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POS > Diagnostic imaging > Flashcards

Diagnostic imaging Flashcards

1
Q

CR

A
  • computed radiography

- used to show moving images

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2
Q

CT

A
  • computed x-ray tomography

- makes images of sections through body

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3
Q

scintigraphy

A

uses gamma rays which are injected to show metabolism

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4
Q

MRI

A
  • magnetic resonance imaging

- uses radiowaves to image things like the brain or spinal cord

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5
Q

ultrasound

A

shows echogenicity of tissues

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6
Q

2 types of x-ray image

A

positive and negative

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7
Q

bone colour of positive x-ray images

A

dark

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8
Q

bone colour of negative x-ray images

A

white

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9
Q

how x-rays are made

A

by electrons colliding into a heavy metal (e.g. tungsten)

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10
Q

where are x-rays produced

A

x-ray tube

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11
Q

components of an x-ray tube

A

glass or metal envelope, -ve cup shape behind the filament, +ve tungsten target with copper behind it.

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12
Q

how are x-rays produced in x-ray tube

A

electorns are fired of by filament and aimed by -ve cup shape at the tungsten target. x-rays are angled down towards patient by angle of tungsten target

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13
Q

function of copper behind tungsten target in x-ray tube

A

conducts heat away from tungsten target

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14
Q

colimator (radiography)

A

found under the x-ray tube it shapes the x-ray beam

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15
Q

x-ray absorption depends on

A

density and thickness of tissue and the atomic number of element sin the tissue

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16
Q

5 types of tissue seen radiographically in order of absorption

A

air, fat, soft tissue, bone and metal

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17
Q

what colour does air show up on radiograph

A

lucent/black

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18
Q

colour of bone on radiograph

A

white/opaque

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19
Q

2 types of contrast medium in radiograph

A

positive and negative

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20
Q

positive contrast medium colour on radiograph

A

radiopaque (white) as it absorbs lots of x-rays

21
Q

example of positive contrast mediums radiograph

A

iodine, or barium sulphate (GIT)

22
Q

negative contrast medium colour radiograph

A

radiolucent (black) as absords no x-rays

23
Q

example positive contrast medium radiograph

A

gasses (air)

24
Q

radiograph mAs

A
  • milliamperes per second

- number of electrons passing accross the x-ray tube

25
Q

increasing mAs

A

increases number of x-rays produced so more will get through and you can decrease exposure time and so reduce motion blur

26
Q

kVp radiograph

A
  • kilovoltage peak

- peak voltage applied accross the x-ray tube

27
Q

increaseing kVp radiograph

A

increases the energy of the beams so more get through

28
Q

values low kVp

A

45-60

29
Q

value middle kVp

A

65-75

30
Q

values high kVp

A

over 80

31
Q

x-ray machine button

A
  • has 2 stages
  • 1st stage prepares machine
  • 2nd stage sends the beam
32
Q

x-ray sunburn

A

caused by low energy x-rays

33
Q

preventing x-ray sunburn

A

aluminium sheet filters out low energy x-rays

34
Q

effects of scattered radiation on the image

A

makes image grey, fuzzy and indistinct

35
Q

4 things that reduce radiation scattering

A
  • use colimator to reduce volume of tissue being irradiated
  • put a layer of lead between table and cassette
  • increase kVp to make beams go through patient better
  • use an x-ray grid to reduce scattered radiation getting to cassette
36
Q

what needs to be done to compensate for use of x-ray grid

A

increase mAs by the grid factor

37
Q

appearance of x-ray grid

A

thin lead strips parallell to 1* beam. about 24 per cm

38
Q

roentgen

A
  • ability of radiation to ionise the air

- measured in couloms per kg of air (C/kg)

39
Q

becquerel

A
  • Bq
  • rate of radioactive decay
  • measured as disintegration per second
40
Q

gray

A
  • Gy
  • absorbed dose of radiation
  • measured in joules per kg of tissue (joule/kg)
41
Q

sievert

A
  • Sv
  • dose equivalent radiation
  • measures the effect of radiation
  • = gray x quality factor
42
Q

max dose of radiation for people at work

A

20 mSv per year

43
Q

Sv measured by

A

film badge or thermoluminescent detector (TLD)

44
Q

ALARA (radiation)

A
  • as low as reasonably possible

- radiation wise it should be ALARA

45
Q

you can achive ALARA radiation in 5 ways

A
  • wear lead aprons and gloves
  • keep as far away from the source as possible
  • use lead mobile barriers or walls
  • do things at arms length
  • have a long line for the exposure button
46
Q

controlled area of radiation

A
  • is the area immediately around the 1* beam in which the radiation dose exceeds permissible limit
  • usually 2 metre radius around 1* beam
  • needs warning signs around it
47
Q

radiation protection adviser

A
  • person who inspects radiography facilities in an area and writes reports on improvements
  • also sets local practice rules
48
Q

radiation protection supervisor

A
  • person in practice
  • responsible for notifying health and safety executive theat radiography is performed at the practice
  • responsible for following local rules
  • looks after dosimeter readings
  • reports radiography problems

POS (13 decks)

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