1. Skull & cranial bones extra handoutBy
Dr. Mohsen Dashti
Imaging Procedures 362
March 15 & 18, 2009
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2. Anatomy Review
Skull
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Slide 2

3. Skull Anatomy Comprised of 22 separate bones divided into two groups:
Cranial bones – 8
Facial bones – 14
Cranial bones further subdivided into
Calvaria
Floor
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4. Skull Anatomy
Diploë = inner layer of spongy bone separating two outer plates of compact tissue
Composition of calvarium bones
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5. Anterior view of skull
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6. Lateral view of skull
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7. Cranial Bones Calvaria Floor Frontal Occipital R. parietal L. parietal
Ethmoid
Sphenoid
R. temporal
L. temporal
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8. Superior view of cranial floor
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9. 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
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10. Skull Anatomy Bregma = junction of coronal and sagittal sutures
Lambda = junction of sagittal and lambdoidal suture
Fontanels = areas of incomplete ossification in Infant skulls, i.e., “soft spots”
Adult cranial size usually achieved by age 12
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11. Cranial Floor Internally, divided into three regions
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
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12. 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
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13. 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
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14. Frontal Bone
Has vertical portion (frontal squama) and horizontal portions
Frontal squama forms forehead and anterior part of cranial vault
Horizontal portions form orbital plates, part of roof of nasal cavity, and greater part of anterior cranial fossa
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15. Frontal Bone Landmarks to note Frontal eminences Supraorbital margins
Supraciliary arches
Supraorbital foramina
Glabella
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16. Frontal Bone
Frontal sinuses contained between the two tables of squama on each side of MSP
Articulates with R and L parietals, sphenoid, and ethmoid, nasal bones, and zygoma
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17. Frontal Bone Anterior view
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18. Ethmoid Bone Consists of Horizontal plate Vertical plate
Two light, spongy masses = labyrinths
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19. Ethmoid Bone
Located between the orbits and forms part of anterior cranial fossa, nasal cavity, orbital walls, and bony nasal septum
Horizontal portion is called cribriform plate
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20. Ethmoid Bone
Cribriform plate contains numerous foramina for transmission of olfactory nerves
Crista galli = conical projection at anterior midline of cribriform plate
Perpendicular plate = vertical portion; forms superior portion of bony nasal septum
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21. Ethmoid Bone Labyrinths
Contain ethmoid sinuses or air cells
Walls form part of medial walls of orbits and lateral walls of nasal cavity
Have two thin, scroll-shaped projections = superior and middle nasal conchae
Articulates with frontal, sphenoid, lacrimal, maxilla, and vomer
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22. Ethmoid Bone Lateral view Anterior view
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23. 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
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24. Parietal Bones
Articulate with each other at the sagittal suture in MSP, the frontal, temporal, occipital, and sphenoid bones
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25. Parietal Bones Interior view
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26. 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
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27. Sphenoid Bone Consists of Body Two lesser wings Two greater wings
Two pterygoid processes
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28. Sphenoid Bone
Body contains two sphenoid sinuses and forms posterior bony wall of nasal cavity
Sella turcica = deep depression on superior surface of body
Houses pituitary gland
Located in MSP of cranium ¾ anterior and superior to EAM
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29. Sphenoid Bone Tuberculum sellae = anterior border of sella
Dorsum sellae = posterior border of sella
Posterior clinoid processes = top borders of dorsum
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30. Sphenoid Bone
Clivus = slanted area of bone posterior and inferior to dorsum
Continuous with basilar area of occipital
Supports pons of the brain
Optic groove extends across anterior portion of tuberculum sellae
Groove ends on each side at the optic canal
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31. Sphenoid Bone
Optic canal = opening into the apex of orbit for transmission of optic nerve and ophthalmic artery
Actual opening is termed optic foramen
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32. Sphenoid Bone
Lesser wings arise from anterior and superior portion of body and lie horizontally on each side
Form posteromedial portion of orbital roofs, the posterior portion of anterior cranial fossa, upper margin of superior orbital fissure, and optic canals
Medial ends form the anterior clinoid processes
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33. Sphenoid Bone
Greater wings arise from sides of body and curve laterally, posteriorly, anteriorly, and superiorly
Form part of middle cranial fossa and posterolateral walls of orbit
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34. Sphenoid Bone Three paired foramina situated on greater wings
Rotundum
Ovale
Spinosum
Pterygoid processes arise from lateral portions of inferior surface of body and medial portions of inferior surfaces of greater wings
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35. Sphenoid Bone Pterygoids articulate with
Palantine bones anteriorly
Vomer as part of the nasal cavity
Sphenoid articulates with each of the other seven bones of the cranium and the zygoma
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36. Sphenoid Bone Lateral view
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37. 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
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38. Occipital Bone
Foramen magnum = large opening through which the medulla oblongata passes as it exits cranium
External occipital protuberance = prominent process on squama
Also called inion
Corresponds to internal occipital protuberance
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39. Occipital Bone
Occipital condyles = project anteriorly from each side of squama
Fuse at basilar portion to complete foramen magnum
Articulates with the two parietals, the two temporals, the sphenoid, and the atlas (C1)
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40. Occipital Bone Posterior view
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41. Occipital Bone Lateral view
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42. Temporal Bones
Situated on each side of cranial base between greater wings of sphenoid and occipital bone
Form large part of middle cranial fossa and a small part of posterior cranial fossa
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43. Temporal Bones Consist of Squamous portion Tympanic portion
Styloid process
Zygomatic process
Petromastoid portion which contain the organs for hearing and equilibrium
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44. Temporal Bones Squamous portion = thin, upper portion of temporal bone
Forms part of side wall of cranium
Zygomatic process = prominent arched process that projects anteriorly to articulate with zygoma and complete the zygomatic arch
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45. Temporal Bones
Articular tubercle = located on inferior border of zygomatic process
Forms anterior boundary of mandibular fossa
Mandibular fossa = receives condyle of mandible to form temporomandibular joint (TMJ)
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46. Temporal Bones
Tympanic portion = located below squama and in front of petromastoid portion
Forms anterior wall, inferior wall and part of posterior walls of the EAM
Styloid process = slender, pointed bone projecting inferiorly, anteriorly, and slightly medially from inferior surface of tympanic portion
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47. Temporal Bones
Petromastoid portion combines petrous and mastoid portions
Forms the inferior, posterior part of the temporal bone
Articulates with parietal bone at its superior border and with occipital bone at its posterior border
Usually contains air cells, which vary greatly in size, number, and pneumatization
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48. Temporal Bones
Mastoid process = conical process projecting from mastoid portion
Petrous portion projects medially and anteriorly between greater wing of sphenoid and occipital bone
Also called petrous pyramid
Conical or pyramidal in shape
Thickest and densest portion of cranium
Contains the organs of hearing and balance
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49. Temporal Bones Auditory ossicles = bones of middle ear
Malleus
Incus
Stapes
Temporal bone articulates with the parietal, occipital, sphenoid, zygoma, and mandible
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50. Temporal Bones Lateral view
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51. Temporal Bones Anterior view
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52. Procedural Considerations
Skull topography
Skull morphology
General body position
Cleanliness
Radiation protection
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53. 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
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55. Radiographic Landmarks
Orbitomeatal line (OML)
From outer canthus to EAM
Infraorbitomeatal line (IOML)
From infraorbital margin to EAM
Glabellomeatal line (GML)
From glabella to EAM
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56. Radiographic Landmarks
Interpupillary line (IPL)
Perpendicular line between pupils of eyes
Acanthiomeatal line (AML)
From acanthion to EAM
Mentomeatal line (MML)
From mental point (center of chin) to EAM
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58. Skull Morphology
Radiographic positioning guidelines are based on mesocephalic skull size and shape
Adjustments to centering and CR and/or part angulation may be required when working with patients with atypical skull shapes
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59. General Body Position
Patient may be examined in upright or recumbent positions
General body position is especially important in hyposthenic, asthenic, and hypersthenic body types
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61. General Body Position
Hyposthenic/asthenic patients usually need support at chest to elevate C-spine
Helps prevent downward tilt of MSP
Hypersthenic patients require radiolucent support at head
Helps prevent upward tilt of MSP
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62. Hyposthenic/Asthenic Patients
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63. Hypersthenic Patients
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64. Cleanliness
Hair and skin of face are naturally oily; illness often increases oiliness
Cranial procedures require direct contact of patient’s face with VBS
Clean device after each patient
Wash your hands!!!
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65. Radiation Protection Collimate to anatomy of interest
Shield gonads/abdomen of pediatric patients and those of reproductive age
Shield thyroid and thymus of pediatric patient when doing so will not interfere with demonstration of anatomy of interest
Good communication and positioning skills reduce chance of need for repeat radiographs
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66. Patient Preparation Remove all radiopaque artifacts Eyeglasses
Dentures and partial plates
Hearing aids
Jewelry
Wigs/hairpieces
Hairpins, barrettes, and pony tail holders
False eyes
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67. Essential Projections: Cranium
Lateral
Right and left lateral positions
Dorsal decubitus position PA
PA axial (Caldwell method) AP
AP axial
AP axial (Towne method)
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68. Essential Projections: Cranium
PA axial (Haas method)
Submentovertical (SMV)
For cranial base
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69. Lateral Projection Patient position Part position
Seated upright or semiprone
Part position
MSP of head parallel to IR
IPL perpendicular
IOML parallel to transverse axis of cassette
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70. Lateral Projection CR Perpendicular to center of IR
Enters 2 superior to EAM
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72. Lateral Projection Patient position Part position Dorsal decubitus
Elevate head on radiolucent support to center to vertical IR
MSP of head vertical
IPL perpendicular to IR
IOML parallel to transverse axis of cassette
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73. Lateral Projection CR Horizontal and perpendicular to center of IR
Enters 2 superior to EAM
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74. Lateral Projection Patient position Part position Supine or semisupine
Elevate head on radiolucent support to place MSP parallel and IPL perpendicular
Turn head toward side of interest
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75. Lateral Projection CR Perpendicular to center of IR
Enters 2 superior to EAM
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76. 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
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77. PA/PA Axial (Caldwell)
CR for PA projection
Perpendicular
Exits nasion
CR for PA axial (Caldwell)
Angled 15 degrees caudad
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78. AP/AP Axial Projection
Note: Provides similar but magnified image when patient cannot be positioned for PA or PA axial projection.
Patient and part position
Supine
MSP centered to midline
MSP and OML perpendicular to IR
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79. AP/AP Axial ProjectionCR
Perpendicular or 15 degrees cephalad for AP axial projection
Enters nasion
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80. 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
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81. AP Axial (Towne Method)CR
Directed through foramen magnum
OML – 30 degrees caudal
IOML – 37 degrees caudal
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82. PA Axial (Haas) Patient position Part position Prone or seated upright
MSP centered to midline
Shoulders in same horizontal plane
Part position
Forehead and nose on table
MSP perpendicular
OML perpendicular to IR
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83. PA Axial (Haas) CR Directed cephalad at angle of 25 degrees to OML
Enters at a point 1.5 (3.8 cm) below external occipital protuberance
Exits 1.5 (3.8 cm) superior to nasion
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84. 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
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85. 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
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86. Essential Projections: Temporal Bone
Axiolateral oblique (modified Law)
Axiolateral oblique (Stenvers)
Axiolateral oblique (Arcelin)
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87. Axiolateral Oblique (Modified Law)
Patient position
Prone or seated upright
Tape auricle forward
Part position
Place head in true lateral position with affected side closer to IR
IOML parallel with IR
IPL perpendicular to IR
MSP angled 15 degrees toward IR
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88. Axiolateral Oblique (Modified Law)CR
Angled 15 degrees caudad to midpoint of IR
Exits mastoid tip closer to IR about 1 (2.5 cm) posterior to EAM
Enters 2 (5 cm) posterior to and superior to upper EAM
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89. Axiolateral Oblique (Stenvers)
Patient position
Prone or seated upright
Part position
Rest head on forehead, nose, and cheek with side of interest on IR
IOML parallel with transverse axis of IR
MSP at 45-degree angle from IR
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90. Axiolateral Oblique (Stenvers)CR
Angled 12 degrees cephalad
Enters about 3 to 4 (7.6 to 10 cm) posterior and ½ (1.3 cm) inferior to upside EAM
Exits 1 (2.5 cm) anterior to downside EAM
IR and CR centered
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91. Axiolateral Oblique Temporal Bone (Arcelin)
Patient position
Supine
MSP centered to midline
Part position
Rotate face away from side of interest to place MSP at 45-degree angle with plane of IR
IOML perpendicular to IR
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92. Axiolateral Oblique Temporal Bone (Arcelin)CR
Angled 10 degrees caudad
Enters temporal area at 1 (2.5 cm) anterior to EAM and ¾ (1.9) cm above it
Center IR and CR
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93. Essential Projections: Optic Canal and Foramen
Parietoorbital oblique (Rhese method)
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94. Parietoorbital Oblique (Rhese)
Patient position
Semiprone or seated upright
Part position
Center affected orbit to center of IR
Rest zygoma, nose, and chin on table or upright Bucky
AML perpendicular to IR
MSP forms 53-degree angle with IR plane
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95. Parietoorbital Oblique (Rhese)CR
Perpendicular to IR center
Enters 1 (2.5 cm) superior and posterior to upside TE
Exits orbit closer to IR
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96. Lesson 2
Image Critique
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Slide 96

97. 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
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99. 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
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100. PA Projection Petrous ridges fill orbits
Penetration of frontal bone without excessive density at lateral borders of skull
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102. PA Axial (Caldwell Method)
Same as for PA projection, except
Petrous ridges demonstrated in lower one third of orbit
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104. AP/AP Axial Projection
Same as PA and PA axial projections
Anatomy more magnified in AP and AP axial projections
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105. 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
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107. 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
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109. 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
Mosby items and derived items © 2007, 2003, 1999 by Mosby, Inc., an affiliate of Elsevier Inc.

110. SMV Projection (Schüller)
Superimposition of mental protuberance over anterior frontal bone, indicating full neck extension
Mandibular condyles anterior to petrous pyramids
Mosby items and derived items © 2007, 2003, 1999 by Mosby, Inc., an affiliate of Elsevier Inc.

111. SMV Projection (Schüller)
Superimposition of mental protuberance over frontal bone – indicates full neck extension
Condyles of mandible anterior to petrous pyramids
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112. Mosby items and derived items © 2007, 2003, 1999 by Mosby, Inc
Mosby items and derived items © 2007, 2003, 1999 by Mosby, Inc., an affiliate of Elsevier Inc.

113. Axiolateral Oblique Temporal Bone (Modified Law)
Mastoid process closer to IR
Air cells centered to IR
Opposite mastoid process inferior and anterior mastoid of interest
Auricle of ear not superimposing mastoid
Superimposition of IAM and EAM
TMJ visible anterior to mastoid process
Close beam restriction
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114. Mosby items and derived items © 2007, 2003, 1999 by Mosby, Inc
Mosby items and derived items © 2007, 2003, 1999 by Mosby, Inc., an affiliate of Elsevier Inc.

115. Axiolateral Oblique Temporal Bone (Stenvers)
Petromastoid portion in profile
Lateral border of skull to lateral border of orbit
Petrous ridge extended to a point about two thirds up lateral border of orbit
Mosby items and derived items © 2007, 2003, 1999 by Mosby, Inc., an affiliate of Elsevier Inc.

116. Axiolateral Oblique Temporal Bone (Stenvers)
Mastoid process in profile below cranium
Posterior margin of mandibular ramus superimposing lateral border of C-spine
Mandibular condyle projecting over atlas near petrosa
Close beam restriction
Mosby items and derived items © 2007, 2003, 1999 by Mosby, Inc., an affiliate of Elsevier Inc.

117. Mosby items and derived items © 2007, 2003, 1999 by Mosby, Inc
Mosby items and derived items © 2007, 2003, 1999 by Mosby, Inc., an affiliate of Elsevier Inc.

118. Axiolateral Oblique Temporal Bone (Arcelin)
Petromastoid portion in profile
Lateral border of skull to lateral border of orbit
Petrous ridge lying horizontal about two thirds up lateral border of orbit
Mosby items and derived items © 2007, 2003, 1999 by Mosby, Inc., an affiliate of Elsevier Inc.

119. Axiolateral Oblique Temporal Bone (Arcelin)
Mastoid process in profile below cranium
Posterior margin of mandibular ramus superimposing lateral border of C-spine
Mandibular condyle projecting over atlas near petrosa
Close beam restriction
Mosby items and derived items © 2007, 2003, 1999 by Mosby, Inc., an affiliate of Elsevier Inc.

120. Mosby items and derived items © 2007, 2003, 1999 by Mosby, Inc
Mosby items and derived items © 2007, 2003, 1999 by Mosby, Inc., an affiliate of Elsevier Inc.

121. Parietoorbital Oblique (Rhese)
Optic canal and foramen visible at end of sphenoid ridge in inferior and lateral quadrant of orbit
Entire orbital rim
Supraorbital margins lying in same horizontal line
Close beam restriction to orbit
Mosby items and derived items © 2007, 2003, 1999 by Mosby, Inc., an affiliate of Elsevier Inc.

122. Mosby items and derived items © 2007, 2003, 1999 by Mosby, Inc
Mosby items and derived items © 2007, 2003, 1999 by Mosby, Inc., an affiliate of Elsevier Inc.