Ch. 10 Digital Image Receptors Flashcards

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1
Q

two groups of digital receptors are

A

computed radiography (CR) and direct radiography (DR)

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2
Q

what are the 4 parts of a CR system

A
  • cassette
  • photostimulable phosphor plate (PSP)
  • plate reader
  • computer workstation
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3
Q

what is the backing material of the CR cassette, used to absorb back-scatter

A

aluminum

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4
Q

what are the layers of the PSP plate

A
  • protective layer
  • phosphor layer
  • reflective layer
  • conductive layer
  • support layer
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5
Q

what is the phosphor layer typically made of

A

barium fluorohalide with europium activator

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6
Q

what are the two types of phosphor layers

A

turbid or structures

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7
Q

phosphor crystals are randomly distributed

A

turbid

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8
Q

contains columnar phosphor crystals that resemble needles standing on end, packed tightly together

A

structured

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9
Q

when the electrons in the phosphor layer are ionized the ejected electrons are trapped in this

A

conduction band

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10
Q

this is what allows the phosphor to store x-ray energy as the latent image

A

europium

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11
Q

this detects the light that is released from the PSP during scanning and amplifies the light in the form of an analog image

A

photodetector

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12
Q

the amplified analog signal is converted to a digital signal by this

A

ADC

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13
Q

two categories of DR

A

direct capture and indirect capture

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14
Q

two different form of indirect capture

A
  • CCD/CMOS
  • TFT
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15
Q

CCDs are coupled with this

A

scintillator plate - cesium iodide

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16
Q

what does the scintillator plate act as

A

phosphor layer of CR - fluoresces when radiated

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17
Q

a sturdy, light-proof container for film. Also a sturdy protective container for the photostimulable phosphor plate in computed radiography

A

cassette

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18
Q

a light-sensitive semiconducting device that generates an electrical charge when stimulated by light and stores this charge in a capacitor

A

charge-coupled device (CCD)

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19
Q

a scintillator device made up of a crystalline silicon matrix

A

complementary metal oxide semiconductor

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20
Q

a digital imaging system that uses a cassette, a photostimulable phosphor plate, a plate reader, and a computer workstation to acquire and display a digital image

A

computed radiography system

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21
Q

a measurement of the efficiency of an image receptor in converting the x-ray exposure it receives to a quality radiographic image

A

detective quantum efficiency (DQE)

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22
Q

the physical component consisting of multiple detectors that efficiently absorb the transmitted radiation and accurately convert it to an electrical signal for display on a computer workstation

A

detector array

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23
Q

the process by which washing works; exposes the film to water that contains less thiosulfate than the film

A

diffusion

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24
Q

a common computer language that allows different systems of a picture archiving and communication system to communicate with each other

A

Digital Imaging and Communications in Medicine (DICOM)

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25
Q

a digital imaging system that uses a detector array in place of the Bucky assembly; the imaging-forming radiation is captured and transferred to a computer from the detector array for almost instant viewing at the control panel

A

direct radiography systems

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26
Q

a measurement of exposure in air, followed by a computation to estimate absorbed dose to the patient

A

dose area product (DAP)

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27
Q

the range of exposure intensities that an image receptor can respond to and acquire image data

A

dynamic range

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28
Q

provides a numeric value indicating the level of radiation exposure to the digital image receptor

A

exposure indicator

29
Q

the range of exposure values to the image that will produce an acceptable range of densities for diagnostic purposes

A

exposure latitude

30
Q

a process in which a computer analyzes the histogram using processing algorithms and compares it to a preestablished histogram specific to the anatomic part being imaged

A

histogram analysis

31
Q

the invisible image that exists on the image receptor before it has been processed

A

latent image

32
Q

the emission of light from the screen when stimulated by radiation

A

luminescence

33
Q

the visible radiographic image on the exposed detector after processing

A

manifest image

34
Q

a measure of the ability of the system to preserve signal contrast (display the contrast of anatomic objects varying in size), and the value will be between 0 (no difference in brightness levels) and 1.0 (maximum difference in brightness levels)

A

modulation transfer function (MTF)

35
Q

a device that absorbs x-rays and creates electrical charges in proportion to the x-ray exposure received

A

photoconductor

36
Q

a device used to sense the light released from the photostimulable phosphor plate during scanning

A

photodetector

37
Q

the release of energy from trapped electrons by a laser during the scanning of a photostimulable phosphor plate

A

photostimulable luminescence

38
Q

a plate made up of several layers that stores x-ray energy as a latent image for cassette-based digital systems

A

photostimulable phosphor (PSP) plate

39
Q

a secure network for transmitting and exchange of patient images and data, display (viewing and workstations), and storage (archive server) systems

A

Picture Archiving and Communication System (PACS)

40
Q

a device equipped with a drive system and optical system that converts the stored image on a photostimulable phosphor plate to an electronic signal for display on a computer workstation

A

plate reader

41
Q

an electronic system that allows patients’ electronic records (medical information and imaging studies) to be accessed from various workstations within or outside of a facility

A

teleradiology

42
Q

electronic components layered onto a glass substate that include the readout, charge collector, and light-sensitive elements

A

thin-film transistor (TFT)

43
Q

established values within histogram models that determines what part of the data set should be incorporated into the displayed image

A

values of interest (VOI)

44
Q

a material that absorbs x-ray energy and emits visible light in response

A

x-ray scintillator

45
Q

the scintillator plate is coupled to CCD using this

A

fiber-optics or optical lens system

46
Q

each CMOS detector has this

A

own amplifier, photodiode, and storage capacitor and surrounded by transistors

47
Q

what makes CMOS not as good as CCD

A

not as light sensitive as CCD and doesn’t provide as good resolution as CCD

48
Q

what makes CMOS better than CCD

A

more efficient and take much less power

49
Q

thin-film transistor (TFT) arrays are coupled with this

A

amorphous silicon which acts as the photodetector

50
Q

in indirect capture systems this is used to convert radiation into light

A

scintillator

51
Q

this type of system is able to reduce resolution loss by cutting out the conversion of radiation to light

A

direct capture

52
Q

what do direct capture systems use

A

TFT arrays with photoconductor made of amorphous selenium

53
Q

this is what’s able to absorb radiation as an input and create an electric charge as an output in direct capture

A

amorphous selenium

54
Q

what is the charge stored in, in direct capture

A

storage capacitors

55
Q

during image acquisition the computer creates what is called this

A

histogram

56
Q

graphic representation of a given data set

A

histogram

57
Q

what does the histogram’s x-axis represent

A

amount of exposure

58
Q

what does the histogram’s y-axis represent

A

how many pixels were radiated for each exposure level

59
Q

this the imaging plate moving through the reader at a very precise speed

A

slow scan

60
Q

this is the actual laser array being cast onto the imaging plate

A

fast scan

61
Q

sampling frequency must be at least what of the original bandwidth of the analog signal in order to accurately digitize the signal

A

2 times

62
Q

what is the principle of the sample frequency being at least two times the original bandwidth of the analog signal in order to accurately digitize the signal called

A

Nyquist Theorem

63
Q

the range of exposure values that a receptor can receive and still produce a diagnostic image

A

exposure latitude

64
Q

these are numerical values that represent how much radiation exposure a receptor received

A

exposure indicator

65
Q

some DR systems use this as exposure indicators which measures the exposure in air

A

dose area product (DAP)

66
Q

for CR systems the imaging plates must be cleaned how often

A

at least every 3 months

67
Q

integral part of digital imaging is divided into these 3 sections

A
  • acquisition
  • network
  • storage
68
Q

this is a file format that allows for exams from all modalities to be able to be stored and used at any PACS terminal across the network

A

digital imaging and communication in medicine (DICOM)