Oblique ribs X-ray positioning (supine)
An extra chest view, used when a routine one is not enough. The patient lies on their back, turned at an angle, the beam passes front to back (AP), straight on to the receptor, and the centring point is the axillary ribs of the side examined.
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
Oblique, supine. Roll the patient 45° with a pad under the uninjured side; raise the upper arm above the head.
Centring & collimation
Central ray
APCentre: the axillary ribs of the side examined.
Beam: AP, perpendicular to the receptor.
Collimate: the full hemithorax
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: R or L marker on the side nearest the detector
- Breathing: Breathe in 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 | 2.5 | 2.5 |
| S | 70 | 4 | 4 |
| M | 70 | 5 | 5 |
| L | 70 | 8 | 8 |
These start from a classic film-screen chart (70 kV, 20 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
- Axillary ribs shown without overlap.
- The whole hemithorax is included.
- 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 |
|---|---|---|
| Ribs foreshortened | Rotation less than 45° | Pad the patient to a true 45°. |
Common questions
- Where do you centre for a ribs oblique supine X-ray?
- The centring point is the axillary ribs of the side examined.
- What distance and beam angle does a ribs oblique supine 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 in and hold it while you expose.
- What goes wrong most often on a ribs oblique supine?
- Ribs foreshortened. Usual cause: rotation less than 45°. The fix: pad the patient to a true 45°.
Try it in ScanFlo: the ScanFlo XR X-ray Room, coming soon, lets you set up a ribs oblique supine in a 3D room and score your positioning. See ScanFlo XR →
Written by the ScanFlo team from everyday radiographic practice.