Mandible Submentovertical (SMV) is a radiography positioning projection of the Skull. SMV mandible. Entire mandible. IOML parallel to IR. The centering point is located midway between the angles of the mandible, about 1.5 inches below the mandibular symphysis. IOML (infraorbitomeatal line) parallel to IR. The central ray is perpendicular to IOML, centered midway between the angles of the mandible (about 1.5 inches below the mandibular symphysis). Image-quality criteria include entire mandible visualized from symphysis through both angles, mandibular symphysis superimposing the frontal bone. The SID is 40 inches (102 cm).
Anatomy demonstrated
- Mandibular body from symphysis to angle.
- Ascending mandibular rami.
- Mandibular angles and gonial angle.
- Condyles, coronoid processes.
- Mentum and mandibular symphysis.
Patient preparation
- Trauma patient: rule out cervical spine fracture or subluxation before attempting this projection.
- Verify patient identity.
- Remove glasses, earrings, dentures, hairpins.
- Position patient supine or upright with head tilted back.
- Vertex of head against IR; chin fully extended upward.
- IOML (infraorbitomeatal line) parallel to IR.
- MSP perpendicular to the midline of the grid, with no head rotation or tilt.
- Suspend respiration during exposure.
Position & centering point
Midway between the angles of the mandible, about 1.5 inches below the mandibular symphysis. IOML (infraorbitomeatal line) parallel to IR.
Central ray
Perpendicular to IOML, centered midway between the angles of the mandible (about 1.5 inches below the mandibular symphysis).
Exposure / technique
- kVp
- N/A
- mAs
- N/A
- SID
- 40" (102 cm)
- Notes
- Chin extension critical. IOML must be parallel to IR. On the 2022 ARRT outline (submentovertex, full basal), through February 28, 2027. Off the 2027 outline from March 1, 2027. Bontrager prints digital 80 +/- 5 kV and no mAs; Merrill's chart has no mandible SMV row, so no mAs is printed.
Image-quality criteria
- Entire mandible visualized from symphysis through both angles.
- Mandibular symphysis superimposing the frontal bone.
- Mandibular condyles projected anterior to the petrous ridges.
- No rotation: symmetric mandibular condyles.
- No tilt: equal distance from the mandible to the lateral skull border.
- Mandible centered on IR with margin.
Common errors
- 1 Head not extended enough: the symphysis fails to superimpose the frontal bone.
- 2 IOML not parallel to IR: condyles not anterior to the petrous ridges.
- 3 Rotation: mandibular condyles not symmetric.
- 4 Tilt: unequal distance from the mandible to the lateral skull border.
Clinical indications
- Fractures of the mandible.
- Evaluation of mandibular body, rami, and angles.
- Neoplastic or inflammatory processes of the mandible.