Radiography of the facial bones and sinuses

Question 1

Sinus projections

Answer 1

Occipitomental (waters/OM)
Occipitofrontal 20 (Caldwell’s/OF 20)
Lateral

Question 2

Facial bone projections

Answer 2

Occipitomental (waters/OM)
Occipitomental 30 (waters axial/OM 30)
Occipitofrontal 20 (Caldwell’s/OF 20
Lateral)

Question 3

Occipitomental (waters) purpose:

Answer 3

To demonstrate the upper and middle thirds of the face, including the orbital margins, frontal sinuses, zygomatic arches, maxillary sinuses

Question 4

Occipitomental (waters) angulation/head tilt:

Answer 4

RBL should be 45 to the image receptor. Correct angulation indicated by petrous ridges being displayed in the inferior aspect of maxillary sinus

Chin lifted too far up/RBL greater than 45 to IR: Alveolar processes projected into the maxillary sinus

Chin dipped too far down/RBL less than 45 to IR: Petrous ridges creep into the maxillary sinus

Question 5

Occipitofrontal 20 (Caldwell’s) difference between skull and sinuses

Answer 5

In radiography of skull, we angle the tube 20 degrees, but in radiography of sinuses we can not use angles (looking at fluid levels). To compensate, we angle the RBL 20 degrees up and use HB. Head is in quite a neutral position

Question 6

Occipitofrontal 20 (Caldwell’s) purpose

Answer 6

To better visualise frontal bones and facial features

Question 7

Occipitofrontal 20 (Caldwell’s) angulation:

Answer 7

RBL to CR angle more than 20/chin too far up: Petrous ridges below infraorbital margin

RBL to CR angle less than 20/chin too far down: Petrous ridges above inferior orbital margin.

Question 8

Lateral purpose:

Answer 8

To demonstrate all sinus groups, especially sphenoid sinus.

Question 9

Lateral tilt:

Answer 9

Orbital roofs should be superimposed –> to correct make sure that inter-pupillary line is perpendicular to IR.

Question 10

Lateral rotation:

Answer 10

If there is rotation, anterior cranial cortices and greater sphenoid wings are not superimposed –> to correct ensure that the MSP is parallel with IR

Question 11

Occipitomental 30 (waters axial) purpose:

Answer 11

To demonstrate zygomatic arches & walls pf maxillary sinus

Question 12

Sinusitis

Answer 12

• Look at air fluid levels
• Air cavities SHOULD appear radiolucent in healthy sinus
• patient must be erect

Question 13

Maxillary tumour

Answer 13

Increased density in maxillary sinus (tumour can spread and damage infraorbital margin)

Question 14

Polyps

Answer 14

Masses which arise from mucosal membranes of nose and paranasal sinuses

Question 15

Black eyebrow sign/orbital emphysema:

Answer 15

• Emphysema: collection of pockets of air within soft tissue
• these air pockets are visible on x-ray
• look for orbital fractures too

Question 16

Blowout fracture

Answer 16

Occurs when there is direct impact towards orbit, the force transmission fractures the floor of the orbit

Question 17

Tripod fractrue

Answer 17

Fracture: through maxillary sinus wall, floor of orbit, and zygomatic arch

Question 18

Lefort 2 fracture

Answer 18

Fracture line which goes through: medial orbital walls, lacrimal bones, lateral aspect of maxillary antra.