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Radiology! > Imaging techniques > Flashcards

Imaging techniques Flashcards

1
Q

how many meters should the controlled area be?

A

1.5-2m

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2
Q

what is the controlled area?

A

the required distance between the operator and the X-ray beam

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3
Q

Why do periapical radiographs?

A
  • assess periodontal problems
  • endodontics
  • trauma/fractures
  • tooth morphology (pre-extraction)
  • evaluation of implants
  • detect apical inflammation/infection (incl cysts)
  • presence/position of un-erupted teeth
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4
Q

what two techniques can you use for a periapical radiograph?

A
  1. paralleling technique

2. bisected angle technique

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5
Q

what is the paralleling technique?

A

the tooth is parallel to the film and the X-ray beam at right angles to the film/tooth using a holder.

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6
Q

what are the 3 benefits of the paralleling technique ?

A
  • reproducible image given
  • accurate geometry
  • minimises magnification
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7
Q

the negative point of using the paralleling technique is..

A

the holder may not be tolerated by the patient as relatively bulky.

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8
Q

when would you carry out the bisected angle technique?

A

if your patient isn’t co-operating and you want to reduce the number of repeat images = reducing the exposure.

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9
Q

benefit of the bisected angle technique?

A

more comfortable for the patient

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10
Q

3 disadvantages of bisected angle technique?

A
  1. operator dependant
  2. not reproducible
  3. easily distorted (foreshortening and elongating)
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11
Q

what are the 3 components of the holder?

A
  1. bite block
  2. indicator arm/rod
  3. aiming ring
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12
Q

for paralleling technique, the horizontal positioning is..

A

horizontal plane of the film must be parallel to the occulsal plane of the teeth being examined.

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13
Q

for paralleling technique, the vertical positioning is..

A

the vertical plane of the film must be parallel to the long axis of the tooth

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14
Q

if the horizontal plane is incorrect then..

A

crossover

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15
Q

if the vertical plane is incorrect then..

A

elongation or foreshortening of the teeth

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16
Q

if the X-ray beam is not at right angles to the teeth/film then you will get…

A

elongation or foreshortening or crossover of the teeth

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17
Q

name the two things affecting image size.

A
  1. the X-ray source (focal spot) to film distance

2. the tooth to film distance

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18
Q

if the tooth to film distance increases then…

A

the magnification will increase.

19
Q

if the X-ray source (focal spot) to film distance increases then…

A

the magnification will decrease

20
Q

the 2 things you need to reduce magnification are…

A
  1. a long X-ray source (focal spot) to film distance

2. a short tooth to film distance

21
Q

Why would you use a bitewing radiograph? 4 points

A
  • detect caries
  • monitor caries progression
  • assess periodontal status
  • asses existing restorations
22
Q

give 4 points about vertical bitewings

A
  • long axis of the tooth and film vertical to one another
  • pre-molars and molars
  • usually need two on each side
  • will show more of the roots (incl bone levels)
23
Q

give 4 points about horizontal bitewings

A
  • long axis of the film and tooth horizontal
  • shows distal of the 4 to medial of the 8
  • usually only need 1 each side
  • will demonstrate crowns and 1/3 of root
24
Q

which technique do you need for bitewings?

A

the paralleling technique (must always se a holder)

25
Q

give the two types of holder you can use for bitewings.

A
  1. rigid plastic holder

2. paper tab

26
Q

when is it difficult to avoid horizontal overlap?

A
  1. crowding

2. tilting

27
Q

a bitewing must show … & … for it to be diagnostically acceptable

A
  1. the ADJ

2. at least half of enamel

28
Q

if the vertical plane in a bitewing is wrong then..

A
  1. separation of cusps (they should be almost fully superimposed upon each other)
29
Q

by what % does a rectangular collimator reduce the dose?

A

50%

30
Q

for adults which size of psp do you use for bitewings?

A

size 2

31
Q

for children over 10 which psp size for bitewings?

A

size 2

32
Q

for children under 10 which size of psp used for bitewing?

A

size 1 or 0

33
Q

what is the size of an occulsal film?

A

5.7 - 7.6cm

34
Q

why would you take an occlusal radiograph? 5 things

A
  • unerupted teeth (bucco-palatal position of 3’s for ortho)
  • supernumerancy teeth
  • cysts and tumour
  • assessment of canine fractures and surrounds alv bone
  • periodical assessment of upper anteriors
35
Q

what technique is used for an occlusal radiograph?

A

modified bisected angle technique

36
Q

the process of taking an occlusal radiograph, 4 points

A
  1. film placed in mouth
  2. head positioned horizontal to occlusal plane
  3. film inserted as far back as patient can tolerate
  4. X-ray beam angled (dependant upon area)
37
Q

name the two types of maxillary occlusal projections.

A
  1. anterior (standard) oblique occlusal

2. lateral oblique occlusal

38
Q

what angulation is use for an anterior oblique occlusal maxilla?

A

65 degrees to occlusal plane (tube at nose)

39
Q

what angulation is used for a literal oblique occlusal maxilla?

A

60-70 degrees to the occlusal plane (tube at cheek)

40
Q

name the 3 types of mandibular occlusal projections

A
  1. true occlusal mandible
  2. anterior (standard) oblique occlusal
  3. lateral oblique occlusal
41
Q

the angulation for a true mandible is?

A

90 degrees to the occlusal plane (pt head tilted back)

42
Q

the angulation for an anterior oblique occlusal mandible is?

A

45 degrees to the occlusal plane (pt sitting straight)

43
Q

the angulation for a lateral oblique occlusal mandible is?

A

45 degrees to the occlusal plane

Radiology! (10 decks)

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