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1456: Rad Tech 2 > Unit One: CR > Flashcards

Unit One: CR Flashcards

1
Q

Digital Imaging

A

Any image acquisition process that produces an electronic image that can be viewed and manipulated on a computer

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2
Q

Teleradiology

A

Moving images via telephone lines to an from remote locations

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3
Q

Early PACS developed by _____ to send images between VA hospitals.

A

Military

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4
Q

What year did the military develop PACS?

A

1980s

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5
Q

Where and when did the teleradiology concept begin?

A

Canada in the 1950s

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6
Q

Primary advantage of digital imaging

A

Increased contrast resolution

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7
Q

Increased contrast resolution

A

Increased ability to distinguish between and to image similar tissues as being separate and having different shades of gray

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8
Q

How many levels of gray is CR capable of producing?

A

10,000

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9
Q

Advantages of Digital Imaging

A

PACS and Informatics
Image archive and retrieval
Post processing/image manipulation
Teleradiology
Share images/reports
Electronic medical record

Reduced patient turn around time

No film, darkrooms, processing chemicals

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10
Q

Modular Transfer Function (MTF)

ARRT DEFINITION

A

The ability of an imaging system to preserve signal contrast as a function of spatial resolution

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11
Q

Modular Transfer Function (MTF)

BRIAN DEFINITION

A

How accurately a system converts the x-ray inputs signal into a useful output image

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12
Q

Spatial Resolution and MTF have what type of relationship?

A

Direct

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13
Q

Objects with higher spatial frequency are (more difficult/easier) to image than those with lower spatial frequency

A

More difficult

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14
Q

Detective Quantum Efficiency (DQE)

A

A measure of x-ray absorption efficiency of the IR

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15
Q

Imaging plate layers

A
  1. Protective layer
  2. Phosphor layer
  3. Reflective layer
  4. Conductive layer
  5. Support layer
  6. Light shielding layer
  7. Backing layer
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16
Q

Protective layer

A

A very thin, tough, clear plastic for protection of the phosphor layer

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17
Q

Phosphor layer

A

A layer of photostimulable phosphor that “traps” electrons during exposure.

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18
Q

Reflective Layer

A

Sends light in a forward direction, towards the photodetector when released in the cassette reader

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19
Q

Conductive layer

A

Absorbs and reduces static electricity

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20
Q

Support layer

A

Semi-rigid material that gives the imaging sheet some strength

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21
Q

Light shielding layer

A

Serves to protect the imaging plate from light leaks, which can erase or degrade the image that is stored within the phosphors

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22
Q

Backing layer

A

Soft polymer that protects the back of the cassette

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23
Q

Europium

A

An activator that is responsible for electrons being trapped in the metastable state

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24
Q

Histogram

A

A graphical display of the pixel intensity distribution for a digital image

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25
Q

Histogram Analysis

A

Identifies the useful pixels “values of interest” which are used for processing

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26
Q

Rescaling

A

Adjusts the pixel values to fit the normal histogram of the body part and adjust for small exposure errors

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27
Q

Lookup Table

A

Used to give the image just the right amount of brightness and contrast

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28
Q

Bit depth

A

The number of gray each pixel is capable of displaying.

The number of bits per pixel.

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29
Q

Dynamic range

A

What the system is capable of

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30
Q

Dose creep

A

Overexposure of patients due to the ability of the software to make corrections

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31
Q

Exposure latitude

A

The amount of exposure error that still results in a quality image at an appropriate dose

32
Q

Window width

A

Used to adjust the contrast of an image

33
Q

Window level

A

Used to adjust where on the scale the window level is set (brightness of an image)

34
Q

Annotation

A

Allows text to be added to an image

35
Q

Image flip

A

Allows for flipping of an image for proper interpretation

36
Q

Image Inversion

A

Allows for the changing of the image from negative (bone is white) to positive (bone is dark)

37
Q

Magnification

A

Used to better view smaller objects in an image

38
Q

Edge Enhancement

A

Increases the contrast along the edge of a structure through a software function

39
Q

Smoothing

A

A function to suppress noise that results from averaging of the frequency of each pixel with surrounding pixel values to remove high-frequency noise

40
Q

Equalization

A

Software function that allows underexposed areas (light areas) to be made darker and overexposed areas (dark areas) to be made lighter.

41
Q

Region of interest

A

A quantitative function of digital imaging that allows for the pixel value of a selected area of interest to be calculated

42
Q

What was first gen digital radiography?

A

Computed Radiography

43
Q

Contrast Resolution

A

The smallest exposure change or signal difference that can be detected by the IR. Directly related to Dynamic Range.

44
Q

Control of Contrast Resolution

A

The number of shades of gray a digital image can display is controlled by bit depth and dynamic range of the pixels.

45
Q

Scale of contrast on digital images is also ‘predetermined’ by you when ______

A

when you select a thumbnail of the anatomy

46
Q

This predetermined contrast is adjusted by a

A

Histogram

47
Q

Each pixel contains bits of information, and the gray level is determined by ___

A

How many photons struck the imaging plate in that particular location

48
Q

Spatial Resolution

A

Refers to the amount of detail present in any image

49
Q

Thinner phosphor layer = ______ SR

A

Higher

50
Q

What contributes to SR in CR?

A

Sampling frequency of the laser and the pixel size of the display monitor

51
Q

A thinner diameter laser = _____ sampling frequency

A

Higher

52
Q

How is SR measured?

A

Lp/mm

53
Q

Nyquist Theorem

A

States that when sampling a signal, the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect

54
Q

Thinner laser = ____ SR

A

Higher

55
Q

Dynamic Range underexposure and overexposure

A

50% under
200% over

56
Q

Exposure Latitude

A

The amount of exposure error that still results in a quality image at an appropriate dose

57
Q

Exposure Index

A

Radiation exposure to an IP that is given in numerical values

58
Q

Objects with higher SR are more difficult to image than those with lower SR

A
59
Q

DQE from highest to lowest

A

DR, CR, Film

60
Q

Detective Quantum Efficiency (DQE)

A

How efficiently a system converts the x-ray input signal into a useful output image

61
Q

Higher DQE receptors require _____ x-rays to produce an image. This translates to _____ pt. dose

A

Less
Less

62
Q

If FOV remains constant and the size of the matrix is increased, pixel size and pitch will _____, which _____ SR

A

Decrease
Increase

63
Q

How is pixel pitch measured?

A

Center to center

64
Q

How is pixel size measured?

A

Edge to edge

65
Q

What is the size of the matrix determined by?

A

The number of pixels

66
Q

Smaller pixels = _____ matrix = _____ SR

A

Larger
Improved

67
Q

As the matrix in the monitor remains the same, the pixel size must _____ to fit into the matrix

A

Decrease

68
Q

Always use the smallest cassette size (FOV) possible for the ________ SR

A

Greatest

69
Q

A thinner diameter laser will create a

A

Higher sampling frequency

70
Q

A thinner laser will create a _____ number of samples/information/data

A

Greater

71
Q

What are CR system speeds a reflection of?

A

The amount of photostimulable luminescence given off by the imaging plate while being scanned by the laser.

72
Q

The amount of photostimulable luminescence given off by the IP is determined by

A

The speed at which the plate is scanned by the laser source (alters speed class)

The wider the laser, the faster the speed class.

The thicker the phosphor later, the faster the speed class

The slower the speed class, the greater the amount of radiation required.

73
Q

Generally, a higher laser speed, or speed class, will result in _____ ____ due to greater light spread.

A

Less SR

74
Q

The wider the laser, the _____ the speed class, due to more light being released from the PSP during processing. This will _____ SR due to a greater light spread.

A

Faster
Decrease

75
Q

The thicker the phosphor layer, the ____ the speed class due to more light being released from the PSP. This will ____ SR due to greater light spread.

A

Faster

Decrease

76
Q

A thicker phosphor layer is more efficient at absorbing radiation so _____ is required

A

Less radiation

1456: Rad Tech 2 (4 decks)

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