Cranium

Coronal suture

• between frontal and parietal bones

• immovable

Sagittal suture

• on top of head between two parietal bones

• immovable

Squamous Suture

• between temporal bone and parietal bones

• immovable

Lambdoidal suture

• between occipital and parietal bones

• immovable

Bregma

junction of coronal and sagittal sutures

Lambda

junction of sagittal and lambdoidal sutures

Fontanels

areas of incomplete ossification in infant skulls (i.e., “soft spots”)

Anterior cranial fossa

houses frontal lobes of cerebrum; extends from anterior frontal bone to lesser wings of sphenoid

middle cranial fossa

houses temporal lobes; extends from lesser wings of sphenoid to apices of petrous ridges

posterior cranial fossa

deep depression posterior to petrous ridges; protects cerebellum, pons, and medulla oblongata

Mesocephalic

Typical skull = Petrous pyramids project anteriorly and medially at 47-degree angle from midsagittal plane (MSP)

brachycephalic

• Petrous pyramids project anteriorly and medially at 54-degree angle from MSP

• Short from front to back, broad from side to side, and shallow from vertex to base

Dolichocephalic

• Petrous pyramids project anteriorly and medially at 40-degree angle from MSP

• Long from front to back, narrow from side to side, and deep from vertex to base

Cranial bones

8

Facial bones

14

Mentomeatal line (MML)

From mental point to EAM

Acanthiomeatal line (AML)

From acanthion to EAM

Infraorbitomeatal line (IOML)

From infraorbital margin to EAM

Orbitomeatal line (OML)

From outer canthus to EAM

Glabellomeatal line (GML)

From glabella to EAM

Interpupillary line (IPL)

Perpendicular line between pupils of eyes

EAM

external auditory meatus

TEA

top of ear attachment

Adult cranial size usually achieved by

age 12

sella turcica

• deep depression on superior surface of body

• Houses pituitary gland

• Located in MSP of cranium ¾ inch (1.9 cm) anterior and superior to external acoustic meatus (EAM)

Dorsum sella

posterior border of sella

Foramen magnum

large opening through which medulla oblongata passes as it exits cranium

Hyposthenic/asthenic patients

usually need support at chest to elevate cervical spine (C-spine).

Hypersthenic patients

require radiolucent support at head

Lateral projection patient positions

• Upright or recumbent anterior oblique

• Dorsal decubitus

• Supine or recumbent posterior oblique position

Lateral projection part positions

• MSP of head parallel to IR

• IPL (interpupillary line) perpendicular

• IOML (infraorbitomeatal line) parallel to transverse axis of cassette

• If decubitus, elevate head on radiolucent support to center to vertical IR

Lateral projection central ray

• Perpendicular to center of IR

• Enters 2 inches superior to EAM

• (horizontal and perpendicular) if dorsal decubitus

Lateral projection evaluation criteria

• Entire cranium without rotation or tilt, demonstrated by:

  • Superimposed orbital roofs and greater wings of sphenoid

  • Superimposed mastoid regions and EAM

  • Superimposed TMJs

  • Sella turcica in profile

Lateral projection respiration

suspend

Lateral projection collimation

extend 1 inch (2.5 cm) beyond the skin line of the skull.

PA/PA Axial (Caldwell Method) patient position

• Seated erect or prone

• MSP centered to midline

• Forehead and nose resting on table or upright Bucky

PA/PA Axial (Caldwell Method) part position

• OML perpendicular to IR plane

• MSP perpendicular to IR

• IR centered to nasion

PA/PA Axial (Caldwell Method) respiration

suspend

Central Ray for PA projection

• Perpendicular

• Exits nasion

Central Ray for PA axial (Caldwell)

• Angled 15 degrees caudad

• Exits nasion

PA/PA Axial (Caldwell Method) evaluation criteria

• Entire cranium without rotation or tilt, demonstrated by:

  • Equal distances from lateral borders of skull to lateral borders of orbits on both sides

  • Symmetric petrous ridges

  • MSP of cranium aligned with long axis of collimated field

• PA projection demonstrates orbits filled by petrous ridges

• PA axial (Caldwell) demonstrates petrous pyramids in lower third of orbit

AP Axial (Towne Method) patient and part position

• Supine or seated erect

• MSP centered to midline

• MSP perpendicular

• OML or IOML perpendicular

AP Axial (Towne Method) central ray

• Directed through foramen magnum

• OML – 30 degrees caudal

• IOML – 37 degrees caudal

AP Axial (Towne Method) evaluation criteria

• Entire cranium, without rotation or tilt, demonstrated by:

  • Equal distances from lateral borders of skull to lateral margins of foramen magnum on both sides

  • Symmetric petrous pyramids

  • MSP of cranium aligned with long axis of collimated field

• Dorsum sellae and posterior clinoid processes visible within foramen magnum

AP Axial (Towne Method) respiration

suspend

PA Axial (Haas Method) Patient position

• Prone or seated upright

• MSP centered to midline

• Shoulders in same horizontal plane

PA Axial (Haas Method) Part position

• Forehead and nose on table

• MSP perpendicular

• OML perpendicular to IR

PA Axial (Haas Method) Central ray

• Directed cephalad at 25-degree angle to OML

• Enters at a point 1½ inches below external occipital protuberance (inion)

• Exits 1½ inches superior to nasion

PA Axial (Haas Method) respiration

suspend

PA Axial (Haas Method) evaluation criteria

• Dorsum sellae and posterior clinoid processes visible within foramen magnum

• Entire cranium, without rotation or tilt, evidenced by:

  • Equal distances from lateral borders of skull to lateral margins of foramen magnum on both sides

  • Symmetric petrous pyramids

  • MSP of cranium aligned with long axis of collimated field

SMV Projection (Schüller Method) Patient position

• Seated upright or supine

• Torso elevated if supine

SMV Projection (Schüller Method) Part position

• MSP centered to midline

• IOML parallel with IR

• MSP perpendicular to IR

SMV Projection (Schüller Method) central ray

• Through sella turcica perpendicular to IOML

• Enters MSP of throat between angles of mandible

• Passes through a point ¾ inch anterior to level of EAM

SMV Projection (Schüller Method) respiration

suspend

SMV Projection (Schüller Method) evaluation criteria

• Entire cranium, without tilt, evidenced by:

  • Equal distances from lateral borders of skull to mandibular condyles on both sides

  • Symmetric petrosae

• IOML is parallel to IR (full neck extension), evidenced by:

  • Mental protuberance superimposed over anterior frontal bone

  • Mandibular condyles anterior to petrosae

inion

Posterior surface of the occipital bone

vertex

Superior aspect of the cranium; where the parietal bones join together

nasion

Midpoint of the frontonasal suture

gonion

Angle of the mandible; lateroposterior aspect of the mandible

glabella

Smooth elevation between the superciliary arches

acanthion

Midpoint of the anterior nasal spine

mental point

Midpoint of the mental protuberance; anterior

aspect of the mandible; where the two mandibular bodies join together

outer canthus

Lateral aspect of each orbit; where the two eyelids originate

superciliary arch

Raised prominence just above each orbit on

the frontal bone; coincides with the eyebrows

cranial bones and quantity

• frontal (1)

• occipital (1)

• ethmoid (1)

• sphenoid (1)

• parietal (2)

• temporal (2)

the bones of the cranial fault are considered

flat bones

OML and IOML angle

7 degrees

OML and GML

8 degrees

AP projection differs from PA projection by

the orbits are considerably magnified