Radiology- Skull Views And Anatomy Flashcards
What are the main types of skull radiographs?
Occipitomental
Postero-anterior mandible (PA mandible)
Reverse Towne’s
True lateral skull (similar to lateral ceph except position not standardised)
What is the use of occipitomental radiographs?
Fractures of the midface
What is the use of postero-anterior mandible radiographs?
Fractures of the posterior mandible (excluding condyles)
What is the use of reverse towne’s radiographs?
Fractures of mandibular condyles
What is the reference line used in patient positioning for most skull radiographs?
Orbitomeatal line
From outer canthus of eye to center of external auditory meatus
What are the 2 typical angles of OM radiographs used?
10 degrees and 40 degrees
What are the indications for an OM radiograph?
Middle third fractures
- Le fort I, II and III
- zygomatic complex (including arch)
- nano-ethmoidal complex
- orbital blow out
And coronoid process fractures
How is patient positioned for OM radiograph?
Face towards the receptor
Head tipped back so that orbitomeatal line is at 45 degrees to receptor
The x ray beam can then be 0 degrees (perpendicular to receptor, centered through occiput) or 30 degrees (30degrees above perpendicular centered through lower border of orbit)
What does a PA mandible show?
Posterior part of mandible
What are the indications for PA mandible?
Lesions and fractures involving:
- posterior third of body
- angles
- rami
- low condylar necks
Mandibular hypoplasia/ hyperplasia
Maxilofacial deformities
How is patient positioned for a PA mandible?
Face toward the receptor
Head tipped forward so orbitomeatal line is perpendicular to receptor (and parallel to floor if pt is standing)
X ray beam is perpendicular to receptor and centered through cervical spine at level of rami
What is the x ray beam projected from posterior in OM and PA mandible?
Reduced magnification of the face (as closer to receptor)
- less distortion of relevant structures
Reduced effective dose
- x ray beam attenuated by back of skull before reaching face (radiosensitive tissues eg eyes)
What does a reverse Townes image?
Condylar heads and necks
Similar to PA mandible but different x ray beam and mouth open
What are the indications for reverse Townes?
High fractures of condylar heads
Intracapsular fractures of the TMJ
Condylar hypoplasia/ hyperplasia
How should the patient be positioned for reverse Townes?
Face towards receptor
Head tipped forward so orbitomeatal line is perpendicular to receptor
Mouth open - to move coronoid processes out of glenoid fossa
X ray beam 30 degrees below perpendicular line and centered through condyles
