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From Flashcardlet > rad bio ch 10 > Flashcards

rad bio ch 10 Flashcards

1
Q

spatial resolution

refers to the ability to image small objects that have ____subject contrast

A

refers to the ability to image small objects that have high subject contrast

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2
Q

the use of high mas , low -kvp and of slower image receptors reduces ____ _____

A

quantum mottle

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3
Q

spatial resolution improves as 3

A

screen blur decreases
motion blur decreases
geometric blur decreases

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4
Q

lower noise improve

A

contrast resolution

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5
Q

radiographic image quality

A

refers to fidelity wih which the anatomical structure that is being examined is rendered on the radiograph

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6
Q

most important characteristics of radiographic image quality(4)

A

spatial resolution
contrast resolution
noise
artifacts

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7
Q

contrast resolution

ability to distinguish anatomical structures of similar ____contrast such as liver-spleen, gray matter-white matter

A

ability to distinguish anatomical structures of similar subject contrast such as liver-spleen, gray matter-white matter

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8
Q

detail and recorded detail aka 2

A

spatial resolution

contrast resolution

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9
Q

main source of noise

A

scatter

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10
Q

structure mottle

refers to the _____ of radiographic intensifying screen but is like film graininess

A

refers to the phosphors of radiographic intensifying screen but is like film graininess

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11
Q

quantum mottle

  • refers to the random nature by which x-rays interact with the image receptor
  • main contributor to radiographic ____ contributor
A
  • refers to the random nature by which x-rays interact with the image receptor
  • main contributor to radiographic noise contributor
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12
Q

radiographic noise

A

random fluctuation in the OD of the image

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13
Q

noise four components

A

film grainess
structure mottle
quantum mottle
scatter radiation

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14
Q

visibility of detail

ability to visualize recorded detail when image ____and optical ____ are optimized

A

ability to visualize recorded detail when image contrast and optical density are optimized

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15
Q

film graininess

distribution in size and space of silver ____grains in emulsion

A

distribution in size and space of silver halide grains in emulsion

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16
Q

radiographic quality rules 3

A
  • fast image recptors have high noise and low spatial resolution and low contrast resolution
  • high spatial resolution and high contrast resolution require low noise and slow image receptors
  • low noise accompanies slows image recptors with high spatial resolution and high contrast resolution
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17
Q

sensitometry

study of relationship between the ___of the exposure of the film and the ___of the processing

A

study of relationship between the intensity of the exposure of the film and the blackness of the processing

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18
Q

two principal measurements involved in sensitmorety is exposure to film and percentage of light transmitted through hthe processing films

A

exposure to film and percentage of light transmitted through hthe processing films

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19
Q

radiographic quality

A

film factors

  • characteristic curve
  • density
  • contrast
  • speed
  • latitiude

processing

  • time
  • temperature
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20
Q

radiographic quality cont…

A

geometric geometry

  • distortion
  • magnification
  • blur

subject factors

  • contrast
  • thickness
  • density
  • atomic number

motion

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21
Q

Characterisitc curve relationship of two

A

relationship between OD and radiation exposure

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22
Q

larger variations in exposure result in only small change in OD these portions of the characteristic curve ____ and ___

A

toe

Shoulder

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23
Q

Straight line portion

A

intermediate radiation exposure levels , small changes result in large changes in OD

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24
Q

two pieces equipment used for characteristic curve

A

sensitometer

optical step wedge

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25
Q

log relative exposure is used as the scale along which axis?

A

x

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26
Q

an increase in LRE of 0.3 results in _____ the radiation exposure

A

doubling

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27
Q

optical density formula

A

log10 lo
——
lt

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28
Q

optical density of unexposed film are

A

base density

fog density

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29
Q

base density

A

the OD that is inherent in the base film

( incident light is brighter light). IT is the composition of the base and tint added to base

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30
Q

Fog density

A

development of silver grains that contain no useful info.
- results from inadvertent exposure pf film during storage, chemical contamination, improper processing, and number of other influences

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31
Q

higher fog density reduces _____of the radigraph

A

contrast

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32
Q

LRE formula

A

incident light
__________
light trasnmitted

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33
Q

useful range of OD

A

0.25-2.5

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34
Q

base plus fog OD has range of

A

0.1-0.3

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35
Q

reciprocity law states the OD wil be the same if the ___ vale is constant

A

mAS

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36
Q

reciprocity law states that the ___ on a radiograph is proportionate only to the total energy imparted to the radiographic film and independent of time

A

OD

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37
Q

reciprocity fails for screen film at exposure times less than ____ or longer than aprox __

A

10ms

2s

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38
Q

contrast

A

difference in OD

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39
Q

major difference in OD is _____ contrast

A

high

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40
Q

less difference in OD is _____contrast

A

low

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41
Q

radiographic contrast is product of two

A

image receptor contrast

subject contrast

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42
Q

image receptor contrast

A

inherent in the screen film combo and in influenced somewhat by processor of the film

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43
Q

subject contrast

A

determined by the size, shape, and x-ray attenuation characteristics of the anatomy that is being examined and the energy of the kvp of the x-ray beam

44
Q

best to keep the image receptor contrast constant and change the ________ _________

A

subject contrast

45
Q

film contrast is related to the slope of the straight line portion of the _____ curve

A

characteristic

46
Q

average gradient

A

numberical method used to describe image contrast.

47
Q

average gradient formaula

A

OD2-OD1
_______
LRE2-LRE1

48
Q

most radiographic receptors average gradient range

A

2.5-3.5

49
Q

gradient

A

any slope point on thethe tangent at anycharacteristic curve

50
Q

speed of image receptor or sensitivity

A

ability of image receptor to respond to low xray exposure

51
Q

cont pg 171

A

cards

52
Q

par speed

A

numbers expressed speed relative to 100

53
Q

high speed image receptors

A

numbers higher than 100

54
Q

detail speed

A

numbers less than 100

55
Q

image receptor speed formula

A

1/ exposure in roentgens to produce

56
Q

speed vs mAs

A

new image receptor speed old mas
____________________ = __________
old image receptor speed new mas

57
Q

latitude

A

range of exposures over which hthe image receptor responds with ods in diagnostically useful range

58
Q

latitude and contrast are _____ proportionate

A

proportional

59
Q

factors that may effect the finished radiograph

A

concentration of processing chemicals
degree of chemistry agitation during development
development time
development temp

60
Q

image receptor with wide latitude are_____

A

long gray sscale

61
Q

image receptor with less latitude are____

A

short gray scale

62
Q

geometric factors

A

magnification
distortion
focal spot blur

63
Q

magnifiation

A

images on radiograph are larger thanobjects on radiograph actually are

64
Q

___ magnification is best

A

small

65
Q

mag factor formula

A

image size SID Image size sid
________ or _______ or _______=___
Object size SOD obj size sod

66
Q

Minimizing Magnification

  • LArge SID
  • Small OID
A
  • use as large source to image receptor distance as possible

- place the object as close to the image receptor as possible

67
Q

shape distortion

A

unequal magnification of different portions of the same object

68
Q

distortion depends on

A

object thickness
object position
object shape

69
Q

Thick objects are more distorted than ____objects

A

thin

70
Q

if object plane and the image plane are not ____, distortion occurs

A

parallel

71
Q

foreshortened

A

image of an inclined object can be smaller than object itself

72
Q

amount of foreshortening the extent of reduction in image size, increases as the angle of inclination ____

A

increases

73
Q

spatial distortion

A

misrepresentation in the image of the actual spatial reltatioship among objects

74
Q

focal spot blur occurs because the focal spot is not a ___

A

point

75
Q

focal spot blur is the most important factor for determine ____ _____

A

spatial resolution

76
Q

focal spot blur formula

A

SOD effective focal spot (effective focal spot)OID
____= _______________ ______________
OID focal spot blur SOD

77
Q

for the anode heel effect, the focal spot blur is small on the ___ side and ____ on the cathode side of the image

A

small

large

78
Q

subject contrast

A

contrast of a radiograph viewed on an illuminator

79
Q

radiographic contrast

A

product of image receptor contrast and subject contrast

80
Q

subject factors

A
  • subject contrast
  • patient thickness
  • tissue mass density
  • effective atomic numer
  • object shape
  • kilovolt peak
81
Q

radiographic contrast=

A

image receptor contrast X subject contrast

82
Q

effect of subject contrast is a ___ result difference in attenuation in body tissues

A

direct

83
Q

thick body section attenuates a____number of xrays than does thin section

A

greater

84
Q

degree of subject contrast is ___ proportionate to relative number of xrays leaving sections of the body

A

direct

85
Q

___ mass density affects subject contrast

A

tissue

86
Q

__ ____of tissues being examined affects subject contrast, influenced by effective atomic number

A

atomic number

87
Q

absorption blur

A

anatomical shapes have reduced subject contrast because of the change in thickness across the xray beam

  • reduces spatial resolution and contrast resolution
88
Q

__ is the most important influence on subject contrast

A

kvp

89
Q

low kvp results in _____subject contrast called ___ ___ ___ showing ___ and ___with few shades of grey

A

high
short gray scale
black and white

90
Q

long scale contrast

A

high kvp results in low subject contrast

91
Q

low kvp radiograph disadvantages

A
  • as the kvp is loewered for any radiographic exam, the xray beam becomes less penetrating, requiring a higher mas to produce an acceptable range of OD’s. Result is higher patient dose
  • radiographic technique that produces low subject contrast allows for wide latitude in exposure factors. Optimization of radiographic technique by mas selection is not so critical when high kvp is used
92
Q

motion blur

A

movement of the patient or the xray tube during exposure results in blurring of a radiographic image

93
Q

____ motion is usually the cause of motion blur

A

patient

94
Q

procedures for reducing motion blur

A
  • use the shortest possible exposure time
  • restrict patient motion by providing instruction or using a restraining device
  • use a large source to image receptor distance (SID)
  • use a small OID
95
Q

two types of motion

A

voluntary

involuntary

96
Q

___ resolution intensifying screen produce great images with limited patient dose

A

high

97
Q

Principles to be considered when planning a particular exam

A
  • use of intesyfying screen decrease patient dose by factor of at least 20
  • speed of image recptor increases , radiographic noise increases, and spatial resolution is reduced
  • low contrast imaging procedureshave wider latitude, or margin of error, in producing an acceptable radiograph
98
Q

three phase and high frequency are better generators due to ___ exposure times

A

shorter

99
Q

as kvp increases, both quantity and quality is ______

A

increased

100
Q

Compton interaction increases with ____ kvp, resulting in less differential absorption and reduced subject contrast

A

increasing

101
Q

increased kvp, the scatter reaches the IR is ______: radiographic noise is _____. Result kvp is loss of contrast. Contrast is ___, latitude is high and margin of error is increased

A

greater
greater
low

102
Q

principal advantage of use of high KvP

A
  • reduces patient dose

- wide exposure lattitude

103
Q

use of grids can compensate for ___ of contrast accompanying high kvp

A

loss

104
Q

primary control of OD

A

density

105
Q

mas increased, rad quantity ____, the number xrays arriving at IR increases, resuting in high density and lower noise but ___patient radiation dose

A

increases

higher

106
Q

adding filtration to xray tube reduces xray beam intensity but enhances ____

A

quality

107
Q

SID results in a change in OD because xray ___ varies with distance

A

intensity

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