WATERS PROJECTION
Paranasal Sinuses • Occipitomental • Evaluation of maxillary and frontal sinuses
Anatomy of the paranasal sinuses
Waters Projection - Reference image
Exposure Factors
70-75
Kilovoltage (kV)
20
Milliampere-seconds (mAs)
Large Focal Spot
Focal Spot Type
105-115 cm
Source-to-Image Distance (SID)
Equipment: With bucky. Patient Position: Upright (seated or standing).
Cassette Size
18 × 24 cm
Longitudinal
Visible Anatomical Structures
- Maxillary sinuses - Both cavities
- Frontal sinuses - Above the orbits
- Ethmoid sinuses - Between the orbits
- Orbital walls - Inferior and lateral
- Nasal cavities - Septum and turbinates
- Zygomatic arches - Cheekbones
Patient Positioning
Patient in upright position (seated or standing)
Place the chin against the bucky
Keep the mouth open normally
Align the MSP (midsagittal plane) with the midline of the IR
Position the OML (orbitomeatal line) at 37° to the IR
Position the EAM (external auditory meatus) equidistant to the bucky
Place hands on both sides of the head for support
Head perpendicular to the IR
Central Ray Direction
Perpendicular to the IR
The central ray exits through the mouth, centering the IR
Direction: cranial → caudal
Patient Instructions
"Hold your breath during the exposure"
Maintain complete immobility for 1-2 seconds
Additional Considerations
Trauma
In facial trauma, evaluate for possible CSF leak before Waters positioning.
Pediatric
In children, consider reducing kV and mAs according to the ALARA protocol.
Image Quality
Clear visualization of sinus bony walls without superimposition.