Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

RADIO PHYS > Image quality > Flashcards

Image quality Flashcards

1
Q

recap: define density

A
  • degree of blackening of image
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

recap: density influenced by (5)

A
  • mAs
  • kV
  • distance
  • filtration
  • scatter radiation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

recap: define contrast

A
  • degree of diff in density btw 2 areas
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

recap: contrast influenced by (3)

A
  • kV
  • filtration
  • scatter radiation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

recap: define detail (sharpness)

A
  • degree of sharpness of recorded lines on image
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

recap: detail influenced by (4)

A
  • distance
  • focal spot size
  • motion
  • magnification
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

recap: define distortion

A
  • deviation of image of the true shape of object
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

recap: distortion influenced by (2)

A
  • positioning

- magnification

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

recap: define artefacts

A
  • appearance on film that is not normally present on film

- prod by artificial means

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

recap: artefacts influenced by (3)

A
  • external objects
  • equipment
  • processing
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

xray beam: ways of xrays entering patient (3)

A
  • absorbed
  • scattered
  • transmitted
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

xray beam: exit radiation

A
  • combo of transmitted + scattered radiation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

xray beam: type of radiation leaving patient in og trajectory? and prod?

A
  • transmitted radiation

- prod diagnostic image

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

scatter radiation: define

A
  • secondary radiation emitted from interaction of xrays w matter
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

scatter radiation: general features

A
  • generally lower in energy
  • changes direction
  • no useful info for radiographic image
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

scatter radiation: reflected scatter will (2)

A
  • may be reflected off surrounding objects

- source of exposure to personnel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

scatter radiation: effect

A
  • lead to reduction in radiation contrast

- increased density

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

scatter radiation: best time to remove scatter

A
  • before reaching image receptor

- greatly improve image contrast

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

scatter radiation: solutions (3) before hitting receptor

A
  • collimators
  • grids
  • air gap technique
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

scatter radiation: list factors increasing scatter (3)

A
  • size of object
  • xray beam energy
  • field size
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

scatter radiation: features- size of object

A
  • increase in tissue thickness increase amount of scatter = more possible interactions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

scatter radiation: features- xray beam energy

A
  • the higher the energy (higher kV) = more scatter

- lower energy beams more likely to be absorbed vs. scattered

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

scatter radiation: features- field size

A
  • larger field sizes = more scatter

- more possible interactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

scatter radiation: name (3) beam restricting devices

A
  • collimators
  • diaphragms
  • cones
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

scatter radiation: features- beam restricting devices (3)

A
  • restrict field size to area of interest
  • limit patient exposure in unnecessary areas
  • improve image contrast by decreasing scatter
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

scatter radiation: collimators

A
  • present on all xray machines
  • defines size, shape of 1˚ xray beam
  • light beam outlines area of exposure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

scatter radiation: diaphragms

A
  • added to collimator: further limit exposed area

- diaphragm changes rectangular shape -> circle (at point of exit of xray beam)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

scatter radiation: cones

A
  • added to collimator: further limit exposed area

- cone brings point of exit of xray beam closer to patient (limit to circular shape= more effective at limiting scatter)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

scatter radiation: pros of diaphragms/cones

A
  • good for spot views where improved image contrast is necessary
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

grids: general features and comprised of

A
  • dev by Bucky 1913 for greater image contrast
  • modern grid: series of lead strips (grid material: radiopaque) alternated w plastic/Al strips (interspace material: radiolucent)
  • reduces amount scatter radiation within exit radiation reaching film
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

grids: designed for

A
  • allowing passage of transmitted radiation (xrays in straight direction from source)
  • scattered xrays absorbed by grid matter
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

grids: improves?

A
  • radiographic contrast

- reduce scatter radiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

grids: cons- (3)

A
  • absorbs portion of transmitted (‘useful’) radiation, reduced xray quantity and density
  • grid lines prod in film, lessens diagnostic value of image
  • may be prone to grid cut off
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

grids: cons- absorbed transmitted radiation solution

A
  • maintain optical density: mAs increased = higher patient dose
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

grids: cons- grid lines prod in film lessening diagnostic value solution

A
  • moving grid overcomes this
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

grids: cons- grid cut off solution

A
  • needs to be correctly positioned w respect to image receptor
  • centre of xray should be centre of grid
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

grids: grid cut off features

A
  • undesirable absorption of 1˚ rays by grid

- misalignment of transmitted beam, lead strips increases progressively toward edges of grid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

bucky: features

A
  • grid placed in front of bucky, in front of image receptor
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

grid ratio: determines? and depends on

A
  • determines amount of scatter radiation removed by grid

- depends on height of grid strip and distance btw grid strips

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

grid ratio: the higher the grid ratio? effectiveness

A
  • more effective cleaning up scatter

- angle of scatter allowed less than lower ratios

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

grid ratio: higher grid ratio- gap size?

A
  • smaller gap btw strips/ increased height of strips
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

grid ratio: needs increased/decreased mAs? to maintain density

A
  • need increased mAs (higher patient dose)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

grid ratio: define

A
  • ratio of height of lead strips to dist btw lead strips (thickness of interspace)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

grid ratio: formula

A

GR = h/D

height, dist

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

grid ratio: typical range

A

from 5:1 - 16:1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

grid ratio: cons

A
  • while removing scatter is difficult to align properly
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

grid freq: define

A
  • no. of lead strips per cm
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

grid freq: higher grid freq means? (2)

A
  • thinner strips

- less visible on radiographic image

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

grid freq: assoc w higher/lower grid ratio and better at?

A
  • assoc higher grid ratio
  • higher patient dose
  • better reduction of scatter radiation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

grid freq: typical range

A

24 - 80 lines/cm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

bucky (grid) factor: features

A
  • how much scatter removed by grid

- technical factors adjusted to prod same optical density

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

bucky (grid) factor: scatter?

A
  • accounts for sig portion of density of final radiograph
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

bucky (grid) factor: compensation

A
  • increase exposure when removing scatter

- compensates for decreased xrays hitting image receptor

54
Q

bucky (grid) factor: B?

A
  • ratio of mAs required w grid to mAs w/o grid

= prod same optical density

55
Q

bucky (grid) factor: B formula

A

mAs (grid) ÷ mAs (without grid)

56
Q

bucky (grid) factor: always greater than?

A

1

57
Q

bucky (grid) factor: typical range

A

3 - 5

58
Q

bucky (grid) factor: the higher bucky factor, the higher?

A

higher grid ratio and freq

59
Q

linear parallel grids: consists of

A
  • parallel strips
60
Q

linear parallel grids: effect

A
  • high ˚ of grid cutoff (esp outer edges due to diverging xrays)
61
Q

linear parallel grids: define grid cut off

A
  • undesirable absorption of transmitted rays by grid
62
Q

linear parallel grids: cut off features

A
  • misalignment of transmitted beam + lead strips increases progressively towards edges of grid
  • cut off at periphery (both sides)
63
Q

linear parallel grids: cut off reduced by?

A
  • increasing SID

- less divergence of xray beam

64
Q

linear parallel grids: tilted cut off

A
  • xray beam not perpendicular to grid
  • poor tube positioning
  • cut of one half of image
65
Q

linear focus grids: features

A
  • grid material aligned to coincide w diverging beam
  • allows less grid cut off, more expensive to prod
  • take care when positioning grid compared to xray tube (due to geometric limitations)
  • intended dist and side must face xray tube marked on grid (when backwards = extreme grid cutoff)
66
Q

linear focus grids: cut off

A
  • when correctly positioned: no cut off

- incorrect SID: falls outside focal range of grid

67
Q

cross parallel grids: features

A
  • as parallel only clean up scatter one direction, crossed overcomes this
  • 2 linear grids perpendicularly opposed
68
Q

cross parallel grids: pros

A
  • efficient scatter cleanup
  • improves contrast
  • positioning critical
69
Q

cross parallel grids: central beam?

A
  • central beam must coincide w centre of grid
70
Q

cross parallel grids: can u use angle techniques?

A
  • no

- due to grid cutoff

71
Q

crossed focused grids: features

A
  • 2 linear focused grids opposed
72
Q

crossed focused grids: need? (3)

A
  • central beam positioned correctly
  • correct dist
  • correct placement of grid in bucky
73
Q

moving/reciprocating grids: features

A
  • reduces grid lines on image (grid vibrated during exposure
  • heard as audible ‘rattle’
  • grid moved by bucky
74
Q

air gap technique: features (2)

A
  • alt method for reducing scatter grid

- uses increased OID

75
Q

air gap technique: approx gap used

A

10 - 15cm

76
Q

air gap technique: used in eg.

A
  • lateral cervical spine radiographs

- shape of normal anatomy

77
Q

air gap technique: cons

A
  • increased magnification, focal spot blur
78
Q

air gap technique: to maintain same optical density?

A
  • increased mAs
79
Q

air gap technique: increased mAs same as using what grid?

A

8:1 grid

80
Q

image detail: define

A
  • degree of sharpness of recorded lines on image

- smallest separation of 2 lines/edges that can be recognised as separate objects on image

81
Q

image detail: define spatial resolution

A
  • quantification of image detail

- measured: line pairs/mm

82
Q

image detail: decreased image detail assoc w high/low contrast

A
  • low contrast
83
Q

image detail: features penumbra aka

A
  • area of decreased image detail

- aka geometric unsharpness

84
Q

image detail: affected by (2)

A
  • blur

- magnification

85
Q

image detail: blur factors (3)

A
  • focal spot size
  • distance
  • motion
86
Q

image detail: magnification factors (1)

A
  • distance
87
Q

focal spot: features

A
  • xrays not emitted from point, rather from rectangular-shaped focal spot
  • most xray tubes have 2 focal spot sizes
88
Q

focal spot: changing spot size (w constant kV and mAs) does not change (2)

A
  • xray quality or quantity
89
Q

focal spot: does limit?

A
  • limits max possible xray quantity
90
Q

focal spot: sml/lrg spot used for normal imaging? features (2)

A
  • lrg spot
  • allows sufficient mAs for denser body parts
  • assoc w decreased image detail
91
Q

focal spot: sml/lrg spot used for fine detail imaging? and features (3)

A
  • sml spot
  • areas don’t need v high mAs to penetrate
  • able to get improved image detail
  • extremity radiography
92
Q

focal spot blur: combo

A
  • combo of xray beam, rectangular size of focal spot = focal spot blur
93
Q

focal spot blur: larger the focal spot, more/less focal spot blur?

A
  • more spot blur
94
Q

focal spot blur: most vital factor for?

A
  • spatial resolution
95
Q

focal spot blur: eg. poor resolution (less detail) w smaller/larger focal spot

A
  • larger focal spot
96
Q

anode heel effect: features

A
  • angles anode prod xray beam w more intensity on cathode side
97
Q

anode heel effect: why less intense on anode side?

A
  • xrays running parallel to anode angulation absorbed by anode, giving decreased intensity
98
Q

anode heel effect: focal spot blur greater on anode/cathode side xray tube?

A
  • cathode

- decreased xrays on anode side -> smaller effective focal spot, less blur

99
Q

focal spot blur: divergence of beam (interacting w object) will increase/decrease when increase SOD (source to image dist)?

A
  • divergence decreases w increased SOD
100
Q

focal spot blur: increasing SOD increase/decrease focal spot blur

A
  • will decrease spot blur
101
Q

focal spot blur: SOD increased/decreased by increasing SID?

A
  • increased SID (source to image dist)
102
Q

focal spot blur: divergence of transmitted radiation (exiting from an object) will increase/decrease when increase OID (object to image dist)?

A
  • divergence increases w increased OID
103
Q

focal spot blur: decreasing OID will increase/decrease focal spot blur?

A
  • decrease spot blur
104
Q

focal spot blur: increased/decreased SOD by increasing SID?

A
  • increased SOD (?)
105
Q

focal spot blur: decreased by- list (4)

A
  • smaller focal spot
  • larger SID (larger SOD): if change SID need to consider image density affected
  • smaller OID (larger SOD)
  • anode side of tube
106
Q

motion blur: define and is major cause of?

A
  • blur caused by patient moving during xray exposure

- one of major causes: repeat radiographs

107
Q

reducing motion blur: list (2)

A
  • time

- stabilisation

108
Q

reducing motion blur: time and controls what movement?

A
  • shortest possible exposure times

- controls for involuntary movement of heart and lungs

109
Q

reducing motion blur: stabilisation and controls what movement?

A
  • restrict patient motion by instrument, restraining device

- controls for voluntary movement

110
Q

linear tomography: features

A
  • xray tube deliberately moved during exposure time while image receptor is moved in opp direction
  • used to blur structures on either side of plane of interest (see slice of subject vs. structures superimposed)
  • position of fulcrum determines object plane
111
Q

linear tomography: greater angle = the thicker/thinner slice

A
  • thinner the slice
112
Q

magnification: define

A
  • enlargement of object on resultant image
113
Q

magnification: due to

A
  • divergence of xray beam
114
Q

magnification: measured by?

A
  • magnification factor (MF)

- ratio of image size to object size

115
Q

magnification: formula

A

MF = i ÷ O

image size : object size

116
Q

magnification: magnification of 1 means?

A
  • same size as object
117
Q

magnification: MF is also proportional to? (when object size is unknown helpful)

A
  • SID to OID
118
Q

magnification: MF formula using SID, OID

A

MF = SID ÷ SID-OID

119
Q

magnification: how to minimise

A
  • min divergence of beam:
  • larger SID
  • smaller OID
120
Q

magnification: at 100cm MF approx?

A

1.1

121
Q

magnification: at 180cm MF approx?

A

1.05

122
Q

magnification: formula to find size of og object (O) using image (i), SID, OID

A

O = i(SID-OID) ÷ SID

123
Q

decreased image detail assoc w: list (7)

A
  • decreased SID
  • decreased SOD
  • increased OID
  • increased focal spot size
  • cathode side of xray tube
  • increased motion
  • increased magnification
124
Q

distortion: define

A
  • unequal magnification of diff portions of same object
125
Q

distortion: depends on (3)

A

object:

  • thickness
  • position
  • shape
126
Q

distortion: object thickness

A
  • thicker = more distortion
127
Q

distortion: object position- depends on

A
  • depends on relative position of object, image receptor, central xray beam
128
Q

distortion: object position- (2) eg.

A
  • object plane vs image plane not parallel (increased OID in some areas)
  • objects positioned off central ray beam (more xray divergence)
129
Q

distortion: object position- shape distortion? (2)

A
  • elongation

- foreshortening

130
Q

distortion: object position- patient positioning

A
  • important to prevent distortion and magnification as possible
131
Q

distortion: object shape

A
  • irregular objects produce irregular distortion
132
Q

image assessment: check (5)

A
  • contrast
  • density
  • detail
  • distortion
  • artefacts

RADIO PHYS (2 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions