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RADT 251 - Advanced Imaging Modalities > Digital Imaging > Flashcards

Digital Imaging Flashcards

1
Q

system that uses a thin, active layer within a protective case to record and store x-ray energy as an unprocessed image

A

computed radiography (CR)

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2
Q

initial exposure of a CR plate results in what

A

latent image

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3
Q

5 layers of a CR cassette

A

protective layer, photostimulable phosphor, conductive layer, support layer (base), reflective layer (light shield)

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4
Q

active component of the CR plate

A

photostimulable phosphor

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5
Q

component that grounds the CR plate and reduces electrostatic charge

A

conductive or antistatic layer

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6
Q

component that directs emitted light in the imaging plate reader

A

reflective layer

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7
Q

where the latent image is produced in a CR plate

A

photostimulable phosphor

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8
Q

layer composed of extremely small particles which store and release energy in a CR plate

A

photostimulable phosphor

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9
Q

the photostimulable phosphor in a CR plate is commonly made of

A

barium fluorohalide bromides and iodides with europium activators

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10
Q

energy transfer process that takes place in photostimulable phosphor

A

photoelectric absorption

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11
Q

the number of electrons trapped during photoelectric absorption is proportional to

A

the number of x-ray photons that interact with the imaging plate

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12
Q

what is the conductor layer within the CR plate responsible for?

A

decreasing electrostatic charge

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13
Q

the term latent image in CR is used to describe the

A

stored energy within the fluorohalides

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14
Q

what is another name for the conductive layer of a CR plate?

A

antistatic layer

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15
Q

what type of laser is used in a CR imaging plate reader

A

helium neon laser

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16
Q

which component of a CR reader monitors and stabilizes the laser?

A

reference detector

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17
Q

what motion does the laser move in along the CR plate in a CR imaging reader?

A

Raster pattern (like we read text)

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18
Q

laser from CR plate reader interacts with the CR imaging plate, doing what?

A

causes each individual phosphor to glow in photostimulated luminescence, which is then directed to the photomultiplier tube

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19
Q

how are light photons from photomultiplier tube in CR image reader turned into an image?

A

analog to digital converter collects light and converts it to a string of numbers, creating a digital signal

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20
Q

how is a CR plate erased ?

A

entire plate is exposed to an intense white light

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21
Q

what takes the place of the photomultiplier tube in some CR imaging readers?

A

charge-coupled device

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22
Q

what is responsible for storing the latent image within the CR imaging plate?

A

photo-stimulable phosphor

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23
Q

what is the purpose of the laser within the CR digitizer?

A

release latent image from the photo-stimulable phosphor layer

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24
Q

what is the role of the photomultiplier tube within the CR system?

A

collect and multiply light photons and convert them to electrons

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25
Q

what is the primary function of the analog to digital converter within the CR plate digitizer?

A

convert electrical signals into a digital signal

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26
Q

what is the order of events after the imaging plate is inserted into the CR reader?

A

imaging plate is extracted by rollers, hit with a laser, laser moves in a raster pattern, and energy is released as light photons

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27
Q

For which reason is conventional film radiography advantageous over digital radiography?

A

spatial resolution

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28
Q

what happens after the computer reconstructs a digital image?

A

the image is re scaled according to the predetermined algorithm

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29
Q

digital images are further enhanced by the computer program through:

A

digital filtering

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30
Q

in order to increase contrast resolution to better visualize small fine detailed structures, the image can be manipulated by

A

decreasing window width

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31
Q

The fundamental component of a computer involved with feeding information into the CPU is termed a

A

input device

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32
Q

what does the dynamic range of digital imaging refer to?

A

the number of signal values an IR is capable of capturing

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33
Q

what does one pixel represent?

A

one value of brightness

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34
Q

what does spatial resolution of a digital image depend on?

A

matrix size

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35
Q

failure of the IR laser reader to find the collimation edges of an image during image processing will result in

A

the image being too bright or too dark

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36
Q

what is the end result of automatic rescaling of images?

A

uniform contrast and image brightness

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37
Q

what does the DQE or detective quantum efficiency refer to?

A

the ability of the image detector to create an output signal that accurately reflects the input signal

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38
Q

T / F: the higher the sampling frequency of the reader, the more information is extracted from the image receptor thus higher resolution

A

true

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39
Q

what is a histogram of pixel values used to do?

A

make adjustments in image brightness, determine the level of brightness of pixels in image, determine the level of the exposure

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40
Q

T / F: air kerma is the measurement of radiation energy absorbed in a unit of air

A

true

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41
Q

what is an advantage of direct capture digital radiography?

A

no loss of resolution from converting analog to digital data

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42
Q

a wider window width increases the range of densities and therefore:

A

lowers contrast

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43
Q

when an image reader is unable to detect image exposure borders as a result of misalignment, what occurs?

A

the reader reads all information outside the borders creating an unacceptable image

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44
Q

what is the active element in a CR imaging plate storage phosphor

A

barium fluorohalide

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45
Q

what is the standard that allows the CPU to communicate to OUTPUT devices?

A

DICOM

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46
Q

the term used in digital imaging to indicate the exposure latitude (range) is

A

dynamic range

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47
Q

the process of digital imaging programs automatically changing the appearance of an image based on predetermined image quality factors

A

rescaling

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48
Q

conversion of x-rays for direct conversion digital radiography

A

converts x-rays directly to electronic signals

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49
Q

conversion of x-rays for indirect conversion digital radiography

A

converts x-rays to visible light, then into electronic signals

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50
Q

what is the photoconductor in a direct conversion digital imaging system plate made of?

A

amorphous selenium

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51
Q

path of x-ray to digital signal in direct conversion digital radiography

A

electrical charge applied to photoconductor before exposure, charge is collected by DEL storage capacitors, charge converted to signal by ADC

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52
Q

two versions of indirect conversion DR systems

A

either scintillation layer connects to charged coupled device, or scintillation layer connects to photodiode which connects to a thin film transistor

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53
Q

what is the scintillation layer in indirect conversion DR made of?

A

cesium iodide or gadolinium

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54
Q

what does the scintillation layer in indirect DR systems convert?

A

x-ray photons into light photons

55
Q

what does the charged coupled device convert in an indirect DR system?

A

light photons into an electrical signal, which passes to ADC

56
Q

what is the photodiode layer in indirect DR plates made of ?

A

amorphous silicon

57
Q

what does the photodiode layer convert in indirect DR plates?

A

light photons into an electrical signal, which is sent to the TFT, then to ADC

58
Q

which indirect conversion system is generally used for angiography and fluoroscopy?

A

thin film transistor system

59
Q

which imaging modality uses direct conversion DR systems?

A

mammography

60
Q

which component of an indirect capture detector converts visible light into electrons?

A

photodiode

61
Q

what does the thin film transistor layer of a flat panel detector system do?

A

collects electrical charge

62
Q

which two flat-panel detector components can collect and convert light into an electrical signal?

A

photodiode and charge-coupled device

63
Q

what element used in the construction of a flat-panel detector is able to convert x-ray photons directly into an electrical signal?

A

amorphous selenium

64
Q

which device acts as a switch within a flat-panel detector to release the electric charge collected by the detector element?

A

thin film transistor

65
Q

cesium iodide is the perferred material for the scintillation layer because it can be formed into

A

columns which focus light photons

66
Q

in a CCD system, what two ways do the scintillation layer connect to the CCD sensor chips ?

A

lenses or fiber optics

67
Q

the digital image receptor is comprised of small elements called:

A

Detector elements (DELs)

68
Q

what are the components of a single DEL?

A

capture area, storage capacitor, TFT gate

69
Q

what are the components of the capture area of a DEL?

A

top electrode, detection layer, bottom electrode

70
Q

what part of the DEL detects radiation

A

capture area

71
Q

the storage capacitor of the detector element (DEL) stores what?

A

a positive charge

72
Q

what is the percentage of the DEL devoted to the detection layer called?

A

fill factor

73
Q

what is the relationship between the fill factor and spatial resolution?

A

directly proportional

74
Q

if the fill factor is decreased, what happens to patient dose and beam intensity?

A

beam intensity is increased, patient dose increased

75
Q

what is the term for the distance between the DELs?

A

pitch

76
Q

most common digital imaging pixel matrix size

A

1024 x 1024

77
Q

definition of spatial frequency and how it is measured

A

number of line pairs in a given length, measured in line pairs per millimeter

78
Q

smallest element in a digital image

A

pixel

79
Q

what is the spatial frequency if the pixel size is 0.07mm?

A

7.14 lp/mm

80
Q

total number of possible brightness levels that can be assigned to any given pixel in the digital image

A

bit depth

81
Q

formula for calculating bit depth or amounts of shades of gray per pixel

A

2^x (whatever the bit used is, 2-bit, 8-bit, etc)

82
Q

process of assigning brightness levels to a given pixel

A

quantization

83
Q

during digital image formation and processing, where does quantization take place?

A

analog to digital converter

84
Q

what is the smallest exposure difference that can be detected and displayed by the imaging system?

A

contrast resolution

85
Q

approximate representation of the distribution of numerical data

A

histogram

86
Q

process of assigning a number to identify a set of discrete values within a continuous process

A

quantization

87
Q

range of exposures that produces quality images at an appropriate patient dose

A

exposure latitude

88
Q

what step in digital image processing identifies the useful exposure values in raw image data?

A

histogram analysis

89
Q

what is the process that corrects slight under or over exposure erros made by the technologist

A

rescaling

90
Q

what process is used to display the digital image with ideal brightness and contrast

A

look up table LUT adjustments

91
Q

in a radiographic histogram, what does the Y axis represent

A

frequency of specific signal intensity values

92
Q

In a radiographic histogram, what does the X axis represent

A

specific signal intensity values from low to high

93
Q

T / F: In a digital imaging system, brightness reflects the amount of radiation the image receptor received

A

false, brightness is determined through histogram processing

94
Q

compares the amount of signal in an image to the amount of noise in an image

A

signal to noise ratio

95
Q

mottled appearance caused by an insufficient number of photons striking the image receptor

A

quantum noise, quantum mottle, photon starvation

96
Q

random information created by the electronic components within the imaging system

A

system noise

97
Q

random information created by the background radiation striking the image receptor

A

ambient noise

98
Q

photons that are no longer aligned with the anatomy

A

scatter radiation

99
Q

which type of noise cannot be reduced?

A

ambient noise, caused by presence of background radiation which always exists

100
Q

photons that add information but do not represent the anatomic structures are considered:

A

scatter radiation

101
Q

a score that describes the ability of the imaging system to convert the remnant x-ray beam into a high quality image

A

detective quantum efficiency (DQE)

102
Q

a system with high DQE posesses what?

A

high efficiency in converting the x-ray signal into an image

103
Q

amorphous selenium is a material used in which imaging system?

A

direct digital radiography

104
Q

score that measures accuracy of the image compared to the actual object

A

modulation transfer function (MTF)

105
Q

another name for modulation transfer function (MTF)

A

image fidelity

106
Q

as spatial frequency (lp/mm) increases, modulation transfer function

A

decreases

107
Q

what is the relationship between MTF and spatial frequency?

A

indirect relationship

108
Q

range of exposure values that can be captured by an image receptor

A

dynamic range

109
Q

range of exposures that can produce quality images at an appropriate patient dose

A

exposure latitude

110
Q

formula for calculating pixel size based on spatial resolution

A

1 / (spatial frequency in lp/mm x 2)

111
Q

In adjusting the appearance of a digital image, window levels can be adjusted from

A

-1000 (air) to +1000 (bone)

112
Q

Digital image data is acquired through

A

Direct capture digital sensors

113
Q

Digital filtering enhances the contrast resolution of a digital image by

A

reassigning an average gray scale value to each pixel according to its neighbor’s value

114
Q

Computers store and display visible images in columns and rows possessing depth, each of these cells is called a

A

Voxel

115
Q

in digital imaging, the x-ray beam intensity that interacts with the image receptor is reffered to as

A

signal

116
Q

the range of exposure values the image detector is able to produce is

A

latitude

117
Q

a lead apron could cause an exposure indicator miscalculation because the image data would be misrecognized as

A

gross underexposure

118
Q

how dark or light a digital image appears on a display monitor is known as

A

brightness

119
Q

the ability of a digital system to display subtle changes in shades of gray is called

A

contrast resolution

120
Q

the primary causes of quantum noise/mottle are

A

excessive fog, insufficient signal strength, excessive scatter

121
Q

the x-ray energy is absorbed and the phosphors of the IR emit light, and the latent image is formed by

A

some of the light energy being retained by the plate

122
Q

what determines the density/brightness value of each image pixel?

A

pixel depth

123
Q

when a CR plate is not erased sufficiently, energy will be retained and if used for another exposure, what will occur?

A

a higher signal strength

124
Q

what component of a laser reader is responsible for extracting the light image from the PSP?

A

light collecting guide assembly

125
Q

electrons are released during image conversion and are released from the

A

F traps

126
Q

DELS stands for

A

detector element size

127
Q

once the signal is detected, the algorithm used by KODAK is called

A

tonescaling

128
Q

quantization of collected exposure data occurs by

A

histogram analysis

129
Q

the process of returning pixel values to their original levels by a reverse process is called

A

deconvolution

130
Q

systems using the S number exposure index like Fuji systems are typically

A

200-400 and inverse to the beam intensity

131
Q

LME or Log Mean Exposure Index usually range from

A

1.9 - 2.1

132
Q

what sampling control reduces image blur with PSPs?

A

high frequency sampling

133
Q

The S Number exposure indicator used by Fugi, Konica and Philips maintains what type of relationship with the actual radiation exposure received by the image receptor/ detector?

A

Inverse

RADT 251 - Advanced Imaging Modalities (4 decks)

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