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Ultrasound Physics > Quiz 7 Ch 15 > Flashcards

Quiz 7 Ch 15 Flashcards

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1
Q

Bistable images only contain what 2 shades?

A

Black and white

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2
Q

What is a scan converter?

A

Store information and later display it

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3
Q

Gray scale displays what?

A

Multiple levels of brightness

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4
Q

What does contrast do?

A

Determines the range of brilliances within the displayed image

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5
Q

Are bistable images high or low contrast?

A

High contrast

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6
Q

What is storage in the scan converter called?

When the information is displayed, what is it called?

A

Writing

Read

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7
Q

T/F Data stored in the scan converter can be altered between the writing process and reading process?

A

True

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8
Q

What are analog numbers?

A

Real world
Unlimited number of choices
Continuous values

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9
Q

What are digital numbers?

A

Computer world
Limited choices
Discrete values

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10
Q

What do the electrons do in an analog converter?

A

Contain the information and shoot out of the electron gun

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11
Q

What do the electrons do with the dielectric matrix (silicon wafer) in an analog scan converter?

A

Electrons strike the matrix where they are stored

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12
Q

What is a dielectric matrix?

A

Similar to a picture divided into millions of small dots that contain an electrical storage element

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13
Q

An analog scan converter provides excellent ______ resolution because of the ______ number of storage elements within the matrix.

A

Spatial

Large

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14
Q

What is the spatial resolution?

A

Image detail

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15
Q

What are limitations of analog scan converters?

A

Image fades, flickers, is unstable, and deteriorates

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16
Q

What is a digital scan converter?

A

Converts images into numbers

(AKA digitizing)

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17
Q

How does the digital scan converter store the image?

A

As a series of zeros and ones

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18
Q

What are advantages of digital scan converters?

A

Uniformity (consistent gray scale)

Stability (no fading)

Durable

Speed (almost instant)

Accurate

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19
Q

What are the 2 elements of a digital scan converter?

A

Pixel
Bit

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20
Q

What is a pixel?

A

A single shade of gray

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21
Q

What is pixel density?

A

The number of pixel elements per inch

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22
Q

Low pixel density included what 4 things?

A

Few pixels per inch

Large pixels

Less detailed image

Low spatial resolution

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23
Q

High pixel density includes what 4 things?

A

Many pixels per inch

Small pixels

More detailed image

High spatial resolution

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24
Q

What is a bit?

A

Value of either 0 or 1

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25
What is a binary number?
Group of bits in a series of zeros or ones
26
What is a byte?
Group of 8 bits (01011001)
27
What does a word consist of?
2 bytes or 16 bites
28
Fewer bits per pixel = _____ shades of gray and _____ contrast resolution.
Fewer Degraded
29
More bits per pixel = _____ shades of gray and _____ contrast resolution.
More Improved
30
How do you calculate the number of gray shades represented by a cluster of bits?
Multiply by 2 and how many bits there are. Example: 2^3 =8 (2x2x2)
31
Weak signals are susceptible to what?
Noise
32
In order to avoid noise, the information is converter from what to what?
From analog to digital form
33
Before the image can be displayed it must be converter from what to what?
From digital to analog form
34
What is the first step in translating info from analog form to digital form?
Electrical signals created during reception are converter from analog to digital form by the A&D converter. Only contains zeros and ones
35
What is the second step in translating info from analog form to digital form?
The digital info is stored in the scan converters computer memory.
36
What is preprocessing?
The changing of image data before storage Alters the image forever, cannot be undone Ex: adjusting TGC
37
What is the third step in translating info from analog form to digital form?
Continues to be processed in digital for
38
What is post processing?
Changing the image after storage Can be reversed or undone Ex: adding/deleting measurements
39
What is the forth step in translating info from analog form to digital form?
Digital signals must be converted back into analog form by a D to A converter
40
What is the fifth step in translating info from analog form to digital form?
The signal can now be presented on video display
41
What is not necessary when using a digital display device?
Digital to analog conversion
42
What are the 2 forms of magnification?
Read Write
43
When does the read magnification occur?
Post-process
44
What are the 3 steps of read magnification?
1. Scan anatomy. 2. Image is converted from analog display form and stored in scan converter. 3. Sonographer identifies ROI and the system reads and displays only the original data that includes the ROI.
45
Read magnification is characterized by?
The number of pixels or scan lines in the magnified image is the SAME as in the original image
46
Is spatial resolution changed by read magnification?
No (pixels are just larger)
47
What is write magnification?
Before storage in the scan converter
48
What are the 4 steps of write magnification?
1. Scan anatomy 2. Image is converted from analog to digital form and stored into scan converter 3. Sonographer identifies ROI and the system DISCARDS all the existing data 4. The system RESCANS only the ROI
49
Write magnification can be characterized by?
Number of pixels or scan lines in ROI image is GREATER than the original ROI portion. Pixel size is the same in both images
50
Is spatial resolution improved or not improved by write magnification?
Improved
51
What does coded excitation create?
Creates long sound pulses that contain a wide range of frequencies
52
Coded excitation improves what?
Image quality
53
Coded excitation occurs where?
In the pulser
54
How does coded excitation improve resolution?
By altering the long pulses into a better form for high image quality.
55
Coded excitation ______ the pulse to improve resolution.
Shortens
56
What is spatial compounding?
Taking information from several different imaging angles to make a single image.
57
What does spatial compounding do with the different angle views?
Combines (overlap) to form an image
58
T/F. More frames in spatial compounding = better image quality?
True
59
What does spatial compounding reduce that is helpful for image quality?
Speckle and shadow artifacts
60
What type of steering is required in spatial compounding? With what type of transducers?
Electronic Phased array
61
What is a limitation to spatial compounding?
Degrades frame rate and temporal resolution
62
What does frequency compounding do?
Reduces speckle artifact and noise
63
In frequency compounding, sound pulses contain a ____range of frequencies.
Large
64
How does frequency compounding reduce noise and artifact?
By dividing the reflected sound beam into parts with different frequency ranges
65
What are the different frequency ranges called in frequency compounding?
Sub-bands
66
What happens to noise in frequency compounding when the sub bands are combined?
Noise is reduced
67
What does edge enhancement do?
Make the image look sharper
68
How does edge enhancement make the image look sharper?
By adding subtle bright and dark highlights on either side of the boundaries to make them look more defined.
69
What are other names for temporal compounding?
Persistence and temporal averaging
70
What is temporal compounding?
A technique that displays information from old images (Stacks the images on top of each other)
71
What is the result of using temporal compounding?
Smoother image Reduced noise High signal to noise ratio Improved image quality
72
What is the limitations for using temporal compounding ?
Degrades frame rate and temporal resolution
73
T/F. Temporal compounding is great to use with fast moving objects
False (slow moving objects only)
74
Fill-in interpolation uses what kind of images?
2D from multiple pulses
75
What does fill-in interpolation do?
Fills in the gaps of missing information between the scan lines without being detected
76
How does fill-in interpolation work?
The computer predicts gray scale levels of missing data with known gray scale levels of neighboring pixels
77
Line density increases or decreases with fill-in interpolation?
Increases
78
Fill-in interpolation is a form or pre processing or post processing?
Pre processing
79
Fill-in interpolation improves what ?
Spatial resolution (Makes it possible to view borders of round structures)
80
What is elastography?
A technique that uses tissue deformation to produce an image
81
What 2 things are combined to form an elastogram?
Stiffness and reflections
82
When do we use elastography?
To differentiate malignant and benign lesions
83
An elastogram is based on differences in what?
Stiffness
84
What does PACS stand for?
Picture archiving and communications system
85
What is PACS used for?
Storing medical info on a computer network
86
What does DICOM stand for?
Digital imaging and computers in medicine
87
What is DICOM?
A set of rules/protocols that allow us to share images on a network Connects to the PACS network

Ultrasound Physics (13 decks)

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