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Registry Review > Image Aquistion > Flashcards

Image Aquistion Flashcards

1
Q

matrix size and pixel size relationship

A

inversely related

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2
Q

FOV and pixel size relationship

A

direct

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3
Q

pixel size and resolution relationship

A

inversely related

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4
Q

small pixel size and resolution

A

small pixel size has a high resolution

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5
Q

what pixel size has a 512X512 matrix with a 20 cm FOV

A

.40 mm/pixel

change 20 to mm then take 200/512 =.39

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6
Q

how do you find the pixel size

units?

A

take the FOV (mm) and divide it by the matrix (FOV/matrix)

units: mm/pixels

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7
Q

pixel depth

A

dynamic range

how many shades of gray

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8
Q

bit size equation

so a 6-bit =

A

2^n

6 bit = 2^6 = 64

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9
Q

spatial resolution is measured in?

A

line pairs/mm

lp/mm

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10
Q

matrix is made up of

A

columns and rows

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11
Q

what does filtration do to the intensity of the beam?

A

decreases it bc there are less photons

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12
Q

moire effect definition:

when is the moire effect seen

A

having wavy lines

seen when using stationary grids

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13
Q

grids are composed of

A

lead
aluminum
plastic fibers

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14
Q

kVp and contrast relationship

A

inversely related

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15
Q

what pulse does CT use?

A

short pulse

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16
Q

mAs and density

A

higher mAs has higher density

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17
Q

the component of a CR IP that records the radiologic image

A

PSP

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18
Q

PSP’s store what kind of image

how long does it store it for

A

latent

8 hours

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19
Q

DXA is used to see

A

bone mineral density

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20
Q

radiation dose in DXA

A

low

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21
Q

the luminescent light emitted by the PSP is transformed into the image seen on the CRT by the

A

ADC

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22
Q

insufficient back up time would have what effect on the image

A

underexposed

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23
Q

focal spot size is measured by what tests

A

pinhole camera
slit camera
star pattern type

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24
Q

kVp and exposure rate relationship

A

direct bc an increase in kV (photon energy) will result in a greater number (exposure rate) of scattered photons

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25
Q

as field size decreases, scatter ______, and image quality _______.

A

scatter decreases

image quality increases

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26
Q

what is very important when using AEC

A

accurate positioning

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27
Q

the negative aspect of CR

A

has a limited spatial resolution

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28
Q

best spatial resolution

A

film screen

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29
Q

windowing refers to

A

changing the image brightness and/or contrast

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30
Q

changes in window width

A

changes number of grays, which is contrast resolution

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31
Q

changes in window level

A

changes the image brightness

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32
Q

FOV describes how much ____ is included in the ____

A

pt

matrix

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33
Q

foreshortening can be caused by

A

angling the part

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34
Q

elongation can be caused by

A

angling the tube

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35
Q

size distortion is aka

A

magnification

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36
Q

each cm increase in pt thickness requires what adjustment to kVp?

A

increase 2 kV to the exposure

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37
Q

what is the proper way to store film screen inventory (if you were stocking) bc

A

upright bc if they are stacked on top of each other there is a loss of contrast

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38
Q

what contributes to film fog?

A

the age of the film
excessive exposure to safelight
processor chemistry

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39
Q

outdated film will have what kind of contrast

A

loss of contrast, which causes fog

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40
Q

photon energy and wavelength relationship

A

inverse
as kV is increased, more high energy photons are produced, the overall energy of the beam is increased. so the wavelength is decreased

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41
Q

an increase in mA does what to the number of photons produced at the target

A

increases

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42
Q

for an abdomen xray, which needs more exposure, supine or erect? why?

A

erect because everything in the stomach sits lower when they are standing, whereas when they lay everything spreads out and thickness of the stomach decreases

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43
Q

solid state detector plates (in DR) are made of

A

barium fluorohalide

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44
Q

height of the lead strips to the width of the interspaces describes

A

grid ratio

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45
Q

what type of grid ratio allows for more centering latitude?

A

low grid ratio

high grid ratios need to be accurate

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46
Q

TECHNICAL FACTORS

INCREASE OR DECREASE

A

TECHNICAL FACTORS

INCREASE OR DECREASE

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47
Q

Ascites

A

fluid in the abdomen

increase

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48
Q

Osteoporosis

A

weakening of bone

decrease

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49
Q

Osteomalacia

A

softening of bones

decrease

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50
Q

Rheumatoid arthritis

A

hardening of the joints

increase

51
Q

paget disease

A

increase

52
Q

pneumoperitoneum

A

air in the abdomen

decrease

53
Q

pneumonia

A

fluid filled air sacs of the lungs

increase

54
Q

atelectasis

A

collapsed lung

increase

55
Q

emphysema

A

breaks down air sacs in the lungs

decrease

56
Q

congestive heart failure

A

increase

57
Q

edematous tissue

A

fluid in the tissues

increase

58
Q

degenerative arthritis

A

decrease

58
Q

atrophic and necrotic conditions

A

shrinkage or death

decrease

59
Q

BREAK

A

BREAK

60
Q

low ratio grids and high ratio grids allow for how much scatter to reach the IR

A

low ratio grids allow for a great percentage of scatter to reach the IR
high ratio grids allow for a small percentage of scatter to reach the IR bc it will clean up more scatter

61
Q

mAs and scatter

A

no relation

62
Q

grids and contrast

A

grids improve contrast

63
Q

exposure rate is determined by

A

kV
mA (most)
distance

64
Q

high kV and scatter

A

high kV increases scatter

65
Q

thick/dense structures and scatter

A

increases scatter

66
Q

the degree of difference between adjacent denstities

A

radiographic contrast

67
Q

mA and contrast

A

no relation

68
Q

what is the equation for grid ratio

A

the height of the strips / the width between them

69
Q

a 5 in object to be radiographed at 44 in. SID lies 6 in. from the IR. what will be the image width

A

Image size SID X 44in
__________ = _______ _____ = ______ = 5.78
object size SOD (SOD=SID-OID) 5in 38in

70
Q

SOD =

A

SID-OID

71
Q

in comparison with 60 kV, 80 kV will do what to scatter and exposure latitude

A

produce more scatter
and
allow for greater exposure latitude (margin of error)

72
Q

two-dimensional, pixel element, thats measured in XY direction

A

pixel

73
Q

how much of the patient is included in the matrix describes?

A

FOV

74
Q

mosiaicked

A

pixelly

75
Q

misalignment of the tube-part-IR relationship results in

A

shape distortion (elongation/foreshortening)

76
Q

focal spot blur is caused by..

A

the use of a large focal spot

77
Q

size distortion

A

magnification

78
Q

what can cause grid cut-off when using a focused reciprocating grid?

A

inadequate SID

79
Q

central ray angulation in the direction of the lead strips causes:
central ray angulation against the direction of the lead strips causes:

A

in the direction: causes nothing

against the direction: causes grid cut off

80
Q

phantom images are a result of

A

incomplete erasure of the previous image on the PSP

81
Q

what increases the anode heel effect

A

short SID with large IR

10 degree or less angle

82
Q

low ratio grids and exposure latitude

A

low ration grids offer more exposure latitude than high grid ratios

83
Q

Z direction in a matrix

A

voxel

volume element

84
Q

to magnify an object 2X

A

the OID must be half the distance of the SID

85
Q

what is the main difference between direct capture and indirect capture DR

A

direct capture has no scintillator

indirect capture has a scintillator

86
Q

the direction electrons travel in the xray tube is

A

cathode to anode

87
Q

Charges
Anode:
Cathode:
Which way do these charges travel in an xray tube

A

Anode: positive
Cathode: Negative
Cathode to Anode so negative to positive

88
Q

when tissue densities are very different (like a chest xray) what can be done to “even out” the densities on the image

A

increase kV to use a longer scale of contrast (which results in more grays)

89
Q

for the same FOV, spatial resolution will be improved using..

A

a larger matrix
or
smaller (NOT FEWER) pixels

matrix and pixel size are inversely related

90
Q

FOV and resolution relationship

A

inverse relationship

Decreasing the FOV, decreases the pixel size, which improves resolution

91
Q

which of the following are methods of limiting the production of scattered radiation and why/why not?

  1. using moderate grid ratios
  2. using prone position for abdominal xrays
  3. restricting the field size
A
  1. using prone position for abdominal xrays: because it will compress the stomach, causing less scatter
  2. restricting the field size: most effective means of reducing scatter
    not 1. using grids: because grids cleanup scatter and have nothing to do with the PRODUCTION of scatter
92
Q

the absorption of useful radiation by a grid is called?

A

grid cut off

93
Q

radiographic density is found by what factors?

A

mAs and distance

high mAs with short distance produces the greatest density

94
Q 
which factor will produce the shortest scale of contrast
70 kV, 8:1 grid
70 kV, 6:1 grid
95 kV, 12: grid
95 kV, 8:1 grid
A

70 kV, 8:1 grid
want low kVp, bc low kV, high contrast, short scale
and
higher grid ratio cleans up scatter reaching the IR, therefor fewer grays

95
Q

long scale contrast has___ kV and what type of grid ratio?

A

high kV, low contrast, long scale

lower grid ratio bc more scatter will reach the IR (producing more grays)

96
Q

kV and exposure latitude relationship

A

direct

97
Q

actual focal spot and effective focal spot size

A

actual focal spot is larger than the effective/projected focal spot

98
Q

focal spot blur is greatest at what part of the xray beam

A

toward the cathode end of the x-ray beam

99
Q

BREAK

A

BREAK

100
Q

mAs and pt dose relationship

A

direct relationship

101
Q

IPs can be made from?

A

carbon fiber
and
magnesium

102
Q

if the grid failed to move throughout the exposure, how would the image look?

A

there would be grid lines throughout the image

103
Q

if the central ray was off center, how would the image look?

A

it would have a uniform loss of density

the whole image would have a loss of density/ increased brightness

104
Q

if the SID is above or below the recommended focusing distance, what will the image look like?

A

there would be an increased brightness/loss of density at its lateral edges

105
Q

what can be done to reduce the exposure time?

A

increase mA
or
increase kV

106
Q

energy and wavelength

A

inverse

high energy, short wavelength

107
Q

film processing order

A

develop, fix, wash, dry

108
Q

SID and exposure factors relationship

A

direct

increased SID causes for increased exposure factors (kV or mA)

109
Q

SID and density relationship

A

inverse

short SID, more density

110
Q

Grid cut off is due to

A

Improper tube and grid alignment

111
Q

Grid cut off and contrast relationship

A

Grid cut off increases contrast

112
Q

the function of the developer in the film processor

A

change the EXPOSED silver bromide crystals to black metallic silver

113
Q

quantum noise is due to what factor

whats its appearance

A

too low mAs
or too much kV
grainy

114
Q

short SID results in? under/over exposure

A

overexposure

115
Q

does the HVL affect tissue density?

A

no

116
Q

magnification factor (MF)=

A

image size/ object size

117
Q

DR patient dose

A

low

118
Q

major advantage to CR

A

has best/widest dynamic range/latitude

119
Q

screen speed and contrast

A

faster the screens the higher the contrast

direct relationship

120
Q

health informatics aka

ex

A

health care information technology
PACS
HIS
RIS

121
Q

the xray image seen on the computer monitor is?

A

analog image

122
Q

.3mm or smaller focal spot size is for?

A

magnification

123
Q

is the anode heel effect good for….
lateral T-spine
AP femur
RAO sternum

A

lateral T-spine

AP femur

Registry Review (3 decks)

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