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Exam > Radiology > Flashcards

Radiology Flashcards

1
Q

oblique occlusal

A

similar to a large periapical

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2
Q

true occlusal

A

more of a plain view of the floor of the mouth
film packet parallel with the occlusal plane

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3
Q

indications for oblique occlusal radiographs (4)

A
  1. if pathology is too large to be seen on a periapical
  2. if there has been trauma causing fractures to the teeth or alveolus
  3. periapical assessment when periapicals are not possible
  4. localisation using parallax
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4
Q

head position for oblique occlusal

A

mandible - corner of mouth to tragus line should be horizontal & beam centring point should be through lower border of mandible
maxilla - ala-tragus line should be horizontal & beam centring point should be 1cm above ala-tragus line

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5
Q

indications for true occlusal (4)

A
  1. detection of submandibular duct calculi
  2. assessment of bucco-lingual position of unerupted teeth
  3. evaluation of pathological bucco-lingual expansion
  4. horizontal displacement of fractures
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6
Q

true occlusal head position

A

head tipped back as far as possible and x ray beam directed at 90 degree to film in the midline or point of interest

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7
Q

rectangular collimation

A

lead placed around the circular cone to produce a rectangular image to cut down radiation to make it ALARP for practitioner’s safety

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8
Q

paralleling technique

A

for periapicals & bitewings; image receptor & object are parallel but not in contact as x ray beams are never truly parallel so long spacer cone is used to reduce divergence of beam making it more parallel - at least 20cm but 30cm in GDH

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9
Q

size 0

A

used for vertical anteriors

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10
Q

size 2

A

used for horizontal posteriors

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11
Q

bitewing film sizes for kids and adults

A

adults = size 2
kids = size 0

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12
Q

bisecting angle technique

A

for occlusals; image receptor & object partially in contact but not parallel. distance from receptor & object = different at different parts of tooth so x ray beam must be at an angle between perpendicular to the tooth and perpendicular to the film packet to produce an image on the receptor of the correct size

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13
Q

angles used in bisecting angle technique

A

maxilla = molar 60, premolar 55, canine 50, anterior 45
mandible = molar premolar canine 40, anterior 35

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14
Q

radiopaque v radiolucent

A

Radiolucent – Refers to structures that are less dense and permit the x-ray beam to pass through them. Radiolucent structures appear dark or black in the radiographic image e.g. periodontal ligament
Radiopaque - Refers to structures that are dense and resist the passage of x-rays. Radiopaque structures appear light or white in a radiographic image e.g. lamina dura

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15
Q

cervical burnout

A

causes radiolucency at cervical margin mimicking caries
caused by change in volume of structure the x ray beam is going through as at cervical portion of root there is only dentine

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16
Q

circular lesion

A

expanding at same speed in all directions - includes oval shapes

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17
Q

unilocular lesion

A

just a single cavity in the bone

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18
Q

multilocular lesion

A

has a bumpy/scalloped edge - worrying as it is growing irregularly in different directions

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19
Q

irregular lesion

A

very worrying as it may be aggressive

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20
Q

corticated margins

A

thickened cortical bone surrounding the lesion (will appear as a white line) - slow growing

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21
Q

uncorticated margins

A

fast growing so no time to placed thickened layer of bone so is non corticated

22
Q

when discussing lesions what do you say

A

site / size / shape / margins / provisional or differential diagnosis
e.g. approx 1cm, well defined cortical margins, related to apices of 25 and maybe 26, provisional diagnosis of cystic lesion or maybe remnant pathology from previous cyst

23
Q

limitations of panoramic radiography (4)

A
  • width of layers so what we are looking for may be omitted e.g. anteriors
  • long exposure time ptx struggles to stay still etc
  • positioning difficulties with ptx of atypical occlusions i.e. class II & III, elderly, obese
  • if too close to beam the image will be magnified horizontally and further away shorted vertically
24
Q

true lateral cephalogram

A

film and mid sagittal plane will be parallel and x ray beam will be perpendicular to both

25
Q

lateral oblique

A

film and mid sagittal plane will not be parallel and the x ray beam is not perpendicular

26
Q

what collimation is used on lateral cephalograms

A

triangular collimation

27
Q

positioning for lateral cephalogram

A

ptx position with frankfurt plane horizontal then MSP should be vertical and parallel to cassette, teeth should be in centric occlusion, ear rods in external acoustic meatus and nasion support may be necessary, thyroid collar should be placed on ptx and x ray beam will travel centred through ear rods from right to left

28
Q

positioning for lateral oblique

A

cassette held by ptx next to side of head and region of interest, head then rotated so region of interest is parallel to cassette, chin raised and tilted to cassette
for mandible beam should be placed below aiming at area of interest and to get upper and lower teeth bimolar technique should be used

29
Q

bimolar technique

A

an oblique lateral view only with the upper and lower teeth on the same film. right & left sides may also be incorporated onto same film too using lead shielding
when bitewings not practical these are indicated
positioned same as for oblique lateral

30
Q

Frankfort plane

A

connects inferior infraorbital rim with porion (superior external auditory meatus)
should be parallel in lateral cephs and panoramics

31
Q

orbitomeatal line

A

links central part of the external auditory meatus with outer canthus of eye - differs from frankfort plane by 10 degrees

32
Q

interpupillary line

A

joins the 2 pupils and when ptx is seated this should be parallel to the floor

33
Q

mid sagittal plane

A

passes through centre of the head and face - in seated / standing position it should be parallel to the floor

34
Q

PA mandible indications

A

posterior anterior of mandible
1. fracture of angle/posterior body/ramus - taken with OPT & used to see medial / lateral displacement
2. cysts / tumours of angle, posterior body, ramus - for medial / lateral expansion or destruction
3. facial deformity - often taken in a cephalostat

35
Q

positioning of PA mandible

A

‘nose forehead’ position
nose & forehead often touching image receptor. orbitomeatal line will be perpendicular to image receptor, mid sagittal plane perpendicular to floor & image receptor, x ray beam perpendicular to image receptor and will be angled between angles of mandible

36
Q

to view entirety of maxillary sinus

A

CBCT

37
Q

when do you need radiographic localisation

A
  • unerupted tooth position
  • location of root canals
  • relationship to pathological lesions
  • trauma
  • pocket depths
  • soft tissue swellings
38
Q

localisation at right angles

A

take 2 views at right angles to work out position e.g.
- periapical & mandibular true occlusal
- panoramic & lower true occlusal
- paralleling periapical & lower true occlusal
- lateral / PA cephs & CBCT

39
Q

localisation not at right angles

A

when there is a stable reference point but horizontal / vertical tube shift will move rest of image e.g. parallax

40
Q

parallax

A

apparent change in position of object caused by a real change in position of observer
the further back the object the more it will move with the observer
my PAL goes with me i.e. if palatal it moves with & buccal it moves away

41
Q

indications for CBCT

A

impact planning, impacted teeth, pathology, orthognathic surgery, hypodontia, cleft palate & bone defects, dental abnormalities, endo problems & autotransplantation

42
Q

guidelines on CBCT

A

SEDENTEXCT
EADMFR - use only when question cannot be answered with lower dose method, use smallest volume compatible with clinical situation & choose resolution compatible

43
Q

quality of radiograph

A
  1. excellent - no errors in ptx prep, exposure positioning or film handling
  2. diagnostically acceptable - some of the above errors do not distract from diagnostic utility
  3. unacceptable - errors make film diagnostically unacceptable so needs to be retaken
44
Q

4 official legal personnel names in radiography

A

employer
referrer
practitioner
operator
in practice dentist may be all of these

45
Q

employer

A

may be the hospital board / principal GDP - responsibilities include setting up standard operating and quality assurance procedures

46
Q

referrer

A

individual requesting the radiograph & required to give following info to practitioner:
- info to enable IRMER practitioner to justify examination
- unique ID of ptx
- clinical info to justify exposure
- info on pregnancy
- unique identifying signature

47
Q

practitioner

A

IRMER practitioner so qualified & follow these standards, responsible for confirming justification & authorising & ensure dose is ALARP

48
Q

operator

A

entitled to carry out practical aspects of radiographic exposure
can take radiograph once practitioner has justified exposure & will evaluate images

49
Q

clinical evaluation report

A

must be undertaken as a legal requirement after each radiograph taken by dentist

50
Q

3 characteristics of a ghost image

A
  1. Always on opposite side of radiograph
  2. Always magnified
  3. Always higher to compensate for curve of Monson
51
Q

to reduce scatter of x rays

A
  1. increasing focal to skin distance
  2. collimation which lowers area irradiated
  3. lead foil included within film packet to prevent back scatter of photons
52
Q

optimisation to reduce dose of radiograph

A
  1. use e speed film or faster where possible
  2. use kV rang of 60-70kV
  3. focus to skin distance of 200mm or greater
  4. rectangular collimation should be adopted for bitewing and PA radiographs
  5. use film holders for bitewings & PA

Exam (14 decks)

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