PA mandible X-ray positioning
One of the routine face & sinuses views. The patient sits, the beam passes back to front (PA), straight on to the receptor, and the centring point is the angles of the mandible, midline.
By the ScanFlo Editorial Team · Updated
In this section · X-ray positioning
- X-ray positioning guides
- Skull positioning
- Face & sinuses positioning
- Soft tissue neck positioning
- C-spine positioning
- Chest positioning
- Shoulder positioning
- Humerus positioning
- Elbow positioning
- Forearm positioning
- Wrist positioning
- Hand positioning
- T-spine positioning
- Abdomen positioning
- L-spine positioning
- Sacrum & SI joints positioning
- Pelvis positioning
- Hip positioning
- Femur positioning
- Knee positioning
- Tibia & fibula positioning
- Ankle positioning
- Foot positioning
X-ray positioning/Face & sinuses
Still being checked: a radiographer is reviewing this guide. If your department does it differently, follow your department.
Patient position
Sitting. Remove dentures, earrings, hair clips and anything in the hair. Seat the patient facing the bucky, forehead and nose touching, mouth open, orbitomeatal line perpendicular.
Centring & collimation
Central ray
PACentre: the angles of the mandible, midline.
Beam: PA, perpendicular to the receptor.
Collimate: the whole mandible
Distance, receptor & grid
| Setting | Value | Notes |
|---|---|---|
| SID | 100 cm | |
| Receptor | 24 × 30 cm | portrait |
| Placement | Erect (wall) bucky | Grid in |
| Angulation | None | Perpendicular to the receptor |
Marker & breathing
- Marker: R or L marker on the side nearest the detector
- Breathing: No breathing instruction needed.
Exposure by patient size
Treat these as a starting point. Your detector, your generator and the patient in front of you will all move the numbers.
| Patient size | kV | mAs (chart) | mAs (DR default) |
|---|---|---|---|
| XS | 70 | 8 | 3.2 |
| S | 70 | 12.5 | 5 |
| M | 70 | 16 | 6.3 |
| L | 70 | 25 | 10 |
These start from a classic film-screen chart (70 kV, 32 mAs at 140 cm) and are adjusted for a digital detector at 100 cm. The DR column is what ScanFlo's console suggests; each step up or down changes the mAs by about a quarter.
Image quality checklist
- Both rami symmetric.
- The body of the mandible clear of the spine.
- The anatomical side marker is visible, correct and clear of the anatomy.
- Collimation borders are visible on all sides, no wider than the area requested.
Faults & how to fix them
| Fault | Cause | Fix |
|---|---|---|
| Rami asymmetric | Rotation | Centre the mid-sagittal plane. |
Common questions
- Where do you centre for a mandible PA X-ray?
- The centring point is the angles of the mandible, midline.
- What distance and beam angle does a mandible PA need?
- 100 cm from the tube to the receptor. The beam passes back to front (PA), straight on to the receptor.
- What size receptor, and do you need a grid?
- Use a 24 × 30 cm receptor, portrait, in the wall bucky. A grid is needed.
- Where does the lead marker go?
- R or L marker on the side nearest the detector.
- What goes wrong most often on a mandible PA?
- Rami asymmetric. Usual cause: rotation. The fix: centre the mid-sagittal plane.
Try it in ScanFlo: the ScanFlo XR X-ray Room, coming soon, lets you set up a mandible pa in a 3D room and score your positioning. See ScanFlo XR →
Written by the ScanFlo team from everyday radiographic practice.