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RADIO PHYS > Radiography history, image production > Flashcards

Radiography history, image production Flashcards

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1
Q

when was xrays discovered by Roentgen:

A

1895

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2
Q

how was it discovered:

A
  • Crookes tube
  • fogging of photographic plate
  • no visible ligt emitted from tube
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3
Q

x in xray stands for:

A
  • unknown
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4
Q

list (9) properties of xrays discovered:

A
  • EM waves
  • 1/10,000 wavelength of visible light
  • can’t penetrate lead
  • attenuation of xray beam depends on substance
  • causes certain substances to fluoresce
  • produces biological changes
  • can ionise gases
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5
Q

yr of first medical use of xrays in diagnosis and therapy:

A
  • 1896

- Hall-Edwards, Frost, Lyle

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6
Q

exposure times of ‘shadow graphs’ initially and effects

A
  • 30min (long)
  • low voltage
  • blurred images w high radiation dose
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7
Q

intensifying screen in 1896 sig:

A
  • reduced time to take image
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8
Q

1898 Edison’s fluoroscope:

A
  • xray tube under table
  • xray enters viewing device
  • able to visualise moving images in real time
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9
Q

most sig discoveries to improve image quality:

A
  • collimation

- filtration

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10
Q

when was Coolidge xray tube dev:

A

1913

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11
Q

coolidge tube sig: list (5)

A
  • basis of xray tubes today
  • hot cathode xray tube
  • vacuum tube: allowed xray intensity, energy to be selected separately
  • used snook transformer to increase current, voltage
  • start of modern radiology
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12
Q

1917 cellulose nitrate film: sig

A
  • due to lack of glass in WWI

- better than glass but highly flammable

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13
Q

1918 double emulsion film: sig

A
  • exposure time halved

- image enhanced

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14
Q

soluble iodine contrast media used in:

A

1920

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15
Q

1921 Potter-bucky grid intro: sig

A
  • improved image contrast
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16
Q

1922 Compton scatter rays: sig

A
  • large cont to image fogging
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17
Q

modern radiology: 1923 ‘safety’ film intro- sig

A
  • cellulose acetate

- not flammable

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18
Q

modern radiology: 1928 defined xray intensity units in

A

roentgen

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19
Q

modern radiology: 1929 rotating anode into- sig

A
  • extended tube life
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20
Q

modern radiology: 1930 tomography dev- sig

A
  • ability to image structures at certain depth in body

- allowed visualisaiton of structures without overlying structures obscuring anatomy

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21
Q

modern radiology: 1953 defined unit of absorbed dose as

A

rad

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22
Q

modern radiology: 1960 more durable film used-

A
  • polyester
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23
Q

modern radiology: diagnostic ultrasound intro

A

1966

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24
Q

modern radiology: first CT scanner

A

1972

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25
modern radiology: first MRI prod
1973
26
modern radiology: rare-earth intensifying screens
1974
27
modern radiology: digital fluoroscopy
1979
28
modern radiology: SI units of radiation
1980
29
modern radiology: 1982 PACS available-- sig
- picture archiving and communication sys
30
radiation injury: Edison, Morton, Tesla warned
- radiation injury | - reported eye irritations from experimenting w xrays
31
first xray fatality in:
1904
32
radiation injury: list effects (5)
- skin damage - burns - loss of hair - anaemia common in early yrs - all due to long exposure time
33
radiation injury: 1910 controlled radiation techniques-
- biological effects of xrays began to be studied - collimation - filtration - shielding
34
radiation injury: decreased injuries due to intro of
- coolidge tube - snook transformer - less exposure
35
radiation injury: radiologists found to have higher rate of- and solution
- aplastic anemia - leukaemia - lead-lined protective devices being used
36
radiation injury: list (3) guidlines to minimise radiation exposure
- time - distance - shielding
37
radiation injury: radiographic guidelines- time= time/lvl of exposure
- decrease time/lvl of exposure: coolidge tube, snook transformer, intensifying screens, double emulsion film
38
radiation injury: radiographic guidelines- time= repeat exposures
- decrease - shorter time - potter-bucky grid - positioning - procedure
39
radiation injury: radiographic guidelines- time= inappropriate imaging
- clinical guidlines
40
radiation injury: radiographic guidelines- distance
- inverse square law: when 2x distance, xray intensity drops by 1/4
41
radiation injury: radiographic guidelines- shielding
- lead shielding - collimation - filtration
42
analogue vs digital xrays: list image prod concepts (5)
- kV and mA - film type - filters - processing and dev - storage
43
analogue vs digital xrays: safety issues btw modes
- digital usually assoc w less repeat exposures
44
sig of xray vs CT/MRI:
- not obsolete - minimal visualisation of soft tissues BUT: - better bone visualisation than MRI - cheaper, quicker - less radiation than CT - often rec 1st line of imaging prior to further imaging
45
radiographic image: features
- xray beam emerges from tube as uniform beam - beam is attenuated as pass through patient - exit beam is varied in intensity depending on characteristics of tissue through which it passed - exit beam interacts w image receptor to form radiographic image
46
radiographic image: define attenuation
reduction of xray beam intensity, resulting from: - absorption - scattering
47
xray attenuation: thicker/thinner body parts attenuate more xrays
thicker
48
xray attenuation: increase of 4cm of soft tissue=
- decreases exit radiation by factor of 2
49
xray attenuation: list (5) from least to most attenuated material
- air - fat - water - bone - metal
50
exposure parameters: why?
- proper exposure in necessary to produce diagnostic radiograph - exposure parameters determine xray quantity and quality - correct selection enables creation of high quality xrays of good diagnostic value
51
exposure parameters: list 1˚ parameters (2)
- kV | - mAs
52
exposure parameters: list 2˚ parameters (2)
- distance | - filtration
53
optical density: define image density
- amount of BLACKENING of processed image | - greater image density, less light can pass through image
54
optical density: higher image density =
blacker image
55
optical density: equation
OD = log(Ii/It)
56
optical density: OD of 0=
clear image
57
optical density: OD of 4=
black image
58
optical density: OD in diagnostic radiology range from
0.25 - 2.5
59
optical density: useful diagnostic range
0.5 - 1.25
60
optical density: just possible to read newspaper through film w OD of
1
61
xray quantity: define and measured in
- output intensity of xray imaging sys | - measured in mGy
62
xray quantity: also aka (2)
- xray intensity - radiation exposure same as xray quantity
63
xray quantity: directly affects
optical density
64
mAs: mA?
exposure current: - current determines no. of xrays prod - controls xray beam quantity
65
mAs: s?
exposure time: - controls time xray beam prod for - controls xray beam quantity
66
mAs: features (controls? doesn't affect?)
- exposure current (mA) x exposure time (s) - controls xray beam quantity - does NOT affect beam quality - controls OD on radiograph
67
xray intensity is directly proportional to:
mAs
68
mAs: meaning when mAs is 2x?
- no. electrons striking tube target 2x | = no. xrays emitted 2x
69
mAs: the higher mAs, higher/lower image density?
higher
70
mAs: mAs and xray intensity ratio
i1 / i2 = mAs 1 /mAs 2
71
mAs: must be at particular lvl to achieve correct-
optical density
72
mAs: if mAs remains constant, same OD can be achieved through combo of (2)
- exposure current | - time
73
mAs: if mAs remains constant, same OD can be achieved- techniques (2)
- kept short as possible= min movement blur | - decreased time, needs increase in current to ensure sufficient quantity
74
maintaining OD: equation
mA1 x s1 = mA2 x s2
75
mAs: eg (1) technique req increased time to allow for movement- compensation?
- autotomography | - mA must be decreased proportionally to allow for constant OD
76
autotomography: eg. (2)
- controlled patient movement can blur overlying structures (ribs, scapulae) through breathing - flapping jaw technique
77
distance: SID affects
source to image distance (SID): influences xray beam quantity at image receptor
78
distance: SID no effect on
xray beam quality
79
distance: relatively fixed at
- 100cm/ 180cm depending on anatomical region
80
distance: increased SID increases/reduces xray beam quantity?
reduces quantity
81
distance: inverse square law aka
- xray intensity (quantity) varies inversely w distance from xray tube-> target (SID)2
82
distance: inverse square law equation
i1/i2 = (d2/d1)2
83
the square law: when SID increased, what needs to be increased to maintain constant OD?
mAs must also be increased
84
corollary to inverse square law: equation
mAs 2/mAs 1 = (d2/d1)2
85
the square law: if 2x SID, mAs must be increased by factor of: to keep OD same
mAs increased by factor of 4
86
image contrast: define
degree of diff in density btw 2 areas on xray image
87
image contrast: features
- contrast reflects no. of shades of grey btw lightest/darkest areas
88
image contrast: high contrast image
- fewer shades grey | - more diff btw them
89
image contrast: low contrast image
- many shades of grey | - less diff btw them
90
xray quality: aka the
energy
91
xray quality: if energy increases, so does
penetrability
92
xray quality: define penetrability
- xrays range within tissue | - able to pass through tissue
93
xray quality: high energy xrays can
- penetrate deeper tissue, 'hard' xrays
94
xray quality: low energy xrays can
- penetrate far less | - termed 'soft' rays
95
xray quality: xray energy (quality) identified numerically by
- half value layer (HVL)
96
xray quality: higher the HVL, =
higher xray quality/penetrability/energy
97
HVL: define
- HVL of xray beam is thickness of absorbing material necessary to reduce xray intensity to 1/2 og value (attenuation)
98
HVL: diagnostic xray beam range for soft tissue?
3 - 6cm
99
HVL: affected by (2)
- kV (kilovoltage) | - added filtration
100
HVL: xray quality is also affected by
- kV | - filtration
101
HVL: factors affecting beam quality also influence
radiographic contrast
102
HVL: radiation quality NOT affected by
- distance | - mAs
103
kV: define
- kilovoltage | - 1˚ control of xray beam/penetrability
104
kV: influences
xray beam quantity
105
kV: increasing kV effects- (5)
increases: - xrays emitted (increases quantity) - energy of xrays - penetrability - Compton effect, scatter radiation decreases: - contrast
106
kV: controls
- image contrast | - image density
107
kV: if kV increased and so does xray beam quality, what else?
- increases penetrability = HVL
108
kV: when increased xray beam can penetrate more/less tissue
- more tissue
109
kV: low kV effect of beam
- aka low quality xray beam - beam largely attenuated by most tissue (white parts) - beam only penetrates low density tissues (=black parts) - v white/ v black image = HIGH CONTRAST IMAGE
110
kV: high kV effect of beam
- aka high quality xray beam - beam able to penetrate most of tissues - degree of attenuation will differ depending on tissue density and thickness - many shades of grey LOW CONTRAST IMAGE
111
kV: what varies rapidly w changes in kV and is proportional to kV2?
xray quantity
112
kV: xray quantity change is proportional to what of kV?
- proportional to square of kV | - ie. if kV 2x, xray intensity increases by factor of 4
113
kV: intensity and kV equation
i1/i2 = (kV1/kV2) 2
114
kV: density linked to ? which can be manipulated to highlight..
- contrast | - highlight particular image qualities
115
kV: if kV increased, will increase/decrease image contrast, and increase/decrease image density
- decrease image contrast | - increase image density
116
kV: 15% rule
- 15% increase in kVp will increase density - same as 2x mAs - 2x OD
117
filtration: features
- reduces no. of low energy xray that reach patient
118
filtration: low energy xray sig
- cont nothing useful to image | - only increases patient dose
119
filtration: increasing beam quality and penetrability will increase/decrease contrast?
decrease contrast
120
filtration: decreasing beam quality will increase/decrease density
decrease density
121
filtration: inherent features
- affects all xray beams - glass/metal envelope of xray tube, collimator, additional Al filter btw xray tube housing and collimator - required total filtration of 2.5mm Al
122
filtration: added features
- additional filtration may be used for examination of tissues w higher subject contrast: extremities, joints, chest - requires diff radiographic technique charts - not required w digital imaging
123
parameters affecting density and contrast: mA increase
- increase density | - unchanged contrast
124
parameters affecting density and contrast: mA decrease
- decreases density | - unchanged contrast
125
parameters affecting density and contrast: time increase
- increase density | - unchanged contrast
126
parameters affecting density and contrast: time decrease
- decrease density | - unchanged contrast
127
parameters affecting density and contrast: kVp increase
- increase density | - decreases contrast
128
parameters affecting density and contrast: kVp decrease
- decrease density | - increase contrast
129
parameters affecting density and contrast: SID increase
- decrease density | - unchanged contrast
130
parameters affecting density and contrast: SID decrease
- increase density | - unchanged contrast
131
parameters affecting density and contrast: filtration increase
- decreases density | - decrease contrast
132
parameters affecting density and contrast: filtration decrease
- increase density | - increase contrast

RADIO PHYS (2 decks)

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