AP oblique foot X-ray positioning
An extra foot view, used when a routine one is not enough. The patient sits, the beam passes front to back (AP), tilted 15° towards the head, 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
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- 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
Sitting. Sitting on the table, the foot angled on the detector.
Centring & collimation
Central ray
APCentre: the base of the third metatarsal.
Beam: AP, angled 15° toward-head.
Collimate: the whole foot
Distance, receptor & grid
| Setting | Value | Notes |
|---|---|---|
| SID | 100 cm | |
| Receptor | 18 × 24 cm | portrait |
| Placement | Tabletop | No grid |
| Angulation | 15° | toward-head |
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
- Tarsal bones shown with less overlap.
- 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 |
|---|---|---|
| Overlap | Foot flat | Angle the foot. |
Common questions
- Where do you centre for a foot AP oblique X-ray?
- The centring point is the base of the third metatarsal.
- What distance and beam angle does a foot AP oblique need?
- 100 cm from the tube to the receptor. The beam passes front to back (AP), tilted 15° towards the head.
- 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 AP oblique?
- Overlap. Usual cause: foot flat. The fix: angle the foot.
Try it in ScanFlo: the ScanFlo XR X-ray Room, coming soon, lets you set up a foot ap oblique in a 3D room and score your positioning. See ScanFlo XR →
Written by the ScanFlo team from everyday radiographic practice.