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RADIO PHYS > Radiography history, image production > Flashcards

Radiography history, image production Flashcards

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
Q

modern radiology: first MRI prod

A

1973

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26
Q

modern radiology: rare-earth intensifying screens

A

1974

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27
Q

modern radiology: digital fluoroscopy

A

1979

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28
Q

modern radiology: SI units of radiation

A

1980

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29
Q

modern radiology: 1982 PACS available– sig

A
  • picture archiving and communication sys
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30
Q

radiation injury: Edison, Morton, Tesla warned

A
  • radiation injury

- reported eye irritations from experimenting w xrays

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31
Q

first xray fatality in:

A

1904

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32
Q

radiation injury: list effects (5)

A
  • skin damage
  • burns
  • loss of hair
  • anaemia common in early yrs
  • all due to long exposure time
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33
Q

radiation injury: 1910 controlled radiation techniques-

A
  • biological effects of xrays began to be studied
  • collimation
  • filtration
  • shielding
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34
Q

radiation injury: decreased injuries due to intro of

A
  • coolidge tube
  • snook transformer
  • less exposure
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35
Q

radiation injury: radiologists found to have higher rate of- and solution

A
  • aplastic anemia
  • leukaemia
  • lead-lined protective devices being used
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36
Q

radiation injury: list (3) guidlines to minimise radiation exposure

A
  • time
  • distance
  • shielding
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37
Q

radiation injury: radiographic guidelines- time= time/lvl of exposure

A
  • decrease time/lvl of exposure: coolidge tube, snook transformer, intensifying screens, double emulsion film
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38
Q

radiation injury: radiographic guidelines- time= repeat exposures

A
  • decrease
  • shorter time
  • potter-bucky grid
  • positioning
  • procedure
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39
Q

radiation injury: radiographic guidelines- time= inappropriate imaging

A
  • clinical guidlines
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40
Q

radiation injury: radiographic guidelines- distance

A
  • inverse square law: when 2x distance, xray intensity drops by 1/4
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41
Q

radiation injury: radiographic guidelines- shielding

A
  • lead shielding
  • collimation
  • filtration
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42
Q

analogue vs digital xrays: list image prod concepts (5)

A
  • kV and mA
  • film type
  • filters
  • processing and dev
  • storage
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43
Q

analogue vs digital xrays: safety issues btw modes

A
  • digital usually assoc w less repeat exposures
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44
Q

sig of xray vs CT/MRI:

A
  • 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
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45
Q

radiographic image: features

A
  • 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
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46
Q

radiographic image: define attenuation

A

reduction of xray beam intensity, resulting from:

  • absorption
  • scattering
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47
Q

xray attenuation: thicker/thinner body parts attenuate more xrays

A

thicker

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48
Q

xray attenuation: increase of 4cm of soft tissue=

A
  • decreases exit radiation by factor of 2
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49
Q

xray attenuation: list (5) from least to most attenuated material

A
  • air
  • fat
  • water
  • bone
  • metal
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50
Q

exposure parameters: why?

A
  • 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
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51
Q

exposure parameters: list 1˚ parameters (2)

A
  • kV

- mAs

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52
Q

exposure parameters: list 2˚ parameters (2)

A
  • distance

- filtration

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53
Q

optical density: define image density

A
  • amount of BLACKENING of processed image

- greater image density, less light can pass through image

54
Q

optical density: higher image density =

A

blacker image

55
Q

optical density: equation

A

OD = log(Ii/It)

56
Q

optical density: OD of 0=

A

clear image

57
Q

optical density: OD of 4=

A

black image

58
Q

optical density: OD in diagnostic radiology range from

A

0.25 - 2.5

59
Q

optical density: useful diagnostic range

A

0.5 - 1.25

60
Q

optical density: just possible to read newspaper through film w OD of

A

1

61
Q

xray quantity: define and measured in

A
  • output intensity of xray imaging sys

- measured in mGy

62
Q

xray quantity: also aka (2)

A
  • xray intensity
  • radiation exposure

same as xray quantity

63
Q

xray quantity: directly affects

A

optical density

64
Q

mAs: mA?

A

exposure current:

  • current determines no. of xrays prod
  • controls xray beam quantity
65
Q

mAs: s?

A

exposure time:

  • controls time xray beam prod for
  • controls xray beam quantity
66
Q

mAs: features (controls? doesn’t affect?)

A
  • exposure current (mA) x exposure time (s)
  • controls xray beam quantity
  • does NOT affect beam quality
  • controls OD on radiograph
67
Q

xray intensity is directly proportional to:

A

mAs

68
Q

mAs: meaning when mAs is 2x?

A
  • no. electrons striking tube target 2x

= no. xrays emitted 2x

69
Q

mAs: the higher mAs, higher/lower image density?

A

higher

70
Q

mAs: mAs and xray intensity ratio

A

i1 / i2 = mAs 1 /mAs 2

71
Q

mAs: must be at particular lvl to achieve correct-

A

optical density

72
Q

mAs: if mAs remains constant, same OD can be achieved through combo of (2)

A
  • exposure current

- time

73
Q

mAs: if mAs remains constant, same OD can be achieved- techniques (2)

A
  • kept short as possible= min movement blur

- decreased time, needs increase in current to ensure sufficient quantity

74
Q

maintaining OD: equation

A

mA1 x s1 = mA2 x s2

75
Q

mAs: eg (1) technique req increased time to allow for movement- compensation?

A
  • autotomography

- mA must be decreased proportionally to allow for constant OD

76
Q

autotomography: eg. (2)

A
  • controlled patient movement can blur overlying structures (ribs, scapulae) through breathing
  • flapping jaw technique
77
Q

distance: SID affects

A

source to image distance (SID): influences xray beam quantity at image receptor

78
Q

distance: SID no effect on

A

xray beam quality

79
Q

distance: relatively fixed at

A
  • 100cm/ 180cm depending on anatomical region
80
Q

distance: increased SID increases/reduces xray beam quantity?

A

reduces quantity

81
Q

distance: inverse square law aka

A
  • xray intensity (quantity) varies inversely w distance from xray tube-> target (SID)2
82
Q

distance: inverse square law equation

A

i1/i2 = (d2/d1)2

83
Q

the square law: when SID increased, what needs to be increased to maintain constant OD?

A

mAs must also be increased

84
Q

corollary to inverse square law: equation

A

mAs 2/mAs 1 = (d2/d1)2

85
Q

the square law: if 2x SID, mAs must be increased by factor of: to keep OD same

A

mAs increased by factor of 4

86
Q

image contrast: define

A

degree of diff in density btw 2 areas on xray image

87
Q

image contrast: features

A
  • contrast reflects no. of shades of grey btw lightest/darkest areas
88
Q

image contrast: high contrast image

A
  • fewer shades grey

- more diff btw them

89
Q

image contrast: low contrast image

A
  • many shades of grey

- less diff btw them

90
Q

xray quality: aka the

A

energy

91
Q

xray quality: if energy increases, so does

A

penetrability

92
Q

xray quality: define penetrability

A
  • xrays range within tissue

- able to pass through tissue

93
Q

xray quality: high energy xrays can

A
  • penetrate deeper tissue, ‘hard’ xrays
94
Q

xray quality: low energy xrays can

A
  • penetrate far less

- termed ‘soft’ rays

95
Q

xray quality: xray energy (quality) identified numerically by

A
  • half value layer (HVL)
96
Q

xray quality: higher the HVL, =

A

higher xray quality/penetrability/energy

97
Q

HVL: define

A
  • HVL of xray beam is thickness of absorbing material necessary to reduce xray intensity to 1/2 og value (attenuation)
98
Q

HVL: diagnostic xray beam range for soft tissue?

A

3 - 6cm

99
Q

HVL: affected by (2)

A
  • kV (kilovoltage)

- added filtration

100
Q

HVL: xray quality is also affected by

A
  • kV

- filtration

101
Q

HVL: factors affecting beam quality also influence

A

radiographic contrast

102
Q

HVL: radiation quality NOT affected by

A
  • distance

- mAs

103
Q

kV: define

A
  • kilovoltage

- 1˚ control of xray beam/penetrability

104
Q

kV: influences

A

xray beam quantity

105
Q

kV: increasing kV effects- (5)

A

increases:

  • xrays emitted (increases quantity)
  • energy of xrays
  • penetrability
  • Compton effect, scatter radiation

decreases:
- contrast

106
Q

kV: controls

A
  • image contrast

- image density

107
Q

kV: if kV increased and so does xray beam quality, what else?

A
  • increases penetrability = HVL
108
Q

kV: when increased xray beam can penetrate more/less tissue

A
  • more tissue
109
Q

kV: low kV effect of beam

A
  • 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
Q

kV: high kV effect of beam

A
  • 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
Q

kV: what varies rapidly w changes in kV and is proportional to kV2?

A

xray quantity

112
Q

kV: xray quantity change is proportional to what of kV?

A
  • proportional to square of kV

- ie. if kV 2x, xray intensity increases by factor of 4

113
Q

kV: intensity and kV equation

A

i1/i2 = (kV1/kV2) 2

114
Q

kV: density linked to ? which can be manipulated to highlight..

A
  • contrast

- highlight particular image qualities

115
Q

kV: if kV increased, will increase/decrease image contrast, and increase/decrease image density

A
  • decrease image contrast

- increase image density

116
Q

kV: 15% rule

A
  • 15% increase in kVp will increase density
  • same as 2x mAs
  • 2x OD
117
Q

filtration: features

A
  • reduces no. of low energy xray that reach patient
118
Q

filtration: low energy xray sig

A
  • cont nothing useful to image

- only increases patient dose

119
Q

filtration: increasing beam quality and penetrability will increase/decrease contrast?

A

decrease contrast

120
Q

filtration: decreasing beam quality will increase/decrease density

A

decrease density

121
Q

filtration: inherent features

A
  • 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
Q

filtration: added features

A
  • 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
Q

parameters affecting density and contrast: mA increase

A
  • increase density

- unchanged contrast

124
Q

parameters affecting density and contrast: mA decrease

A
  • decreases density

- unchanged contrast

125
Q

parameters affecting density and contrast: time increase

A
  • increase density

- unchanged contrast

126
Q

parameters affecting density and contrast: time decrease

A
  • decrease density

- unchanged contrast

127
Q

parameters affecting density and contrast: kVp increase

A
  • increase density

- decreases contrast

128
Q

parameters affecting density and contrast: kVp decrease

A
  • decrease density

- increase contrast

129
Q

parameters affecting density and contrast: SID increase

A
  • decrease density

- unchanged contrast

130
Q

parameters affecting density and contrast: SID decrease

A
  • increase density

- unchanged contrast

131
Q

parameters affecting density and contrast: filtration increase

A
  • decreases density

- decrease contrast

132
Q

parameters affecting density and contrast: filtration decrease

A
  • increase density

- increase contrast

RADIO PHYS (2 decks)

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