Paranasal Sinuses Radiographic Positioning

A set of 20 vocabulary flashcards covering radiographic projections, positioning lines, angles, central ray landmarks, and image evaluation criteria for the paranasal sinuses.

PA axial projection — Caldwell method

Projection used primarily to demonstrate the frontal sinuses and anterior ethmoidal air cells.

Parietoacanthial projection — Waters method

Projection that best demonstrates the maxillary sinuses.

Open-mouth Waters method

Projection that shows the sphenoidal sinuses projected through the open mouth.

Lateral projection (paranasal sinuses)

Projection that shows all four sinus groups, with the sphenoidal sinus best demonstrated.

Submentovertex (SMV) projection

Projection that demonstrates the sphenoidal and ethmoidal sinuses and a symmetric view of the anterior skull base.

OML angle (Caldwell method)

An angle of $15\text{ degrees}$ formed between the orbitomeatal line and the horizontal central ray when using a vertical IR.

OML angle (Waters method)

An angle of $37\text{ degrees}$ that the orbitomeatal line forms with the IR.

Infraorbitomeatal line (IOML) positioning in SMV

Positioned as nearly parallel as possible to the IR.

Infraorbitomeatal line (IOML) positioning in lateral sinus

Positioned horizontally.

Central ray landmark (lateral sinus projection)

Directed horizontally to a point $\frac{1}{2}\text{ to }1\text{ inch}$ ($1.3\text{ to }2.5\text{ cm}$) posterior to the outer canthus.

Central ray exit landmark (Caldwell method)

Nasion.

Central ray exit landmark (Waters method)

Acanthion.

Central ray pathway (SMV projection)

Passes through the sella turcica, perpendicular to the IOML.

Petrous pyramids criterion (Waters method)

Projected immediately below the floors of the maxillary sinuses on a correctly positioned image.

Petrous ridges criterion (Caldwell method)

Visualized in the lower third of the orbits.

Insufficient neck extension (Waters method)

Positioning error that causes the petrous ridges to overlap the lower maxillary sinuses.

Excessive neck extension (Waters method)

Positioning error that can foreshorten the maxillary sinuses and hide their floors.

Patient respiration during sinus projections

Suspend respiration.

Upright position and horizontal CR rationale

Technique required to demonstrate air-fluid levels in the paranasal sinuses.

Lateral sinus positioning evaluation criteria

The sella turcica is seen in profile; the orbital roofs and mandibular rami are superimposed.

PA Axial Projection (Caldwell Method)

A radiographic projection used primarily to demonstrate the frontal sinuses and anterior ethmoidal air cells.

Parietoacanthial Projection (Waters Method)

A radiographic projection that best demonstrates the maxillary sinuses.

Open-Mouth Waters Method

A modified parietoacanthial projection that demonstrates the sphenoidal sinuses projected through the open mouth.

Lateral Sinus Projection

A radiographic projection that displays all four sinus groups, with the sphenoidal sinus best demonstrated.

Submentovertex (SMV) Projection

A radiographic projection that demonstrates the sphenoidal and ethmoidal sinuses along with a symmetric view of the anterior skull base.

OML Angle for Caldwell Method

The angle of $15\text{ degrees}$ that the orbitomeatal line (OML) makes with the horizontal central ray when using a vertical image receptor (IR).

OML Angle for Waters Method

The angle of $37\text{ degrees}$ that the orbitomeatal line (OML) should form with the image receptor (IR).

IOML Alignment in SMV Projection

The positioning requirement where the infraorbitomeatal line (IOML) is placed as nearly parallel as possible to the image receptor (IR).

IOML Alignment in Lateral Projection

The positioning requirement where the infraorbitomeatal line (IOML) is positioned horizontally.

Central Ray Landmark for Lateral Projection

The horizontal central ray entrance located $\frac{1}{2}\text{ to }1\text{ inch}$ ($1.3\text{ to }2.5\text{ cm}$) posterior to the outer canthus.

Nasion (Caldwell Method)

The central ray exit landmark for the PA axial (Caldwell) projection.

Acanthion (Waters Method)

The central ray exit landmark for the parietoacanthial (Waters) projection.

SMV Central Ray Trajectory

The central ray path that passes through the skull via the sella turcica, perpendicular to the infraorbitomeatal line (IOML).

Petrous Pyramids (Waters Method)

The anatomical structures that must lie immediately below the floors of the maxillary sinuses on a correctly positioned Waters image.

Petrous Ridges (Caldwell Method)

The anatomical structures that should be projected in the lower third of the orbits in a correctly positioned Caldwell view.

Insufficient Neck Extension (Waters Method)

A positioning error on the Waters projection that causes the petrous ridges to overlap the lower maxillary sinuses.

Excessive Neck Extension (Waters Method)

A positioning error on the Waters projection that causes foreshortening of the maxillary sinuses and hides their floors.

Suspend Respiration

The breathing instruction given to the patient during radiographic exposures of the paranasal sinuses.

Upright Position with Horizontal CR

The preferred patient and beam positioning orientation utilized to demonstrate air-fluid levels in the paranasal sinuses.

Lateral Sinus Image Criteria

The radiographic criteria requiring the sella turcica to be seen in profile and the orbital roofs and mandibular rami to be superimposed.