AP forearm X-ray positioning
One of the routine forearm views. The patient sits, the beam passes front to back (AP), straight on to the receptor, and the centring point is the mid-forearm.
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
Still being checked: a radiographer is reviewing this guide. If your department does it differently, follow your department.
Patient position
Sitting. Seat the patient at the holder, forearm on the detector, elbow and wrist both included. Plaster: increase exposure.
Centring & collimation
Central ray
APCentre: the mid-forearm.
Beam: AP, perpendicular to the receptor.
Collimate: wrist and elbow joints
Distance, receptor & grid
| Setting | Value | Notes |
|---|---|---|
| SID | 100 cm | |
| Receptor | 24 × 30 cm | portrait |
| Placement | On the holder | 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 | 0.5 | 0.5 |
| S | 53 | 0.63 | 0.5 |
| M | 53 | 0.8 | 0.5 |
| L | 53 | 1.25 | 0.5 |
These start from a classic film-screen chart (53 kV, 10 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. In plaster: 60 kV, 4 mAs (green 400).
Image quality checklist
- Both wrist and elbow joints included.
- Radius and ulna parallel.
- 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 |
|---|---|---|
| Bones crossed | Hand pronated | Supinate the hand. |
Common questions
- Where do you centre for a forearm AP X-ray?
- The centring point is the mid-forearm.
- What distance and beam angle does a forearm 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 a 24 × 30 cm receptor, portrait, on the holder. 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 forearm AP?
- Bones crossed. Usual cause: hand pronated. The fix: supinate the hand.
Try it in ScanFlo: the ScanFlo XR X-ray Room, coming soon, lets you set up a forearm ap in a 3D room and score your positioning. See ScanFlo XR →
Written by the ScanFlo team from everyday radiographic practice.