Skull Waters (parietoacanthial) is a radiography positioning projection of the Skull. Waters method. Maxillary sinuses, facial bones. MML perpendicular to IR. The centering point is located CR exits at the acanthion. MML (mentomeatal line) perpendicular to IR, chin touching IR, OML forms ~37° angle with IR. The central ray is CR perpendicular to IR. Centered to exit at the acanthion (junction of upper lip and nose). Image-quality criteria include petrous ridges projected just below the maxillary sinus floor, maxillary sinuses clearly visualized without overlap. A sample technique is 85 kVp with DR 8 or CR 16 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Inferior orbital margins.
- Maxillae and maxillary sinuses.
- Bony nasal septum.
- Zygomatic bones and zygomatic arches.
- Anterior nasal spine.
Patient preparation
- Trauma patient: rule out cervical spine fracture, subluxation or dislocation before moving or manipulating the head or neck.
- Verify patient identity.
- Remove glasses, earrings, dentures.
- Position patient prone or upright (upright preferred for sinus air-fluid levels).
- Chin against the IR.
- Mentomeatal line (MML) perpendicular to IR; OML forms ~37° angle.
- MSP perpendicular to the midline of the grid, with no head rotation or tilt.
- Suspend respiration.
Position & centering point
CR exits at the acanthion. MML (mentomeatal line) perpendicular to IR, chin touching IR, OML forms ~37° angle with IR.
Central ray
CR perpendicular to IR. Centered to exit at the acanthion (junction of upper lip and nose).
Exposure / technique
- kVp
- 85
- mAs
- DR 8 / CR 16
- SID
- 40" (102 cm)
- Notes
- For air-fluid level evaluation: take upright (not supine). Suspended respiration. Sample technique: DR 8 / CR 16 mAs at 85 kVp, 40 in SID, for a 24 cm part. Adjust for your equipment.
kVp and mAs are sample values. Use caution when applying them in your department.
Image-quality criteria
- Petrous ridges projected just below the maxillary sinus floor.
- Maxillary sinuses clearly visualized without overlap.
- No rotation: equal distance from lateral skull margin to mid-orbit bilaterally.
- No rotation or tilt: orbits and maxillary sinuses symmetric on each side (Merrill's).
- Inferior orbital margins, maxillae, nasal septum, and zygomatic bones demonstrated.
Common errors
- 1 Under-extending the neck leaves the petrous ridges superimposed on the maxillary sinuses.
- 2 Over-extending foreshortens the maxillary sinuses and hides the antral floors.
- 3 Rotation: unequal distance from each midlateral orbital margin to the lateral cranial cortex.
- 4 Setting the OML rather than the MML perpendicular, which is the 37 degree distinction.
Clinical indications
- Maxillary sinusitis evaluation (air-fluid level if upright).
- Facial bone fractures (zygomatic arch, orbital floor blowout, Le Fort).
- Foreign body localization.
- Neoplastic or inflammatory processes of the facial bones.