Facial Bones

By Prof. J. Stelmark

LATERAL POSITION—RIGHT OR LEFT LATERAL: FACIAL BONES

Pathology DemonstratedFractures and neoplastic/inflammatory processes of the facial bones, orbits, and mandible are shown.

The facial bone routine commonly includes only a single lateral, whereas the skull routine may include bilateral positions.

Patient PositionRemove all metallic or plastic objects from head and neck. Patient position is erect or semiprone.

Part Position• Rest lateral aspect of head against table or upright Bucky surface, with side of interest closest to IR.

• Adjust head into a true lateral position and oblique body as needed for patient's comfort.

• Align midsagittal plane (MSP) parallel to IR.

• Align interpupillary line (IPL) perpendicular to IR.

• Adjust chin to bring the IOML perpendicular to front edge of IR

Central Ray

• Align CR perpendicular to IR.

• Center CR to zygoma (prominence of the cheek), midway between outer canthus and EAM.

• Center IR to CR.

• Minimum SID is 40 inches (100 cm).

Structures Shown: Superimposed facial bones, greater wings of the sphenoid, orbital roofs, sella turcica, zygoma, and mandible.

Position: An accurately positioned lateral image of the facial bones demonstrates no rotation of vertical structures such as mandibular rami and no tilt of horizontal structures such as orbital roofs, which normally are superimposed in this position.

PARIETOACANTHIAL PROJECTION: FACIAL BONESWaters Method

Pathology DemonstratedFractures (particularly tripod and Le Fort fractures) and neoplastic/inflammatory processes are shown. Foreign bodies in the eye also may be demonstrated on this image.

Tripod fracture. Le Fort fractures

Part Position

• Extend neck, resting chin against table/upright Bucky surface.

• Adjust head until MML is perpendicular to the plane of the image receptor. The OML will form a 37° angle with the table/Bucky surface.

• Position the MSP perpendicular to the midline of the grid or the table/Bucky surface, preventing rotation and/or tilting of head. (One way to check for rotation is to palpate the mastoid processes on each side and the lateral orbital margins with the thumb and fingertips to ensure that these lines are equidistant from the tabletop.)

Central Ray

• Align CR perpendicular to IR, to exit at acanthion.

• Center IR to CR.

• Minimum SID is 40 inches (100 cm).

Radiographic CriteriaStructures Shown: Inferior orbital rim, maxillae, nasal septum, zygomatic bones, zygomatic arches, and anterior nasal spine.

Position: Correct neck extension demonstrates petrous ridges just inferior to the maxillary sinuses. No patient rotation exists, as indicated by equal distance from the midlateral orbital margin to the outer skull margin on each side.

PA AXIAL PROJECTION: FACIAL BONES Caldwell Method

Pathology DemonstratedFractures and neoplastic/inflammatory processes of the facial bones are shown.

Part Position• Rest patient's nose and forehead against tabletop.

• Tuck chin, bringing OML perpendicular to image receptor.

• Align MSP perpendicular to midline of grid or table/Bucky surface. Ensure no rotation or tilt of head.

Central Ray• Angle CR 15° caudad, to exit at nasion.

• Center CR to IR.

• Ensure minimum SID of 40 inches (100 cm).

Structures Shown: Orbital rim, maxillae, nasal septum, zygomatic bones, and anterior nasal spine.

Position: Correct patient position/CR angulation is indicated by petrous ridges projected into the lower one-third of orbits with 15° caudad CR. If the orbital floors are the area of interest, the 30° caudad angle projects the petrous ridges below the inferior margins of the orbits. • No rotation of cranium is indicated by equal distance from midlateral orbital margin to the outer skull margin on each side; superior orbital fissures are symmetric

LATERAL POSITION: NASAL BONES

Pathology DemonstratedNasal bone fractures are shown.

Both sides should be examined for comparison, with the side closest to the IR demonstrated.

Part Position• Rest lateral aspect of head against the table/upright Bucky surface, with side of interest closest to IR.

• Position nasal bones to center of image receptor.

• Adjust head into a true lateral position and oblique body as needed for patient's comfort (placing sponge block under chin if needed).

• Align MSP parallel with a table/upright Bucky surface.

• Align IPL perpendicular to table/upright Bucky surface.

• Position IOML perpendicular to front edge of image receptor.

Note: To obtain a sharply detailed image of the nasal bones, use a small focal spot, close collimation, and detail screens with film-screen imaging.In addition, with CR and DR digital imaging, accurate central ray centering, tabletop masking, and close collimation are essential because of the image reader function and the sensitivity of the image receptor to scatter exposure.

Structures Shown: Nasal bones with soft tissue nasal structures and the anterior nasal spine.

Position: Nasal bones are demonstrated without rotation.

SUPEROINFERIOR TANGENTIAL (AXIAL) PROJECTION: NASAL BONES

Pathology DemonstratedFractures of the nasal bones (medial-lateral displacement)

Part Position• Extend and rest chin on IR. Place angled support under IR, as demonstrated, to place IR perpendicular to GAL (glabelloalveolar line).

• Align MSP perpendicular to CR and to IR midline.

Central Ray• Center CR to nasion and angle as needed to ensure that it is parallel to GAL. (CR must just skim glabella and anterior upper front teeth.)

• Minimum SID is 40 inches (100 cm).

Structures Shown: Tangential projection of midnasal and distal nasal bones (with little superimposition of the glabella or alveolar ridge) and nasal soft tissue.

Position: No patient rotation is evident, as indicated by equal distance from anterior nasal spine to outer soft tissue borders on each side. • Incorrect neck position is indicated by visualization of alveolar ridge (excessive extension) or visualization of too much glabella (excessive flexion).

SUBMENTOVERTEX (SMV) PROJECTION: ZYGOMATIC ARCHES

Pathology DemonstratedFractures of the zygomatic arch and neoplastic/inflammatory processes are shown.

Part Position• Raise chin, hyperextend neck until IOML is parallel to IR.

• Rest head on vertex of skull.

• Align MSP perpendicular to midline of the grid or the table/upright Bucky surface, avoiding all tilt and/or rotation.

Central Ray• Align CR perpendicular to IR.

• Center CR midway between zygomatic arches, at a level 1 ½ inches (4 cm) inferior to mandibular symphysis.

• Center IR to CR, with plane of image receptor parallel to IOML.

• Minimum SID is 40 inches (100 cm).

Structures Shown: Zygomatic arches are demonstrated laterally from each mandibular ramus. Position: • Correct IOML/CR relationship, as indicated by superimposition of mandibular symphysis on frontal bone. • No patient rotation, as indicated by zygomatic arches visualized symmetrically.

OBLIQUE INFEROSUPERIOR (TANGENTIAL) PROJECTION: ZYGOMATIC ARCHES

Pathology DemonstratedFractures of the zygomatic arch are shown. This projection is especially useful for depressed zygomatic arches caused by trauma or skull morphology.

Radiographs of both sides generally are taken for comparison.

Part Position• Raise chin, hyperextending neck until IOML is parallel to IR.

• Rest head on vertex of skull.

• Rotate head 15° toward side to be examined; then also tilt chin 15° toward side of interest.

Central Ray• Align CR perpendicular to image receptor and IOML.

• Center CR to zygomatic arch of interest (CR skims the mandibular ramus and passes through the arch.

• Adjust image receptor so it is parallel to IOML and perpendicular to CR.

• Minimum SID is 40 inches (100 cm).

Notes: If patient is unable to sufficiently extend neck, angle CR perpendicular to IOML. If equipment allows, the IR should be angled to maintain the CR/IR perpendicular relationship.This position is very uncomfortable for the patient; complete the projection as quickly as possible.

Structures Shown: Single zygomatic arch, free of superimposition.

Position: Correct patient position provides for demonstration of zygomatic arch without superimposition of parietal bone or mandible.

AP AXIAL PROJECTION: ZYGOMATIC ARCHESModified Towne Method—“Jug Handle View”

Pathology DemonstratedFractures and neoplastic/inflammatory processes of the zygomatic arch are shown

Part Position• Rest patient's posterior skull against table/upright Bucky surface.• Tuck chin, bringing OML (or IOML) perpendicular to image receptor • Align MSP perpendicular to midline of the grid or the table/upright Bucky surface to prevent head rotation or tilt.

Central Ray• Angle CR 30° caudad to OML or 37° to IOML.• Center CR to 2.5 cm (1 inch) superior to glabella (to pass through midarches.) • Center image receptor to projected CR.• Minimum SID is 40 inches (100 cm).

Structures Shown: Bilateral zygomatic arches.

Position: Zygomatic arches are visualized without patient rotation as indicated by symmetric appearance of arches bilaterally.

AXIOLATERAL OBLIQUE PROJECTION: MANDIBLE

Pathology DemonstratedFractures and neoplastic/inflammatory processes of the mandible are shown.

Both sides are examined for comparison.

Part Position• Place head in a true lateral position, with side of interest against IR.

• If possible, have patient close mouth and bring teeth together.

• Extend neck slightly to prevent superimposition of the gonion over the cervical spine.

• Rotate head toward the IR to place the mandibular area of interest parallel to the IR. The degree of obliquity depends on which section of the mandible is of interest.

• Head in true lateral position best demonstrates ramus.

• 30° rotation toward IR best demonstrates body.

• 45° rotation best demonstrates mentum.

• 10° to 15° rotation best provides a general survey of the mandible.

Central Ray

Angle CR 25° cephalad

Direct CR to exit mandibular region of interest.

Center IR to projected CR.

Minimum SID is 40 inches (100 cm).

Structures Shown: • Rami, condylar and coronoid processes, body, and mentum of mandible nearest the image receptor.

PA OR PA AXIAL PROJECTION: MANDIBLE

Pathology DemonstratedFractures and neoplastic/inflammatory processes of the mandible are shown.

Part Position• Rest patient's forehead and nose against table/upright Bucky surface.

• Tuck chin, bringing OML perpendicular to IR.

• Align MSP perpendicular to midline of the grid or the table/Bucky surface (ensuring no rotation or tilt of head).

• Center image receptor to projected CR (to junction of lips).

Central Ray• PA: Align CR perpendicular to IR, centered to exit at junction of lips. For trauma patients, this position is best performed supine.

• Minimum SID is 40 inches (100 cm).

Structures Shown: Mandibular rami and lateral portion of body are visible.

AP AXIAL PROJECTION: MANDIBLE Towne Method

Pathology DemonstratedFractures and neoplastic/inflammatory processes of the condyloid processes of the mandible are shown.

Part Position• Rest patient's posterior skull against table/upright Bucky surface.• Tuck chin, bringing OML perpendicular to image receptor, or place IOML perpendicular and add 7° to CR angle.• Align MSP perpendicular to midline of the grid or the table/upright Bucky surface to prevent head rotation or tilt.

Central Ray• Angle CR 35° to 42° caudad.• Center CR to glabella.• Center IR to CR.• Minimum SID is 40 inches (100 cm).

Structures Shown: Condyloid processes of mandible and temporomandibular fossae.

SUBMENTOVERTEX (SMV) PROJECTION: MANDIBLE

Pathology DemonstratedFractures and neoplastic/inflammatory process of the mandible are shown.

Part Position• Hyperextend neck until IOML is parallel to image receptor.• Rest head on vertex of skull.• Align MSP perpendicular to midline of the grid or the table/upright Bucky surface to prevent head rotation or tilt.

Central Ray• Align CR perpendicular to image receptor or IOML (see Notes).• Center CR to a point midway between angles of mandible, or at a level 1½ inches (4 cm) inferior to mandibular symphysis.• Center image receptor to projected CR.• Minimum SID is 40 inches (100 cm).

Structures Shown: Entire mandible and coronoid and condyloid processes.