1. Cranium
RTEC 233
Fall 2008
Week 1 & 2

2. Cranial Anatomy Calvaria Floor Frontal Occipital Left Parietal
Right Parietal
Floor
Ethmoid
Sphenoid
Left Temporal
Right Temporal
The skull is made of 22 separate bones.
There are 8 cranial bones and 22 facial bones.
The cranial bones are further divided in the calvaria and the floor.
The calvaria consists of 1 frontal bone, 1 occipital bone, and left and right parietals.
The floor consists of 1 ethmoid, 1 sphenoid and right and left temporals.
The cranial bones serve as a protective housing for the brain. Why the 14 facial bones give structure and differentiating facial features for each individual person.

3. The regions of the Cranial Floor
Anterior: extends form anterior frontal bone to the lesser wings of the sphenoid
It is associated with frontal lobes of cerebellum
Middle: Extends from lesser wings to the apices of petrous ridges of temporal bone
Accommodates temporal lobes and associated neurovascular structures
Posterior: deep depression posterior to petrous ridge
which protects cerebellum, pons and medulla oblongata

4. Frontal Bone Has a vertical and horizontal portion
Vertical portion- forms the forehead and anterior part of the vault
Horizontal portion- forms roof of orbits, part of the roof of nasal cavity, and greater part of anterior cranial fossa.

5. Parietal Bone Forms large part of sides of the cranium
Forms posterior portion of the cranial floor
Parietal eminence is used to measure width of head

6. Occipital Bone Inferosuperior portion of calvaria
Squamous portion is superior to inion
Ext. occipital protuberance – prominent bulge
Contains foramen magnum and articulates with atlas (C1)

7. Ethmoid Bone Horizontal portion is called cribiform plate
Vertical portion is called perpendicular plate
2 light spongy labyrinths

8. Sphenoid Bone Resembles shape of a bat
Consists of a body, 2 lesser wings, 2 greater wings, 2 pterygoid processes
Contains Sella turcica- important for positioning errors

9. Sella Turcica Lies in the MSP
¾” anterior & superior to EAM
Deformity of the sella is often the only clue that a lesion exists intracranially

10. Temporal Bone Divided in 3 parts
Squamous: upper portion forming part of the wall of skull
Mastoid: Posterior to EAM contains mastoid tip (process)
Petrous: dense & houses organs of hearing and balance
Thickest most dense bone in cranium
Level of TEA

11. Superior Cranium Visualized more clearly: Not well visualized:
Sphenoid
Temporals
Occipital
Frontal
Not well visualized:
Ethmoid
Parietals
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12. From this view you can visualize all the cranial bones
Lateral Cranium
From this view you can visualize all the cranial bones
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13. Infant Sutures & Fontanels
Anterior
Close approx 2 years
2 Mastoids
2 Sphenoidal
1-3 months old
Posterior
1-3 months
In a newborn child the bones of the cranium are thin. At this time the cranium is not fully developed and contains small amounts of calcium.
There are 6 areas in which the bones are not completely developed and ossified called fontanels.
The anterior fontanel is located at the junction of the two parietal bones and the frontal bone.
Where the occipital bone, parietal bone and mastoid portion of the temporal bone meet is where the mastoid fontanels are located (one on each side of the head.
The place where the parietal bone, squamosal suture and greater wing of the sphenoid meet is at the sphenoidal fontanel.
The posterior fontanel is located where the lamboidal and sagittal sutures meet.
The anterior and mastoid fontanels close in the 2nd year of life, while the sphenoidal and posterior fontanels close in the first 1-3 months of life.
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14. Adult Sutures and Junctions
Coronal
Sagittal
Squamosal
Lamboidal
Junctions
Bregma
Lambda
Pterion
Asterion
The coronal suture is found between the parietals and frontal bone.
The sagittal suture is located on top of the head just between the two parietals posterior to the coronal suture.
The squamosal suture is located between the temporal and parietal bones.
The lamboidal suture is located between the occipital bone and the parietal bones.
The bregma is where the coronal and sagittal sutures meet.
The lambda is where the lamboidal and sagittal sutures meet.
The pterion is where the parietal bone, squamosal suture and greater wing of the sphenoid meet.
The asterion is where the occipital bone, parietal bone and mastoid portion of the temporal bone meet.
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15. Lets compare Infant Adult Anterior fontanel Posterior fontanel
Sphenoidal fontanels
Mastoidal fontanels
Adult
Bregma
Lambda
Pterions
Asterions

16. Anterior Cranium Not able to visualize: Able to visualize: Occipital
Ethmoid
Able to visualize:
Parietals
Frontal
Sphenoid
Temporals
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17. Cranial Topography

18. Surface Landmarks

19. Skull morphology Mesocephalic: average Brachycephalic: Short and broad
47 degrees
Brachycephalic: Short and broad
Width 80% or greater than length
54 degrees
Dolichocephalic: long and narrow
Width is less than 75% than the length
40 degrees
Skull morphology

20. Skull Positioning Lines

21. 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

22. 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

23. 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

24. Positioning Aids
Use any straightedge:
Straw
Pen/pencil

25. Most Common Positioning Errors
Rotation
Tilt
Excessive Flexion
Excessive Extension
Incorrect CR angle
Rotation
Rotation and tilt are the two most common errors that cause a repeat. Rotation is when the MSP is rotated and not parallel to the grid device or IR. In a lateral position this means that the MSP is parallel to the IR.
Tilt is when the MSP is slanted or tilted not parallel with the grid device or IR. In the lateral projection there is tipping or slanting of the MSP laterally.
Flexion and extension errors can be made by lowered or elevating the chin too much or too little.
Many projections is skull radiography are very similar such as Waters, Lateral and Caldwell. The positioning for each projection is very similar and often it is the CR angle that makes the projection different. There are different CR angles for Caldwell projections depending on the area of interest.
Tilt
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26. Indications for Cranial Radiography
Skull fractures
Linear
Depressed
Basal skull
Gunshot wounds
Pituitary Adenomas
Subdural hematoma
Neoplasms
Metastases
Osteolytic
Osteoblastic
Combo of both
Multiple myeloma
Paget’s Disease
Acoustic neuroma
Indications for skull radiography has decreased because of more new technology such as CT and MRI. Although skull radiography is great for spatial resolution of bone it is not indicative of a brain injury. Additional modalities such as MRI and CT are used to assess brain tissue injury.
Linear fractures are FX’s of the skull that appear jagged or irregular lines.
Depressed fractures are sometimes called ping pong FX’s. A piece of fragmented bone that is separated and depressed into the cranial cavity.
Basal skull FX are fractures seen through the denser structures of the temporal bone. These are very difficult to see because of the complex anatomy in the temporal region. If there is bleeding in this area sometimes an air-fluid level can been seen in the sphenoidal sinus if a horizontal beam is used for the lateral view.
Gunshot wounds are usually used to localize bullets and bullet fragments. They are done antemortem and postmortem.
Pituitary adenomas are tumors of the pituitary gland. Usually any findings of this disease is indicated by an enlarged sella turcica and erosion of the dorsum sellae. But more often than not, this is an incidental finding, if they are suspected of having this disease a CT or MRI are usually performed.
Subdural hematoma: is an accumulation of blood in the subdural space due to injury of the head. Often occurs with a strong blow to the cranium, causing cortical or bridging veins surrounding the subdural space to tear.
Neoplasms are new and abnormal growths. A metastatic neoplasms is one that is spread through blood and the lymphatic system. The skull is a common site for metastatic lesions. Metastatic lesions are characterized and visualized on the image as follows:
Osteolytic- destructive lesions with irregular margins
Osteoblastic- are proliferative bony lesions of increased density
Combo- have a moth-eaten or cotton ball appearance because of the mix of osteolytic and osteoblastic lesions.
Multiple myeloma consists of 1 or more bone tumors that originate in the bone marrow causing destruction of the bone.
Paget’s disease is a disease of unknown origin that is marked by a stage of bone destruction followed by a bony repair. It involves many bony sites and skull is a common site. In the destructive phase there are many areas of lucency in a cotton wool appearance. Then there are areas of increased density (sclerosis) when in the reparative stage.
Acoustic neuroma: a benign tumor arising from the Schwann cells of the 8th cranial nerve.

28. Disinfect the Table or Bucky!!

29. 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!!!

30. 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

31. 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

32. Hyposthenic/Asthenic Patients

33. Hypersthenic Patients

34. Positioning: Lateral Skull
Seated upright or semi-prone
MSP is parallel to IR
Interpupillary line is perpendicular to IR
Suspend respiration
CR enters 2” superior to EAM
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35. Positioning Trauma Lateral Skull
Supine with sponge under head
MSP is parallel to IR
Interpupillary line is perpendicular to IR
Suspend respiration
CR enters 2” superior to EAM
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36. Lateral Skull

37. Lateral Skull Radiograph
Entire cranium without rotation/tilt
SI orbital roofs, greater wings of sphenoid, and TMJ’s
Sella turcica in profile
Penetration of parietal
No overlap c-spine by mandible
Rotation would be evident by an ANTERIOR and POSTERIOR separation of symmetric bilateral structures such as EAM”S, mandibular rami,and greater wings of the sphenoid.
Tilt would be evident by SUPERIOR and INFERIOR separation of the orbital roodfs, EAM’s and lesser wings of sphenoid.
Side of interest closest to cassette. MSP is parallel to IR. IOML is perpendicular to the front edge of IR and IOML should be parallel to the long axis of the IR.
CR enters 2” superior to the EAM.
Pathology of interest for this projection usually includes: skull fractures, neoplastic processes and Paget’s disease.
Copyright © 2003, Mosby, Inc.

38. Common PA projections
O degree- Frontal bone, crista galli, internal auditory canals, frontal and anterior ethmoidal sinuses, petrous ridges, greater and lesser wings of sphenoid, and dorsum sellae.
15 degree caudal, commonly referred to as the Caldwell projection, demonstrates greater and lesser sphenoid wings, frontal bone, superior orbital fissures, frontal and anterior ethmoidal air sinuses, superior orbital margins and crista galli.
25-30 caudal demonstrates the same as the Caldwell and the following additional structures: the foramen rotundum, and the entire superior orbital fissures located within the orbits.

39. Positioning PA, PA Axial & Caldwell
Prone or seated upright
Forehead and nose against bucky or table
OML perpendicular to IR
MSP perpendicular to IR
Respiration: suspend
CR: 0, 15 caudal or caudal, exiting nasion
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40. Trauma PA and PA Axial Skull
Semi supine: 1 side elevated to place head in true lateral
Sponge under head
Nose and forehead against vertical IR
OML perpendicular to IR
Direct horizontal CR perpendicular or 15 degrees caudad to exit nasion
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41. PA and Caldwell Radiographs
Entire skull with no rotation or tilt
Petrous ridges in lower 1/3 of orbits with 15 caudal
Petrous ridges fill orbits with horizontal beam
Density and contrast are sufficient
No motion
Nasion in center of film, close collimation
No rotation is evident by assessing that there is equal distance from lateral border of skull to lateral border of orbits on each side. Superior orbital fissures symmetric within orbits.
Density and contrast are sufficient to visualize the frontal bone, and sellar structures without overexposure.
Sharp bony detail indicates no motion.
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42. Similarities and Differences
Exit nasion
Require close collimation
OML is perpendicular to plane of IR
All axials have caudal angles
Respiration suspended
Position of petrous ridges
Best seen
Body position
Where the CR enters
All PA and PA AXials exit nasion. All require close collimation so that that scatter does not degrade the image and cause the lateral borders to have excessive density. All axial projections the CR is projected caudally.
All projections respiration is suspended for exposure.
The petrous ridges are filling the orbits for a PA, in lower 1/3 for 15 degrees caudal. What is best seen changes based on the CR angulation. The position of the body changes whether they are semi-supine, prone, or upright. The CR will have to enter the body differently so the CR always exits the nasion.

43. Positioning: AP & AP Axial Skull
Supine
OML perpendicular to IR
CR directed at nasion with a horizontal beam or 15 degrees cephalic
Suspend respiration

44. AP Skull Radiograph Entire skull with no rotation or tilt
Petrous ridges in lower 1/3 of orbits with 15 cephalad
Petrous ridges fill orbits with horizontal beam
Density and contrast are sufficient
No motion
Nasion in center of film, close collimation
Image is magnified compared to PA
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45. Positioning AP Axial (Towne)
Supine or seated upright
MSP perpendicular to plane of IR
OML or IOML perpendicular to IR
Suspend respiration
CR 30 degrees caudal (OML) or 37 caudal (IOML).
CR enters 2 ½” above glabella through the level of EAM
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46. AP Axial (Towne) Radiograph
Equal distance from lateral border of skull to foramen magnum
Symmetric petrous ridges
Dorsum sellae and posterior clinoid processes visible through foramen magnum
Penetration of occipital bone without excessive density

47. Sella Turcica

48. Townes Comparison

49. Positioning PA Axial (Haas)
Prone or seated upright
Forehead and nose on table or grid device
MSP perpendicular to the grid
OML perpendicular to IR
Suspend respiration
CR 25 degrees cephalad entering 1 1/2 “ below occipital protuberance.
R exits 1 ½” superior to nasion

50. PA Axial (Haas) Radiograph
Prone or seated upright
MSP & OML perpendicular
Suspend respiration
Directed cephalic 25 degrees to enter 1 ½” below the inion.
Exit 1 ½” superior to nasion.
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51. Haas PA Axial

52. Positioning SMV (Schüller)
Supine or seated upright
IOML parallel to IR
MSP perpendicular to IR
Suspend respiration
CR enters the MSP of the throat between angles of mandible and passes through a point ¾”anterior to EAMS.

53. SMV (Schüller) Radiograph
Adequate penetration of cranial base
Equal distance from lateral border of skull to condyles
SI of mental protuberance over anterior frontal bone
Condlyes anterior to petrous ridges
Symmetric petrosae

54. Positioning VSM (Schüller)
Prone
Chin resting on table
MSP perpendicular to IR
Suspend respiration
CR directed perpendicular to IOML.
CR passes through ¾” anterior to level of EAMS

55. VSM (Schüller) Radiograph
Adequate penetration of cranial base
Equal distance from lateral border of skull to condyles
SI of mental protuberance over anterior frontal bone
Condlyes anterior to petrous ridges
Symmetric petrosae

56. SMV

57. What is wrong with this Caldwell?

58. What is wrong with this lateral skull?

59. What is wrong with this Towne’s?