Radiographic techniques Flashcards
(49 cards)
1
Q
What affects the quality of a radiographic image?
A
- the relationship of the x-ray source, object and receptor
2
Q
What are the 3 intra oral radiographs?
A
- peri-apical
- bitewing: horizontal and vertical
- occlusal: maxilla and mandible
3
Q
what are the 5 most common extra oral radiographs?
A
- Dental panoramic tomogram (DPT)
- Lateral cephalogram
- Posterio-anterior mandible
- lateral oblique mandible
- occipto-mental views of facial bone
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
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
6
Q
what is occlusal radiograph?
A
- maxillary occlusal: shows anterior part of maxilla and teeth
- Submandibular occlusal: shows: shows floor of mouth and mandibular teeth
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
8
Q
What is an advantage and disadvantage of a DPT?
A
- adv: tolerable by patients
- disadvantage: body shape can man positioning difficult
8
Q
What is an advantage and disadvantage of a DPT?
A
- adv: tolerable by patients
- disadvantage: body shape can man positioning difficult
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
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
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
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
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)
14
Q
What affects the details shown in an image?
A
- how close the receptor is to the image
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
16
Q
What are the two most important radipgrahic techniques?
A
- paralleling technique
- bisected angle technique
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
18
Q
which technique is the technique of choice ?
A
- paralleling
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
what is computed radiology?
- When the type of receptor used is a phosphor plate, this is processed, erased and reused
25
what is digital radiology?
- conventional film with chemical processing
26
The relationship of receptor to tooth affects final image, describe the position of receptor in relation to the tooth.
- 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
if an image produced has elongated roots, what is the issue with the technique?
- The receptor and tooth are not parallel vertically
28
if teeth appear overlapped, what is the problem with technique?
- the horizontal plane of film is not parallel to dental arch (difficult around 3 and 4's due to bending of arch)
29
another variable affecting image geometry is direction of X-ray beam to receptor an teeth. what must the position of beam be in?
- beam must be perpendicular to receptor and tooth
30
what mistake in the position of x-ray beam causes elongation of teeth in the image?
- the x-ray beam is angled too much upwards
31
what mistake in the position of x-ray beam cause foreshortening of teeth in the image? (makes them look short and stubby)
- x-ray beam positioned too downwards
32
what affects horizontal angulation of x-ray beam and what mistake occurs in the final image?
- 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
what do we mean by magnification in radiology?
- how much larger the size of object under investigation is compared to the object's size in real life
34
what two factors affect image size (magnification)?
1. the distance of the x-ray source to the receptor
| 2. the distance between receptor and object
35
The source to object distance must be long, explain why?
- 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
the receptor to object distance must be short, explain why?
- it reduces the time the beam has to diverge and magnify the image after passing through the image.
37
what should the image receptor orientation be for posterior teeth and anterior teeth?
- film should be landscape for posterior teeth and horizontal bitewings
- portrait for anterior teeth and vertical bitewings
38
what causes cone cutting as shown in image ?
- caused when the corners of collimator haven't touched guiding ring and absorbed radiation, preventing receptor being exposed and forming the image
39
what are some barriers to good position of x-ray?
- mouth size
- gag reflec
- film size
- digital sensor shape and size
- patient in pain etc.
40
what are the 4 most common receptor sizes?
- 0, 1, 2 and 4
41
what size do we use for anterior teeth in adults ? (periapical)
- size 0 or 1
| - can use size 2 for bisected angle technique
42
what size do we use for posterior teeth in adults ? (periapical)
- always size 2
43
what size do we use for children anterior teeth? (periapical)
- size 0
44
what size do we use for children's deciduous posterior teeth? (periapical)
- size 0
45
what size do we use for children posterior permanent teeth? (periapical)
- size 2
46
What size do we use for horizontal and vertical bitewings in adults?
- 2 only
47
what size do we use for horizontal and vertical bitewings in children?
- children under 10: 0 or 1
| - children over 10: size 2
48
why is there a dot/ small circle on radiographs? where should this dot be positioned?
- 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
