Pns waterview postioning and tube distance
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Waters view PNS paranasal sinuses positioning radiograph
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PNS Waters view positioning tube distance radiography technique
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PNS Waters view occipitomental radiograph positioning
Here is a complete breakdown of the PNS Waters' View (Occipitomental / Parietoacanthial Projection):
PNS Waters' View - Positioning & Technical Factors
Other Names
- Occipitomental (OM) view
- Parietoacanthial projection
- Waters' projection (named after radiologist Charles Alexander Waters)
Indications
- Best view for maxillary sinuses (both sides)
- Frontal sinuses, ethmoid sinuses (partially)
- Sphenoid sinus (when mouth is open - "open mouth Waters")
- Facial fractures (zygomatic arch, orbital floor "blowout", Le Fort)
- Rhinosinusitis assessment
Patient Position
| Parameter | Detail |
|---|---|
| Posture | Patient erect, facing the image receptor (PA projection) |
| Chin | Raised/extended, resting chin against the bucky/detector |
| Midsagittal plane | Perpendicular to the receptor (no rotation) |
| Line alignment | Mentomandibular Line (MML) perpendicular to the receptor |
| Result | Orbitomeatal Line (OML) forms 37° angle with the image receptor |
| Head position | Slightly extended, looking slightly upward |
Key tip: The patient may need to "slouch forward" or do a slight "limbo" position to get the chin high enough. Check from above for any tilt or rotation.
Tube / Central Ray
| Parameter | Detail |
|---|---|
| Beam direction | Horizontal (perpendicular to the image receptor, 0° angulation) |
| Centering point | CR exits at the acanthion (base of the anterior nasal spine, between nose and upper lip) |
| SID (Source-to-Image Distance) | 100 cm (40 inches) |
| Grid | Yes (departmental variation applies) |
Exposure Factors
| Parameter | Value |
|---|---|
| kVp | 75-80 kVp |
| mAs | 20-25 mAs |
| Detector size | 24 cm x 30 cm |
| Orientation | Portrait |
Image Evaluation Criteria
- Petrous ridges should be projected below the maxillary sinuses (this is the key criterion)
- Petrous pyramids seen just below or at the floor of the maxillary antrum
- No rotation: assess symmetry of the coronoid processes bilaterally
- Base of mandible and occiput may be superimposed
- Both maxillary sinuses, frontal sinuses, and orbits visible
Structures Visualized
- Maxillary sinuses - best view (fluid levels visible when erect)
- Frontal sinuses
- Orbits and orbital rims
- Nasal septum
- Zygomatic arches
- Sphenoid sinus - only with open mouth modification
Comparison: Waters vs. Caldwell View
| Feature | Waters' View | Caldwell's View |
|---|---|---|
| Primary target | Maxillary sinuses | Frontal sinuses |
| Tube angulation | 0° (horizontal beam) | 15° caudad |
| OML angle to film | 37° | ~15° |
| Petrous ridges | Below maxillary sinuses | Lower 1/3 of orbits |
| CR exits at | Acanthion | Nasion |
Modified / Open Mouth Waters'
- Patient opens mouth wide during exposure
- Allows visualization of the sphenoid sinus through the open oral cavity
- All other positioning remains the same
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