Ch. 11 Workbook (Nasal, Orbits, Mandible, TMJ)

Which structure of the sphenoid bone allows for the passage of the optic nerve and is the actual opening into the orbit?

Optic foramen

Identify the three foramina found within the orbits.

• Optic foramen

• Superior orbital fissure

• Inferior orbital fissure

Small section of bone within the orbits.

Sphenoid strut

From anterior to posterior, the cone-shaped orbits project upward at an angle of __ degrees and toward the midsagittal plane at an angle of __ degrees.

30, 37 degrees

Bilateral horizontal fractures of the maxillae describe a _______ fracture.

Le Fort

What is the name of the fracture that results from a direct blow to the orbit leading to a disruption of the inferior orbital margin?

Blow-out fracture

A “free-floating” zygomatic bone is the frequent result of a ______ fracture.

Tripod

True/False: Lateral projections for nasal bones generally are taken bilaterally for comparison.

True

The three aspects of the face that should be in contact with the head unit or tabletop when beginning positioning for the parieto-orbital oblique projection are the ______, ______ and _____. The final angle between the midsagittal plane and the IR should be _______, with the _______ line perpendicular to the IR. This places the optic foramen in the _____ quadrant of the orbit.

• Cheek, nose, chin

• 53 degrees

• Acanthiomeatal

• Lower outer

Floor of orbits (blowout fractures)

Modified Waters method

Optic foramen

Parieto-orbital oblique projection

Profile image of nasal bones and nasal septum

Lateral (nasal bones)

Inferior orbital rim, maxillae, nasal septum, nasal spine, zygomatic bone, and arches

Parietoacanthial projection

True/False: The PA axial projection of the mandible produces an elongated view of the condyloid processes.

True

Which projection of the mandible projects the opposite half of the mandible away from the side of interest?

Axiolateral oblique

What must be done to prevent the ramus of the mandible from being superimposed over the cervical spine with an axiolateral oblique projection of the mandible?

Extend the chin

What is the maximum CR angle needed for all of these projections?

(Body of the mandible, Mentum region, Ramus region, General survey of the mandible)

25 degrees cephalad

What specific positioning error has been committed if both sides of the mandible are superimposed with an axiolateral oblique projection?

Insufficient cephalic CR angle or skull tilt

Where should the CR exit for a PA axial projection of the mandible?

Acanthion (at lips for PA projection)

Which cranial positioning line is placed perpendicular to the IR for a PA or PA axial projection of the mandible?

OML

True/False: For a true PA projection of the mandibular body (if this is the area of interest), the AML should be perpendicular to the IR.

True

True/False: The CR should be angled 20° to 25° caudad for the PA axial projection of the mandible.

False, change to cephalad

Which aspect of the mandible is best visualized with an AP axial projection?

Condyloid process

What CR angle is required for the AP axial projection of the mandible if the OML is placed perpendicular to the IR?

35° caudad

What CR angle is required for the AP axial projection of the mandible if the IOML is placed perpendicular to the IR?

42° caudad

Where is the CR centered for an AP axial projection of the mandible?

1 inch (2.5 cm) superior to glabella

Which projection of the mandible demonstrates the entire mandible, including the coronoid and condyloid processes?

SMV

True/False: The modified Law method provides a bilateral and functional study of the TMJ.

True

True/False: The mandibular condyles move anteriorly as the mouth is opened.

True

Which projection/method of the TMJ requires that the skull be kept in a true lateral position?

Schuller

The axiolateral (Schuller method) projection for the TMJ requires a CR angle of ________ degrees (caudad or cephalad).

25° to 30° caudad

• The axiolateral oblique projection of the TMJ is commonly referred to as the ________ method, which requires a ___ degree head rotation from lateral and a ___ degree caudad CR angle.

Modified Law; 15; 15

If the area of interest is the temporomandibular fossae, angle the CR _______ to the OML for the AP axial (modified Towne) projection to reduce superimposition of the temporomandibular fossae and mastoid portions of the temporal bone.

40° caudad

A radiograph of a parieto-orbital oblique (Rhese) projection shows the optic foramen is located in the upper outer quadrant of the orbit. Is this an acceptable image for this projection? If not, what must be done to correct this problem during the repeat exposure?

No. Increase extension of the head and neck. AML should be perpendicular to the IR so the optic foramen is open and is projected into the lower outer quadrant of the orbit.

A radiograph of an axiolateral oblique projection of the mandible shows the body of the mandible is severely foreshortened. The body of the mandible is the area of interest. What positioning error led to this radiographic outcome?

Insufficient rotation of the skull toward the IR. The skull should be rotated 30° (from lateral) toward the IR to prevent foreshortening of the body.

A patient with a possible fracture of the nasal bones enters the emergency room. The physician is concerned about deviation of the bony nasal septum along with possible fracture of nasal bones. What radiographic routine would be best for this situation?

Parietoacanthial (Waters) and Lateral

A patient with a possible blowout fracture of the right orbit enters the emergency room. In addition to the basic facial bone routine, what single projection would best demonstrate this type of injury?

Modified parietoacanthial (modified Waters method) projection

A radiograph of a parietoacanthial projection shows the distance between the midsagittal plane and the outer orbital margin is not equal. What positioning error is present on this radiograph?

Rotation of the skull

Where is the CR centered for a lateral projection of the nasal bones?

½ inch (1.25 cm) inferior to nasion

What is the maximum amount of CR angulation that should be used for an axiolateral oblique projection of the mandible?

25° cephalad

How much skull rotation (from the lateral position) toward the IR is required for the axiolateral oblique projection specifically for the mentum?

45°

What type of CR angulation should be used for a PA axial projection of the mandible?

20° to 25° cephalad

What structures are better defined when the CR angulation is increased from 35° to 40° caudad for the AP axial projection of the mandible?

Temporomandibular fossae

Where is the CR centered for an SMV projection of the mandible?

1½ inches (4 cm) inferior to mandibular symphysis (or midway between angles of the mandible)

What CR angulation is used for the AP axial projection of the TMJ with the OML perpendicular to the IR?

35° caudad

True/False: The modified Law method requires a tube angulation of 25° caudad.

False, 15° caudad

True/False: The Schuller method requires that the skull be placed in a true lateral position.

True

True/False: A grid is not required for the lateral projection of the nasal bones.

True

Which positioning line should be perpendicular to the IR for the parieto-orbital oblique (Rhese method) projections for optic foramina?

AML