Cranium, Facial Bones, and Paranasal Sinuses Study Notes
Chapter 11
Part B: Cranium, Facial Bones, and Paranasal Sinuses
Positioning of the Cranium
Copyright: © 2018, Elsevier Inc. All Rights Reserved.
Cranium Series
Routine Projections
AP axial (Towne)
Lateral
PA 15° (Caldwell)
PA 25° to 30°
PA 0°
Special Projections
PA axial (Haas)
SMV (submentovertex)
AP Axial (Towne Method)
CR (Central Ray): 30° caudad to OML (Orbitomeatal Line) or 37° to IOML (Iliomeatal Line)
CR Location: 2.5 inches (6.5 cm) above the glabella.
Routine: AP axial (Towne)
Evaluation Criteria: AP Axial
Dorsum sellae projected within foramen magnum.
Entire skull visualized.
No rotation or tilt.
Petrous ridges symmetric.
Optimal exposure factors.
Right Lateral Skull Positioning
MSP (Mid-Sagittal Plane): Parallel to the IR (Image Receptor).
IOML: Interpupillary perpendicular.
CR: 2 inches (5 cm) superior to EAM (External Auditory Meatus).
Routine: AP axial (Towne), Lateral.
Trauma Lateral Skull
Cross-table for air-fluid levels.
Evaluation Criteria: Lateral Skull
Entire skull visualized.
Cranium seen without rotation or tilt.
Correct flexion and extension of skull.
Optimal exposure factors.
PA Cranium
CR: 15° caudad exit at nasion; 0° exit at glabella.
Routine: AP axial (Towne), Lateral, PA 15° or PA 0°.
Evaluation Criteria: PA 15° (Caldwell)
Entire skull visualized.
No rotation.
Petrous ridges over lower ⅓ of orbits.
Optimal exposure factors.
Comparison of PA Projections
0° PA Projection: Petrous ridges over supraorbital margin.
15° Caldwell: Petrous ridges over lower ⅓ of orbits.
PA (Axial) Projections Variations
0 degree angulation: best demonstrates the squamous portion of the frontal bone.
15° Caldwell
0° PA
30° PA
Evaluation Criteria: AP 0° to OML
Entire skull visualized.
No rotation.
Petrous ridges superimpose superior orbital regions.
Optimal exposure factors.
SMV Projection
CR: Perpendicular to IOML and IR.
CR Location: 1.5 inches (4 cm) inferior to mandibular symphysis.
Special: SMV.
Evaluation Criteria: SMV
Entire skull visualized.
Mandibular condyles anterior to petrous pyramids.
No rotation or tilt.
Optimal exposure factors.
The chin or mentum free of superimposition.
PA Axial (Haas Method)
OML: Perpendicular to IR.
CR: 25° cephalad; CR exits at 1.5 inches (4 cm) superior to nasion.
Special: PA axial (Haas).
Evaluation Criteria: PA Axial (Haas)
Similar to AP axial except:
Dorsum sellae appears larger within foramen magnum.
Magnification of occipital bone evident.
Optimal exposure factors.
Positioning of Facial Bones and Paranasal Sinuses
Copyright: © 2018, Elsevier Inc. All Rights Reserved.
Lateral Facial Bones
CR: Perpendicular, centered to zygoma.
Routine: Lateral.
Evaluation Criteria: Lateral Facial Bones
Zygomatic bones centered in radiograph.
No rotation or tilt (rotation indicated if mandibular rami are not superimposed).
Optimal exposure factors.
Parietoacanthial (Waters) Projection
MML (Mentomeatal line): Perpendicular to IR.
CR: Perpendicular to IR, exiting at acanthion.
Angle: 37° between OML and plane of IR.
Significance: Best demonstrates a deviated septum.
Routine: Lateral, Parietoacanthial (Waters).
Erect Parietoacanthial
CR: Horizontal, 37° angulation with OML and IR (MML perpendicular to IR).
Evaluation Criteria: Parietoacanthial
Petrous ridges below maxillary sinuses.
No rotation.
Optimal exposure factors.
PA Axial (Caldwell)
OML: Perpendicular to IR.
CR: 15° caudad, exits at nasion.
Routine: Lateral, Parietoacanthial (Waters), PA axial (Caldwell).
Evaluation Criteria: PA Axial (Caldwell)
Petrous ridges projected into lower ⅓ of orbits.
No rotation.
Optimal exposure factors.
Modified Parietoacanthial (Modified Waters)
CR: Perpendicular, exiting at acanthion.
LML (Lip-Menton Line): Perpendicular to IR.
OML: 55° angle to IR.
Special: Modified parietoacanthial; ideal for demonstrating possible orbital fractures and foreign bodies in the eye and floor of orbits.
Evaluation Criteria: Modified Parietoacanthial
Petrous ridges projected in lower ⅓ of maxillary sinuses.
Orbital floors not distorted.
No rotation.
Optimal exposure factors.
Nasal Bone Routine
Routine: Lateral, Parietoacanthial (Waters).
Special: PA axial (Caldwell), Superoinferior tangential (axial).
Lateral Nasal Bones
Interpupillary line: Perpendicular to IR.
CR: Perpendicular, centered to ½ inch (1.25 cm) inferior to nasion.
Routine: Lateral.
Evaluation Criteria: Lateral Nasal Bones
Nasal bones centered.
No rotation.
Optimal exposure factors.
Close collimation.
Superoinferior Tangential: Axial
IR: Perpendicular to GAL (Glenioal Line).
CR: Parallel to GAL.
Significance: Demonstrates possible medial-lateral displacement.
Special: Superoinferior.
Evaluation Criteria: Superoinferior Tangential
Nasal bones free of superimposition.
No rotation.
Optimal exposure factors.
Zygomatic Arch Routine
Routine: SMV, Oblique inferosuperior (tangential), AP axial (modified Towne).
Special: Parietoacanthial (Waters), Lateral.
SMV Zygomatic Arches
CR: Perpendicular to IOML; IOML parallel to IR.
If patient cannot extend their neck enough for proper positioning, angle CR to be perpendicular to IOML.
Routine: SMV.
Evaluation Criteria: SMV Zygomatic Arches
Zygomatic arches well demonstrated in profile.
Zygomatic arches symmetric.
No rotation.
Optimal exposure factors.
Oblique Inferosuperior: Tangential
IOML: Parallel to IR.
Skull Rotation and Tilt: 15° toward affected side.
CR: Perpendicular to IR and IOML, directed to the arch of interest.
Routine: SMV, Oblique inferosuperior.
Evaluation Criteria: Oblique Inferosuperior
Zygomatic arches well demonstrated.
No superimposition.
Optimal exposure factors.
AP Axial (Modified Towne)
CR: 30° to OML or 37° to IOML.
CR Location: 1 inch (2.5 cm) superior to glabella (to pass through mid arches).
Routine: SMV, Oblique inferosuperior, AP axial (modified Towne).
Evaluation Criteria: AP Axial
Zygomatic arches centered.
No rotation.
Optimal exposure factors.
Mandible Routine
Routine: Axiolateral oblique, PA (or PA axial).
Special: Submentovertex, Panorex.
Axiolateral Oblique Positioning
Head in true lateral position best demonstrates ramus.
30° rotation toward IR best demonstrates body.
45° rotation best demonstrates mentum.
10° to 15° rotation best provides a general survey of mandible – routine.
Axiolateral Oblique Positioning Techniques
Employ a combination of tilt on the head and CR angle not to exceed 25° (Example: Angle the CR 10° and add 15° of head tilt).
OR employ 25° cephalad angle toward the IR with no head tilt.
Chin extended to avoid superimposition of C-spine.
Evaluation Criteria: Axiolateral Oblique
Area of interest demonstrated.
Mandible not foreshortened.
Optimal exposure factors.
PA and PA Axial Mandible
OML: Perpendicular to IR.
CR Orientation: Perpendicular to exit at lips.
Routine: Axiolateral oblique, PA.
Optional PA axial: CR 20° to 25° cephalad to better visualize condyles (heads) and neck.
Evaluation Criteria: PA Mandible
Entire mandible included.
No rotation.
Optimal exposure factors.
AP Axial Mandible
OML or IOML: Perpendicular to IR.
CR: 35° (OML) - 42° (IOML) caudad.
CR Location: Centered to glabella.
Routine: Axiolateral oblique, PA, AP axial.
Evaluation Criteria: AP Axial Mandible
Best for visualization of condyloid processes demonstrated and symmetric.
No rotation.
Optimal exposure factors.
SMV Mandible
IOML: Parallel to IR.
CR: Midway between mandibular angles, perpendicular to IOML.
Special: SMV.
Evaluation Criteria: SMV Mandible
Entire mandible demonstrated.
No rotation or tilt.
Optimal exposure factors.
Panorex
Special: SMV, Panorex; IOML parallel to floor.
Evaluation Criteria: Panorex
Entire mandible and all teeth demonstrated.
No rotation or tilt.
Optimal exposure factors.
TMJ Routine
Routine: AP axial (modified Towne), Axiolateral 15° oblique (modified Law), Axiolateral (Schuller), Tomography.
AP Axial (Modified Towne) TMJ
OML: Perpendicular to IR.
CR: 35° caudad, CR level of TMJ (2 inches [5 cm] anterior to EAM).
Routine: AP axial.
Evaluation Criteria: AP Axial TMJ
Condyloid processes and TM fossa demonstrated.
No rotation.
Optimal exposure factors.
Axiolateral Oblique (Modified Law Method) TMJ
Skull Rotation: 15° toward IR (Brachycephalic skull requires less rotation compared to an average shaped skull).
CR Location: 1.5 inches (4 cm) superior to upside EAM, angled 15° caudad.
Routine: AP axial, Axiolateral oblique (Law).
Evaluation Criteria: Axiolateral Oblique TMJ
TMJ closest to IR demonstrated.
Open and closed mouth projections.
Optimal exposure factors.
Axiolateral TMJ (Schuller Method)
Positioning: True lateral – no rotation (open and closed mouth positions).
CR Angle: 25° to 30° caudad (larger angulation).
CR Location: 0.5 inches (1.3 cm) anterior and 2 inches (5 cm) superior to upside EAM.
Routine: AP axial, Axiolateral oblique (Law), Axiolateral (Schuller).
Evaluation Criteria: Axiolateral (Schuller)
TMJ closest to IR demonstrated.
Open and closed mouth projections.
Optimal exposure factors.
Optic Foramina Routine
Routine: Parietoorbital oblique (Rhese), Parietoacanthial (Waters), PA (Caldwell).
Special: Modified parietoacanthial (modified Waters).
Parietoorbital Oblique Projection (Rhese Method)
Projections: Bilateral for comparison.
CR: Perpendicular to downside orbit.
MSP: 53° to IR.
AML (Acanthiomeatal Line): Perpendicular to IR.
Routine: Rhese method, Waters, PA Caldwell.
Evaluation Criteria: Rhese Method
Optic foramen in lower outer quadrant.
Close collimation.
Optimal exposure factors.
Paranasal Sinus Routine
Routine (Erect, using a horizontal beam for air/fluid levels): Lateral, PA Caldwell (no angulation), Parietoacanthial (Waters), Submentovertex (SMV).
Special: Parietoacanthial transoral (open mouth Waters).
Technical Considerations for Sinuses
kV Range:
Analog: 65-75
Digital systems: 75-85.
Positioning: Erect, horizontal beam (no angulation), AEC not recommended.
Lateral Sinus Positioning
CR Location: Midway between outer canthus and EAM.
Routine: Lateral.
Evaluation Criteria: Lateral Sinuses
All four sinuses demonstrated.
Cranium not rotated or tilted.
Optimal exposure factors.
PA Caldwell Sinuses
OML: Perpendicular to IR, 15° tilt; OML 15° from horizontal.
CR: Horizontal, exiting at nasion.
Routine: Lateral, PA Caldwell.
Evaluation Criteria: PA (Caldwell) Sinuses
Frontal and ethmoid sinuses demonstrated.
Petrous ridges in lower ⅓ of orbits.
No rotation or tilt.
Optimal exposure factors.
Parietoacanthial (Waters) Sinuses
MML: Perpendicular to IR.
CR: Horizontal, exiting at acanthion.
Routine: Lateral, PA Caldwell, Parietoacanthial.
Evaluation Criteria: (Waters) Sinuses
Maxillary sinuses demonstrated.
No rotation of cranium.
Petrous ridges below maxillary sinuses.
Optimal exposure factors.
SMV Sinuses
IOML: Parallel to IR.
CR: Horizontal, between angles of mandible.
Routine: Lateral, PA Caldwell, Parietoacanthial, SMV.
Evaluation Criteria: SMV Sinuses
Mandibular condyles anterior to petrous ridges.
No rotation or tilt.
Correct collimation.
Optimal exposure factors.
PA Transoral (Waters)
MML: Perpendicular to IR; open mouth.
CR: Horizontal, exiting at acanthion.
Special: Parietoacanthial transoral.
Evaluation Criteria: PA Transoral (Waters)
Sphenoid sinus visualized.
Frontal and maxillary sinuses also included.
No rotation or tilt.
Petrous ridges below maxillary sinuses.
Optimal exposure factors.
Radiographs for Critique Cranium
Criteria: Determine presence of positioning errors in radiographic images such as A, B, etc.
Quiz Me (selected questions)
The width of the dolichocephalic skull is less than ___ of the length: 65%, 75%, 80%, 90%.
The angle between the midsagittal plane and the long axis of the petrous portion of the temporal bone in the brachycephalic skull is: 45°, 40°, 38°, 47° or greater.
The midline point at the junction of the upper lip and the nasal septum is called: Acanthion, Nasion, Glabella, Mentum.
The tragus is located on the: Lateral border of the orbit, Point above the superciliary arch, External ear, Bridge of the nose.
There is a ___ difference between the orbitomeatal and infraorbitomeatal lines: 2° to 3°, 5°, 7° to 8°, 10° to 12°.