Extra-oral views + other plain views

Question 1

What do maxillofacial views show

Answer 1

facial bones/skull from either a lateral or an anterior/posterior or a basal perspective (basal is rarely indicated nowadays)

Question 2

What equipment is there

Answer 2

x-ray tubehead
casette with film or digital direct/indirect
grid
special collimator

Question 3

What were cassettes and film previously used with

Answer 3

intensifying screens that have a phosphor layer in them that give out light when x-rays interact with them with a minimum speed of 400

Question 4

What is the grid

Answer 4

The grid is put between the x-ray source and the image receptor to try and cut out x-rays that aren’t approaching the image receptor straight on and instead are approaching obliquely

Question 5

What is the grid made of

Answer 5

thin lead straps adjacent to the cassette

Question 6

What is the function of the grid

Answer 6

o Will reject scattered radiation and transmit a majority of primary radiation and therefore will enhance image quality

Question 7

What does collimation do

Answer 7

control of the size and shape of the X-ray beam

Question 8

Where does collimation occur

Answer 8

at the tubehead

Question 9

What is the frankfurt plane

Answer 9

Connects orbitale (inferior infraorbital rim) with porion (superior border of the external auditory meatus)

Parallel to floor in OPT & cephalometric radiographs

Question 10

What is alatragus line

Answer 10

Tragus of the ear to the alar of the nose

Used for upper oblique occlusal

Question 11

What is the orbitomeatal line

Answer 11

Links central part of external auditory meatus with outer canthus of the eye (where the eyelids come together)

Question 12

By how many degrees does the orbitomeatal line differ from the frankfurt

Answer 12

10 degrees

Question 13

What are teh commonly used radiographic/anatomical planes

Answer 13

• frankfort plane
• alatragus line
• orbitomeatal line
• interpupillary
• midsaggital

Question 14

What does PA or PA refer to

Answer 14

direction of the beam and therefore position of the tube and IR relative to the patient

Question 15

What does PA mean

Answer 15

posteroanterior
tube is posterior and the image receptor is anterior

Question 16

What does AP mean

Answer 16

tube is anterior and image receptor is posterior

Question 17

Are maxillofacial views commonly PA or AP

Answer 17

PA

Question 18

Why are views usually PA

Answer 18

Dose reduction

Question 19

How does PA result in dose reduction

Answer 19

as lower energy photons entering the back of the head are attenuated by the dense bone before they reach radiosensitive tissues such as the lens (salivary glands are also radiosensitive but not much can be done due to their presence in the field of view)

Question 20

How does PA result in reduced magnification

Answer 20

Reduced magnification as the objects closer to the film are magnified less than more distant objects

Question 21

What is a lateral skull view similar to

Answer 21

lateral ceph

Question 22

What makes a lateral ceph different from a lateral skull

Answer 22

lateral ceph has a head in a standard position to make it reproducible and comparable

Question 23

What does a lateral view show

Answer 23

a lateral view of the whole skull as well as facial bones and upper cervical spine

Question 24

How is the px positioned for lateral skull

Answer 24

No cephalostat or wedge for soft tissue profile so free positioning, looking at the planes and lines

No image of the soft tissues

Question 25

What are the indications for lateral skull

Answer 25

o Fractures of skull/skull base
o Facial fractures to show vertical and antero-posterior displacement (although both sides are superimposed on each other)
o Skull pathology e.g pagets/myeloma
o Pituitary fossa enlargement
o Sphenoid sinus

Question 26

What are the indications for lateral skull

Answer 26

o Fractures of skull/skull base
o Facial fractures to show vertical and antero-posterior displacement (although both sides are superimposed on each other)
o Skull pathology e.g pagets/myeloma
o Pituitary fossa enlargement
o Sphenoid sinus

Generally superceded by CBCT

Question 27

What is a occipitomental view

Answer 27

• Beam goes in through occipital region of head and comes through the mental region of the chin

Question 28

What does the occipitomental view show

Answer 28

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

Question 29

How is a occipitomental view taken

Answer 29

o Orbitomeatal line is at 45 degrees to the image receptor (nose chin position)
o Mid saggital plane perpendicular to the image receptor
o Interpupillary line parallel to the floor
o X-ray beam perpendicular to the image receptor centred in the midline, level with the region of interest

Question 30

What does changing the angulation of the x-ray beam alter on occiptomental views

Answer 30

alters the projection of bones onto the radiograph and can give a better view of some areas as it changes the middle third of the facial skeleton on the x-ray e.g may be done to view the zygomatic arch & can also give a different view of displacement if required

Question 31

What are the indications for an occiptomental view

Answer 31

o Sinus disease – however it is no longer indicated, CT or CBCT or MRI can be used instead
o Middle 1/3 fractures (zygoma or le fort (le fort go right to left) –> CT or CBCT more likely to be done over this
o Coronoid process fracture (very rare fracture)

Question 32

What does a PA mandible show

Answer 32

o Good view of posterior body, angle and ramus of mandible
o Superimposition of cervical spine obscures anterior mandible
o Superimposition of mastoid process and zygomatic arch obscure condyle (CBCT better for condyle)

Question 33

How is a PA mandible taken

Answer 33

o Orbitomeatal line perpendicular to image receptor (forehead-nose position)
o Mid-saggital plane perpendicular to floor and IR, interpupillary line parallel to floor
o X-ray beam perpendicular to IR centred between angles of mandible

Question 34

What are the indications for a PA mandible

Answer 34

o Fracture of angle, posterior body and ramus of mandible and lateral displacement (still widely used), may be used with OPG to look for displacement of fracture line
o Cysts/tumours (same areas of mandible) – medial and lateral expansion/destruction
 Superseded by CBCT
o Facial deformity (often then taken in a cephalostat when considering surgery)

Question 35

What is a submentovortex view

Answer 35

• Enters from underneath the chin and comes out at the top of the head

Question 36

What does a submentovortex view show

Answer 36

o Base of the skull (including foramina)
o Sphenoid sinus
o Maxillary sinus
o Plain view of mandible including condyle
o Zygomatic arches  won’t always show as so thin and therefore normal beam is too penetrating so the energy and quantity need to be reduced. Skull is therefore underexposed and so shows up as white

Question 37

What are the indications for a submentovertex view

Answer 37

o Fracture of zygomatic arch
o Expansion of more posterior mandible (if pathology is in the anterior jaw then better seen with a true occlusal)
o Cranial base pathology (now replaced by CT)

Question 38

How is a submentovertex view taken

Answer 38

o Ensure no history of neck injury/disease
o Extend head and neck as far as possible
o Orbitomeatal line parallel to image receptor (IR)
o Mid-saggital plane perpendicular to IR and floor
o Vertex of head contacts IR
o Beam centred between angles of mandible

Question 39

Which view shows the anterior wall of the maxillary sinus

Answer 39

o Lateral
o Axial CT/MRI
o CBCT

Question 40

Which views show the posterior wall of the maxillary sinus

Answer 40

o Panoramic
o Lateral
o Axial CT/MRI
o CBCT

Question 41

Which views show the medial wall of the maxillary sinus

Answer 41

o Panoramic
o Occipitomental
o Axial + coronal CT/MRI
o CBCT

Question 42

Which views show the lateral wall of the maxillary sinus

Answer 42

o Occipitomental
o Axial + coronal CT/MRI
o CBCT