulatory of the machine

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14
Q

We further control the amount of amplification to do what?

A

To satisfy the need to brighten or darken the image

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15
Q

What is the control for amplification? and how is it expressed?

A

The control is the GAIN and is expressed in decibels typically in the range of 60 - 100dB

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16
Q

What are the two reasons why we need to use compensation for images?

A
  1. Sound attenuates as it travels and thus there is a need to compensate for it
  2. Similar signals from reflectors should have the same brightness regardless of how deep you image the reflector
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17
Q

What is the control for the compensation control?

A

TGC is the control responsible and is expressed in dB with a range of around 60dB

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18
Q

TGC can also be called what?

A

DGC

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19
Q

TGC usually operates in what increments?

A

1cm increments and can correct for the main bang artifact and attenuation in the far field

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20
Q

What is the compression control? And what is it used for?

A

The compression control is known as dynamic range, and it is the process of decreasing the difference between the smallest (reject level) and largest (saturation) amplitudes and is expressed in decibels

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21
Q

What is logarithmic amplification?

A

Where the gain is applied exponentially as a function of the input signal level and the result is the compression of the dynamic range

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22
Q

What is the rejection function also known as?

A

Threshold or suppression

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23
Q

What is the rejection control used for?

A

To eliminate or suppress low level echoes that may represent noise and therefore, improve the signal to noise ratio

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24
Q

What does rejection control help with?

A

Reduce the dynamic range and may or may not be operator controlled

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25
What is the demodulation?
The process which converts the radio frequency (RF) signal into a video signal for monitor display
26
Demodulation is the two stage process that includes what?
1. Rectification 2. Smoothing
27
Rectification turns all negative portions of the signal into what?
Positive ones
28
What is the basic instrumentation path?
1. TX 2. Beam former 3. Signal processor 4. Image processor 5. Display
29
What is the image processing path?
1. From signal processor 2. Scan converter 3. Pre processor 4. Memory 5. Post processor 6. DAC 7. To display
30
What is scan conversion?
A simple function of the scan converter is to write the vertical acquired ultrasound data horizontally to memory
31
The Scan converter or memory of a analog scan converter is similar to what?
CRT except that the phosphor face is replaced with a wafer or silicon called the dielectric matrix
32
For analog scan converters electrons emitted by the filament, pass through what?
The deflection plates and strike the silicon wafer leaving a negative charge proportional to the amplitude of the signal strengths
33
The electron beam of the analog converter moves across what?
Dielectric matrix in what is called a raster format
34
What is pre- processing?
Simply any processing of the wave signal before it is transferred and stored to memory
35
For preprocessing different ultrasound machines offer what?
Different processing
36
What are some pre- processing functions?
1. Receiver functions 2. Maps 3. Interpolation 4. Edge enhancement 5. Write zoom 6. Persistence *Rip mew*
37
Maps are “curves” applied to what?
The shades of gray to accentuate different levels
38
The purpose of maps is to do what?
Enhance the visualization of certain aspects of the image
39
In preprocessing it has become apparent that there is a gap present between scan lines in the image, how do we correct for this?
Interpolation is used, which averages pixel grey scale values to fill in information where non exists.
40
What does Interpolation do in terms of appearance of pre- processing?
Improve the appearance but the trade off is “what is real”
41
Too much interpolation could do what?
Misrepresent the image
42
What is edge enhancement?
1. Another tool to improve the look of the image 2. It will sharpen the boundaries to make them more distinguishable and help make measurements more precise
43
What is a “kernel”?
Applied to the pixels to sharpen the boundaries to make them look more distinguishable
44
What is write zoom?
Expands the image before storage in the memory
45
What is the benefit of Write zoom for the sonographer?
The region of interest is adjustable by sonographer
46
What is ROI (region of interest)?
The box that occurs when we press zoom
47
What is the advantage of ROI?
Is that the ROI is rescanned and additional scan lines are added which increases spatial resolution, detailed and pixel ratio
48
What is persistence?
Takes data from several ultrasound frames and averages them before displaying the image to improve the signal to noise ratio
49
What is persistence also known as?
Frame average
50
What is the biggest negative portion of persistence?
Frame rate drops
51
Over use or “sampling” over time will decrease what?
The temporal resolution so the rate of movement must be small otherwise blurring occurs.
52
Because of the decrease of temporal resolution, persistence is not used for what?
1. Echo 2. Obstetrics
53
What is post processing?
An processing that occurs after the information has been stored into memory
54
Some examples of post processing include what?
1. Measuring 2. Annotations 3. Post- processing curves 4. Read zoom 5. Color doppler mapping 6. Angle correction 7. B-Color (coloured 2-D) *crab map*
55
What is the post processing curves function?
Curves can be applied to a frozen image and is the assignment of the display intensity (brightness) to a digital value
56
What is an example of an operator controlled function that is accomplished in the DAC?
Curves that are applied to a frozen image and is the assignment of display intensity
57
In terms of curves, how does each model vary?
Vary by the manufacturer
58
What is the most commonly used probe for Curves?
Linear curve
59
What is read zoom?
Post processing function that magnifies a frozen image by reassigning the pixel size.
60
What is an disadvantage of read zoom?
There is a decrease in resolution
61
What is the B colour function?
Uses various colour schemes from oranges to purples to blues.
62
Why would we use B colour?
It may help improve the contrast resolution of the image
63
What is the DAC (digital analog converter)?
The function that reconverts the digital information into voltage signal
64
Label the image
65
Label the image
66
Label the basic instrumentation pathway
67
Label the beam former pathway
68
Label the beam former pathway
69
Label the image processing pathway

Phys 254 (19 decks)

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