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BDS4 Radiology > Extra-Oral and Other Plain Views > Flashcards

Extra-Oral and Other Plain Views Flashcards

1
Q

What equipment is required to take an EO radiograph?

A

X-ray tubehead

Cassette - film or digital

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2
Q

What is collimation?

A

Collimation is the control of the size and shape of the X-Ray beam
-> should be as small as possible in line with diagnostic requirement

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3
Q

How is collimation checked?

A

Light beam shows area on patient which will be exposed to primary beam

-> middle of cross is central beam

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4
Q

What are the cassette sizes?

A

18 x 24

24 x 30

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5
Q

What is the minimum speed of the intensifying screen in EO radiography?

A

400

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6
Q

What is the function of the grid?

A

Thin lead strips adjacent to cassette prevent oblique rays disrupting the image
 Attenuates a lot of photons- film dose is increased to allow enough blackening

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7
Q

Which lines are commonly used in EO radiography?

A

Frankfort plane- OPTs/cephs

Orbitomeatal line (OM line)

Interpupillary line

Mid-sagittal plane- down middle of head

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8
Q

Where is the OM line located?

A

centre of EAM to outer canthus of the eye (where upper and lower eyelids come together)

Known as radiographic baseline
-> 10 degrees difference from FP

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9
Q

Where is the Frankfort plane located?

A

Connects orbitale (most inferior infraorbital rim) with porion (superior external auditory meatus)

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10
Q

What are the features of a lateral skull radiograph?

A

Does not include all of the facial bones

Different from lateral ceph as there is no cephalostat (free positioning)

Doesn’t include soft tissues

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11
Q

What are the uses of a Lateral Skull radiograph?

A

Fractures of skull/skull base

Facial fractures to show vertical and anteroposterior displacement (although both sides are superimposed on each other – not widely used)

Skull pathology (e.g. Pagets, myeloma)

Pituitary fossa enlargement

Sphenoid sinus pathology

If CT not available or managable

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12
Q

What is the difference between AP/PA?

A

PA- tube posterior to head and image receptor anterior (AP is opposite)

-> most commonly used for maxillofacial views

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13
Q

Why is PA preferred?

A

Reduced magnification

Dose Reduction- low energy photons entering back of head are attenuated before they reach radiosensitive tissues (e.g. lens, salivary glands)

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14
Q

Where does the beam pass through in the occiptomental view?

A

Beam goes in through occipital region of head then mental region (point of the chin)

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15
Q

What is shown in the occiptomental view?

A

Orbit
Frontal sinus
Maxillary sinus
Zygoma, zygomatic arch
Nasal septum
Coronoid process
Odontoid peg/dens of C2

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16
Q

How is an occiptomental radiograph taken?

A

OM line at 45 degrees to image receptor

Mid-sagittal plane perpendicular to IR

Interpupillary line parallel to floor

X-Ray beam perpendicular to IR centred in midline, level with region of interest

17
Q

What does varying the beam angulation (vertical angle) in occiptomental radiographs achieve?

A

Changes way facial skeleton looks in middle third (can make fractures more obvious)- multiple views are required for diagnosis

18
Q

How do steeper OMV views make the mandible look?

A

Mandible becomes more curved

19
Q

What are the indications for Occipitomental radiographs?

A

Sinus disease - no longer indicated (CT/CBCT)

Maxillary, frontal and ethmoid sinuses

Middle 1/3 facial fractures- zygoma/Le Fort

Coronoid process fracture

20
Q

In what instance would CT be better option for middle face fractures?

A

If there is a suspected brain injury

21
Q

What are le fort fractures?

A

Go across right to left (3 levels- separation of midface from the skull base)

22
Q

What does a posterior mandible radiograph show?

A

Good view- posterior body, angle and ramus of mandible

Superimposition of cervical spine obscures anterior mandible

Superimposition of mastoid process and zygomatic arch obscure condyle

23
Q

How is a posterior mandible radiograph taken?

A

Forehead and nose touch image receptor (OM line is parallel)

Mid-sagittal plane perpendicular to floor and IR, interpupillary line parallel to floor

X-Ray beam perpendicular to IR centred between angles of mandible

24
Q

What are the indications for taking a posterior mandible?

A

Fractures of angle, posterior body and ramus of mandible (medial and lateral displacement)

Cysts/tumours* (same areas of mandible) - medial and lateral expansion/destruction

Facial deformity- if surgery a ceph is preferred

*CBCT preferred

25
Q

What can weaken the mandible and make it more prone to fracture?

A

Unerupted 8s at angle of the mandible

26
Q

What does a Submentovertex view show?

A

Base of skull (including foramina)
Sphenoid sinus
Maxillary sinus
Plan view of mandible, including condyle
Zygomatic arches*

27
Q

Where does the beam pass through in the SMV view?

A

Through chin and out through top of the head

28
Q

What must be checked when taking an SMV radiograph?

A

Patient has no head or neck disease that would prohibit them from tilting head all the way back

-> this has to be done as chest would obscure view otherwise

29
Q

How is an SMV radiograph taken?

A

Extend head and neck as far as possible

Orbitomeatal line parallel to image receptor

Mid-sagittal plane perpendicular to IR and floor

Vertex of head contacts IR

Beam centred between angles of mandible

30
Q

What are the indications for SMV radiographs?

A

Fracture of zygomatic arch

Expansion of more posterior mandible- buccal and lingual cortical plates

Cranial base pathology (now replaced by CT)

31
Q

Why does reducing the exposure factor in SMV radiographs help surgeons with zygomatic arch fractures?

A

Makes everything else become white but allows you to see zygomatic arch (allows surgeon to understand what part exactly needs to be replaced)

32
Q

Which wall of the maxillary sinus in not seen on an OPT

A

Lateral wall (medial wall and posterior are seen)

33
Q

What radiographs are best for looking at anterior wall of maxillary sinus?

A

Lateral

Axial CT/MRI

CBCT

34
Q

What radiographs are best for looking at posterior wall of maxillary sinus?

A

OPT

Lateral

Axial CT/MRI

CBCT

35
Q

What radiographs are best for looking at the medial wall of maxillary sinus?

A

OPT

Occipitomental

Axial + coronal CT/MRI*

CBCT

36
Q

What radiographs are best for looking at the lateral wall of maxillary sinus?

A

Occipitomental

Axial + coronal CT/MRI*

CBCT

BDS4 Radiology (8 decks)

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