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Physics 2 > Ch. 9 Image Quality and Characteristics > Flashcards

Ch. 9 Image Quality and Characteristics Flashcards

1
Q

any unwanted image on a radiographic image

A

artifact

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2
Q

number of bits that determines the amount of precision in digitizing the analog signal, and therefore the number of shades of gray that can be displayed in the image

A

bit depth

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3
Q

the amount of luminance (light emission) of a display monitor

A

brightness

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4
Q

differences in the brightness levels to differentiate among the anatomic tissues

A

contrast

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5
Q

used to describe the ability of the imaging system to distinguish between small objects that attenuate the x-ray beam similarly in digital imaging

A

contrast resolution

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6
Q

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

A

contrast-to-noise ratio

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7
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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8
Q

results from the radiographic misrepresentation of either the size (magnification) or shape of the anatomic part

A

distortion

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9
Q

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

A

dynamic range

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10
Q

refers to image of objects that appear longer than the true objects

A

elongation

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11
Q

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

A

exposure indicator

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12
Q

the dimensions of an anatomic area displayed on the monitor

A

field of view

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13
Q

refers to images that appear shorter than the true objects

A

foreshortening

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14
Q

the number of different shades of gray that can be stored and displayed by a computer system in digital imaging

A

grayscale

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15
Q

tissues that attenuate the x-ray beam very differently

A

high subject contrast

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16
Q

tissues that attenuate the x-ray beam similarly

A

low subject contrast

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17
Q

an increase in the image size of an object compared with its true, or actual, sizes; also known as size distortion

A

magnification

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18
Q

combination of rows and columns (array) of pixels that make up a digital image

A

matrix

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19
Q

a measure of the ability of the system to reserve 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)

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20
Q

also called number of bits, it affects the number of shades of gray available for image display

A

pixel bit depth

21
Q

number of pixels per unit area

A

pixel density

22
Q

the pixel spacing or distance measured from the center of a pixel to an adjacent pixel

A

pixel pitch

23
Q

visible as brightness fluctuations on the image. Caused by too few photons reaching the image receptor to form the image

A

quantum noise

24
Q

the ability of the imaging system to resolve or distinguish between two adjacent structures and can be expressed in the unit of line pairs er millimeter (lp/mm)

A

resolution

25
Q

when the image receptor is extremely overexposed, cannot be properly processed, and the quality is severely degraded

A

saturation

26
Q

the accuracy of the structural line is achieved by maximizing the amount of spatial resolution and minimizing the amount of distortion

A

sharpness factors

27
Q

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

A

signal-to-noise ratio

28
Q

refers to an increase in the object’s image size compared with its true, or actual, size; also known as magnification

A

size distortion

29
Q

a term used to evaluate accuracy of the anatomic structural lines

A

spatial resolution

30
Q

refers to the absorption characteristics of the anatomic tissue radiographed along with the quality of the x-ray beam

A

subject contrast

31
Q

factors that make the anatomic structures visible and include the brightness and contrast of the image

A

visibility factors

32
Q

sets the midpoint of the range of brightness visible in the digital image. in CT, it determines the midpoint of the range of CT numbers to be displayed

A

window level (WL)

33
Q

a control that adjusts the radiographic contrast on the digital image. In CT, it adjusts how many CT numbers are visible in the image

A

window width

34
Q

visibility factors of a quality radiograph include

A

brightness and contrast

35
Q

this results in poor quality digital image because of improper processing due to extreme over exposure to the image receptor

A

saturation

36
Q

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

A

exposure indicator

37
Q

anatomic tissues that attenuate the x-ray beam equally are said to have this

A

low subject contrast

38
Q

an imaging system that can resolve 10 Lp/mm instead of 6 Lp/mm is said to have this

A

improved sharpness

39
Q

unwanted scatter exposure to the image receptor will likely increase this

A

fog

40
Q

what is defined as “the range of exposure intensities an image receptor can accurately detect”

A

dynamic range

41
Q

for a given field of view, a large matrix size will result in this

A

more pixels

42
Q

in digital imaging, which of the following determines the range of grayscale available for display

A

pixel bit depth

43
Q

during digital image display, the contrast can be lowered by increasing this

A

window width

44
Q

the ability of the imaging system to distinguish between small objects that attenuate the x-ray beam similarly defines this

A

contrast resolution

45
Q

increasing the displayed field of view for a fixed matrix size will result in this

A

increased pixel size

46
Q

the visibility of anatomic structures is increased with this

A

increased CNR and increased SNR

47
Q

an imaging system with a higher detective quantum efficiency (DQE) does this

A

more efficient in converting x-ray exposure to a quality image

48
Q

double exposing an image receptor will likely result in this

A

image artifact

Physics 2 (15 decks)

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