What is the angle between the OML and the plane of the IR for the Parietoacanthial waters projection?

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Chapter 8

Skull, Facial Bones, and Paranasal Sinuses

• Cranial positioning lines

Cranium (Skull Series)

Trauma (Skull Series)

Facial Bones

Trauma (Facial Bone Series)

Optic Foramina

Zygomatic Arches

Nasal Bones

Mandible

Temporomandibular Joints

Paranasal Sinuses

    (R) Routine, (S) Special

Cranial landmarks and positioning lines used in skull and facial bones positioning.

Fig. 8-1Positioning lines.

A Glabellomeatal line (GML)

B Orbitomeatal line (OML)

C Infraorbitomeatal line (IOML) (Reid’s base line, or “base line,” base of cranium)

D Acanthiomeatal line (AML)

E Lips-meatal line (LML) (used for modified Waters)

F Mentomeatal line (MML) (used for Waters)

Fig. 8-2Cranial landmarks.

AP (PA) Axial Skull*

AP Towne (or PA Haas Method)

• 24 × 30 cm L.W. (10 × 12″)

• Grid

Position

Fig. 8-3AP axial (Towne)—CR 30° caudad to OML.

• Seated erect, or supine, midsagittal plane aligned to CR and centerline, perpendicular to IR; no rotation or tilt

• Depress chin to bring OML or IOML perpendicular to IR.

• Center IR to projecting CR.

Fig. 8-4PA axial (Haas method), OML ⊥ CR 25° cephalad, through level of EAMs.

Central Ray:

• CR 30° caudal to OML; or 37° caudal to IOML

• CR to ≈2.5″ or 6 cm above glabella (through 2 cm or 0.75″ superior to level of EAMs)

SID:

40-44″ (102-113 cm)

Collimation:

On four sides to skull margins

Respiration:

Suspend during exposure.

Note:

PA Haas (p. 436 in text) is an alternate to AP Towne. Adjust head to bring OML ⊥ to IR.

AP Axial

(Modified Towne Method)

Evaluation Criteria

Anatomy Demonstrated:

• Occipital bone, petrous pyramids, and foramen magnum

Position:

• Dorsum sellae within foramen magnum

• No rotation evident by symmetry of petrous pyramids

Exposure:

• Optimal density (brightness) and contrast to visualize occipital bone

• Sharp bony margins; no motion

Fig. 8-5AP axial skull.

Lateral Skull*

• 24 × 30 cm C.W. (10 × 12″)

• Grid

Fig. 8-6Lateral skull.

Position

• Seated erect or semiprone on table

• No rotation or tilt, midsagittal plane parallel to IR, and IPL perpendicular to IR

• Adjust chin to place IOML parallel to upper and lower IR edges

• Center IR to CR.

Central Ray:

CR ⊥ to IR, ≈2″ (5 cm) superior to EAM

SID:

40-44″ (102-113 cm)

Collimation:

On four sides to skull margins

Respiration:

Suspend during exposure.

Lateral Skull

Evaluation Criteria

Anatomy Demonstrated:

• Superimposed cranial halves

• Entire sella turcica and dorsum sellae

Fig. 8-7Lateral skull.

Position:

• No tilt, evident by superimposition of orbital plates (roofs)

• No rotation, evident by superimposition of greater wings of sphenoid and mandibular rami

Exposure:

• Optimal density (brightness) and contrast to visualize sellar structures

• Sharp bony margins; no motion

PA (0° and 15°) Caldwell Skull*

Note: Some departmental routines include a 0° PA to better demonstrate the frontal bone in addition to the 15° PA axial Caldwell.

• 24 × 30 cm L.W. (10 × 12″)

• Grid

Position

• Seated erect, or prone on table, head aligned to CR and centerline of IR

• With forehead and nose resting on tabletop, adjust head to place OML perpendicular to IR.

• No rotation or tilt, midsagittal plane perpendicular to IR

• Center IR to projected CR.

Fig. 8-8PA—0°.

Fig. 8-9PA axial—15° Caldwell.

Central Ray:

• PA 0°: CR ⊥ to IR, centered to exit at glabella

• PA axial (Caldwell): CR 15° caudad to OML, centered to exit at nasion (25°–30° best demonstrates orbital margins)

SID:

40-44″ (102-113 cm)

Collimation:

On four sides to skull margins

Respiration:

Suspend during exposure.

PA (0°) and PA Axial Caldwell (15° Caudad)

Evaluation Criteria

Anatomy Demonstrated:

• PA 0°: Frontal bone and crista galli demonstrated without distortion

• PA axial 15°: Greater/lesser wings of sphenoid, frontal bone, and superior orbital fissures

Fig. 8-10PA—0°.

Position:

• PA 0°: Petrous ridges at level of superior orbital margin. No rotation; equal distance between orbits and lateral skull

• PA axial 15°: Petrous ridges projected in lower ⅓ of orbits. No rotation; equal distance between orbits and lateral skull

Exposure:

• Optimal density (brightness) and contrast to visualize frontal bone and surrounding structures

• Sharp bony margins; no motion

Fig. 8-11PA axial—15° Caldwell.

Submentovertex (SMV) Skull*

• 24 × 30 cm L.W. (10 × 12″)

• Grid

• AEC optional

Fig. 8-12SMV—CR ⊥ to IOML.

Position

• Seated erect or supine with head extended over end of table resting top of head against grid IR (may tilt table up slightly)

• Adjust IR and head to place IOML parallel to IR.

• Ensure no rotation or tilt.

• Center IR to CR.

Central Ray:

CR angled to be ⊥ to IOML, centered to 0.75″ (2 cm) anterior to level of EAMs (midpoint between angles of mandible)

Note:

If patient cannot extend head this far, adjust CR as needed to remain perpendicular to IOML.

SID:

40-44″ (102-113 cm)

Collimation:

On four sides to skull margins

Respiration:

Suspend during exposure.

Submentovertex (SMV) Skull

Evaluation Criteria

Anatomy Demonstrated:

• Base of skull, including mandible and occipital bone

• Foramen ovale and spinosum

Position:

• Mandibular condyles are anterior to the petrous bones

• No tilt; equal distance between mandibular condyles and lateral skull

• No rotation; MSP parallel to edge of radiograph

Fig. 8-13 SMV.

Exposure:

• Optimal density and contrast (brightness) to visualize outline of foramen magnum

• Sharp bony margins; no motion

Lateral Trauma Skull*

Warning: Do NOT elevate or move patient’s head before cervical spine injuries have been ruled out.

• 24 × 30 cm C.W. (10 × 12″)

• Grid

Fig. 8-14Lateral, with possible spinal injury.

Position

• Supine, without removing cervical collar if present

• With possible spinal injury, move patient to back edge of table and place IR about 1″ (2.5 cm) below tabletop and posterior skull (move floating tabletop forward).

• Center IR to horizontal beam CR (to include entire skull).

• Ensure no rotation or tilt.

Central Ray:

CR horizontal, ⊥ to IR, centered to ≈2″ (5 cm) superior to EAM

SID:

40-44″ (102-113 cm)

Collimation:

On four sides to skull margins

Respiration:

Suspend respiration.

AP Trauma Skull Series*

Warning: With possible spine or severe head injuries, take all projections AP without moving head or without removing cervical collar if present.

• 24 × 30 cm L.W. (10 × 12″)

• Grid (Bucky)

Fig. 8-15AP—0° to OML.CR—parallel to OML—centered to glabella

Position

• Patient carefully moved onto x-ray table in supine position

• All projections taken as is without moving head

SID:

40-44″ (102-113 cm)

Collimation:

On four sides to skull margins

Respiration:

Suspend during exposure, or take “as is.”

CR Angle and Centering

• As indicated under each photo

• IR centered to projected CR

Fig. 8-16AP reverse Caldwell. CR—15° cephalad to OML—centered to nasion

Fig. 8-17AP axial (Towne). CR—30° caudad to OML—centered to midpoint between EAMs

Lateral Trauma Skull

Evaluation Criteria

Anatomy Demonstrated:

• Superimposed cranial halves

• Entire sella turcica and dorsum sellae

Position:

• No rotation or tilt (see p. 229 for specific criteria)

Exposure:

• Optimal density (brightness) and contrast to visualize sellar structures

• Sharp bony margins; no motion

Fig. 8-18Lateral trauma skull.

Trauma AP (0°) and AP Axial (15° Cephalad) Projections

Fig. 8-19AP—0° to OML.

Fig. 8-20AP axial (“reverse” Caldwell) (15° cephalad).

Evaluation Criteria

Anatomy Demonstrated:

• AP 0°: Frontal bone and crista galli demonstrated (magnified because of OID)

• AP axial 15°: Greater/lesser wings of sphenoid, frontal bone, and superior orbital fissures (magnified)

Position:

• AP 0°: Petrous ridges at level of superior orbital margin. No rotation; equal distance between orbits and lateral skull

• AP axial 15°: Petrous ridges projected in lower ⅓ of orbits. No rotation; equal distance between orbits and lateral skull

Exposure:

• Optimal density (brightness) and contrast to visualize frontal bone and surrounding structures

• Sharp bony margins; no motion

Facial Bones—Lateral*

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