Skull Radiographic Views & Anatomy

Question 1

What are ‘skull radiographs’?

Answer 1

group of plain radiographs used primarily for assessing maxillofacial trauma

Question 2

What are the main types of skull radiographs?

Answer 2

• occipitomental
• postero-anterior mandible
• reverse Towne’s
• true lateral skull

Question 3

What radiograph is a true lateral skull similar to? How do they differ?

Answer 3

Similar to a Lateral Cephalogram
- true lateral skull positioning is not standardised with a cephalostat

Question 4

What is a occipitomental radiograph typically used for?

Answer 4

assessing fractures of the midface

Question 5

What is a postero-anterior mandible radiograph typically used for?

Answer 5

assessing fractures of posterior mandible (excluding condyles)

Question 6

What is a Reverse Towne’s radiograph typically used for?

Answer 6

assessing fractures of mandibular condyles

Question 7

Why are skull radiographs not typically taken in general dental practise?

Answer 7

Need specialist equipment (specialised skull unit)

Question 8

How can the receptor for skull radiographs be described?

Answer 8

digital & large enough to capture relevant areas (eg entire head including jaws)

Question 9

What reference line is used in patient positioning for most skull radiographs?

Answer 9

Orbitomeatal line

Question 10

What are the landmarks of the orbitomeatal line?

Answer 10

• outer canthus of eye
• centre of external auditory meatus

Question 11

Why is it essential that skull radiographs are aligned with the orbitomeatal line?

Answer 11

So the radiographs are not distorted by other anatomy

Question 12

What is shown on an occipitomental (OM) radiograph?

Answer 12

Facial skeleton, avoiding superimposition of skull base

Question 13

What angles can occipitomental radiographs be taken at??

Answer 13

• 0 degrees
• 10 degrees
• 30 degrees
• 40 degrees

Question 14

If you were evaulating facial trauma with an occipitomental radiograph, what views would you perhaps use?

Answer 14

10 degrees & 40 degrees toegther (2 radiographs)

Question 15

What are some indications for taking an occipitomental radiograph?

Answer 15

Middle third fractures
- Le Fort I, II & III
- Zygomatic complex (including arch)
- Naso-ethmoidal complex
- Orbital blow-out

Coronoid process fractures

Question 16

Describe the patient positioning for an occipitomental radiograph?

Answer 16

• face towards receptor
• head tipped back: obitomeatal line at 45 degrees to receptor
• roughly a nose-chin position

Question 17

If a patient was standing for an occipitomental radiograph, what angle would the orbitomeatal line be to the floor?

Answer 17

45 degrees to floor

Question 18

Where is the x-ray beam positioned in a 0 degree occipitomental radiograph in relation to the receptor?

Answer 18

perpendicular to receptor & centred through occiput

Question 19

Where is the x-ray beam positioned in a 30 degree occipitomental radiograph in relation to the receptor?

Answer 19

30 degrees above perpendicular line to receptor & centred through lower border of orbit

Question 20

What skull radiograph would NOT be appropriate for viewing the facial skeleton? why?

Answer 20

Postero-anterior mandible radiograph
- superimposition of base of skull & nasal bones

Question 21

What is shown on a postero-anterior mandible radiograph?

Answer 21

posterior parts of mandible

Question 22

What are some indications for taking a postero-anterior mandible radiograph?

Answer 22

Lesions & fractures involving:
- posterior third of body
- angles
- rami
- low condylar necks

• mandibular hypo/hyperplasia
• maxillofacial deformities

Question 23

How is the patient positioned for a postero-anterior mandible radiograph?

Answer 23

• face towards receptor
• head tipped forward so that orbitomeatal line is perpendicular to receptor
• ‘forehead-nose’ position

Question 24

How is the x-ray beam angulated for a postero-anterior mandible radiograph?

Answer 24

perpendicular to receptor & centred through cervical spine at level of rami

Question 25

Why is the x-ray beam projected from posterior of head for skull radiographs?

Answer 25

1. reduced magnification of face (since closer to receptor)
   - reduced effective dose (partly attenuated by back of skull b4 reaching face)

Question 26

Projecting the x-ray beam from posterior of skull reduces the effective dose to patient, why is this good?

Answer 26

lower radiation dose to radiosensitive tissues (eg lens of eye) as a result

Question 27

What does a Reverse Towne’s radiograph show?

Answer 27

Condylar heads & neck

Question 28

What are some indications for taking a Reverse Towne’s radiograph?

Answer 28

• high fractures of condylar necks
• intracapsular fractures of TMJ
• condylar hypo/hyperplasia

Question 29

How is the patient positioned for a Reverse Towne’s radiograph?

Answer 29

• face towards receptor
• head tipped forward so that orbitomeatal line is perpendicular to receptor (parallel to floor if pt standing)
• MOUTH OPEN

Question 30

How is the x-ray beam angled in a Reverse Towne’s radiograph?

Answer 30

30 degrees below perpendicular line to receptor & centred through condyles