Positioning and radiographic anatomy of the skull

1. Positioning and Radiographic
Anatomy of the Skull

2. RADIOGRAPHIC ANATOMY
Skull
As with other body parts, radiography of the
skull requires a good understanding of all
related anatomy. The anatomy of the skull is
very complex, and specific attention to detail
is required of the technologist.
The skull, or bony skeleton of the head,
rests on the superior end of the vertebral
column and is divided into two main sets of
bones—the 8 cranial bones and the 14
facial bones.

4. CRANIAL BONES (8)
The eight bones of the cranium are divided into the
calvaria (skullcap) and the floor. Each of these two
areas primarily consists of four bones:
Calvaria (Skullcap)
1. Frontal
2. Right parietal
3. Left parietal
4. Occipital
Floor
5. Right temporal
6. Left temporal
7. Sphenoid (sfe′-noid)
8. Ethmoid (eth′-moid)

12. POSITIONING CONSIDERATIONS
Erect versus Recumbent
Projections of the skull may be taken with the patient in the recumbent or
erect position, depending on the patient's condition. Images can be
obtained in the erect position with the use of a standard x-ray table in the
vertical position or an upright Bucky. The erect position allows the patient
to be quickly and easily positioned and permits the use of a horizontal
beam. A horizontal beam is necessary to visualize any existing air-fluid
levels within the cranial or sinus cavities

13. Patient Comfort
Patient motion almost always results in an
unsatisfactory image. During skull radiography,
the patient's head must be placed in precise
positions and held motionless long enough for
an exposure to be obtained. Always remember
that a patient is attached to the skull that is
being manipulated. Every effort should be made
to make the patient's body as comfortable as
possible, and positioning aids such as sponges,
sandbags, and pillows should be used if
needed.
Except in cases of severe trauma, respiration
should be suspended during the exposure to
help prevent blurring of the image caused by
breathing movements of the thorax. This is
especially important when the patient is in a
prone position.

14. Hygiene
Cranial and facial radiography may require
the patient's face to be in direct contact
with the technologist's hands and the
table/upright Bucky surface. Therefore, it is
important that proper handwashing
techniques and surface disinfectants be
used before and after the examination.

15. Exposure Factors
The principal exposure factors for
radiography of the skull include the
following:
•Medium kV (65 to 85 kV film-based)
(70 to 80 kV digital radiography [DR]
and computed radiography [CR])
•Small focal spot <250 mA (if
equipment allows)
•Short exposure time

16. SID
The minimum SID with the image receptor in the
table or upright Bucky is 40 inches (100 cm).
Radiation Protection
The best techniques for minimizing radiation
exposure to the patient in skull radiography are to
(1) use good collimation practices, (2) immobilize
the head when necessary, minimizing repeats,
and (3) center properly.
Gonadal shielding
Generally, with accurate collimation, no
detectable contribution to gonadal exposure
occurs during radiography of the skull. However,
lead shields should be used to reassure the
patient

17. Digital Imaging Considerations
Guidelines for digital imaging (CR and DR) of the skull are:
1.Correct central ray angle and centering to body part and image
receptor. This provides for accurate post-processing of the image by the
image reader.
2.Close collimation. Improves image quality by reducing scatter and
secondary radiation to the highly sensitive digital image receptors.
3.Following ALARA principles (exposure to patient As Low As
Reasonably Achievable) in determining exposure factors (highest kV
and lowest mAs that will result in desirable image quality). An increase
in kV over film-screen imaging may be desirable, both for reducing
patient exposure and for improving image quality. (Sufficient mAs is
required to produce a high-resolution image.)
4.Post-processing evaluation of exposure indices (for assurance that
optimum quality image was achieved with least possible radiation to
patient). Examine the amount of kV and mAs used for a particular
exposure if the exposure index is above or below the recommended
range.

18. Skull Series
BASIC:
• AP axial (Towne method)
• Lateral
• PA axial 15° (Caldwell method) or PA axial 25° to
30°
• PA 0°
SPECIAL
• Submentovertex (SMV)
• PA axial (Haas method)

19. AP AXIAL PROJECTION: SKULL
SERIES
Towne Method
Pathology Demonstrated
Skull fractures

20. Technical Factors
• IR size—24 × 30 cm (10 × 12 inches), lengthwise
• Moving or stationary grid
• 70 to 80 kV range
• Small focal spot

21. Part Position
• Depress chin, bringing OML perpendicular
to IR. For patients unable to flex their neck
to this extent, align the IOML perpendicular
to the IR. Add radiolucent support under the
head if needed.
• Align midsagittal plane to CR and to
midline of the grid or the table/Bucky
surface.
• Ensure that no head rotation and/or no tilt
exists.
• Ensure that vertex of skull is in x-ray field.

22. Collimation
Collimate to outer margins of skull.
Respiration
Suspend respiration.
If patient is unable to depress the chin sufficiently to
bring the OML perpendicular to the IR even with a
small sponge under the head, the infraorbitomeatal
line (IOML) can be placed perpendicular instead and
the CR angle increased to 37° caudad. This maintains
the 30° angle between the OML and the CR and
demonstrates the same anatomic relationships. (A 7°
difference exists between the OML and the IOML.)

23. Central Ray
• Angle CR 30° caudad to OML, or 37° caudad to
IOML (see Note below).
• Center at the midsagittal plane 2½ inches (6.5 cm)
above the glabella to pass through the foramen
magnum at the level of the base of the occiput.
• Center IR to projected CR.
• Minimum SID is 40 inches (100 cm).

24. Structures Shown: • Occipital bone, petrous pyramids,
and foramen magnum are shown with the dorsum
sellae and posterior clinoids visualized in the shadow
of the foramen magnum.

25. LATERAL POSITION—RIGHT AND/OR LEFT
LATERAL: SKULL SERIES
Pathology Demonstrated
Skull fractures. A common general skull routine includes both
right and left laterals.

26. Part Position
• Place the head in a true lateral position, with
the side of interest closest to IR and the
patient's body in a semiprone position as
needed for comfort. • Align midsagittal plane
parallel to IR, ensuring no rotation or tilt.
• Align interpupillary line perpendicular to IR,
ensuring no tilt of head (see Note below).
• Adjust neck flexion to align IOML
perpendicular to front edge of IR

27. Central Ray
• Align CR perpendicular to IR.
• Center to a point 2 inches (5 cm) superior to EAM .
• Center IR to CR.
• Minimum SID is 40 inches (100 cm).

28. Structures Shown: • Superimposed cranial halves with superior
detail of the lateral cranium closest to the IR are demonstrated.
The entire sella turcica, including anterior and posterior clinoids
and dorsum sellae, is also shown. The sella turcica and clivus
are demonstrated in profile.

29. PA AXIAL PROJECTION: SKULL SERIES
15° CR (Caldwell Method) or 25° to 30° CR
Pathology Demonstrated
Skull fractures (medial and lateral displacement)

30. Part Position
• Rest patient's nose and forehead against table/Bucky
surface.
• Flex neck as needed to align OML perpendicular to
IR.
• Align midsagittal plane perpendicular to midline of the
grid or table/Bucky surface to prevent head rotation
and/or tilt.
• Center IR to CR.

31. Central Ray
• Angle CR 15° caudad and center to exit at nasion.
• Alternate with CR 25° to 30° caudad, and center to
exit at nasion.
• Minimum SID is 40 inches (100 cm).

32. Alternate 25° to 30°: An alternate projection is a 25°
to 30° caudad tube angle that allows better
visualization of the superior orbital fissures (black
arrows), the foramen rotundum (small white arrows),
and the inferior orbital rim region. CR exits at level of
nasion.

33. Structures Shown: • Greater and lesser sphenoid wings,
frontal bone, superior orbital fissures, frontal and anterior
ethmoid sinuses, superior orbital margins, and crista galli are
shown.

34. PA PROJECTION: SKULL SERIES
0° CR
Pathology Demonstrated
Skull fractures (medial and lateral displacement)

35. Part Position
• Rest patient's nose and forehead against
table/Bucky surface.
• Flex neck, aligning OML perpendicular to IR.
• Align midsagittal plane perpendicular to midline of
table/Bucky to prevent head rotation and/or tilt
(EAMs same distance from table/Bucky surface).
• Center IR to CR.

37. Structures Shown: • Frontal bone, crista galli, internal
auditory canals, frontal and anterior ethmoid sinuses,
petrous ridges, greater and lesser wings of sphenoid.

38. SUBMENTOVERTEX (SMV) PROJECTION: SKULL
SERIES
Warning: Rule out cervical spine fracture or subluxation
on trauma patient before attempting this projection.

39. Part Position
• Raise patient's chin and hyperextend the neck if
possible until IOML is parallel to IR.
• Rest patient's head on vertex.
• Align midsagittal plane perpendicular to the midline
of the grid or table/Bucky surface, thus avoiding tilt
and/or rotation.

40. Central Ray
• CR is perpendicular to infraorbitomeatal line.
• Center 1½ inch (4 cm) inferior to the mandibular
symphysis, or midway between the gonions.
• Center image receptor to CR.
• Minimum SID is 40 inches (100 cm)

41. Structures Shown: • Foramen ovale and spinosum,
mandible, sphenoid and posterior ethmoid sinuses, mastoid
processes, petrous ridges, hard palate, foramen magnum,
and occipital bone are shown.

42. PA AXIAL PROJECTION: SKULL SERIES
Haas Method
Pathology Demonstrated
Occipital bone, petrous pyramids, and foramen magnum,
with dorsum sellae and posterior clinoids in its shadow

43. Part Position
• Rest patient's nose and forehead against the
table/Bucky surface.
• Flex neck, bringing OML perpendicular to IR.
• Align midsagittal plane to CR and to the midline of the
grid or table/Bucky surface.
• Ensure that no rotation or tilt exists (midsagittal plane
perpendicular to IR).

44. Central Ray
• Angle CR 25° cephalad to OML.
• Center CR to midsagittal plane to pass through level of
EAMs and exit 1½ inches (4 cm) superior to the nasion.
• Center image receptor to projected CR.
• Minimum SID is 40 inches (100 cm).

45. Structures Shown: • Occipital bone, petrous pyramids,
and foramen magnum are shown, with the dorsum sellae
and posterior clinoids visualized in the shadow of the
foramen magnum.

60. 60
Waters Projection
•Waters projection
demonstrates:
•Cloudy maxillary
sinuses worse on left.
•Sinus infection that
needed antibiotics.

61. 61
9.1 P-A Skull
•Measure: A-P at the
Glabella
•Protection: Full coat
apron with lead to back or
half apron draped over
back of chair.
•SID: 40” Bucky
•No tube angle
•Film: 10” x 12” regular
I.D. down (portrait)

62. 62
P-A Skull
•Patient seated or
standing facing the
Bucky.
•Nose and forehead
touching the Bucky to
get the canthomeatal
line perpendicular to
film.

63. 63
P-A Skull
•Horizontal CR: exit
through the glabella.
•Vertical CR: mid-sagittal
plane
•Center film to
horizontal CR
•Collimation: slightly less
than film size.
•Breathing Instructions:
Suspended respiration

64. 64
P-A Skull
•Make exposure and let
patient relax.
•Note: If the patient is
done seated, place Bucky
tray in the lower Bucky
slot. This will allow the
patient to get their legs
under the Bucky.

65. 65
P-A Skull Film
•The entire skull should
be on the film.
•There should be no
rotation.
•The petrous ridges will
be superimposed with
the orbits.
•To clear the ridges, the
Caldwell view can be
taken.

66. 66
9.2 Chamberlain-Townes
•The Townes Projection is
part of a routine skull
series.
•The tube is angled to
throw the anterior part of
the skull away from the
occipital region of the
skull.

67. 67
Chamberlain-Townes
•Measure: A-P at Glabella
•Protection: Half apron or
Coat Apron
•SID: 40” Bucky
•Tube angle: 35 degrees
Caudal
•Film: 10” x 12“ regular
I.D. Down (portrait)

68. 68
Chamberlain-Townes
•Patient is seated facing
the tube.The chin is
tucked into the chest until
the canthomeatal line is
perpendicular to film. A
chair the allows some
reclining will make this
easier for the patient.

69. 69
Chamberlain-Townes
•Horizontal CR: Through
the EAM. The Horizontal
CR will usually pass
through the hair line.
•Vertical CR: mid-sagittal
•Film centered to
horizontal CR
•Collimation: slightly less
than film size or soft
tissue of skull

70. 70
Chamberlain-Townes
•Breathing Instructions:
Suspended respiration
•Make exposure
•Let patient breathe and
relax

71. 71
Chamberlain-Townes Film
•The entire skull and
especially the occipital
region of the skull must
be on the film.
•Structure seen include
the foramen magnum,
petrous ridges, IAC’s
and TM Joints
•No rotation of skull

72. 72
9.3 Skull Lateral
•Measure: Lateral at EAM
•Protection: Full coat
apron or half apron
draped over back of chair
•SID: 40” Bucky
•Tube angle: none but
may be angled parallel to
interpupillary line.
•Film: 12” x 10” I.D. to
face (landscape)

73. 73
Skull Lateral
•Patient seated of
standing facing the
Bucky. Rotate the body
into an oblique position.
•Turn skull so the
affected side is next to
the Bucky.
•The interpupillary line
must be perpendicular
to film and tube.
•Mid sagittal plane
parallel to the film.

74. 74
Skull Lateral
•Horizontal CR:
3/4”superior to EAM
•Vertical CR: 3/4”
anterior to EAM or mid
skull
•Center film to
horizontal CR.
•Collimation: slightly
less than film size
•Breathing
Instructions:
Suspended respiration
•Make exposure and let
patient relax.

75. 75
Skull Lateral Film
•Entire skull must be on
the film.
•There should be no
rotation of the skull,
orbits and mandible
ramus superimposed.
•The facial bones are
sinuses will be dark
(over exposed).
•Usually both lateral
views are taken.

76. 76
9.5 Base Posterior Skull
•Routine skull view that
can be used to evaluate
the upper cervical spine.
•Provides an axial view of
C-1 and C-2 as well as
the foramen magnum.

77. 77
9.5 Base Posterior Skull
•Measure: A-P at Glabella
•Protection: Half apron
•SID: 40” Bucky
•Tube Angle: None but if
patient cannot extend
head back far enough to
get inferior orbital meatal
line perpendicular to
horizontal CR tube angle
may be needed.

78. 78
Base Posterior Skull
•Film Size: 10” x 12”
regular I.D. down
(Portrait)
•Patient is seated in a
reclining chair. The
chair is placed about 6”
to 10” from Bucky.
•Patient is asked to
extend neck back until
inferior orbital meatal
line is parallel to film
with top of skull
touching the Bucky.

79. 79
Base Posterior Skull
•Horizontal CR: EAM
•Vertical CR: mid-
sagittal
•Center film to
horizontal CR
•Collimation: slightly
less than film size or
skin of skull
•Breathing
Instructions:
suspended respiration
•Make exposure

80. 80
Base Posterior Skull
•Assist patient get out
of the position. Be
very careful that the
patient does not hit
face on x-ray tube.
•The ability of the
patient to lay back in
the chair will make
the view much easier
for all concerned.

81. 81
Base Posterior Skull Films
•This basilar view of
skull has the patient’s
head not extended
back far enough. The
mandible and frontal
skull should be
superimposed.
•The I.D. Blocker is on
the skull.
•The skull is rotated.

82. 82
Base Posterior Skull Films
•If the upper cervical
spine or mastoid
processes and
internal auditory
canals are the areas
of interest, it is
appropriate to cone
down to this area.
•Note the ear ring left
on the patient.
•There is some
rotation.

83. 83
Base Posterior Skull Films
•The entire skull is
visualized.
•The mandible and
frontal region of skull
are superimposed.
•With a bright light, the
zygomatic arches can
usually be seen.

84. 84
9.6 Schullers Projection
•The Schullers
Projection can be
used to evaluate the
temporal mandibular
joints and mastoid air
cells and inner ear.

85. 85
9.6 Schullers Protection
•Measure: lateral at EAM
•Protection: Lead apron
•SID: 40” Bucky
•Tube angle: 25 degrees
caudal
•Film size: 8” x 10” I.D. up
(portrait)

86. 86
Schullers Protection for TMJ
•Patient is seated facing
the Bucky. Head is
turned to place the
affected TMJ next to
Bucky.
•Skull should be in a true
lateral position. Align
the TMJ to the center
line of the Bucky.
•The vertical CR should
be aligned with TMJ
away from film.

87. 87
Schullers Protection for TMJ
•If the affected TMJ and
the side away from the
Bucky is aligned with
the Center of the Bucky
and Vertical CR, the
skull will be in the true
lateral position.
•The horizontal CR is
aligned with the
Affected TMJ (closest
to film).

88. 88
Schullers Protection for TMJ
•Center film to
horizontal CR.
•Collimation: 5” x 5”
•Breathing
instructions: Keep
mouth closed and don’t
breathe move or
swallow.
•Make exposure.
•Let patient breathe
but remain in the
position.

89. 89
Schullers Protection for TMJ
•Change cassettes to a
new 8” x 10”
•Ask patient to open
mouth as far as
possible.
•Recheck positioning.
•Breathing
Instructions: With
mouth wide open, don’t
breathe move or
swallow.
•Make exposure and let
patient relax.

90. 90
Schullers Protection for TMJ
•Open and closed mouth
view are taken of both
TM joints.
•The TMJ closest to the
Bucky will be the one
seen at the center or top
of the film.
•Accurate positioning is
essential to being able to
compare joints.

91. 91
9.7 Caldwell Sinus Projection
•The Caldwell Projection
will have the petrous
ridges below the orbits.
•Positioning is exactly like
the P-A skull with the
exception of the use of a
15 degree caudal tube
angle to lower the petrous
ridges.

92. 92
9.7 Caldwell Sinus Projection
•Measure: A-P at Glabella
•Protection: Coat apron
backwards or half apron
draped over back of chair.
•SID: 40” Bucky
•Tube angle: 15 degrees
caudal
•Film: 8” x 10” Regular
I.D. Down (portrait)

93. 93
Caldwell Sinus Projection
•Patient is seated facing
Bucky. Their legs should
be under the Bucky. Get
chair as close to the
Bucky as possible.
•Ask patient to place their
nose and forehead on
center line of Bucky.
•Check for rotation.

94. 94
Caldwell Sinus Projection
•Horizontal CR: exits
through the Glabella or
Nasion
•Vertical CR: mid-sagittal
•Center film to
horizontal CR
•Collimation: 6” or 7”
square.
•Breathing Instructions:
Suspended Respiration

95. 95
Caldwell Sinus Projection Film
•This view will provide
a clear view of the
frontal and ethmoid
sinuses.
•The super orbital rims
can be evaluated for
fracture when facial
bone are of interest.
•To project the petrous
ridges farther down,
increase angle to 25
degrees

96. 96
9.8 Waters Projection Sinus
•The most important view
for sinus problems or
injury involving the
maxilla or orbits.
•By taking the view erect,
fluid levels within the
maxillary sinuses can be
seen.

97. 97
9.8 Waters Projection Sinus
•Measure: A-P at Glabella
•Protection: Half apron
over back of chair or coat
apron backwards
•SID: 40” Bucky
•No tube angle
•Film: 8” x 10” regular I.D.
Down (portrait)

98. 98
Waters Projection Sinus
•Patient is seated facing
the Bucky. Get the chair
as close to the Bucky as
possible. Patient may
spread legs to get chair
as close as possible. May
also be taken standing.
•Mentomeatal line should
be perpendicular to film
with mouth closed.

99. 99
Waters Projection Sinus
•The nose will be one to
two centimeters from
Bucky with chin resting
on Bucky.
•The mouth may be
opened to see the
sphenoid sinus. When
this is done, the
canthomeatal line should
be 35 to 40 degrees to
the Bucky.

100. 100
Waters Projection Sinus
•Horizontal CR: exit
through the base of nose
or acantha.
•Vertical CR: mid-sagittal
•Center film to
horizontal CR
•Collimation: 6” or 7”
square
•Breathing Instructions:
Suspended Respiration

101. 101
Waters Projection Sinus Film
•This is an example of the
open mouth waters view.
•The facial bones and
sinuses should be on the
film.
•There should be no
rotation.
•The petrous ridges must
be below the floor of the
maxilla.

102. 102
Waters Projection Sinus Film
•The facial bones and
sinuses should be on the
film.
•There should be no
rotation.
•The petrous ridges must
be below the floor of the
maxilla.

103. 103
9.9 Sinus Lateral
•The lateral view of the
sinuses and facial bones
will under exposed for the
skull.
•This view is very useful
for seeing fluid levels in
all of the sinuses.
•

104. 104
9.9 Sinus Lateral
•Measure: Lateral at EAM
•Protection: Coat apron
or half apron draped over
back of chair.
•SID: 40” Bucky
•No Tube Angle
•Film: 8” x 10” regular I.D.
down (portrait)

105. 105
Sinus Lateral
•Patient is seated or
standing facing the
Bucky. Turn patient
toward the affected side.
Turing the body will make
it easier for the patient.
•Patient’s skull should be
in a true lateral position.
The interpupillary line
perpendicular to film.

106. 106
Sinus Lateral
•Horizontal CR: Outer
canthus of the eye with
mid sagittal plane parallel
to film.
•Vertical CR: Outer
canthus of eye
•Center film to
horizontal CR.

107. 107
Sinus Lateral
•Collimation Top to
Bottom: Frontal Sinuses
to Mandible
•Collimation Side to
side: Nose to EAM
•Breathing Instructions:
suspended respiration
•Make exposure and let
patient relax

108. 108
Sinus Lateral
•There should be no
rotation of the patient’s
skull.
•The orbits, sella, maxilla
and visualized mandible
should be superimposed.

109. 109
9.10 Basilar View of Sinuses
•The base view of the
sinuses is positioned just
like the base posterior
view.
•The horizontal CR is
moved to the center of
the facial bones and
sinuses.
•The positioning view
demonstrates a patient
that cannot extend their
neck.

110. 110
9.10 Basilar View of Sinuses
•Measure: A-P at glabella
•Protection: Half or coat
apron
•SID: 40” Bucky
•Tube angle: none if
patient can extend neck
until the inferior orbital-
meatal line is parallel to
film.

111. 111
Basilar View of Sinuses
•If patient cannot extend
back far enough, angle
tube to get the CR
perpendicular to the
inferior orbital-meatal line.
•Film: 8” x 10” regular I.D.
down (portrait)

112. 112
Basilar View of Sinuses
•Position chair about 6” to
10” from Bucky. Patient
seated facing the tube.
•Have patient lean back or
recline in chair.
•Patient extend neck as
far as possible until the
inferior orbital-meatal line
is parallel to film.

113. 113
Basilar View of Sinuses
•Horizontal CR: 1.5”
superior to EAM or
middle of mandible.
•Vertical CR: mid-sagittal
plane
•Center film to
horizontal CR.
•Collimation: slightly less
than film size or skin of
facial region

114. 114
Basilar View of Sinuses
•Breathing Instructions:
Suspended respiration
•Make exposure
•Carefully assist patient
raise head without
hitting head on x-ray
tube.

115. 115
Basilar View of Sinuses
•Mandible and frontal
bone should be
superimposed.
•No rotation of skull
•Maxilla, sphenoid and
ethmoid sinuses and
mandible will be seen.