Mandible PA Axial (Rami) is a radiography positioning projection of the Skull. PA Axial mandible. Rami and body. CR 20-25° cephalad. The centering point is located CR exits at the acanthion. OML perpendicular to IR. The central ray is CR angled 20-25° cephalad to exit at the acanthion. Image-quality criteria include mandibular rami shown; central body not well shown because of the superimposed spine (Merrill's), no rotation: rami symmetric, lateral to the cervical spine. A sample technique is 80 kVp with DR 7 or CR 14 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Mandibular body, central part obscured by the spine.
- Mandibular rami visualized clearly.
- Mandibular angles and ascending rami.
- TMJs above rami, condyles visible.
- Condyloid processes, slightly elongated.
Patient preparation
- Trauma patient: rule out cervical spine injury before moving the head or neck.
- Verify patient identity.
- Remove glasses, earrings, dentures, hairpins.
- Position patient prone or upright.
- Forehead and nose against IR; OML perpendicular to IR.
- MSP perpendicular to the midline of the grid, with no head rotation or tilt.
- Suspend respiration during exposure.
Position & centering point
CR exits at the acanthion. OML perpendicular to IR.
Central ray
CR angled 20-25° cephalad to exit at the acanthion.
Exposure / technique
- kVp
- 80
- mAs
- DR 7 / CR 14
- SID
- 40" (102 cm)
- Notes
- CR angle 20-25 degrees cephalad. Small focal spot for detail. Sample technique: DR 7 / CR 14 mAs at 80 kVp, 40 in SID, for a 17 cm part. Adjust for your equipment.
kVp and mAs are sample values. Use caution when applying them in your department.
Image-quality criteria
- Mandibular rami shown; central body not well shown because of the superimposed spine (Merrill's).
- No rotation: rami symmetric, lateral to the cervical spine.
- TMJ regions and condyle heads seen through the mastoid processes.
- Angles of mandible equally demonstrated.
- Condyloid processes well shown, slightly elongated.
- No overlap: bilateral rami clearly outlined.
Common errors
- 1 Rotation: angles of mandible asymmetrical.
Clinical indications
- Mandibular fracture evaluation of body and rami.
- Neoplastic or inflammatory processes of the mandible.
- Trauma to lower jaw evaluation.