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Radiology module 3 > Radiographic techniques > Flashcards

Radiographic techniques Flashcards

1
Q

What affects the quality of a radiographic image?

A
  • the relationship of the x-ray source, object and receptor
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2
Q

What are the 3 intra oral radiographs?

A
  • peri-apical
  • bitewing: horizontal and vertical
  • occlusal: maxilla and mandible
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3
Q

what are the 5 most common extra oral radiographs?

A
  1. Dental panoramic tomogram (DPT)
  2. Lateral cephalogram
  3. Posterio-anterior mandible
  4. lateral oblique mandible
  5. occipto-mental views of facial bone
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4
Q

What os a peri-apical radiograph?

A
  • x-ray shows from the crown of tooth to the root and surrounding bone, also shows between teeth
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5
Q

what is a horizontal and vertical bitewing radiograph?

A
  • horizontal bitewing: shows crown of tooth and bone levels, doesn’t show entire root
    - aim to see from distal edge of 4 to medial edge of 8 - approx. 3 teeth
  • vertical bitewing: shows crown of tooth and more bone but not entire root
  • good for identifying inter proximal caries and alveolar bone crest
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6
Q

what is occlusal radiograph?

A
  1. maxillary occlusal: shows anterior part of maxilla and teeth
  2. Submandibular occlusal: shows: shows floor of mouth and mandibular teeth
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7
Q

What is a DPT radiograph? what are other alternative names for a DPT?

A
  • X-ray tube rotates around the patient’s head with a constant long exposure of 14 seconds forming a panoramic view image of teeth and supporting structure.
  • OPT/ OPG: orthopantomography
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8
Q

What is an advantage and disadvantage of a DPT?

A
  • adv: tolerable by patients

- disadvantage: body shape can man positioning difficult

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8
Q

What is an advantage and disadvantage of a DPT?

A
  • adv: tolerable by patients

- disadvantage: body shape can man positioning difficult

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9
Q

What is a lateral cephalogram? When is it commonly used?

A
  • radiograph taken from a lateral side of the head, used to show the relationship between teeth to the jaws and the mandible to the rest of the facial skeleton - orthodontists
  • Image also shows the soft tissue pattern of the nose and lips - useful in surgical planning
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10
Q

what is a postero-anterior mandible view? what is it useful for? Why is it key to take two views at right angle to each other in fractures?

A
  • PA mandible is used to show fracture of mandible (must be used alongside DPT)
  • To show full extent of fracture: must take two views at right angle to each other
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11
Q

What is a lateral oblique mandible?

A
  • view taken of mandible and maxilla from the side
  • commonly used for children in hospital that can’t tolerate bitewing
  • can be used for mandibular fracture if DPT not available
  • useful in showing the buccal teeth both erupted and unerupted
  • useful in showing position of unerupted third molars
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12
Q

what is occipto-mental views of facial bones?

A
  • OM views of face most. commonly done as first form of diagnosis when patients report facial trauma in A&E
  • shows fractures of orbits, maxilla and zygomatic arches
  • two views taken: first beam is angled at 10 degrees and second beam angled 30 degrees
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13
Q

why is it useful to take OM radiographs whilst standing?

A
  • helps show fluid levels in the antra (cavity e.g. maxillary sinus)
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14
Q

What affects the details shown in an image?

A
  • how close the receptor is to the image
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15
Q

What are the main clinical indications for use of peri-apical radiographs?

A
  • detection of apical infection or inflammation
  • detailed evaluation of apical cysts and other lesions within the bone
  • assessment of periodontal status - bone resorption
  • after trauma to the teeth and associated bone
  • assessment of root morphology before extraction
  • assessment of presence and position of unerupted teeth
  • during Endodontics
  • pre-operative assessment and post-operative appraisal of apical surgery
  • evaluation of implants postoperatively
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16
Q

What are the two most important radipgrahic techniques?

A
  • paralleling technique

- bisected angle technique

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17
Q

What is the difference between the two techniques: paralleling and bisected angle technique?

A

Paralleling

  • uses a holder to facilitate the positioning
  • the holder keeps receptor parallel to the tooth and x-ray beam
  • an accurate reproducible image

bisected angle

  • can be done without holder, making it easier for patient
  • technique is operator dependent so each Time it will be done slightly different meaning image is not reproducible
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18
Q

which technique is the technique of choice ?

A
  • paralleling
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19
Q

Describe the position of the holder in relation to the teeth and x-ray source in paralleling technique.

A
  • Receptor parallel to the tooth

- x-ray beam is perpendicular to tooth/receptor

20
Q

explain why a holder is useful in paralleling technique.

A
  • it minimises magnification of object to the film so gives an accurate reproducible image
21
Q

what is the downside of the paralleling technique

A
  • holder is bulky and patient may not tolerate it
22
Q

we have different types of holders, what are the 3 main components of every holder?

A
  • a bite block - keeps receptor in place
  • a metal arm/rod - fits into the bite block
  • locator ring - slides onto the metal arm, allows the collimator to align with receptor
23
Q

In DDH, the holder used has 4 colors: blue, yellow, red and green. what are they each for?

A
  • Blue: anterior teeth
  • Yellow: posterior teeth
  • Red: bitewings
  • Green: Endodontics procedures
24
Q

what is computed radiology?

A
  • When the type of receptor used is a phosphor plate, this is processed, erased and reused
25
Q

what is digital radiology?

A
  • conventional film with chemical processing
26
Q

The relationship of receptor to tooth affects final image, describe the position of receptor in relation to the tooth.

A
  • the vertical plane of the film should be parallel to long axis of the tooth
  • horizontal plane of film must be parallel to dental arch
27
Q

if an image produced has elongated roots, what is the issue with the technique?

A
  • The receptor and tooth are not parallel vertically
28
Q

if teeth appear overlapped, what is the problem with technique?

A
  • the horizontal plane of film is not parallel to dental arch (difficult around 3 and 4’s due to bending of arch)
29
Q

another variable affecting image geometry is direction of X-ray beam to receptor an teeth. what must the position of beam be in?

A
  • beam must be perpendicular to receptor and tooth
30
Q

what mistake in the position of x-ray beam causes elongation of teeth in the image?

A
  • the x-ray beam is angled too much upwards
31
Q

what mistake in the position of x-ray beam cause foreshortening of teeth in the image? (makes them look short and stubby)

A
  • x-ray beam positioned too downwards
32
Q

what affects horizontal angulation of x-ray beam and what mistake occurs in the final image?

A
  • the ring must fit in the correct position on metal arm
  • the beam has a rectangle collimator that must fit the ring
  • this ensures the beam is in the correct position horizontally
  • if beam position horizontal is wrong, it will make the teeth overlapped in the image
33
Q

what do we mean by magnification in radiology?

A
  • how much larger the size of object under investigation is compared to the object’s size in real life
34
Q

what two factors affect image size (magnification)?

A
  1. the distance of the x-ray source to the receptor

2. the distance between receptor and object

35
Q

The source to object distance must be long, explain why?

A
  • x-ray beam spreads out in all directions and continues to spread as it passes through the object and makes the object appear larger on receptor
  • increasing distance between source and object ensures the beam diverges less and image is more accurate in size
36
Q

the receptor to object distance must be short, explain why?

A
  • it reduces the time the beam has to diverge and magnify the image after passing through the image.
37
Q

what should the image receptor orientation be for posterior teeth and anterior teeth?

A
  • film should be landscape for posterior teeth and horizontal bitewings
  • portrait for anterior teeth and vertical bitewings
38
Q

what causes cone cutting as shown in image ?

A
  • caused when the corners of collimator haven’t touched guiding ring and absorbed radiation, preventing receptor being exposed and forming the image
39
Q

what are some barriers to good position of x-ray?

A
  • mouth size
  • gag reflec
  • film size
  • digital sensor shape and size
  • patient in pain etc.
40
Q

what are the 4 most common receptor sizes?

A
  • 0, 1, 2 and 4
41
Q

what size do we use for anterior teeth in adults ? (periapical)

A
  • size 0 or 1

- can use size 2 for bisected angle technique

42
Q

what size do we use for posterior teeth in adults ? (periapical)

A
  • always size 2
43
Q

what size do we use for children anterior teeth? (periapical)

A
  • size 0
44
Q

what size do we use for children’s deciduous posterior teeth? (periapical)

A
  • size 0
45
Q

what size do we use for children posterior permanent teeth? (periapical)

A
  • size 2
46
Q

What size do we use for horizontal and vertical bitewings in adults?

A
  • 2 only
47
Q

what size do we use for horizontal and vertical bitewings in children?

A
  • children under 10: 0 or 1

- children over 10: size 2

48
Q

why is there a dot/ small circle on radiographs? where should this dot be positioned?

A
  • the receptor has a radiopaque mark which should always be positioned to the crown of the tooth
  • it indicates whether image is right or left
  • on bitewing, dot should always be placed next to the palate

Radiology module 3 (2 decks)

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