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Rad science > Rad Science contrast > Flashcards

Rad Science contrast Flashcards

1
Q

one of the 2 properties that make visibility of detail (photographic factor)

A

contrast

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2
Q

contrast is the difference between

A

adjacent densities

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3
Q 
_contrast
few shades of grey
low kV
short scale
narrow latitude
A

High

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4
Q 
_contrast
many shades of gray
high kV
long scale
wide latitude
A

low

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5
Q

what is the controlling factor of contrast

A

kV

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6
Q

kV and contrast have an _ relationship

A

indirect

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7
Q

as kV increases, contrast

A

decreases

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8
Q

_controls the amount of scatter produced. Increasing _ increases the possibility of scatter, decreasing contrast

A

kV

kV

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9
Q

increasing _ increases the average energy of the beam

A

kV

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10
Q

increasing _ increases more uniform penetration of parts by the shorter wavelength x-rays

A

kV

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11
Q

increasing _ increases the potential difference

A

kV

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12
Q

compton /scatter is what color

A

grey

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13
Q

PE is what color

A

white

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14
Q

increasing OID= better

A

contrast

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15
Q

distance- _ affects density using the air-gap technique. As your _ increases, there is less chance of scatter reaching the IR increasing

A

OID

OID

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16
Q

what changes the average energy of the beam

A

filtration

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17
Q

filtration makes the beam more

A

homogenous

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18
Q

raising the average energy is the same as raising the _ which raises the chance for compton interactions, thus reducing contrast

A

kV

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19
Q

collimating reduces the amount of tissue being irradiated, reducing the amount of Compton interactions possible, increasing contrast

A

beam restriction

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20
Q

as the part size increases, more chances for compton interactions, increasing scatter, reducing

A

contrast

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21
Q

additive diseases will _ subject contrast and increase radiographic contrast

A

increase

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22
Q

what removes scatter before it reaches the IR, improving contrast

A

grids

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23
Q

contrast improvement factor

A

k= contrast w/grid
——————-
contrast w/out grid

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24
Q

Grid ratio=

A

D

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25
Q

what is the formula for contrast improvement

A

k= contrast w/grid
——————
contrast w/out grid

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26
Q

as kV increases, contrast

A

decreases

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27
Q

as OID increases, contrast

A

increases

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28
Q

as grid ratio decreases, contrast

A

decreases

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29
Q

as filtration decreases, contrast

A

increases

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30
Q

as collimation decreases, contrast

A

decreases

31
Q

as patient size increases, contrast

A

decreases

32
Q

degree of geometrical sharpness or accuracy of the structural lines actually recorded on the image

A

detail

33
Q

Detail is also known as

A

definition
sharpness
spatial resolution
recorded detail

34
Q

unit of resolution is

A

line pairs per millimeter

35
Q

there is always some loss of _ on all images

A

detail (sharpness)

36
Q 
for optimal detail
eliminate
reduce
reduce
reduce
Increase
A 
motion
OID
focal spot size
intensifying screen, phosphor size & concentration
SID
37
Q

factors affecting recorded detail and formula

A

Distance

SOD =OID=SID

38
Q

OID decreases, detail

A

increases

39
Q

SID increases, detail

A

increases

40
Q

use a large _ to compensate for a large OID ex; C-spine

A

SID

41
Q

sharp shadow around object

A

umbra

42
Q

unsharp shadow around object (focal spot blur)

A

penumbra

43
Q

as focal spot size increases, penumbra _, detail _

A

increases

decreases

44
Q

as film/screen speed is decreased, detail

A

increases

45
Q

as film/screen speed increases, detail

A

decreases

46
Q

if the total # of incident photons reaching the intensifying screen are insufficient to activate enough phosphors to emit light over the entire radiograph

A

quantum mottle

47
Q

quantum mottle is caused by low

A

mAs

48
Q

_ is the only way to fix quantum mottle; grainy appearance

A

mAs

49
Q

There must be good contact between the film and intensifying screen. Poor contact makes bad resolution. Cassette must be discarded

A

wire mesh test

50
Q

3 types of motion

A

pt. motion
tube motion
excessive reciprocating grid motion

51
Q

voluntary motion (breathing) can best be controlled by

A

communication

52
Q

Involuntary motion (peristalsis, heartbeat) can be best controlled by a _ and _ to maintain density

A

short exposure time

increased mA

53
Q

as motion decreases, detail

A

increases

54
Q

as OID increases, detail

A

decreases

55
Q

as SID decreases, detail

A

decreases

56
Q

as focal spot size decreases, detail

A

increases

57
Q

as phosphor size increases, detail

A

decreases

58
Q

as film/screen speed decreases, detail

A

increases

59
Q

misrepresentation of the size or shape of the structures being examined

A

distortion

60
Q

2 kinds of distortion

A

size-mag. OID/SID

shape-elongation/foreshortening

61
Q

as size magnification decreases, detail

A

increases

62
Q

to minimize size distortion, max. _ and min. _

A

SID

OID

63
Q

as SID increases, distortion

A

decreases

64
Q

as OID decreases, distortion

A

decreases

65
Q

shape distortion can be

A

elongation

forshortening

66
Q

elongation is caused by the

A

tube or IR improperly aligned

67
Q

foreshortening is caused by the

A

prt. being improperly aligned

68
Q

The CR should be _ to the part and IR

A

perpendicular

69
Q

The CR is the only portion of the beam w/out

A

shape distortion

70
Q

as SID decreases, distortion

A

increases

71
Q

as OID decreases, distortion

A

decreases

72
Q

as tube alignment decreases, distortion

A

increases

73
Q

as IR alignment increases, distortion

A

decreases

74
Q

as part alignment increases, distortion

A

decreases

Rad science (12 decks)

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