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COPY BDS3 University of Adelaide Dentistry > Radiography > Flashcards

Radiography Flashcards

1
Q

What are 2 different ways of getting localisation?

A
  1. Two views at right angles to each other

2. Two views at less than 90 degrees to each other (Parallax)

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2
Q

What is the main indication for radiographic localisation

A

Endodontics - mesial shift to view obstructed multiple roots

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3
Q

What is parallax?

A

Displacement of apparent position of an object based on change of position of the point of observation

Rational: hidden objects can be seen from a different vantage point, but actual relationship of the objects hasn’t changed, only the observer’s viewpoint

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4
Q

What are the 2 techniques to accomplish parallax?

A

Horizontal Cone Shift

Vertical Cone Shift

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5
Q

You have an upper 1st molar with two roots. If you move the x-ray beam mesially to the right, what direction does the lingual root move?

A

SLOB rule: Same Lingual, Opposite Buccal

Moving to the right, lingual also moves to the right

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6
Q

You have an upper 1st molar with two roots. If you move the x-ray beam distally to the left, what direction does the buccal root move?

A

SLOB rule: Same Lingual, Opposite Buccal

Moving to the left, buccal moves opposite to the right

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7
Q

For a vertical cone shift there are 2 objects - one buccal and lingual superimposed on the tooth.

If the shift is done superiorly, what direction does the lingual object move on the radiograph

A

The Lingual object appears more superiorly

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8
Q

What is an alternative to Radiographic Localisation?

A

3D imaging using CBCT

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9
Q

Why might you do radiographic localisation when planning an impacted tooth extraction? What sort of localisation would you do?

A

PA/BW won’t tell you how far lingual/buccally placed the tooth is on a 2D image. This would be vitally important so the incision is made on the correct aspect of the dental arch.

You would do localisation 90 degrees to the PA/BW. This would be an occlusal radiograph

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10
Q

In the ADH, which direction does the black side of protective sleeve does the phosphor plate face?

A

The black side of the protective sleeve faces the beam. Otherwise Clinic 1.2 David gets very very angry. This helps in terms of digital orientation

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11
Q

What is the scope of practice for Dentists for OPGs

A

BOH + BDS

  • Exposing Panoramic Images
  • Recognition of Anatomical Structures
  • Recognition of Normal vs Abnormal

BDS Only

  • Prescribing Panoramic Images
  • Diagnosis
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12
Q

What are the contraindications for taking an OPG?

A

Caries Detection
Routine Screening
Young Children

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13
Q

What are the indications for taking an OPG?

A

Bottom line - radiographs only taken when there is an expectation that the diagnostic yield will affect patient care

1. Bony Lesions
2Unerupted Tooth size and positioning
3. Grossly Neglected Mouths
4. Periodontal Bone Assessment (albeit with limitations)
5. Wisdom Teeth assessment prior to surgery
6. Orthodontic Assessment
7. Educational/Motivational Aid
Mandibular Fractures
8. Antral (Maxillary Sinusitis) Disease
9. TMJ Pathology
10. Vertical Alveolar bone height / position of anatomical structures prior to implant planning
11. Full view of pathology
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14
Q

What charge codes need to be entered into Titanium for an OPG?

A

037_ORDERED: during examination
037: When it’s taken
037_VIEWED: your clinical notes as operator what is visible
037_REPORT: summary of radiologist report

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15
Q

Why might you opt to use an OPG over a Full Mouth Survey?

A
  1. When less sharpness is required
  2. Picking up all surrounding structures
  3. When reproduction for series records needed
  4. Picking up asymptomatic symptoms
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16
Q

What are disadvantages of OPGs?

A 
Less Detail 
Superimposition
Patient needs to be very still
Anatomical Variation can make imaging difficult
Equipment more expensive
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17
Q

T/F: You would use a thyroid shield for a pregnant patient when taking an OPG

A

False - the thyroid shield would obstruct the centre of the image. Use a collarless lead apron instead.

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18
Q

What safety measures are needed for operators when taking an OPG?

A

1) Be at least 2m away from the x-ray tube

2) Stand behind the lead shield barrier

19
Q

T/F: A Radiation badge is required for CBCT radiography

A

True, they are not required for OPG or Bitewing radiographs

20
Q

What is the purpose of the secondary vertical slit collimator in an OPG?

A

Progressive moves along the cassette during exposure so that one continuous exposure can be taken onto the film/sensor during the full rotation of the x-ray beam

21
Q

What is the benefit of a Photostimulable Storage Plate (PSP) for an OPG?

A

Reusable plate.

It is able to be retrofitted to non-digital OPG machines.

22
Q

What is the purpose the primary vertical slit collimator on an OPG?

A

Reduce scatter of radiation coming out of the x-ray tube

23
Q

T/F: The movement arc of an OPG is elliptical

A

True, it has 3 centres of rotation to account for the curvature of the mandible and the desired objects of interest within the focal trough

24
Q

What factors could mean that the patient is not positioned within the focal trought

A
  1. Poor Patient Positioning

2. Patient anatomy outside normal range

25
Q

T/F: The medial aspect of the condyle is imaged first on the OPG

A

True

26
Q

Would a structure lying lingual to the trough be reduced or magnified in the image?

A

Magnified - think finger puppets, closer to the light source appears larger on the film

27
Q

Would a structure lying buccal to the trough be reduced or magnified in the image?

A

Reduced- think finger puppets, closer to the film appears smaller on the film

28
Q

How do structures outside the focal trough appear on the OPG?

A

Poorly Defined
Magnified or Narrowed
Distorted in shape
Superimposed

29
Q

How do you ensure good patient position?

A

Machine Head Position
Chin Rest: correct height
Bite-Block: place incisors in the midline
Forehead Rest, Lateral Head supports/Clamps: ensure no movement
Machine laser guide lights

30
Q

How would an OPG appear if the patient is positioned too far forward

A

Image reduced on horizontal plane
Anterior Teeth Narrower
Spine visible

31
Q

How would an OPG appear if the patient is positioned too far backwards

A

Image increased in horizontal plane

Wide Anterior Teeth

32
Q

How would you ensure correct proportions of anteriors for Class II/II occlusion patients on an OPG?

A

Class II: Tell the patient to protrude mandible

Class III: Tell the patient to retrude mandible

33
Q

How would an OPG appear if the patient has rotated their head?

A

Horizontal distortion on both sides:
Side closer to tube: teeth wider, fuzzier
Side closer further from tube: teeth narrower, clearer

34
Q

What is a secondary/ghost image on an OPG?

A

An artefact that exists in front of the centre of rotation (ex earrings)

As it is closer to the tube, it will appear large, blurred, higher and on the opposite side.

35
Q

What is a primary image on an OPG?

A

Occurs when structure lies between centre of rotation and film

36
Q

How do we avoid unnecessary dark images on the OPG?

A

Patient needs to close lips and raise tongue to the roof of their mouth

37
Q

What air spaces are possibly visible on an OPG?

A 
Naso-Pharyngeal Space
Oro-Pharyngeal Space
Palatoglossal Space
Nasal Cavities
Maxillary Sinuses
Mastoid Air Cells
Open Lips
38
Q

What soft tissues are possibly visible on an OPG?

A 
Ear Lobes
Soft Palate
Tongue
Nose
Lips
39
Q

T/F: The rotational speed of an OPG is constant

A

False - the tube has variable speed depending on the distance to the source

40
Q

What are the steps to positioning the patient for an OPG?

A
  1. Raise chin rest to max height
  2. Get patient to enter the unit
  3. Adjust unit height
  4. Tell patient to
    - Stand Straight
    - Grip lower handles
    - Rest Chin on Chin Rest
    - Position feet slightly forward
    - Feet slightly apart for stability
    - Relax Shoulders
  5. Turn on mid-sagittal / horizontal positioning beams: adjust accordingly, get patient to look straight forward
  6. Bite on bite block and adjust for class II/III occlusion
  7. Immobilise heads with support
  8. Ask patient to stay still, swallow, close eyes, place tongue on roof of mouth and keep it there, breathe through nose
41
Q

What are some patient positioning problems that can occur when taking an OPG?

A
  • Midsagittal plane not vertical (Head Tilted)
  • Patient leaning forward (Neck not vertical)
  • Head not centred (Rotated)
  • Frankfurt Horizontal not horizontal (Chin Up/Down)
42
Q

If interpretting an OPG via zones, what is the order to view the image?

A 
Zone 1 - Nose and Sinus
Mandibular Canal, Mental Foramen, Genial Tubercles
Zone 2 - Mandibular Body
Zone 3 - Upper Corners
Condyles, Articular Eminence, Coronoid Notch, Mandibular Notch
Zone 4 - Lower Corners
Thyroid Cartilage
Hyoid Bone
Zone 5 - Mandibular Ramus and spine
Zone 6 - Dentition
43
Q

What terms would you describe an abnormality or pathology on an OPG?

A 
Site
Size
Shape
Border
Centre
Density - Radiolucent, Radiopaque, Mixed
Impact on adjacent structure
44
Q

What is a stafne bone defect?

A

Normal anatomical variant, the void in the mandible is created by ectopic salivary gland tissue associated with the submandibular gland

Not a pathologic lesion

COPY BDS3 University of Adelaide Dentistry (28 decks)

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