Sinuses SMV is a radiography positioning projection of the Skull. Upright SMV. Vertex on IR. IOML parallel. Sphenoid + ethmoid sinuses. The centering point is located 3/4 inch anterior to the eam, midway between the angles of the mandible. ioml parallel to ir.. The central ray is perpendicular to ioml. centered 3/4 inch anterior to the eam.. Image-quality criteria include sphenoid and posterior ethmoid sinuses visible., mandibular symphysis projected over the anterior frontal bone.. Standard exposure ranges from 75 to 85 kVp, 25 to 40 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Sphenoid sinus at the cranial base.
- Posterior ethmoid air cells.
- Mandible projected over the anterior frontal bone.
- Bony nasal septum.
- Maxillary sinuses adjacent to the cranial base.
- Air-fluid levels in the sphenoid when present.
Patient preparation
- Verify patient identity.
- Remove glasses, earrings, dentures, and hairpins.
- Position patient upright with head fully extended.
- Rest vertex of head against the IR.
- IOML parallel to IR. MSP perpendicular with no rotation.
- Suspend respiration during exposure.
Position & centering point
3/4 inch anterior to the EAM, midway between the angles of the mandible. IOML parallel to IR.
Central ray
Perpendicular to IOML. Centered 3/4 inch anterior to the EAM.
Exposure / technique
- kVp
- 75–85
- mAs
- 25–40
- SID
- 40" (102 cm)
- Notes
- Upright required for air-fluid levels. Head extension critical. Grid required.
Image-quality criteria
- Sphenoid and posterior ethmoid sinuses visible.
- Mandibular symphysis projected over the anterior frontal bone.
- No rotation: distance from mandibular ramus to lateral skull equal.
- Symmetric appearance of petrous pyramids and mastoids.
- Air-fluid levels demonstrated when present.
- Sharp bony detail of the cranial base and sinus walls.
Common errors / ARRT traps
- 1 Recumbent positioning hides air-fluid levels.
- 2 Inadequate head extension foreshortens the sinuses.
- 3 Rotation: mandible asymmetric relative to skull margins.
- 4 IOML not parallel: petrous pyramids displaced anteriorly or posteriorly.
Clinical indications
- Evaluation of sphenoid sinusitis.
- Detection of air-fluid levels in basal sinuses.
- Sinus trauma workup of the cranial base.
- Pre-operative endoscopic sinus surgery planning.
Aligned to the 2025 ARRT Content Specifications.