Digital Imaging Flashcards
1
Q
_____ computers handle data composed of continuous signals (current)
A
analog
2
Q
______ computers handle data in definite quantities (discrete numbers)
A
digital
3
Q
______ connections are a simultaneous transmission
A
parallel
4
Q
______ connections are slower, info is transferred in a sequence
A
series
5
Q
Specialized peripheral computer processing units
-use memory to perform simultaneous mathematical calculations in parallel (simultaneously) at high Speeds
A
array processors
6
Q
Extracts information without alteration
A
read memory
7
Q
Replaces old memory with new information
A
write memory
8
Q
Read only memory, basic operating instructions
A
ROM
9
Q
Temp storage of info during use
A
RAM
10
Q
Primary mathematical methods used to convert data to useful information (images)
A
Fourier Transmission
11
Q
process of modifying pixel value by masking image through math calculations- pixel masked with density value, changes image quality
A
convolution
12
Q
process of returning pixel values to their original level by a reverse process , info returns altered image to original state
A
deconvolution
13
Q
Pixels increase, resolution _______
A
increases
14
Q
Digital image qualities data characteristics are measured in:
A
frequency, contrast, noise
15
Q
raw data, the measure of the total amount of contrast within image
A
frequency
16
Q
high frequency, ______ contrast
A
high
17
Q
low frequency, _______ contrast
A
low
18
Q
subject contrast is high, data contrast is ______
A
high
19
Q
signal to noise ratio- high ratio, _____ noise
A
little
20
Q
signal to noise ratio- low ratio, ______ noise
A
high
21
Q
high image noise, _______ contrast
A
low
22
Q
low image noise, ______ contrast
A
high
23
Q
filtering process to suppress frequencies to reassign an average gray scale value to each pixel according to its neighbor’s value
A
masking
24
Q
amplifies or deletes higher frequencies- Reduces contrast / removes high frequency noise
A
low pass filtering
25
amplifies or deletes all frequencies, but a selected range Isolates data - localization of specific densities eg.) Isotope concentration in NM
band pass filtering
26
amplifies or deletes all frequencies, but high frequencies- Increases contrast
high pass filtering
27
window level controls _____
density (midpoint)
28
window width controls _______
contrast (range of visible densities on both sides of the midpoint/ window level)
29
progressive scanning
increases resolution by scanning 525 lines in ORDER = 1-2lp/mm
30
slow scanning
raster pattern- 5-7 lp/mm
31
pixel modification- gray scale expansion does what?
stretches the gray scale to enhance detail
32
pixel modification- histogram modification
reassigns pixels to different density values to equalize the number of pixels for each gray scale
33
digital filtering- masking
filtering process that assigns an average gray scale value for each pixel according to it's neighbor's value
34
Layers of the phosphor imaging plate
protective layer
phosphor layer
support layer
conductor layer
light shielding layer
35
quantum motle occurs due to what
underexposure (high S number)
36
The phosphors of a CR imaging plate do what?
stores the energy of exit x-rays until processed
37
The smallest picture element with one gray scale value
pixel
38
A histogram of pixel values is used to (3)
determine the level of exposure
determine the level of brightness of pixels in the image
make adjustments in brightness levels to improve image
39
The process of subtracting an earlier image from a later image
temporal subtraction
40
Manipulating the gray scale values of pixels in the image is called
Contrast enhancement post processing
41
Window levels can be adjusted to _____ for air and ______ for bone
-1000, 1000
42
Image noise makes an image appear
grainy
43
Regarding data acquisition, as the matrix size increases, data acquisition ______
decreases
as the resolution increases we can acquire less data
44
Pixel with volume
voxel
45
Spatial Resolution: Horizontal
Pixels going right to left
46
Spatial Resolution: Vertical
Pixels going up and down
47
Ensures that all equipment speaks the same language for output devices
DICOM
48
Ensures that all equipment speaks the same language for input and output devices
DICOM2
49
Digital Image display qualities are measured by (3)
density
contrast
resolution
50
Contrast in digital imaging measures what?
the differences between data values
51
CR imaging plate: phosphor layer
energizes during exposure- photostimulable phosphors
52
CR imaging plate: support layer is made of what?
polyester
53
CR Imaging plate: conductor layer
grounds plate to reduce static discharge- absorbs light to increase sharpness
54
Smaller the pixel, _______ spatial resolution
greater
55
Pre-Image processing: Sampling looks at what 2 factors
orientation to plate
number of projections on plate
56
What type of sampling adjusts the latitude and sensitivity for the image and is used for multi images on one plate
Fuji's Exposure Data Recognition (automatic)
57
Adjusts latitude but sensitivity is fixed- image is centered but collimation is not equidistant from plate edges
Semi-automatic sampling
58
Latitude and sensitivity are fixed, will not correct exposure deficiencies (most like film screen)
Fixed sampling
59
X-rays are converted to electrical charge directly which is then converted to electrical pulses--- then converted to an image matrix
DIRECT digital
60
TFT used in what?
Direct digital
61
Collects electric charge until gate is activated and signal is sent pixel by pixel
TFT in direct digital
62
IR plate holding a charge creates what?
fogging
63
inadequate exposure causes what?
quantum mottle
64
IR plate exposed to heat causes what?
heat blur
65
incorrect preprocessing selection causes what?
histogram error
66
Advantages of digital (4)
Image manipulation
Image storage
Image retrieval
Transmission of images
67
Disadvantages of digital
Patient exposure (single exposure)
Cost: Technology & Imaging Plates
Technology errors: Pre-processing selection
Decreased latitude for technical errors: Collimation & Positioning
68
Range of gray scale values that can be assigned to each pixel the number of signal values that the receptor is capable of capturing.
dynamic range
69
dynamic range of digital imaging
256 to 4096 shades of gray
70
Selected ranges of brightness values subtracted from the image producing an image with structures at those values subtracted from the image
image subtraction
71
Resolution of conventional film radiography
6-10 lp/mm
72
What is a flat-panel image receptor?
Detector for X-rays
73
How does the receptor recognize the exposure field?
By the number of electrons in detector element
74
What does the exposure level control?
Number of electrons, electrical charges collected by detector element
75
Why is it important to select the correct algorithm for a part?
Incorrect selection leads to information loss
76
gradation processing
fuji
77
tonescaling
Kodak
78
Multiscale image contrast algorithm
Agfa
79
graphically represent a collection of exposure values extracted from the receptor.
Histogram
80
must quantize, or turn, that continuous stream of electrons into unique values
ADC
81
An image is created after...
a histogram of the extracted image data is analyzed using one of two formats:
82
the greater the number of signal values that a receptor is capable of capturing=
the greater the receptor's dynamic range.
83
if an image contains quantum noise is the image over or under exposed?
underexposed
84
Modifies value of pixel to enhance or suppress a visual image characteristic
Convolution / Deconvolution
85
Process of modifying pixel value by masking image through math calculations
Convolution
86
Process of returning pixel values to their original level by a reverse process
Deconvolution
87
The conversion of a radiographic image (film) post chemical processing
Image Digitalization
88
indirect conversion- CR or DDR?
Computed Radiography
89
Direct conversion- CR or DDR?
Direct digital radiography
90
casette based digital image receptors:
PSP photostimuable storage phosphor
91
Cassette-less digital image receptors:
-PSP photostimulable storage phosphor
-Flat Panel
-CCD (charge coupled device)
92
which company invented computed radiography?
FUJI
93
Which company uses photostimulable plates and a laser reader for their CR devices?
FUJI
94
Which company uses silicon flat panel and TFT's for their CR devices?
Phillips, GE, Siemens
95
Which company use rare earth intensifying screens ans CCD's for their CR devices?
SwissRay
96
What is the measure of data quality?
Contrast, frequency, noise
97
What are the qualities of a display image?
Brightness, contrast, resolution
98
What is frequency data?
Raw data; measure of total amount of contrast within the image
99
What is contrast?
Measure of differences between data values
100
High subject contrast =
=high data contrast
101
What is noise?
Random background information that does not contribute to image quality
102
What is the relationship between noise and contrast?
Inverse relationship, high noise decreases contrast
103
What is density/contrast?
Controlled by varying numerical values of each pixel
104
What is the human visual range for shades of gray?
32 or less shades of gray
105
What is the photon beam range for shades of gray?
1,000 shades
106
What is the contrast resolution for digital detectors?
Sensitive to almost 1,000 shades, greater contrast resolution
107
What is Window Level?
Density levels
108
What is Window Width?
Contrast levels
109
What are the factors to evaluate digital images?
Brightness, contrast, image blur, exposure indicator, image noise
110
What is Image Brightness in a digital image equivalent to?
Opposite density in an analog image
111
How is Contrast determined?
By the differences in adjacent densities within an image
112
What is Bone Gray Scale used for?
To visualize bony trabeculae by manipulating the digital image characteristic of contrast
113
What is Soft Tissue Gray Scale used for?
To enhance the difference between adjacent densities and see muscle, organs and fatty patterns better
114
What causes image blur in flat panel detectors?
Larger DELs.
115
How does increasing SID affect image blur?
Decreases blur.
116
How does increasing OID affect image blur?
Increases blur.
117
What are the factors that contribute to geometric unsharpness?
Focal spot size, SID, OID.
118
An image receptor's ability to respond to exposure
dynamic range
119
the range of under- or overexposure that
can occur in producing an acceptable image
exposure latitude
