NASAL AND FACIAL BONES

How should the MSP be positioned for a true lateral facial-bone projection?

Parallel to the IR

Which positioning line should be perpendicular to the IR to prevent head tilt on a lateral facial-bone projection?

IPL

How should the IOML be positioned for a lateral facial-bone projection?

Perpendicular to the front edge of the IR

Where should the CR enter for a lateral facial-bone projection?

Perpendicular to the lateral surface of the zygomatic bone, halfway between the outer canthus and EAM

What evaluation finding helps confirm a true lateral facial-bone position?

The mandibular rami and orbital roofs should be nearly superimposed and the sella turcica should be in profile

A facial-bone image shows the mandibular rami and orbital roofs closely superimposed with the sella turcica in profile. Which projection was most likely performed?

Lateral facial bones

How should the OML be positioned for a parietoacanthial Waters facial-bone projection?

Approximately 37° to the IR

Which positioning line is approximately perpendicular to the IR for a Waters projection?

MML

Where does the CR exit for a Waters facial-bone projection?

At the acanthion

What CR direction is used for a Waters facial-bone projection?

Perpendicular to the IR

Where should the petrous ridges appear on a properly positioned Waters facial-bone image?

Immediately below the maxillary sinuses

Which structures are demonstrated on a Waters facial-bone projection?

Orbits, maxillae, and zygomatic arches

A facial-bone image demonstrates the petrous ridges immediately below the maxillary sinuses. Which projection was most likely performed?

Parietoacanthial Waters

How does the head position for a modified Waters differ from a routine Waters projection?

The neck is extended less, placing the OML approximately 55° to the IR

What CR direction is used for a modified Waters facial-bone projection?

Perpendicular to the IR

Where should the petrous ridges appear on a properly positioned modified Waters image?

Immediately below the inferior orbital borders, about midway through the maxillary sinuses

Which facial-bone projection is especially useful for demonstrating orbital blowout fractures?

Modified Waters

Why is the modified Waters useful for evaluating an orbital blowout fracture?

It places the orbital floor nearly perpendicular to the IR and can show inferior displacement into the maxillary sinus

A facial-bone image shows the petrous ridges midway through the maxillary sinuses just below the inferior orbital margins. Which projection was most likely performed?

Modified Waters

How do Waters and modified Waters differ in OML position?

Waters uses about 37° to the IR; modified Waters uses about 55°

What CR angle is used for a standard PA axial Caldwell facial-bone projection?

15° caudad

How should the OML be positioned for a PA axial Caldwell facial-bone projection?

Perpendicular to the IR

How should the MSP be positioned for a PA axial Caldwell facial-bone projection?

Perpendicular to the IR

Where does the CR exit for a PA axial Caldwell facial-bone projection?

At the nasion

Where should the petrous ridges appear on a properly positioned 15° PA axial Caldwell facial-bone image?

In the lower one-third of the orbits

Which structures are demonstrated on a PA axial Caldwell facial-bone projection?

Orbital rims, maxillae, nasal septum, zygomatic bones, and anterior nasal spine

A facial-bone image demonstrates symmetric petrous ridges in the lower one-third of the orbits. Which projection was most likely performed?

PA axial Caldwell

What CR angle may be used for an exaggerated Caldwell when the orbital rims and floors need greater demonstration?

30° caudad

Where are the petrous ridges projected with a 30° exaggerated Caldwell?

Below the inferior orbital margins

What findings help confirm that a PA axial Caldwell facial-bone image has no rotation?

Equal distances from the lateral skull margins to the lateral orbital margins

How should the MSP be positioned for a lateral nasal-bone projection?

Parallel to the IR or tabletop

Which positioning line should be perpendicular to the IR for a lateral nasal-bone projection?

IPL

How should the IOML be positioned for a lateral nasal-bone projection?

Parallel to the transverse axis of the IR

Why is the mandible supported during a lateral nasal-bone projection?

To help prevent head rotation

Where is the CR centered for a lateral nasal-bone projection?

Perpendicular to the bridge of the nose, approximately 1/2 inch distal to the nasion

Why are both right and left lateral nasal-bone projections commonly obtained?

To compare both nasal bones

What anatomy should be demonstrated on a properly positioned lateral nasal-bone image?

Nasal bones, frontonasal suture, anterior nasal spine, and surrounding soft tissue

What evaluation finding indicates proper lateral nasal-bone positioning?

The nasal bones and surrounding soft tissue should show no rotation

A small-field lateral image is centered 1/2 inch distal to the nasion and demonstrates the nasal bone and surrounding soft tissue. Which projection was most likely performed?

Lateral nasal bones