Skull views and anatomy

Question 1

what are skull radiographic views primarily used for

Answer 1

maxillofacial trauma
may be supplemented by CT and CBCT

Question 2

what are the 3 main types of skull radiographs

Answer 2

Reverse townes
occipitomental
Postero-anterior mandible

Question 3

what line is used as a reference for skull radiographs

Answer 3

orbito meatal line
from outer canthus of eye to centre of external auditory meatus

Question 4

what does an occipitomental radiograph show and what may it be used for

Answer 4

shows facial skeleton avoiding superimposition of skull base
taken from behind the patient
mainly used for middle third facial fractures e.g orbital blow out, zygomatic complex fractures

Question 5

describe patient positioning for a occipitomental radiograph

Answer 5

face towards receptor
head tipped back so orbitomeatal line at 45 degrees to receptor
x ray beam can be at different angles (0,10,30,40), 0 would be perpendicular to the receptor

Question 6

how are occipitomental radiographs utilised

Answer 6

typically use two together which are taken from different angles e.g 0 and 30 or 10 and 40

Question 7

what does a postero-anterior mandible radiograph show and what would be the indications for taking one

Answer 7

shows posterior parts of mandible
(not suitable for viewing facial skeleton due to superimposition of base of skull and nasal bones)
indications - lesions and fractures involving posterior body, angle, rami or low condylar necks

Question 8

what is the patient positioning for a postero-anterior mandible radiograph

Answer 8

face towards receptor
forehead and chin touching receptor
orbitomeatal line perpendicular to receptor
x ray beam perpendicular to receptor and centred through centre spine

Question 9

why is the x ray beam projected from a posterior site in postero-anterior mandible radiographs

Answer 9

reduced magnification of face as its closer to the receptor - therefore less distortion
reduced effective dose to radiosensitive tissues as partially attenuated by back of skull before reaching face

Question 10

what does a reverse townes radiograph show and why would it be indicated

Answer 10

shows condylar heads and necks
similar to PA mandible except different angle and patients mouth is open
indications - high fractures of condylar necks, condylar hypo/hyperplasia

Question 11

positioning for a reverse townes radiograph

Answer 11

head tipped forward to orbitomeatal line perpendicular to receptor
forehead and nose to receptor
mouth open
x ray at 30 degrees below perpendicular line to receptor