Skull Radiographic Views and Anatomy Flashcards
What are the main types of skull radiograph?
Occiptomental
Postero-anterior mandible (PA mandible)
Reverse Towne’s
True Lateral Skull
What are Occipitomental views for?
Why take 2 views
Fractures of the midface without the superimposition of skull base
Typically use two together to evaluate facial trauma (2 different angles increases chances of spotting a fracture)
What are PA mandible views for?
Primarily for fractures of posterior mandible (excluding condyles)
What are Reverse Towne’s views for?
Primarily for fractures of mandibular condyles
What reference line is used for patient positioning for skull radiographs?
What are the landmarks?
Orbitomeatal line
Outer canthus of the eye, centre of external auditory meatus (from eye to ear- diagonal line)
What are the indications for taking an occipitomental x-ray?
Middle third fractures
–Le Fort I,II & III
–Zygomatic complex (including arch)
–Naso-ethmoidal complex
–Orbital blow-out (pressure in the eye and the orbital contents fracture the floor or walls of the orbit)
Coronoid process fractures
What is the positioning for OM(occipitomental) radiographs?
What about the X-ray beam?
Face towards the receptor
Head tipped back so that orbitomeatal line is at 45 degrees to the receptors
X-ray beam;
–0 degrees OM: Perpendicular to receptor & centred through occiput
–30 degrees OM; 30 degrees above perpendicular line to receptor & centres through lower border of orbit (30 degrees from the horizontal)
What are the indications for a PA mandible?
Lesions & fractures involving posterior third of body, angles, rami and low condylar necks
Mandibular hypoplasia/hyperplasia
Maxillofacial deformities
What is the positioning for PA mandibles?
X-ray beam position?
Face towards receptor
Head tipped forward so that the orbitomeatal line is perpendicular to receptor (¶llel to floor if the patient is standing) - roughly a ‘forehead-nose’ position
X-ray beam position;
– perpendicular to receptor & centres through cervical spine at the level of rami
Why is the X-ray beam projected from the posterior side in PA mandibles?
Reduced magnification of the anatomical structures of the face (since closer to receptor)
–less distortion of relevant structures
–back of skull will be magnified more
–less distance for the x-ray beam to diverge before it hits the receptor
Reduced effective dose to certain structures
–X-ray beam partly attenuated by the back of the skull before reaching the face
–lower radiation dose to radiosensitive tissues (e.g. lens of eye) as a result
What are the indications for a Reverse Townes radiograph?
High fractures of condylar necks
Intracapsular fractures of TMJ
Condylar hypoplasia/hyperplasia
What is the positioning for a Reverse Townes Radiograph?
X-ray beam?
Face towards receptor
Head tipped forward so that orbitomeatal line is perpendicular to the receptor
Mouth open (moves condylar head of out glenoid fossa
X-ray Beam
–30 degrees below perpendicular line to receptor & centred through condyles (less superimposition of the temporal bones)
