Waters View X-Ray Guide: Closed & Open Mouth Positioning Notes

Waters (Parietoacanthial) Projection Series

1. Classification & Variants of the Waters Projection

The Waters method is not a single rigid view; it consists of three specialized variations engineered to isolate specific structures of the visceral cranium (facial skeleton) and paranasal sinuses:

• Standard Waters (Parietoacanthial — Closed Mouth):
  • Primary Target: Maxillary sinuses (Antra of Highmore), infraorbital rims, zygomaticomaxillary complexes, and anterior nasal spine.
  • Head Extension: Orbitomeatal Line (OML) forms a 37⁰ angle with the Image Receptor (IR); Mentomeatal Line (MML) is perpendicular.
• Transoral Waters (Open-Mouth Waters):
  • Primary Target: Sphenoid sinuses projected directly through the open oral cavity without superimposition of the teeth or hard palate, alongside maxillary sinuses.
  • Head Extension: Identical 37⁰ OML angle as the standard view, with the mandible dropped maximally.
• Modified Waters (Parietoacanthial — Shallow Angle):
  • Primary Target: Orbital floors (detection of blowout fractures and herniated soft tissue) and inferior orbital rims.
  • Head Extension: Less neck extension; OML forms a 55⁰ angle with the IR; Lips-Meatal Line (LML) is perpendicular. This places the orbital floor parallel to the Central Ray.

2. Comprehensive Clinical Indications & Pathological Findings

A. Paranasal Sinus Pathology

• Acute Sinusitis:
  • Air-Fluid Levels: Sharp, straight horizontal line separating radiolucent air above from radiodense exudate (pus/serous fluid) below. Demonstrable only when the patient is upright with a horizontal beam.
  • Mucosal Thickening: Peripheral soft-tissue thickening > 4 mm running along the bony cortical sinus walls.
  • Complete Opacification: Total loss of aeration in the maxillary antrum (hazy, white appearance).
• Chronic Sinusitis & Polyposis: Soft-tissue polypoid masses (mucoceles, retention cysts, or sinonasal polyps) showing rounded, convex soft-tissue domes protruding into the sinus cavity.
• Fungal Sinusitis & Mycetoma: Dense, irregular calcifications (antroliths) within an opacified sinus.
• Sphenoid Sinusitis (Open-Mouth): Opacification or fluid levels inside the sphenoid sinuses, critical because untreated sphenoid sinusitis can lead to cavernous sinus thrombosis or intracranial abscess.

B. Maxillofacial & Orbital Trauma

• Blowout Fractures of the Orbit:
  • Direct blunt force to the eyeball increases intraorbital pressure, fracturing the paper-thin orbital floor (maxillary sinus roof).
  • “Teardrop Sign”: A soft-tissue polypoid density herniating down through the fractured orbital floor into the superior aspect of the maxillary sinus (composed of orbital fat and the inferior rectus muscle, leading to diplopia and enophthalmos).
• Tripod (Zygomaticomaxillary Complex – ZMC) Fractures: Tripartite disruption involving:
  1. Zygomaticofrontal suture (lateral orbital wall).
  2. Infraorbital rim and maxillary sinus wall.
  3. Zygomatic arch.
• Le Fort Midfacial Fractures:
  • Le Fort I: Horizontal fracture across the alveolar process of the maxilla.
  • Le Fort II (Pyramidal): Extends through the nasal bones, lacrimal bones, infraorbital rim, and maxillary sinus walls.
  • Le Fort III (Craniofacial Dysjunction): Complete separation of the facial skeleton from the cranial base traversing the zygomatic arches, orbits, and nasofrontal suture.
• Basilar Skull Fractures (Sphenoid Hemosinus): On Open-Mouth Waters, blood pooling in the sphenoid sinus (hemosinus) serves as an indirect sign of a fracture through the sella turcica or sphenoid bone.

3. Absolute & Relative Contraindications

• Suspected / Uncleared Cervical Spine Trauma:
  • Contraindication: Hyperextending the neck to achieve MML perpendicularity can compress or transect the spinal cord if an unstable C-spine fracture (e.g., Jefferson, Hangman’s, or odontoid fracture) is present.
  • Trauma Adaptation (Reverse Waters / AP Axial): Keep the patient strictly supine with the head and neck neutral in a C-collar. Angle the Central Ray 30⁰ to 37⁰ Cephalad directed to the acanthion.
• Inability to Sit or Stand Erect (Erect vs. Recumbent Conflict):
  • If a patient is placed recumbent (prone/supine) for sinus evaluation, fluid layers along the posterior sinus wall rather than creating a meniscus, causing pseudo-diffuse opacification and masking air-fluid levels.
  • Solution: If the patient cannot sit, use a Cross-Table Lateral (Horizontal Beam) to evaluate fluid levels.

4. Technical Factors & Exposure Physics

5. Biomechanical Patient Positioning Protocols

Method A: Standard Waters (Parietoacanthial — Closed Mouth)

1. Initial Alignment: Seat the patient erect facing the vertical Bucky. Align the midsagittal plane (MSP) perpendicular to the central vertical axis of the grid.
2. Head Extension: Have the patient extend their neck, resting the tip of the chin (mentum) firmly against the face of the Bucky.
3. Reference Line Check:
   • Adjust extension until the Mentomeatal Line (MML) is strictly perpendicular to the IR plane.
   • This mechanical orientation ensures the Orbitomeatal Line (OML) forms an exact 37⁰ angle with the receptor surface (or 53⁰ relative to the central ray).
   • The tip of the nose should rest approximately 1 to 2 cm off the surface of the Bucky board.
4. Tilt & Rotation Check: Ensure the Interpupillary Line (IPL) is parallel to the floor (verifying zero lateral head tilt).

Method B: Transoral Waters (Open-Mouth Parietoacanthial)

1. Position the patient identically to the Standard Waters position (Chin on Bucky, MML perpendicular, OML at 37⁰, MSP perpendicular).
2. Instruct the patient: “Drop your lower jaw open as wide as possible without moving your head or lifting your chin from the board.”
3. Technologist Check: Ensure the patient opens their mouth via mandibular depression only (hinging the TMJ) rather than hyperextending the neck further.
4. The open oral cavity allows the horizontal X-ray beam to pass unobstructed beneath the maxillary dentition, penetrating directly through the sphenoid sinuses.

Method C: Modified Waters (For Blowout Fractures)

1. Seat the patient erect facing the Bucky.
2. Extend the neck slightly less than the standard view, placing both the chin and nose in contact with the Bucky face.
3. Adjust the head until the Lips-Meatal Line (LML) is perpendicular to the IR. This sets the OML at a 55⁰ angle to the receptor.
4. This positions the orbital floor perpendicular to the IR and parallel to the CR, eliminating perspective distortion of the inferior orbital rim and orbital floor.

6. Central Ray (CR), Beam Alignment & Collimation

• Central Ray Trajectory: Strictly perpendicular (0⁰) to the image receptor and parallel to the floor.
• Exit Point: Directed through the parieto-occipital region to exit precisely at the Acanthion (the midline junction of the upper lip and the base of the nasal septum).
• Field Collimation: Collimated tightly on four sides:
  • Superiorly: Just above the frontal sinuses (supraorbital ridge level).
  • Inferiorly: Lower margin of the mandibular symphysis (chin).
  • Laterally: To the skin margins of the zygomatic arches.

7. Errors, Artifacts & Corrective Actions

8. Radiographic Anatomy & Quality Evaluation Criteria

• Petrous Ridge Clearance (Primary Quality Hallmark):
  • The superior borders of the petrous pyramids must be projected immediately inferior to the floor of the maxillary sinuses bilaterally.
• Maxillary Sinuses:
  • Symmetrical, unobstructed projection of both maxillary antra with clear aeration and sharply defined cortical bone boundaries.
• Transoral Clearance (Open-Mouth Waters):
  • The sphenoid sinuses are clearly visualized within the radiolucent window of the open mouth, unobstructed by the alveolar process of the maxilla or the mandibular teeth.
• Midfacial & Orbital Symmetry:
  • Symmetrical infraorbital margins, zygomatic processes, and frontal processes of the maxillae.
  • Distance between the lateral orbital rim and the outer lateral calvarium is identical on both sides.
  • Nasal septum is vertical and aligned along the central axis without rotational distortion.
• Tissue Contrast: High-contrast resolution distinguishing mucosal soft-tissue swelling from aerated sinus cavities, with sharp, unblurred trabecular detail across all facial bones.