Mandible PA (Rami) is a radiography positioning projection of the Skull. PA mandible. Body and rami. CR perpendicular to IR. The centering point is located junction of the lips, where the CR exits (Bontrager); acanthion in Merrill's PA rami. OML perpendicular to IR. The central ray is CR perpendicular to IR, exiting at the junction of the lips (Bontrager). Merrill's PA mandibular rami exits the acanthion, and uses lip level for its PA mandibular body. Image-quality criteria include mandibular rami and lateral portion of the body visible, rami symmetric, lateral to the cervical spine (no rotation). A sample technique is 80 kVp with DR 6.3 or CR 12.5 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Lateral portion of the mandibular body.
- Mandibular rami bilaterally.
- Midbody and mentum, faint over the cervical spine.
- Mandibular angles.
Patient preparation
- Trauma patient: this position is best performed supine (Bontrager). 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
Junction of the lips, where the CR exits (Bontrager); acanthion in Merrill's PA rami. OML perpendicular to IR.
Central ray
CR perpendicular to IR, exiting at the junction of the lips (Bontrager). Merrill's PA mandibular rami exits the acanthion, and uses lip level for its PA mandibular body.
Exposure / technique
- kVp
- 80
- mAs
- DR 6.3 / CR 12.5
- SID
- 40" (102 cm)
- Notes
- Small focal spot for detail. Suspended respiration. Sample technique: DR 6.3 / CR 12.5 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 and lateral portion of the body visible.
- Rami symmetric, lateral to the cervical spine (no rotation).
- No overlap: angles of mandible clearly outlined.
- Midbody and mentum faint, superimposed on the cervical spine.
- Mandible centered on IR with margin.
Common errors
- 1 Rotation: mandibular angles appear unequal distance from midline.
Clinical indications
- Mandibular body and rami fracture evaluation.
- Trauma to lower jaw and chin assessment.
- Neoplastic or inflammatory processes of the mandible.