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.. Standard exposure ranges from 75 to 85 kVp, 20 to 40 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
- Verify patient identity.
- Remove glasses, earrings, dentures.
- Position patient prone or upright (upright preferred for sinus air-fluid levels).
- Chin against the IR; tip of nose ~3/4" away from IR.
- Mentomeatal line (MML) perpendicular to IR; OML forms ~37° angle.
- No rotation: shoulders and head symmetrical.
- 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
- 75–85
- mAs
- 20–40
- SID
- 40" (102 cm)
- Notes
- For air-fluid level evaluation: take upright (not supine). Suspended respiration.
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 tilt: zygomatic arches symmetrical.
- Maxillary, lacrimal, zygomatic bones, and orbital floor demonstrated.
Common errors / ARRT traps
- 1 Under-extending the neck leaves the petrous ridges superimposed on the maxillary sinuses.
- 2 Over-extending drops the petrous ridges too far below the maxillary sinuses.
- 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.
- 5 Centering away from the acanthion cuts off the orbital floors.
Clinical indications
- Maxillary sinusitis evaluation (air-fluid level if upright).
- Facial bone fractures (zygomatic arch, orbital floor blowout, Le Fort).
- Foreign body localization.
- Pre/post-surgical sinus follow-up.
Aligned to the current ARRT Radiography Content Specifications.