AP mandible X-ray positioning
An extra face & sinuses view, used when a routine one is not enough. The patient lies on their back, the beam passes front to back (AP), tilted 30° towards the feet, and the centring point is the lips, 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
Supine. Remove dentures, earrings, hair clips and anything in the hair. Supine, mouth wide open (a soft wedge between the teeth if needed), infraorbitomeatal line perpendicular.
Centring & collimation
Central ray
APCentre: the lips, midline.
Beam: AP, angled 30° caudad.
Collimate: the whole mandible
Distance, receptor & grid
| Setting | Value | Notes |
|---|---|---|
| SID | 100 cm | |
| Receptor | 24 × 30 cm | portrait |
| Placement | Table bucky | Grid in |
| Angulation | 30° | caudad |
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
- Condyles shown.
- Symmetric rami.
- 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 |
|---|---|---|
| Condyles hidden | Mouth closed | Open the mouth; use a wedge. |
Common questions
- Where do you centre for a mandible AP X-ray?
- The centring point is the lips, midline.
- What distance and beam angle does a mandible AP need?
- 100 cm from the tube to the receptor. The beam passes front to back (AP), tilted 30° towards the feet.
- What size receptor, and do you need a grid?
- Use a 24 × 30 cm receptor, portrait, in the table 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 AP?
- Condyles hidden. Usual cause: mouth closed. The fix: open the mouth; use a wedge.
Try it in ScanFlo: the ScanFlo XR X-ray Room, coming soon, lets you set up a mandible ap in a 3D room and score your positioning. See ScanFlo XR →
Written by the ScanFlo team from everyday radiographic practice.