Sinuses Lateral is a radiography positioning projection of the Skull. Upright lateral. CR horizontal. Demonstrates air-fluid levels. The centering point is located halfway between the outer canthus and the EAM (Bontrager), or 1/2 to 1 inch posterior to the outer canthus (Merrill's). IOML horizontal, IPL perpendicular. The central ray is horizontal and perpendicular to IR. Centered halfway between outer canthus and EAM (Bontrager). Merrill's enters 1/2 to 1 inch posterior to the outer canthus. Image-quality criteria include all four paranasal sinus groups visible in lateral profile, sella turcica seen in profile. 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
- Frontal sinuses in profile.
- Ethmoid sinuses superimposed.
- Sphenoid sinus in profile, posterior to ethmoids.
- Maxillary sinuses superimposed.
- Sella turcica in lateral profile.
- Air-fluid levels when present.
Patient preparation
- Verify patient identity.
- Remove glasses, earrings, hairpins, and dentures.
- Position patient upright (seated or standing) in a true lateral at the IR.
- Place affected side against the receptor.
- IPL perpendicular to IR. IOML horizontal.
- MSP parallel to IR with no rotation or tilt.
- If the patient was recumbent, wait at least 5 minutes upright so fluid can settle.
- Suspend respiration during exposure.
Position & centering point
Halfway between the outer canthus and the EAM (Bontrager), or 1/2 to 1 inch posterior to the outer canthus (Merrill's). IOML horizontal, IPL perpendicular.
Central ray
Horizontal and perpendicular to IR. Centered halfway between outer canthus and EAM (Bontrager). Merrill's enters 1/2 to 1 inch posterior to the outer canthus.
Exposure / technique
- kVp
- 85
- mAs
- DR 3.2 / CR 6.3
- SID
- 40" (102 cm)
- Notes
- Erect with a horizontal beam is required to show air-fluid levels. If the patient cannot be upright, keep the beam horizontal: Bontrager points to a horizontal beam lateral, Merrill's to dorsal decubitus. For preoperative measurements, Merrill's uses a 72-inch SID. Grid required. 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
- All four paranasal sinus groups visible in lateral profile.
- Sella turcica seen in profile.
- No rotation: superimposed mandibular rami.
- No tilt: superimposed orbital roofs.
- Air-fluid levels demonstrated when present.
- Sharp bony detail of the sinus walls.
Common errors
- 1 Recumbent positioning hides air-fluid levels.
- 2 Vertical CR fails to show fluid-air interfaces.
- 3 Rotation of head: mandibular rami not superimposed.
- 4 Tilt of head: orbital roofs not superimposed.
Clinical indications
- Evaluation of sinusitis and detection of air-fluid levels.
- Sinus polyps or cysts.
- Preoperative measurements, made at a 72-inch SID (Merrill's).
- Assessment of sphenoid and frontal sinus pathology.