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BDS3 Radiology > review 6 + 7 > Flashcards

review 6 + 7 Flashcards

1
Q

collimation

A
  • Shaping the X-ray beam to radiating less of pt

X-ray beam is circular cross section

  • no collimation large area affected – divergence
  • Only need X ray photons to be hitting small rectangle – exact same size of receptor (approx. 4cm)
    • Any around that is wasn’t – just unnecessarily irradiating the patient
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2
Q

collimation for lateral cephalograms

A

Only need to pass the front of facial bones and small section of cranial base

Need sella turcica in pit fossa

  • Don’t want spine, posterior skull

Want to see angulation of teeth and jaws

  • Traditional – triangular wedge shape instead of cone
    • Top of area is the skull - no longer irradiating
    • Bottom blocks neck and shoulders
    • So only triangle wedge of TMJ, maxilla, mandible, pit fossa
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3
Q

soft tissue collimation in lateral cephalograms

A

Lead filtration collimating beam

  • White line is border of collimation
  • Could be done tighter – still larger area

Usually have another filtration – wavy to follow glabella, nose, chin

  • Aluminium instead of lead (less strong)
    • Some get through
    • Show soft tissue outline in shade of white

Fewer x-ray in area – more attenuation so more likely to see soft tissue

  • Reduce photon intensity in area

Want at source of X-ray to reduce radiation dose to pt

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4
Q

CBCT seen in

A

slices

or as a whole - reconstructed

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5
Q

pathology here

A

Ectopic canine – in midline

  • Is it damaging the teeth crown is butting against

Get more info than from traditional panoramic

  • Root will resorp
  • Crown – enamel more resistant
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6
Q

pro of CBCT slices

A

don’t have superimposition worry

  • as can see exactly whats there
    e. g. sagittal slices, 1mm at a time

Crown of central incisor has root abruptly stopped by ectopic canine crown

  • Significant external root resorption due to crown of canine

2nd to last see same has happened to lateral incisor

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7
Q

radiographs required for parallax

A
  • 2 PAs norm
    • But start with 1 and assess
  • Endo – may need 2 as one root looks short and unable to id which one
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8
Q

parallax example

of extracting max 6

A
  • 3 roots
    • Mesiobuccal, distobuccal and large palatal
  • Can see on 1 PA
  • Assess if straight, curved

If one looks very curvy and unsure what one

  • Get another PA – remove at certain angle
    • Parallax to ID
  • Especially if sectioning
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9
Q

X ray shadow concept

summary

A

Most attenuated – densest – bones – white

No attenuation – went through air – black

Gradient in between

X ray receptor convert different intensities of x ray photons into grey scale

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10
Q

viewing film radiographs

A

need light source (light box)

Ensure consistent level of light coming through

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11
Q

intra oral xray plates

A

3

2 digital

  • Phosphor plate
  • Solid state (wire)

1 film

  • Film
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12
Q

solid state sensor Vs phosphor plate

more durable

A

solid state sensor

as Phosphot plate is a thin rectangle and phosphor crystal layer can be damaged

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13
Q

solid state sensor Vs phosphor plate

sensitive to visible light

A

phosphor plate

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14
Q

solid state sensor Vs phosphor plate

bulkier

A

solid state sensor

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15
Q

solid state sensor Vs phosphor plate

usually wired

A

solid state sensor

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16
Q

solid state sensor Vs phosphor plate

more expensive

A

solid state sensory

more components

but more durable so last longer

17
Q

solid state sensor Vs phosphor plate

require additional scanning stage

A

phosphor plate

18
Q

solid state sensor Vs phosphor plate

storage requires more physical space

A

phophor plate as need more physical ones

whereas solid state sensors single one can be used for whole mouth?

19
Q

solid state sensor Vs phosphor plate

more comfortable for pt

A

phosphor plate as thinner, smaller and no wire

20
Q

digital pros

A
  • Storage less
  • Easily shared
  • No need for chemicals
  • More efficient, less time consuming
  • Can manipulate digitally
  • Hard to lose – back up
21
Q

film pros

A
  • Higher resolution
    • digital imaging size of pixels are determined by manufacturers ability to make pixels in receptor (SS) or scanner (PP)
      • limited (but good enough for dentistry). Whereas film has crystals of black silver – tiny – higher resolution
  • No need for diagnostic level computer monitor
  • Not as bulky (SS) similar to PP
  • Less likely to be misleading – cannot be manipulated
22
Q

issues with film over digital

A

Many things can go wrong in film that can make poor image – unlike digital – consistent (hard to work out which caused issue – need to know before retaking)

23
Q

true or false film radiography

over exposure = lighter image

A

FALSE
be dark

more xrays hitting receptor

24
Q

true or false film radiography

developer solution too warm = dark image

A

TRUE

excited silver halide into black silver particles making darker

25
Q

true or false film radiography

developer solution too concentrated = dark image

A

TRUE

26
Q

true or false film radiography

developer solution too old = dark image

A

FALSE

less effective

not as many silver crystals converted into black silver

27
Q

true or false film radiography

film left in developer solution too ling = dark image

A

TRUE

28
Q

true or false film radiography

inadequate fixation = high contrast image

A

FALSE

white will be grey as inadequately washed away

29
Q

true or false film radiography

film exposed to visible light before processing = light image

A

FALSE
foggy/clouding

30
Q

fixation purpose

A

take black silver particles hardens into black area, unexcited undeveloped area

get rid – wash away

dark areas are darker and light areas are there as unexcited parts washed away

BDS3 Radiology (14 decks)

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