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Image Processing And Production > Ch. 4 > Flashcards

Ch. 4 Flashcards

1
Q

What is the relationship between the display field of view (FOV) and pixel size for a fixed matrix size?

A

Direct

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2
Q

A combination of rows and columns (array) of pixels is called a

A

Matrix

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3
Q

The size of a pixel is measured in:

A

Microns (very small)

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4
Q

Digital image quality is improved with, which of the following?

  • larger size matrix and larger pixel depth
  • larger size matrix and smaller pixel size
  • larger pixel depth and smaller sizes of pixels
A

All options are correct

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5
Q

If the matrix size is increased for a fixed field of view (FOV) the pixel size is _____

A

decreased

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6
Q

If the matrix size is increased for a given FOV: spatial resolution is ____

A

spatial resolution is increased

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7
Q

If the FOV is 500 mm and the matrix size is 1024, what is the pixel size?

Equation - FOV/matrix size = pixel size

A

0.49 mm

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8
Q

The number of bits that determines the amount of precision in digitizing the analog signal and the number of gray shades that can be displayed in the image is the:

A

bit depth

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9
Q

A larger bit depth increases what:

A

increases the number of shades of gray and increases contrast resolution

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10
Q

The pixel bit depth determines the image’s:

A

contrast resolution

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11
Q

A 10-bit pixel depth can display how many shades of gray?

A

1024

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12
Q

A system that can digitize and display a greater number of shades of gray will have _______ contrast resolution

A

increased

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13
Q

The greater the pixel bit depth:

A

the more precise digitization of the analog signal and a greater number of shades of gray will be displayed

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14
Q

The number of pixels per unit area is called the:

A

pixel density

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15
Q

The pixel spacing or distance measured from the center of a pixel to an adjacent pixel is called the:

A

pixel pitch

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16
Q

What two things results in improved spatial resolution?
Increased _____ and decreased _____

A

increased pixel density and decreased pixel pitch

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17
Q

Increasing the number of line pairs per millimeter resolved in the imaging system results in:

A

increased spatial resolution

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18
Q

The measure of the imaging system’s ability to display the contrast of anatomic objects varying in size is the:

A

modulation transfer function (MTF)

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19
Q
  • An MTF of -_____ means a maximum difference in brightness levels.
A

1.0. or 100%

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20
Q

What term refers to the range of exposures that should be used to produce a diagnostic image?

A

exposure latitude

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21
Q

What dose monitoring value measures the exposure in air and estimated absorbed dose?

A

KAP

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21
Q

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

A

detective quantum efficiency (DGE)

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22
Q

The higher the DQE of a system, the radiation exposure required to produce a quality image is:

A

decreased

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23
Q

Which of the following is true concerning computed radiography imaging plates?

  • The CR cassette houses the imaging plate and the tradition exiting the patient interacts with the imaging plate
  • The CR cassette house the IP and the photon intensities are absorbed by the phosphor
  • The radition exiting the patient interacts with the image plate and the photon intensities are absorbed by the phosphor
A

ALL options are correct

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24
Q

What is a term generally used to describe the emission of light from a substance as the result of stimulation by radiation?

A

Luminescence

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25
Q

The CR phosphor layer is composed of:

A

barium flourohalide with europium

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26
Q

The emission of light when stimulated by a high-intensity laser beam is:

A

photostimulable luminescence (PSL)

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27
Q

The CR latent image consists of:

A

electrons trapped in the phosphor layer or F trap, F center

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28
Q
  • This material is composed of barium flourohalide and makes up the primary component of the CR
A

Photostimulable phosphor (PSP)

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29
Q

Which of the following is not a component of the CR IP:
- Thin film transistor layer
- Support layer
- Phosphor Layer
- Protective Layer

A

Thin film transistor layer

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30
Q

With CR, when the x-ray photons are absorbed by the phosphor, the _____ atoms become ionized.

A

europium

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31
Q

With CR, trapped electrons are:

A

proportional to the exit exposure intensity and released during the readout stage

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32
Q

Which of the following is not part of a CR reader unit?

A

Capacitor

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33
Q

The _______ collects, amplifies, and converts visible light to an electrical signal.

A

PMT

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34
Q

In the CR reader unit, the IP is scanned with a:

A

helium-neon laser beam (red in color)

35
Q

What is the sequence of events, from beginning to end, of what happens in the CR reader unit?

A

Stored energy is released as visible light
PMT converts light energy to electrical signal
Analog electrical signal is sampled and digitized

(This was on someone’s registry!)

36
Q

With CR, a higher sampling frequency results in:
Increased ___ ___ and smaller ___ ___

A

increased pixel density and smaller sampling pitch

37
Q

With CR, a larger sampling pitch results in:

Increased ___ ___ & decreased ___ ___

A

increased pixel size and decreased pixel resolution

38
Q
  • How often the analog signal is reproduced in its discrete form is:
A

sampling frequency

39
Q

With a fixed matrix CR reader system, changing to a larger IP, for the same FOV, will result in:

A

larger pixels

40
Q

The distance between the analog points being sampled is the:

A

sampling pitch

41
Q
  • Pixel bit depth is determined by the:
A

ADC

42
Q
  • Immediately before leaving the CR reader unit, the IP is exposed to:
A

intense white light

43
Q

What type of image receptor converts the exit radiation into electrical charges and stores them before readout and digitization?

A

DR

44
Q

DR imaging systems briefly store the electrical charge in the:

A

TFT

45
Q

The ____ array is divided into square detector elements

A

TFT

46
Q
  • The percentage of x-rays that have reached the detector and have been captured is the
A

fill factor (we want this to be high)

47
Q
  • Which of the following is not a component of a flat-panel detector?
  • Phosphor layer
  • Glass Substance
  • X ray converter
  • TFT array
A

Phosphor layer

47
Q

The indirect conversion detector uses

A

a scintillator and a photodetector

48
Q

An example of a scintillator used in an indirect conversion detector is:

A

gadolinium oxysulfide and cesium iodide (gd2o2s) - these convert x-ray into light

49
Q

What is true about the indirect conversion DR systems?

A

x-rays are converted to light and then converted to electrical charges

50
Q

What is the sequence of events for the production of a DR image using direct conversion detectors?

A

exit radiation is converted to electrical charge, charge is stored briefly in TFT array, electronic signal goes to ADC

51
Q

The ability of the detector to accurately capture the variety of photon intensities in the remnant radiation is

A

dynamic range

52
Q

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

A

detective quantum efficiency

53
Q

The higher the DQE of a system, the radiation exposure required to produce a quality image is:

A

Decreased

54
Q

Overexposing a digital image receptor may result in:

A

high SNR and increased patient exposure

55
Q

A method of describing the strength of the radiation exposure compared with the amount of noise apparent in the digital image is the:

A

signal-to-noise ratio

56
Q

A high SNR means that the:

A

signal strength is high

57
Q

_________ the SNR increases the visibility of anatomic details

A

Increasing

58
Q

A method of describing the contrast resolution compared with the amount of noise apparent in a digital image is the:

A

contrast to noise ratio (CNR)

59
Q

T/F

Once the data is in digital format, there is no difference between image processing and display between the CR and DR

A

T

60
Q

_________ the CNR increases the visibility of anatomic details.

A

Increasing

61
Q

T/F

There is no light produced with CR when radiation interacts with the IP

A

F

62
Q

T/F

The quality of the CR latent image will remain the same for up to 6 hours after exposure

A

F

63
Q

T/F

Both CR and DR are electronic detectors that combine image capture and image readout

A

F- only DR

64
Q

T/F

The DR system does not require a separate reader unit

A

T

65
Q

T/F

With an FPD, electrical charges from each DEL are read out separately.

A

T

66
Q

T/F

Exit radiation is converted to visible light with the direct conversion detector.

A

F (if it said indirect it would be true)

67
Q

T/F

Small anatomic objects have higher spatial frequency.

A

T

68
Q

T/F:

Because digital imaging has a large dynamic range, significantly lower than necessary x-ray exposure will still result in a quality image.

A

F

69
Q

T/F

An image with high SNR will have decreased detail visibility

A

F (increased detail visibility)

70
Q

T/F

Bit depth is determined by the matrix size

A

F

71
Q

T/F

The spatial resolution of flat-panel receptors is generally superior to that of CR

A

T

72
Q

T/F

The DQE is higher for DR when compared to CR.

A

T

73
Q

What are the 2 types of digital radiographic imaging systems?

A

computed radiography (CR) and direct radiography (DR)

74
Q

What is the formula that shows the relationship among pixel size, FOV, and matrix size?

A

Pixel size = FOV/Matrix size

75
Q

Bit depth is measured how?

A

2^n

76
Q

Defined by the unit of line pairs per millimeter (lp/mm)

A

spatial frequency

77
Q

define contrast resolution:

A

The ability of the image receptor to distinguish between objects having similar subject contrast

78
Q

Define Pixel Pitch:

A

The distance measured from the center of a pixel to an adjacent pixel

79
Q

a method of describing the strength of the radiation exposure compared with the amount of noise apparent in the digital image is the:

A

signal-to-noise ratio

80
Q

a method of describing the contrast resolution compared with the amount of noise apparent in a digital image it the

A

contrast-to-noise ratio

81
Q

The main difference between Computed Radiography and Direct Radiography is…

A

CR is a two-step process, DR is a one-step process

82
Q

The greater amount of pixels in an image matrix, the ____ their size.

A

Smaller

83
Q

The acquired image data (released energy) are extracted from the ____, and converted to digital data, and computer-processed from image display.

A

Digital Receptor

84
Q

Within how long should you process an exposed IP, and why?

A

Within 1 hour because the latent image dissipates overtime (CR Fading)

  • CR fading occurs because some of the signal (energy released) captured in the IP is lost

Image Processing And Production (8 decks)

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