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KCS: Theme 8 > Intro to Radiology > Flashcards

Intro to Radiology Flashcards

1
Q

Radiographs have similar properties to … but …

A
  • shadows made by light
  • the rays also pass through object to varying degrees
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2
Q

Principles of shadow casting

A
  • radiation source small as possible
  • source-object distance large
  • object-film distance small
  • object and film parallel
  • x-ray beam perpendicular to object/film
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3
Q

Define ‘resolution/sharpness’

A

measures how well the details (boundaries/edges) of an object are reproduced

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4
Q

What does a line pair gauge do?

A

measures sharpness/resolution

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5
Q

4 types of un-sharpness

A
  • movement
  • geometric
  • photographic (if using film)
  • pixel size
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6
Q

What is geometric unsharpness?

A
  • zone of unsharpness along the edge of images in a radiograph
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7
Q

How are magnification and resolution linked?

A
  • source to object distance (the greater, the less divergence of the beam, so less magnification)
  • object to film distance (the greater, the more magnification)
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8
Q

Decreasing the focal spot size increases …

A

sharpness

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9
Q

Increasing the traget-teeth distance increases what?

A

sharpness

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10
Q

2 things that increase sharpness

A
  • decrease focal spot size
  • increase target-teeth distance
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11
Q

Explain photographic unsharpness

A
  • E-speed is normal
  • F-speed show larger crystals and more unsharp image
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12
Q

You may see … due to angulation

A

distortion

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13
Q

How should intra-oral radiography be done for ideal images?

A
  • image recorder absolutely flat
  • film parallel to long axis of object (tooth)
  • recorder as close as possible
  • central of x-ray beam should be perpendicular to both object and film
  • distance between x-ray source and object should be large with small object film distance
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14
Q

If the placement of the radiograph is wrong, correction?

A
  • place receptor according to placement guidelines
  • to cover all structures
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15
Q

If the foreshortening of the radiograph is wrong, correction?

A

decrease vertical angulation of x-ray beam

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16
Q

If the elongation of the radiograph is wrong, correction?

A

increase vertical angulation of PID

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17
Q

If the overlappingof the radiograph is wrong, correction?

A

direct x-rays between contacts of the teeth

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18
Q

If the cone-cutting of the radiograph is wrong, correction?

A

center x-ray beam over the image receptor

19
Q

If the underexposure of the radiograph is wrong, correction?

A

increase exposure factors - check for large patient size

20
Q

What’s the paralleling technique?

A
  • film palced in holder and positioned parallel to long axis of the tooth
  • x-ray beam is aimed at right angles to tooth and film
  • by using a holder the technique is reproducible
21
Q

Explain the bisected angle technique

A
  • film placed as close to the tooth as possible without bending
  • angle between long axis of tooth and film is assessed and bisected
  • beam is aimed at right angles to this bisected line
22
Q

Advantages of the paralleling and bisected techniques

A
  • sharper, less distorted images
  • correct centring of image on film
  • easier to do - less guesswork
  • reproducible
23
Q

Disadvantages of paralleling and bisected angle technique

A
  • difficult or impossible if palate low or floor of mouth shallow
  • can be difficult is using rubber dam clips as in endodontics
24
Q

How to make imaging reproducible?

A
  • film holder with putty matrix attached is the same everytime
  • dismantle from holder and leave putty with bite block for further imaging (same beam angulation next time)
25
Q

Uses of bitewings

A
  • caries in posterior teeth
  • deficient/leaky restorations
  • poor contoured restorations
  • calculus
  • early periodontal bone loss
26
Q

Role of bitewing holders

A
  • improve centring
  • reduces overlapped teeth
  • serial radiographs comparable
27
Q

Bitewing technique

A
  • beam is aimed at right angles to the film and through the interproximal space
  • to prevent overlap
28
Q

Vertical bite wing uses

A
  • useful for demonstrating mild to moderate alveolar bone loss
  • if probe depth is less than 6mm
29
Q

Features seen in occlusal radiography

A
  • maxillary projections
  • mandibular projections
30
Q

Types of maxillary projections

A
  • upper standard occlusal
  • upper oblique occlusal
  • vertex occlusal
31
Q

Types of mandibular projections

A
  • lower 90 degree view (true)
  • low 45 degree view (standard)
  • lower oblique occlusal
32
Q

Uses of upper standard maxillary occlusal radiographs

A
  • periapical assessment of upper anterior teeth
  • presence of unerupted canines, supernumeries
  • for parallax in conjunction with DPR
  • size of cysts/tumours
  • assessment of alveolar fractures
33
Q

What can upper oblique maxillary occlusal show that standard occlusal can’t?

A
  • shows premolar and molar areas
34
Q

Uses of vertex occlusal radiographs
Problem

A
  • similar to standard view
  • but gives plan view of palate - will show buccal/lingual position of unerupted canines
  • not recommended due to beam passing through patient
35
Q

Uses of lower 90 degree mandibular occlusal radiographs

A
  • detection of submandibular calculi
  • assessment of bucco-lingual position of mandibular teeth
  • evaluation of bucco-lingual cortical expansion
  • assessment of mandibular fractures
36
Q

What do lower 45 degree mandibular occlusal radiographs show that true lowers don’t?

A
  • periapical view of lower anterior teeth
37
Q

Use 60KVp on radiograph when …

A

looking for foreign bodies in soft tissues

38
Q

The lower the KVp the increased …

A

contrast

39
Q

What is a dental panoramic radiograph?

A
  • called a tomograph - a slice through the jaws for example
  • gives excellent overview of anatomy of maxilla and mandible
40
Q

Other names for dental panoramic tomogram/DPT

A
  • OPG (orthopantomograph)
  • panoramic
41
Q

Uses of dental panoramic tomographs

A
  • evaluations of periodontal/orthodontic status
  • trauma
  • caries assessment (but not ideal)
  • assessment of third molar position related to ID canals
  • assessment for tumours in jaws
  • TMJ outline (not ideal)
42
Q

What can you do to reduce radiation in radiographs?

A
  • not picture and remove centre sextants
43
Q

When would you do a lateral cephalogram?

A

orthodontic assessment

KCS: Theme 8 (4 decks)

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