Head
Facial Bones
Anatomy
Students should be able to identify the following structures on themselves, the patient or radiographic images:
- Zygoma / zygomatic arch
- Maxilla (body, alveolar process, anterior nasal spine)
- Nasal bones & nasal septum (vomer and perpendicular plate of ethmoid)
- Orbital margins / floors / rims
- Inferior orbital rim, orbital floor (important in blow-out fracture)
- Mandible (body, rami, condyles, symphysis)
- Pterygomaxillary region, infraorbital foramen
Topographic Lines / Reference Planes Used:
- Orbitomeatal line (OML) — often used in positioning for Waters/OM projection.
- Infraorbitomeatal line (IOML) — alternative baseline when OML cannot be aligned.
- Midsagittal plane (MSP) — must be ⟂ IR to avoid rotation artifacts.
- Interpupillary line (IPL) — helps ensure no tilt in lateral facial bones views.
- Acanthiomeatal line (AML) — used in reverse Waters / acanthioparietal trauma views.
Routine Projections (ARRT Required)
Lateral Facial Bones – Right or Left
CR Location & Positioning
- SID: 40″ (102 cm)
- Patient position: Erect or recumbent semiprone, lateral side of interest against IR.
- Adjustments:
- MSP parallel to IR.
- IPL perpendicular to IR.
- IOML perpendicular to front edge of IR.
- Oblique body slightly for comfort if erect.
- CR: Perpendicular to zygoma (midway between outer canthus and EAM).
- Pt. Instructions: Suspend respiration.
- Exposure: 65–80 kV.
Evaluation Criteria
- Coverage (what anatomy must be included and how you verify it’s complete): Entire facial bone region from orbital roofs to mandible, including zygoma.
- Rotation checks (how symmetry or alignment tells you if positioning is correct):
- No rotation → mandibular rami and greater wings of sphenoid superimposed.
- No tilt → orbital roofs superimposed.
- Motion checks (how sharpness confirms patient cooperation/exposure timing): Sharp bony margins.
- Technique checks (what contrast, density, soft tissue visibility, and artifacts to look for): Adequate contrast/density to visualize maxillary and orbital detail.
Parietoacanthial (Waters Method) Facial Bones
CR Location & Positioning
- SID: 40″ (102 cm)
- Patient position: Erect (preferred) or prone. Chin against IR.
- Adjustments:
- MML perpendicular to IR → OML forms ~37° angle.
- MSP perpendicular to IR, no rotation/tilt.
- CR: Perpendicular to IR, exiting at acanthion.
- Pt. Instructions: Suspend respiration.
- Exposure: 70–85 kV.
Evaluation Criteria
- Coverage: IOMs, maxillae, nasal septum, zygomatic bones, anterior nasal spine.
- Rotation checks: Equal distance from lateral orbital margins to cranial cortex.
- Motion checks: Sharp bony margins.
- Technique checks: Petrous ridges projected just inferior to maxillary sinuses; sufficient density for orbital and maxillary detail.
Clinical Tip:
If patient cannot extend the neck enough to place MML perpendicular, accept a slightly steeper OML angle but confirm that petrous ridges fall just below maxillary sinuses.
PA Axial (Caldwell Method) Facial Bones
CR Location & Positioning
- SID: 40″ (102 cm)
- Patient position: Erect (preferred) or prone. Forehead and nose against IR.
- Adjustments: OML perpendicular to IR; MSP perpendicular.
- CR: 15° caudad to exit at nasion. (30° caudad if orbital floors are area of interest.)
- Pt. Instructions: Suspend respiration.
- Exposure: 70–85 kV.
Evaluation Criteria
- Coverage: Orbital rim, maxillae, nasal septum, zygomatic bones, anterior nasal spine.
- Rotation checks: Equal distance midlateral orbital margin to lateral skull cortex; symmetric superior orbital fissures.
- Motion checks: Sharp bony margins.
- Technique checks:
- 15° caudad → petrous ridges in lower 1/3 of orbits.
- 30° caudad → petrous ridges below IOM, better orbital floor view.
Clinical Tip:
If orbital floors are primary concern, use the 30° caudal angle for optimal orbital visualization.
Modified Parietoacanthial Facial Bones (Modified Waters Method)
CR Location & Positioning
- SID: 40″ (102 cm)
- Patient position: Erect (preferred) or prone. Chin and nose against IR.
- Adjustments: LML perpendicular; OML forms ~55° with IR.
- CR: Perpendicular, exiting at the acanthion.
- Pt. Instructions: Suspend respiration.
- Exposure: 70–85 kV.
Evaluation Criteria
- Coverage: Orbital floors perpendicular to IR; orbital rims visualized with minimal distortion.
- Rotation checks: Equal distance midlateral orbital margin to lateral cranial cortex.
- Motion checks: Sharp bony margins.
- Technique checks: Petrous ridges in lower half of maxillary sinuses, below IOMs.
Clinical Tip:
This view is particularly useful for “blowout” fractures—orbital floor is demonstrated without superimposition.
Supplemental Projections
Acanthioparietal Projection (Reverse Waters Method)
CR Location & Positioning
- SID: 40 inches (102 cm)
- Patient position: Supine, usually immobilized on backboard or table.
- Adjustments: Do not move head/neck. Align CR cephalad, parallel to MML (mentomeatal line).
- CR: Directed cephalad to acanthion, parallel to MML. Center IR to projected CR.
- Pt. Instructions: Remain still; no movement of head/neck.
- Exposure: Suspend respiration.
Evaluation Criteria
- Coverage: Maxillae, maxillary sinuses, zygomatic arches, nasal septum, and orbits above petrous ridges.
- Rotation checks: Equal distance from midlateral orbital margins to cranial cortex.
- Motion checks: Sharp bony margins; no motion blur.
- Technique checks: Contrast and brightness sufficient to demonstrate maxillary region and orbital structures.
- Clinical aim: Demonstrates facial bone structures and maxillary sinuses free of superimposition by petrous ridges.
Modified Acanthioparietal Projection (Modified Reverse Waters Method)
CR Location & Positioning
- SID: 40 inches (102 cm)
- Patient position: Supine, immobilized.
- Adjustments: Do not manipulate head/neck. Align CR cephalad, parallel to LML (lips–meatal line).
- CR: Directed cephalad to acanthion, parallel to LML. Center IR to projected CR.
- Pt. Instructions: Remain still.
- Exposure: Suspend respiration.
Evaluation Criteria
- Coverage: Orbital floors and rims, maxillae, nasal septum.
- Rotation checks: Equal distance from lateral orbital margins to cranial cortex.
- Motion checks: Sharp bony detail throughout.
- Technique checks: Petrous ridges projected into midmaxillary sinus region, below orbital rims.
- Clinical aim: Best for demonstrating orbital floor fractures (blowout) and orbital rim integrity.
Trauma Lateral Facial Bones (Horizontal Beam)
CR Location & Positioning
- SID: 40 inches (102 cm)
- Patient position: Supine; immobilized on backboard.
- Adjustments: IR placed vertically at side of head, closest to area of interest.
- CR: Horizontal beam, perpendicular to IR, centered to zygoma (midway between outer canthus and EAM).
- Pt. Instructions: Remain still.
- Exposure: Suspend respiration.
Evaluation Criteria
- Coverage: Superimposed facial bones, zygomatic arch, mandible, orbital roofs, sphenoid wings.
- Rotation checks: Superimposition of mandibular rami and orbital roofs.
- Motion checks: Crisp margins of facial bones.
- Technique checks: Adequate contrast to show facial structures and soft tissue detail.
- Clinical aim: Detects fractures, foreign bodies, and air-fluid levels (especially sphenoid sinus, useful for basal skull fracture assessment).
| Projection | CR Location & Angle | Patient Position | Key Evaluation Points |
|---|---|---|---|
| Lateral | Perpendicular to zygoma (midway between outer canthus & EAM) | Erect or recumbent, side of interest closest to IR; MSP ∥ IR; IPL ⟂ IR; IOML ⟂ front edge of IR | • Facial bones superimposed • Mandibular rami & orbital roofs aligned (no rotation/tilt) • Sharp margins, zygoma centered |
| Parietoacanthial (Waters) | Perpendicular, exiting at acanthion | Erect preferred; chin against IR; MML ⟂ IR (OML ~37° to IR); MSP ⟂ IR | • Petrous ridges just below maxillary sinuses • IOMs, maxillae, zygomas, nasal septum included • Equal orbital margins (no rotation) • Sharp bone detail |
| PA Axial (Caldwell) | 15° caudad to exit nasion (30° if orbital floors) | Erect preferred; forehead & nose on IR; OML ⟂ IR; MSP ⟂ IR | • 15° → petrous ridges in lower 1/3 of orbits • 30° → petrous ridges below IOMs, orbital floors better seen • Symmetry of orbits and superior orbital fissures |
| Modified Waters (Parietoacanthial) | Perpendicular, exiting at acanthion | Erect preferred; chin & nose on IR; LML ⟂ IR (OML ~55° to IR); MSP ⟂ IR | • Orbital floors seen with minimal distortion • Petrous ridges in lower ½ of maxillary sinuses • Equal orbital margins (no rotation) • Best for orbital “blowout” fractures |
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Hows & Whys of Facial Bone Radiography