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, mentum of the mandible projected anterior to the ethmoid sinuses. A sample technique is 85 kVp with DR 14 or CR 28 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
- Trauma patient: rule out cervical spine fracture or subluxation before attempting this projection.
- 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
- 85
- mAs
- DR 14 / CR 28
- SID
- 40" (102 cm)
- Notes
- On the 2022 ARRT outline (submentovertex, horizontal beam), through February 28, 2027. Off the 2027 outline from March 1, 2027. Upright required for air-fluid levels. Head extension critical. Grid required. Sample technique: DR 14 / CR 28 mAs at 85 kVp, 40 in SID, for a 23 cm part. Adjust for your equipment.
kVp and mAs are sample values. Use caution when applying them in your department.
Image-quality criteria
- Sphenoid and posterior ethmoid sinuses visible.
- Mentum of the mandible projected anterior to the ethmoid sinuses.
- No rotation: MSP parallel to the edge of the IR. No tilt: equal distance from mandibular ramus to lateral cranial cortex.
- 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
- 1 Recumbent positioning hides air-fluid levels.
- 2 Insufficient neck extension makes the mandible superimpose the ethmoid sinuses (Merrill's).
- 3 Tilt: unequal distance from mandibular ramus to lateral cranial cortex. Rotation: MSP not parallel to the IR edge.
- 4 IOML not parallel: mandibular mentum not anterior to the ethmoid sinuses.
Clinical indications
- Evaluation of sphenoid sinusitis.
- Detection of air-fluid levels in basal sinuses.
- Inflammatory conditions (sinusitis, secondary osteomyelitis).
- Sinus polyps and cysts.