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exposures > unit 5 review > Flashcards

unit 5 review Flashcards

1
Q

degree of geometric sharpness or accuracy of the structural lines of the image

A

recorded detail

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2
Q

what is the resolution of an image dependent on

A

pixel size(pitch), matrix size, & bit depth

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3
Q

how does phosphor layer thickness effect resolution

A

the thinner the phosphor layer the higher (better) the resolution

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4
Q

do you want a system with high or low spatial resolution?

A

high spatial resolution

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5
Q

what is the measurement of lines that can be seen on an image

A

spatial frequency

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6
Q

how is the trueness of an image determined

A

modulation transfer function (MTF) - measures the spread of light

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7
Q

anything that interferes with the formation of an image

A

noise

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8
Q

why would an image have a mottled appearance

A

lack of incoming photons to expose the IR , not enough mAs (increase/repeat)

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9
Q

the mathematical measurement of noise

A

noise power spectrum

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10
Q

do you want a high or low SNR , why?

A

high SNR , decreases noise

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11
Q

the processing function that averages the incoming analog data between the image detector elements (samples / scans pixels twice)

A

nyquist theory

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12
Q

what controls the sharpness of detail post processing

A

spatial frequency resolution

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13
Q

what are they types of motion

A

voluntary, involuntary, & equipment motion (moving grids)

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14
Q

how to control involuntary motion

A

decrease exposure time

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15
Q

how to control voluntary motion

A

communication

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16
Q

how to control equipment motion

A

lock equipment

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17
Q

how do distances effect detail

A

increase distance, increase detail

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18
Q

when you increase OID , detail

A

decreases

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19
Q

misinterpretation of size or shape of the structure being x rayed

A

distortion

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20
Q

types of distortion

A

size & shape (elongation & foreshortening)

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21
Q

factors affecting distortion

A

distances (SID), (OID), direction of angle, angle of part, CR, & IR

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22
Q

how is distortion & magnification calculated

A

M = SID over SOD

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23
Q

how to calculate actual size

A

object size = image size over mag factor

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24
Q

to avoid distortion - tube alignment

A

the part and IR must always be parallel & CR perpendicular

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25
Q

one of 2 geometric properties of the image (other is distortion)

A

recorded detail

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26
Q

other names for recorded detail

A

definition, sharpness, spatial resolution, detail

27
Q

ability to record 2 adjacent structures as separate structures

A

definition

28
Q

determined by matrix size, pixel size, and grayscale bit depth

A

recorded detail in digital imaging

29
Q

the best spatial resolution has what kind of contrast

A

high contrast for small structures

30
Q

what matrix size improves spatial resolution

A

larger matrix size

31
Q

as resolution increases

A

recorded detail increases

32
Q

the number of lines per millimeter that can be seen

A

special frequency

33
Q

higher special frequency has

A

higher spatial resolution

34
Q

expresses the boundaries of an image by testing the sharpness of lines

A

point spread function

35
Q

fidelity or trueness of an image

A

modulation transfer function (MTF)

36
Q

a system with an MTF of 1 would be

A

100% accurate

37
Q

as background noise increases

A

image noise increases

38
Q

SNR

A

signal to noise ratio

39
Q

the measurement of contrast change present in an image

A

contrast to noise

40
Q

to have a high CNR you must have

A

a high SNR

41
Q

provides increased resolution when motion is present , the relationship between the duration of data acquisition and motion of the structures being studied

A

temporal resolution (TR)

42
Q

shorter acquisition time will demonstrate

A

better TR (temporal resolution) - minimal motion

43
Q

digital imaging should at least sample the pixels

A

twice, in order to form image

44
Q

increases contrast & edge enhancement

A

high pass filtering

45
Q

removes high frequency noise, reduces contrast

A

smoothing - low pass filtering

46
Q

factors affecting recorded detail

A

geometry of the beam
focal spot
distance (SID) (OID)
motion

47
Q

the distinctly sharp of a shadow or region of complete shadow

A

umbra

48
Q

area of unsharp shadow around umbra

A

penumbra

49
Q

as focal spot decreases, what happens to penumbra

A

decrease, increasing resolution

50
Q

what does image processing do?

A

sets limits on detail

51
Q

as motion increases

A

detail decreases

52
Q

best control for involuntary motion

A

decrease exposure time

53
Q

the only possible size distortion in radiography

A

magnification

54
Q

is minification possible in radiography

A

minification is impossible because of divergence of the beam

55
Q

misrepresentation by unequal magnification of the actual shape of the structure

A

shape distortion

56
Q

shape distortion results from

A

how structures normally lie in the body
divergence of the x ray beam
tube, part, & IR alignment

57
Q

object appears longer (tube or IR are improperly aligned)

A

elongation

58
Q

object appears shorter (part is improperly aligned)

A

foreshortening

59
Q

the tube angle will never cause

A

foreshortening

60
Q

how to avoid alignment distortion

A

part & IR must always be parallel & CR perpendicular

61
Q

when the nyquist theory isn’t met, the special frequency is greater than the inquest frequency

A

aliasing

62
Q

equation to find which image will have better spatial resolution

A

pixel = FOV / matrix size

63
Q

in image processing , what sets limits on detail

A

filtering, technical factors (LUT), histogram

exposures (6 decks)

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