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SPI > Displays, Image Processing, Dynamic Range > Flashcards

Displays, Image Processing, Dynamic Range Flashcards

1
Q

What is a bistable display?

A

2, black and white

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2
Q

What is gray scale display?

A
  • variety of grayness
  • spectrum of brightness levels
  • able to differentiate between amplitude differences in reflections
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3
Q

What is contrast?

A

determines the range of “brilliancies” within displayed image

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4
Q

What is brightness?

A

Determines the “brilliance” of the overall displayed image

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5
Q

What are the two functions of scan converters?

A
  1. store info “writing”
  2. display info “reading”
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6
Q

What is the difference in formation of transmitted/reflected pulses and monitors and displays?

A

transmitted/reflected: vertical lines
monitors/displays: horizontal lines

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7
Q

What are analog numbers?

A
  • unlimited, continuous range of values
  • weight, length
  • real world values
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8
Q

What is an example of an analog value?

A

165.8 lbs

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9
Q

What are digital numbers?

A
  • associated with computers
  • discrete, whole values
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10
Q

What is an example of a digital value?

A

166 lbs

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11
Q

What is an analog scan converter?

A
  • first type of converter, made gray scale imaging possible
  • funnel shaped vacuum tube with an electron gun
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12
Q

How does an analog scan converter work?

A
  • Electrons contain image info and are shot out of gun
  • Other end of tube contains dielectric matrix/silicon wafer
  • Electrons strike matrix/wafer, stored
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13
Q

How does the matrix produce an image in an analog scan converter?

A
  • matrix is a picture of a million dots, each with storage element
  • stored electron charge that hits the matrix read to retrieve image info
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14
Q

How is the spatial resolution of analog scan converter images?

A

Excellent because matrix has large storage capability

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15
Q

What are the limitations of analog scan converter?

A
  • image fade
  • image flicker
  • instability
  • deterioration
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16
Q

What is image fade?

A

Stored charges in the matrix dissipate over time

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17
Q

What is image flicker?

A

Caused by switching between write and read modes

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18
Q

What is instability?

A

Image quality depends on factors such as duration of use, room temp, humidity

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19
Q

What is deterioration?

A

Image degrades as the device ages

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20
Q

What is a digital scan converter?

A
  • Use of computers to convert images into numbers
  • Image is stored in a computer memory as 1s and 0s
  • Numerical representation is processed and retranslated into displayed image
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21
Q

What are the advantages of digital scan converter?

A
  • Uniformity: consistent gray scale quality
  • Stability: does not fade
  • Durability: not affected by age/use
  • Speed: instantaneous processing
  • Accuracy: virtually error free
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22
Q

What is a pixel?

A
  • picture element
  • smallest unit of digital picture
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23
Q

How do pixels make up an image?

A
  • Image displayed as grid
  • Each box = pixel
  • Each pixel = one shade of gray
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24
Q

What is pixel density?

A

Number of picture elements per inch

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25
Q

What is the result of higher pixel density?

A

More smaller pixels, increased spatial resolution/detail

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26
Q

What is the result of lower pixel density?

A

Less larger pixels, decreased spatial resolution/detail

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27
Q

What is a bit?

A
  • binary digit
  • smallest unit of computer memory
  • value of 0 or 1
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28
Q

What is a binary number?

A
  • Group of bits
  • Series of zeros and ones
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29
Q

What is a byte?

A

Group of 8 bits

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30
Q

What is a word?

A

Two bytes or 16 bits

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31
Q

How is grayness determined?

A
  • The cluster of bits assigned
  • More bits/pixel = more shades of gray
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32
Q

What does more bits per pixel result in?

A

Increased contrast resolution

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33
Q

How are gray shades calculated?

A
  • 2^n (number of bits)
  • results in max number of gray shades
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34
Q

How many possible shades of gray will 5 bits of memory display?

A

2^5 = 32

35
Q

How is image data converted for display?

A

Analog to digital back into analog for display

36
Q

Why does image data need to be converted to digital form?

A

To reduce susceptibility to noise contamination

37
Q

How are electrical signals created by the transducer converted?

A

Using analog-to-digital converter, digital info is string of 1s & 0s

38
Q

Where is digital info stored after being converted from analog?

A

Scan converter’s computer memory

39
Q

What is preprocessing?

A

Any processing of the reflected signals before storage

40
Q

What is postprocessing?

A

Any processing of the reflected signals after storage in the digital scan converter

41
Q

How are digital signals converted for display on an analog display device?

A

Using the digital-to-analog converter

42
Q

What controls are used in preprocessing?

A
  • TGC
  • gain
  • write magnification
  • compression
  • temporal compounding
  • spatial compounding
  • edge enhancement
  • fill-in interpolation
43
Q

What happens when an image is preprocessed?

A

The image data is permanently altered and cannot be reversed once saved

44
Q

What can be controlled in postprocessing?

A
  • black/white inversion
  • read magnification
  • contrast
  • 3D rendering
45
Q

What happens when an image is postprocessed?

A

All postprocessing changes can be reversed which will restore the image to original values

46
Q

What are the 3 steps of read magnification?

A
  1. system scans anatomy
  2. image converted A-D, stored in scan converter
  3. tech picks ROI, system reads & displays on original data for that area
47
Q

How are the number of pixels affected with read magnification? Spatial resolution?

A

Same number of pixels, same spatial resolution

48
Q

What are the 4 steps of write magnification?

A
  1. system scans anatomy
  2. image converted from A-D, stored in scan converter
  3. tech picks ROI, system discards all existing data in scan converter
  4. system rescans only the ROI and writes new data
49
Q

How are the number of pixels affected with write magnification? Spatial resolution?

A

Greater number of pixels, better spatial resolution

50
Q

Summarize the 6 characteristics of read magnification.

A
  • Uses old data
  • Postprocessing
  • Larger pixel size
  • Same # pixels as orig ROI
  • Same spatial resolution
  • Same temporal resolution
51
Q

Summarize the 6 characteristics of write magnification.

A
  • Acquires new data
  • Preprocessing
  • Identical pixel size
  • More pixels than orig ROI
  • Improved spatial resolution
  • Improved temporal resolution
52
Q

What is coded excitation?

A

Method of improving image quality

53
Q

How does coded excitation improve image quality?

A
  • Keeps max peak intensity within specific limit
  • Creates long pulses with wide freq range
  • Distributes energy over broad freq range
  • Strong pulse within intensity limits
  • Improved penetration
54
Q

What are the 5 characteristics of coded excitation?

A
  • Higher signal to noise ratio
  • Improved axial res
  • Improved spatial res
  • Improved contrast res
  • Deeper penetration
55
Q

What is spatial compounding?

A

Method of using info from multiple imaging angles to produce a single image

56
Q

How is spatial compounding done?

A
  • Acquires frames from multiple angles
  • Frames are combined to form single image
  • # of frames and steering angles varies based on transducer/clinical use
57
Q

What results in better compound image quality?

A

More frames

58
Q

What are the results of spatial compounding on an image?

A
  • Reduces speckle and shadowing artifacts
  • Lower frame rate and temporal res
59
Q

What is frequency compounding?

A

Technique used to reduce speckle and noise artifacts

60
Q

How does frequency compounding work?

A
  • Divides reflected wave into sub-bands of limited frequencies
  • Image is created from each sub-band
  • Images are combined into 1
61
Q

What is the result of frequency compounding?

A
  • Mimics multiple images being created from transducer with different frequencies
  • Reduces overall noise
62
Q

What is edge enhancement?

A

Method used to make images look sharper

63
Q

How is edge enhancement done?

A
  • Computer emphasizes sharp edge boundaries w/i image
  • Increases contrast in area immediately around edge
64
Q

How does the computer make boundaries appear defined?

A

Creates subtle bright and dark highlights on either side of boundaries

65
Q

What is temporal compounding?

A
  • Technique that continues displaying info from older images
  • Prev frames are superimposed on current
66
Q

What is the result of temporal compounding?

A
  • Smoother image, higher signal to noise ratio
  • Improved image quality
  • Lower frame rate
  • Decreased temporal resolution
67
Q

What is fill-in interpolation?

A
  • With sector images, scan lines become further apart as they travel
  • results in gaps
  • Interpolation fills in gaps with simulated data points
68
Q

How does fill-in interpolation work?

A
  • computer programs predict gray scale levels of missing data
  • uses neighboring data
69
Q

What does PACS stand for?

A

Picture Archiving and Communications System

70
Q

What is PACS?

A
  • Digital lab where images/med info are digitized & stored
71
Q

What are the benefits of PACS?

A
  • Instant access to archived studies
  • No degradation of data
  • “Store & forward” info to transmit images/reports to remote locations
72
Q

What does DICOM stand for?

A

Digital Imaging and Computers in Medicine

73
Q

What is DICOM?

A
  • Set of rules/protocols that allow imaging systems to share info on a network
  • Allows a system to connect to PACS
  • Allows devices to share, manage, distribute images regardless of manufacturer
74
Q

What is dynamic range?

A

Method of describing the extent a signal can vary and still maintain accuracy

75
Q

What is an example of dynamic range?

A

Scales weighs 30-300 lbs accurately
- Below 30 lbs, too weak for threshold, needle doesn’t move
- Above 300, too strong, saturates system, reads as 300 lbs

76
Q

How is dynamic range reported?

A

Decibels

77
Q

What kind of measurement is dynamic range?

A

Comparison, relative, measurement or ratio b/w largest and smallest signals within an accurate range

78
Q

What happens to dynamic range of info the more it is processed?

A

Decreases

79
Q

What processes data with the widest dynamic range?

A

Components earliest in imaging change
- Transducer
- Receiver
- Scan converter
- Display
- Archive

80
Q

Dynamic range of a display can be reported as:

A

The number of possible gray shades

81
Q

Narrow dynamic range results in

A
  • Few shades of gray
  • High contrast
82
Q

Wide dynamic range results in

A
  • Many shades of gray
  • Low contrast
83
Q

Spatial compounding can only be done with what type of transducer?

A

Phased array

84
Q

What is temporal compounding also called?

A

Persistence or temporal averaging

SPI (9 decks)

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