Lateral thumb X-ray positioning
One of the routine hand views. The patient sits, the beam passes from side to side, straight on to the receptor, and the centring point is the first metacarpophalangeal joint.
By the ScanFlo Editorial Team · Updated
In this section · X-ray positioning
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- C-spine positioning
- Chest positioning
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- L-spine positioning
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Still being checked: a radiographer is reviewing this guide. If your department does it differently, follow your department.
Patient position
Sitting. Palm down with the fingers closed; the thumb lies naturally lateral.
Centring & collimation
Central ray
lateralCentre: the first metacarpophalangeal joint.
Beam: lateral, perpendicular to the receptor.
Collimate: the thumb and first carpometacarpal joint
Distance, receptor & grid
| Setting | Value | Notes |
|---|---|---|
| SID | 100 cm | |
| Receptor | 18 × 24 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 | 46 | 0.5 | 0.5 |
| S | 46 | 0.8 | 0.5 |
| M | 46 | 1 | 0.5 |
| L | 46 | 1.6 | 0.63 |
These start from a classic film-screen chart (46 kV, 16 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
- A true lateral of the thumb.
- 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 |
|---|---|---|
| Oblique thumb | Hand cupped | Flatten the palm. |
Common questions
- Where do you centre for a thumb lateral X-ray?
- The centring point is the first metacarpophalangeal joint.
- What distance and beam angle does a thumb lateral need?
- 100 cm from the tube to the receptor. The beam passes from side to side, straight on to the receptor.
- What size receptor, and do you need a grid?
- Use an 18 × 24 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 thumb lateral?
- Oblique thumb. Usual cause: hand cupped. The fix: flatten the palm.
Try it in ScanFlo: the ScanFlo XR X-ray Room, coming soon, lets you set up a thumb lateral in a 3D room and score your positioning. See ScanFlo XR →
Written by the ScanFlo team from everyday radiographic practice.