Lateral skull X-ray positioning (horizontal beam)
One of the routine skull views. The patient lies on their back, the beam passes from side to side, straight on to the receptor with the tube horizontal, and the centring point is 2 cm above the external auditory meatus.
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. Remove dentures, earrings, hair clips and anything in the hair. Supine with the head on a thin pad, the side examined against the vertical detector, interpupillary line vertical.
Centring & collimation
Central ray
lateralCentre: 2 cm above the external auditory meatus.
Beam: lateral, perpendicular to the receptor, horizontal beam.
Collimate: the whole skull, front to back
Distance, receptor & grid
| Setting | Value | Notes |
|---|---|---|
| SID | 100 cm | Horizontal beam |
| Receptor | 24 × 30 cm | landscape |
| Placement | Erect (wall) bucky | Grid in |
| 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 | 70 | 4 | 1 |
| S | 70 | 6.3 | 1.6 |
| M | 70 | 8 | 2 |
| L | 70 | 12.5 | 3.2 |
| Child | 70 | 4 | 1 |
These start from a classic film-screen chart (70 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
- Front and back of the skull included.
- Anterior cranial fossa floors superimposed.
- A fluid level in a sinus is visible (horizontal beam).
- 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 |
|---|---|---|
| Double floor of the anterior fossa | Head tilted | Make the interpupillary line vertical. |
Common questions
- Where do you centre for a skull lateral (horizontal beam) X-ray?
- The centring point is 2 cm above the external auditory meatus.
- What distance and beam angle does a skull lateral (horizontal beam) need?
- 100 cm from the tube to the receptor. The beam passes from side to side, straight on to the receptor with the tube horizontal.
- What size receptor, and do you need a grid?
- Use a 24 × 30 cm receptor, landscape, in the wall bucky. A 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 skull lateral (horizontal beam)?
- Double floor of the anterior fossa. Usual cause: head tilted. The fix: make the interpupillary line vertical.
Try it in ScanFlo: the ScanFlo XR X-ray Room, coming soon, lets you set up a skull lateral (horizontal beam) in a 3D room and score your positioning. See ScanFlo XR →
Written by the ScanFlo team from everyday radiographic practice.