AP chest X-ray positioning (infant, erect)
One of the routine chest views. The patient stands, the beam passes front to back (AP), straight on to the receptor, and the centring point is between the nipples.
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
Erect. The child sits upright with the back flat on the bucky, supported under both arms by a carer; a second carer can keep the legs still. Every carer in the room wears a lead apron; give them lead gloves too if the department has them.
Centring & collimation
Central ray
APCentre: between the nipples.
Beam: AP, perpendicular to the receptor.
Collimate: tightly to the thorax
Distance, receptor & grid
| Setting | Value | Notes |
|---|---|---|
| SID | 110 cm | |
| Receptor | 24 × 30 cm | portrait |
| Placement | Erect (wall) bucky | Grid in |
| Angulation | None | Perpendicular to the receptor |
Marker & breathing
- Marker: anatomical side marker on the side being examined, clear of anatomy
- 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 | 90 | 0.5 | 0.5 |
| S | 90 | 0.5 | 0.5 |
| M | 90 | 0.63 | 0.63 |
| L | 90 | 1 | 1 |
These start from a classic film-screen chart (90 kV, 1.6 mAs at 140 cm) and are adjusted for a digital detector at 110 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
- No rotation.
- Exposure in inspiration if possible.
- Holders' hands are outside the field.
- 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 |
|---|---|---|
| Image blurred | Child moving | Expose when the child is still, ideally on inspiration. |
Common questions
- Where do you centre for a chest AP erect (infant) X-ray?
- The centring point is between the nipples.
- What distance and beam angle does a chest AP erect (infant) need?
- 110 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, in the wall bucky. A grid is needed.
- Where does the lead marker go?
- anatomical side marker on the side being examined, clear of anatomy.
- What goes wrong most often on a chest AP erect (infant)?
- Image blurred. Usual cause: child moving. The fix: expose when the child is still, ideally on inspiration.
Try it in ScanFlo: the ScanFlo XR X-ray Room, coming soon, lets you set up a chest ap erect (infant) in a 3D room and score your positioning. See ScanFlo XR →
Written by the ScanFlo team from everyday radiographic practice.