1. Rad 270 Skull Lecture

2. Skull Anatomy Comprised of 22 separate bones divided into two groups:
Cranial bones – 8
Facial bones – 14
Cranial bones further subdivided into
Calvaria
Floor

3. Cranial Bones Calvaria Floor Frontal Occipital R. parietal L. parietal
Ethmoid
Sphenoid
R. temporal
L. temporal

4. Skull Anatomy
Sutures = fibrous joints that connect the bones of the skull
Coronal = between frontal and parietal bones
Sagittal = on top of head between two parietal bones
Squamosal = between temporal bone and the parietal bones
Lambdoidal = between occipital and the parietal bones

5. Skull Morphology Typical skull = mesocephalic Brachycephalic skull
Petrous pyramids project anteriorly and medially at angle of 47 degrees from MSP
Brachycephalic skull
Petrous pyramids project anteriorly and medially at angle of 54 degrees from MSP
Short from front to back, broad from side to side, and shallow from vertex to base

7. Skull Morphology Dolichocephalic skull
Petrous pyramids project anteriorly and medially at angle of 40 degrees from MSP
Long from front to back, narrow from side to side, and deep from vertex to base
Asymmetry of outer features should be noted while positioning; for example, the nose may not always be in the midline

9. Frontal Bone Landmarks to note Frontal eminences Supraorbital margins
Supraciliary arches
Supraorbital foramina
Glabella

12. Ethmoid Bone Consists of Horizontal plate Vertical plate
Two light, spongy masses = labyrinths

15. Parietal Bones Somewhat square-shaped
Have a convex external surface and concave internal surface
Parietal eminence = prominent bulge near center of external surface of each bone
This is the point where the width of the skull should be measured to set technique

17. Sphenoid Bone
Irregular, wedge-shaped bone that resembles a bat (somewhat)
Located in base of cranium anterior to temporal bones and basilar portion of occipital

21. Occipital Bone Situated at posteroinferior part of cranium
Forms posterior half of cranial base and greater portion of posterior cranial fossa
Has four parts
Squama
Two occipital condyles
Basilar portion

24. Temporal Bones Consist of Squamous portion Tympanic portion
Styloid process
Zygomatic process
Petromastoid portion which contain the organs for hearing and equilibrium

27. Skull Topography Be able to locate the following landmarks: Gonion
Mental point
External auditory meatus (EAM)
Auricular point
Top of ear attachment (TEA)
Glabella
Inner canthus
Outer canthus
Nasion
Infraorbital margin
Acanthion

30. Hyposthenic/Asthenic Patients

31. Hypersthenic Patients

32. Essential Projections: Cranium
Lateral PA
PA axial (Caldwell method) AP
AP axial
AP axial (Towne method)
PA axial (Haas method)
Submentovertical (SMV)
For cranial base

34. Lateral Projection Patient position Part position CR
Seated upright or semiprone
Part position
MSP of head parallel to IR
IPL perpendicular
IOML parallel to transverse axis of cassette CR
Perpendicular to center of IR
Enters 2 superior to EAM

35. Lateral Projections Entire cranium without rotation or tilt
Superimposed orbital roofs and greater wings of sphenoid
Superimposed mastoid regions and EAMs
Superimposed TMJs
Sella turcica in profile
Penetration of parietal region
No overlap of C-spine by mandible

37. PA/PA Axial (Caldwell)
Patient position
Seated erect or prone
MSP centered to midline
Forehead and nose resting on table or upright Bucky
Part position
OML perpendicular to IR plane
MSP perpendicular to IR
IR centered to nasion

38. PA/PA Axial (Caldwell)
CR for PA projection
Perpendicular
Exits nasion
CR for PA axial (Caldwell)
Angled 15 degrees caudad

43. PA Projection
Entire cranial perimeter showing three tables of squamous bone
No rotation
Equal distance from lateral borders of skull to lateral border of orbits
Symmetric petrous ridges
Petrous ridges fill orbits
Penetration of frontal bone without excessive density at lateral borders of skull

45. PA Axial (Caldwell Method)
Same as for PA projection, except
Petrous ridges demonstrated in lower one third of orbit

47. AP/AP Axial Projection
Same as PA and PA axial projections
Anatomy more magnified in AP and AP axial projections

48. AP Axial (Towne Method)
Patient and part position
Supine or seated erect
MSP centered to midline
MSP perpendicular
OML or IOML perpendicular
IR top border level with skull vertex
IR center at or near foramen magnum CR
Directed through foramen magnum
OML – 30 degrees caudal
IOML – 37 degrees caudal

50. AP Axial (Towne Method)
No rotation
Equal distance from lateral border of skull to lateral margin or foramen magnum
Symmetric petrous ridges
Dorsum sellae and posterior clinoid processes visible within foramen magnum
Penetration of occipital bone without excessive density at parietals

52. PA Axial (Haas)
Projection of dorsum sellae and posterior clinoid processes within foramen magnum
Equal distance from lateral border of skull to lateral margin of foramen magnum
Symmetric petrous pyramids
Entire cranium

54. SMV Projection (Schüller)
Patient position
Seated upright or supine
Torso elevated if supine
Part position
MSP centered to midline
IOML parallel with IR
MSP perpendicular to IR

55. SMV Projection (Schüller)CR
Through sella turcica perpendicular to IOML
Enters MSP of throat between angles of mandible
Passes through a point ¾ (1.9 cm) anterior to level of EAM
Center IR to CR

57. SMV Projection (Schüller)
No rotation or tilt
Equal distance from lateral border of skull to mandibular condyles
Symmetric petrous pyramids
Penetration sufficient to demonstrate structures of cranial base
Superimposition of mental protuberance over anterior frontal bone, indicating full neck extension
Mandibular condyles anterior to petrous pyramids

58. SMV Projection (Schüller)
Superimposition of mental protuberance over frontal bone – indicates full neck extension
Condyles of mandible anterior to petrous pyramids