PA oblique foot X-ray positioning
One of the routine foot views. The patient lies face down, the beam passes back to front (PA), straight on to the receptor, and the centring point is the base of the third metatarsal.
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
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- 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
Still being checked: a radiographer is reviewing this guide. If your department does it differently, follow your department.
Patient position
Prone. Prone, the foot turned on the detector as shown so the lateral metatarsals separate.
Centring & collimation
Central ray
PACentre: the base of the third metatarsal.
Beam: PA, perpendicular to the receptor.
Collimate: toes to the calcaneus
Distance, receptor & grid
| Setting | Value | Notes |
|---|---|---|
| SID | 100 cm | |
| Receptor | 18 × 24 cm | portrait |
| Placement | Tabletop | No grid |
| 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 | 46 | 0.8 | 0.5 |
| S | 46 | 1.25 | 0.5 |
| M | 46 | 1.6 | 0.63 |
| L | 46 | 2.5 | 1 |
These start from a classic film-screen chart (46 kV, 25 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
- The lateral metatarsals and cuboid are separated.
- 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 |
|---|---|---|
| Metatarsals overlap | Too little rotation | Rotate further. |
Common questions
- Where do you centre for a foot PA oblique X-ray?
- The centring point is the base of the third metatarsal.
- What distance and beam angle does a foot PA oblique 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 an 18 × 24 cm receptor, portrait, on the tabletop. No 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 foot PA oblique?
- Metatarsals overlap. Usual cause: too little rotation. The fix: rotate further.
Try it in ScanFlo: the ScanFlo XR X-ray Room, coming soon, lets you set up a foot pa oblique in a 3D room and score your positioning. See ScanFlo XR →
Written by the ScanFlo team from everyday radiographic practice.