Skull Lateral is a radiography positioning projection of the Skull. True lateral cranium. SID 40". CR perpendicular to IR. The centering point is located 2" (5 cm) superior to the EAM. Mid-sagittal plane parallel to IR; interpupillary line perpendicular to IR. The central ray is perpendicular to IR (horizontal when the patient is erect or for a trauma lateral). Centered to a point 2" superior to the EAM (external auditory meatus). Image-quality criteria include superimposed mandibular rami (no rotation), superimposed orbital roofs. A sample technique is 85 kVp with DR 3.2 or CR 6.3 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Entire cranium with the parietal bones superimposed.
- Sella turcica, including anterior and posterior clinoid processes.
- Dorsum sellae and clivus in profile.
- Greater wings of the sphenoid, superimposed.
- Orbital roofs (plates), superimposed.
- Mandibular rami, superimposed.
Patient preparation
- Trauma patient: this semiprone setup does not apply. A supine horizontal beam lateral is required. Rule out cervical spine fracture, subluxation or dislocation before moving the head or neck.
- Verify patient identity.
- Remove glasses, earrings, hairpins, dentures, hearing aids.
- Position patient semiprone or erect with the side of interest against the IR.
- Align mid-sagittal plane parallel to IR; interpupillary line perpendicular to IR.
- IOML (infraorbitomeatal line) perpendicular to the front edge of the IR.
- Suspend respiration during exposure.
Position & centering point
2" (5 cm) superior to the EAM. Mid-sagittal plane parallel to IR; interpupillary line perpendicular to IR.
Central ray
Perpendicular to IR (horizontal when the patient is erect or for a trauma lateral). Centered to a point 2" superior to the EAM (external auditory meatus).
Exposure / technique
- kVp
- 85
- mAs
- DR 3.2 / CR 6.3
- SID
- 40" (102 cm)
- Notes
- ARRT lists the trauma cross-table (horizontal beam) lateral as its own line in both the 2022 and 2027 outlines. Use a small focal spot for sharper detail of cranial sutures. Sample technique: DR 3.2 / CR 6.3 mAs at 85 kVp, 40 in SID, for a 15 cm part. Adjust for your equipment.
kVp and mAs are sample values. Use caution when applying them in your department.
Image-quality criteria
- Superimposed mandibular rami (no rotation).
- Superimposed orbital roofs.
- Sella turcica seen in profile.
- Cranium centered on IR with ~1" margin all around.
- Detail of cranial bones, sutures, and sella turcica visible.
- No tilt: TMJs superimposed.
Common errors
- 1 Rotation: the mandibular rami separate anteriorly and posteriorly instead of superimposing.
- 2 Rotation: the greater sphenoid wings separate rather than superimpose.
- 3 Tilt: the orbital roofs separate superiorly and inferiorly.
- 4 Neck flexion off, so the IOML is not perpendicular to the front edge of the IR.
Clinical indications
- Skull fractures, neoplastic processes, and Paget disease.
- Trauma: use the horizontal beam lateral, which may show sphenoid air-fluid levels, a sign of basal skull fracture if intracranial bleeding occurs.