AP tibia and fibula X-ray positioning (lower leg)
One of the routine tibia & fibula views. The patient lies on their back, the beam passes front to back (AP), straight on to the receptor, and the centring point is the mid-shaft.
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/Tibia & fibula
Still being checked: a radiographer is reviewing this guide. If your department does it differently, follow your department.
Patient position
Supine. Supine; turn the foot slightly in and steady it. After injury include the joint nearest the injury. Plaster: increase exposure.
Centring & collimation
Central ray
APCentre: the mid-shaft.
Beam: AP, perpendicular to the receptor.
Collimate: knee to ankle (at least the joint nearest the injury)
Distance, receptor & grid
| Setting | Value | Notes |
|---|---|---|
| SID | 100 cm | |
| Receptor | 18 × 43 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 | 53 | 1.25 | 0.5 |
| S | 53 | 2 | 0.5 |
| M | 53 | 2.5 | 0.5 |
| L | 53 | 4 | 0.8 |
These start from a classic film-screen chart (53 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. Including ankle only: 25 mAs.
Image quality checklist
- At least one joint, the nearest to the injury, is shown.
- 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 |
|---|---|---|
| Joint missed | Field too short | Image both ends separately if needed. |
Common questions
- Where do you centre for a lower leg AP X-ray?
- The centring point is the mid-shaft.
- What distance and beam angle does a lower leg AP need?
- 100 cm from the tube to the receptor. The beam passes front to back (AP), straight on to the receptor.
- What size receptor, and do you need a grid?
- Use an 18 × 43 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 lower leg AP?
- Joint missed. Usual cause: field too short. The fix: image both ends separately if needed.
Try it in ScanFlo: the ScanFlo XR X-ray Room, coming soon, lets you set up a lower leg ap in a 3D room and score your positioning. See ScanFlo XR →
Written by the ScanFlo team from everyday radiographic practice.