Human Skull consist of 22 Bones: 8 Bones of the Cranium (Occipital Bone, 2 Temporal
Bones, 2 Parietal Bones, Sphenoid Bone, Ethmoid Bone, Frontal Bone), and 14 Bones of
the Facial (Vomer, 2 Conchae, 2 Nasal Bones, 2 Maxilla, Mandible, 2 Palatine Bones, 2
Zygomatic Bones, 2 Lacrimal Bones).
The Skull also contains the Sinus Cavities, which are Air-Filled Cavities.
Paranasal sinuses are a group of four paired air-filled spaces that surround the Nasal
Cavity.
Patient Preparation
Before undertaking skull radiography, the following specific considerations should be
made:
• Ensure that all metal objects are removed from the patient, e.g. hair clips and hairpins.
• Bunches of hair often produce artifacts and thus should be untied.
• If the area of interest includes the mouth, then false teeth containing metal and metal
dental bridges should be removed.
• The patient should be provided with a clear explanation of any movements and film
positions associated with the normal operation of the skull unit.
Useful Accessories
• The usefulness of foam pads as an aid to immobilization cannot be overstated. The
photograph opposite shows a specially designed pad for skull radiography. It is available
in a range of sizes to accommodate different age groups.
• Forty-five-degree triangular pads are extremely useful for immobilizing children. They
can be held by the parent and support the head without the parent placing their hands in
the primary beam.
• Individual side markers are essential for skull radiography, as the clip-type side markers
are easily lost in the collimation, particularly when using a skull unit.
• Velcro straps are of great use when immobilizing a patient on a skull unit.
General Image Quality Guidelines and Radiation Protection considerations:
• Images should have a visually sharp reproduction of all structures, such as outer and inner
lamina of the Cranial Vault (Cranial Cavity), the trabecular structure of the cranium, the
various sinuses and sutures where visible, vascular channels, Petrous part of the temporal
bone and the pituitary fossa.
• Important image details should be visualized.
• Whenever possible, use an Occipito-frontal (PA) rather than a fronto-occipital (AP) since
this vastly reduces the dose to the eyes.
Portrait:
• Exposure Factors: 70 – 85 kVp.
Lengthwise.
20 mAs.
• Cassette (IR) Size: 24 x 30 cm, (10 x 12 inches).
Landscape:
• Cassette Orientation: Portrait but in Lateral View Landscape.
Crosswise.
• FFD / SID: 100cm, (40 in).
• Always using Bucky (Grid).
• Projections of the skull may be taken with the Patient sitting, standing or Laying
depending on the patient's condition.
1. AP (Fronto occipital).
2. PA (Occipito frontal).
3. Lateral View.
4. Fronto occipital ( AP Axial - TOWNE’S View).
5. Occipito frontal ( PA - CALDWELL’S View).
6. Submentovertex (SMV – Schüller Method).
7. PA Axial (Haas Method).
Positioning:
• The patient typically presents in a supine position in trauma cases.
• Rotate the e Head of Patient to make the Radiographic Baseline (OML) perpendicular to
IR.
Centering Point: Directed to the Nasion.
Central Ray: Perpendicular to the IR / Bucky, Parallel to the radiographic baseline
(Orbitomeatal Line).
Collimation: Outer skin margins of the skull.
Evaluation Criteria
 No rotation is evidenced by The
lateral borders of the orbits to the
lateral borders of the skull are
equidistant on both sides.
 No tilt is evidenced by The
Petrous ridges are horizontal.
Area Covered Collimation:
Shutter A: Open to include the
lateral skin margins of the skull.
Shutter B: Open to include the
entire skull superiorly, and the
maxilla inferiorly.
 Exposure:
• Assess for adequate penetration of
the thickest part of the skull, the
frontal bone.
• Bony trabecular patterns and
cortical outlines are sharply defined.
• Soft tissues are visualized.
Positioning:
Erect
• Patient is standing or sitting facing the upright Bucky.
• Forehead and nose are touching the Bucky.
• The radiographic baseline (Orbitomeatal Line) is perpendicular to the Bucky.
• Ensure no rotation of the head by checking that the EAMs are the same distance from
Bucky.
Prone
• Rest patients nose and forehead against table/ Bucky.
• Flex neck to align OML perpendicular to IR.
Centering Point: Exit at the level of the Glabella.
Central Ray: Perpendicular to the IR / Bucky,
Parallel to the radiographic baseline (Orbitomeatal
Line).
Collimation: Outer skin margins of the skull.
Evaluation Criteria
 No rotation is evidenced by The
lateral borders of the orbits to the
lateral borders of the skull are
equidistant on both sides.
 No tilt is evidenced by The Petrous
ridges are horizontal and will be seen
within the orbits.
Area Covered Collimation:
Shutter A: Open to include the
lateral skin margins of the skull.
Shutter B: Open to include the entire
skull superiorly, and the maxilla
inferiorly.
 Exposure:
• Assess for adequate penetration of
the thickest part of the skull, the
frontal bone.
• Bony trabecular patterns and
cortical outlines are sharply defined.
• Soft tissues are visualized.
Positioning:
• Patient standing or sitting facing the Bucky, Supine or Prone.
• Place the side of interest of the skull closest to the Bucky.
• Oblique the body slightly to assist with positioning and patient comfort.
• Interpupillary line perpendicular to Bucky.
• The midsagittal plane is parallel to the Bucky.
Centering Point: Center to a point 2 inches (5 cm) superior to EAM.
Central Ray: Perpendicular to the IR / Bucky.
Collimation: Outer skin margins of the skull.
Cassette Orientation:
Landscape.
Evaluation Criteria
 No tilt is evidenced by There
is superimposition of the
superior orbital plates of the
frontal bone.
 Area Covered Collimation:
Shutter A: Open to include the
skin margins of the top of skull
superiorly, and the base of the
Occipito inferiorly
Shutter B: Open to include the
skin margins of the anterior and
posterior skull
Exposure:
• Assess for adequate
penetration of the thickest part
of the skull, the frontal bone.
• Bony trabecular patterns and
cortical outlines are sharply
defined.
• Soft tissues are visualized.
Positioning:
• Patient is in an erect position, either standing or sitting or Supine.
• Position the patient so that their back and posterior skull are touching the Bucky.
• Bring the patients chin down until the radiographic baseline Orbitomeatal line (OML) is
perpendicular the Bucky. If the patient is not able to do this, the central ray angle may have
to be increased caudally so that there is a 30 degree angle between the radiographic
baseline (OML) and the central ray.
Centering Point: Directed to 6 cm superior to the Glabella (this is typically the hairline).
Central Ray: CR 30° caudal.
Collimation: Outer skin margins of the skull.
Evaluation Criteria
 No rotation is evidenced by The lateral
borders of the foramen magnum are
equidistant from the lateral borders of the
skull.
 No tilt is evidenced by The Petrous ridges
are horizontal.
 The central ray is at 30 degrees to the
radiographic baseline, evidenced by The
dorsum sellae & posterior clinoid processes
are seen in the foramen magnum.
 Collimation
• Shutter A: Open to include the outer skin
margins of the skull laterally
• Shutter B: Open to include the superior
aspect of the skull
 Exposure
• Assess for adequate penetration of the
thickest part of the skull
• The dorsum sellae and posterior clinoid
processes are seen in the foramen magnum
Bony trabecular patterns and cortical outlines
are sharply defined
• Soft tissues are visualized.
Positioning:
• Let the patient's nose and forehead rest the against table or Bucky surface.
• Slowly flex the patient's neck as needed to align Orbitomeatal Line (OML) perpendicular
to Image Receptor.
Centering Point: Exit at the level of the Nasion.
Central Ray: Angulated Central Ray to 15° caudal.
Alternate with CR 25° to 30° caudal.
Collimation: Outer skin margins of the skull.
Note:
For patients who are unable to be positioned
for a PA projection (e.g., trauma patients),
an AP axial projection may be obtained
with the use of a 15 ° cephalic angle,
with the OML positioned perpendicular
to the IR.
Evaluation Criteria
 No rotation as assessed by equal distance from the midlateral orbital margins to the
lateral wall of cranium on each side, superior orbital fissures symmetric within the orbits,
correct extension of neck.
 In 15° caudal: Petrous pyramids are projected into the lower one-third of the orbits.
 In 25° - 30° caudal: Petrous pyramids are projected at or below the inferior orbital rim
to allow visualization of the entire orbital margin.
 Collimation
• Shutter A: Open to include the outer skin margins of the skull laterally
• Shutter B: Open to include the superior aspect of the skull
 Exposure
• Assess for adequate penetration of the thickest part of the skull, the frontal bone.
• Bony trabecular patterns and cortical outlines are sharply defined.
• Soft tissues are visualized.
Positioning:
• 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.
Centering Point: Entering 1.5 in (3.8cm) inferior to external Occipital Protuberance
(Inion) and exiting 1.5 in (3.8 cm) superior to Nasion.
Central Ray: Angle CR 25° cephalic.
Collimation: Outer skin margins of the skull.
Note:
For patients who are unable to be positioned
for a PA projection (e.g., trauma patients),
an AP axial projection may be obtained
with the use of a 15 ° cephalic angle,
with the OML positioned perpendicular
to the IR.
Evaluation Criteria
No rotation is evident, as indicated by
bilateral symmetric Petrous ridges.
Dorsum sellae and posterior clinoids are
visualized in the foramen magnum, which
indicates correct CR angle and proper
neck flexion and extension.
No tilt as evidenced by correct
placement of anterior clinoids within the
middle of the foramen magnum.
 Collimation
• In Haas Method the entire skull is
visualized in the image with the vertex
near the top and the foramen magnum
and mastoid portions near the bottom.
• Collimation borders are visible to outer
margins of skull.
 Exposure
• Density and contrast are sufficient to
visualize occipital bone and sellar
structures within foramen magnum.
• Sharp bony margins indicate no motion.
Positioning:
• The aim is to get the IOML (Infraorbitomeatal Line) parallel to the IR and Bucky. The
method used to achieve this will depend on the presentation of the patient.
• The following description is for patients who are able to tip their head back, hyper
extending their neck, and are able to sit.
• The patient sits in an AP position in front of the upright Bucky.
• The chin is raised and the head tipped back until the IOML is parallel to the Bucky and
the vertex of the skull is centered and resting against the Bucky.
• If the patient is able to achieve this position then the central ray is perpendicular to both
the Bucky and the IOML.
• If the patient is unable to tip their head back far enough, then angle the central ray so that
it is perpendicular to the IOML.
Centering Point: Directed at the point midway between the Angles of Mandible.
Central Ray: Perpendicular to the IR / Bucky.
Collimation: Outer skin margins of the skull.
Evaluation Criteria
 No rotation is evidenced by The
lateral borders of the foramen
magnum are equidistant from the
lateral borders of the skull.
 No tilt is evidenced by The
Vomer and the bony nasal septum
are aligned with the long axis of
the film.
 Collimation
• Shutter A: Open to include the
soft tissue and lateral borders of
the skull
• Shutter B: Open to include the
mandible superiorly and the
Occipito of the skull inferiorly.
 Exposure
• Assess for adequate penetration
of the thickest part of the skull.
• Bony trabecular patterns and
cortical outlines are sharply
defined.
• Soft tissues are visualized.