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 mental eminence. oml perpendicular to ir.. The central ray is cr angled 20-25° cephalad to exit at mental eminence.. Image-quality criteria include mandibular body and rami visualized without foreshortening., mental eminence in midline, no rotation.. Standard exposure ranges from 75 to 85 kVp, 20 to 30 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Mandibular body from symphysis without foreshortening.
- Mandibular rami visualized clearly.
- Mandibular angles and ascending rami.
- TMJs above rami, condyles visible.
- Coronoid processes demonstrated.
- Mental eminence and mental protuberance.
Patient preparation
- Verify patient identity.
- Remove glasses, earrings, dentures, hairpins.
- Position patient prone or upright.
- Forehead and nose against IR; OML perpendicular to IR.
- No rotation: shoulders and head symmetrical.
- Hands at sides or folded over chest.
- Suspend respiration during exposure.
Position & centering point
CR exits at mental eminence. OML perpendicular to IR.
Central ray
CR angled 20-25° cephalad to exit at mental eminence.
Exposure / technique
- kVp
- 75–85
- mAs
- 20–30
- SID
- 40" (102 cm)
- Notes
- CR angle 20-25 degrees cephalad. Small focal spot for detail.
Image-quality criteria
- Mandibular body and rami visualized without foreshortening.
- Mental eminence in midline, no rotation.
- TMJs projected above and clear of rami.
- Angles of mandible equally demonstrated.
- TMJs projected clear and superior to the mandibular rami without overlap.
- No overlap: bilateral rami clearly outlined.
Common errors / ARRT traps
- 1 CR angle not 20-25 degrees: foreshortening of rami.
- 2 Rotation: angles of mandible asymmetrical.
- 3 Tilt: one ramus appears longer or shorter.
- 4 OML not perpendicular: geometric distortion.
- 5 CR not at mental eminence: mandible off-center.
Clinical indications
- Mandibular fracture evaluation of body and rami.
- TMJ region assessment with mandibular visualization.
- Trauma to lower jaw evaluation.
- Pre- or post-operative mandibular follow-up.
Aligned to the 2025 ARRT Content Specifications.