AP thoracolumbar spine X-ray positioning
An extra T-spine view, used when a routine one is not enough. The patient lies on their back, the beam passes front to back (AP), straight on to the receptor, and the centring point is T12.
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
Supine. Supine with the knees flexed, mid-sagittal plane central.
Centring & collimation
Central ray
APCentre: T12.
Beam: AP, perpendicular to the receptor.
Collimate: T10 to L2 and beyond as requested
Distance, receptor & grid
| Setting | Value | Notes |
|---|---|---|
| SID | 100 cm | |
| Receptor | 35 × 43 cm | portrait |
| Placement | Table bucky | Grid in |
| Angulation | None | Perpendicular to the receptor |
Marker & breathing
- Marker: anatomical side marker on the side being examined, clear of anatomy
- Breathing: Breathe out and hold.
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 | 70 | 12.5 | 5 |
| S | 70 | 20 | 8 |
| M | 70 | 25 | 10 |
| L | 70 | 40 | 16 |
These start from a classic film-screen chart (70 kV, 50 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
- Thoracolumbar junction central.
- No rotation.
- 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 |
|---|---|---|
| Junction off-centre | Centring at L3 | Centre at T12. |
Common questions
- Where do you centre for a thoracolumbar spine AP X-ray?
- The centring point is T12.
- What distance and beam angle does a thoracolumbar spine 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 35 × 43 cm receptor, portrait, in the table bucky. A grid is needed.
- What should the patient do with their breathing?
- Ask them to breathe out and hold it while you expose.
- What goes wrong most often on a thoracolumbar spine AP?
- Junction off-centre. Usual cause: centring at L3. The fix: centre at T12.
Try it in ScanFlo: the ScanFlo XR X-ray Room, coming soon, lets you set up a thoracolumbar spine ap in a 3D room and score your positioning. See ScanFlo XR →
Written by the ScanFlo team from everyday radiographic practice.