Skull Positoning Flashcards
For a typical skull (mesocephalic) how do the petrous pyramids project?
Petrous pyramids project anteriorly and medially at 47-degree angle from midsagittal plane (MSP)
For a Brachycephalic skull how does the petrous pyramids project?
Petrous pyramids project anteriorly and medially at 54-degree angle from MSP
What skull morphology is Short from front to back, broad from side to side, and shallow from vertex to base
Brachycephalic skull
what skull morphology is Long from front to back, narrow from side to side, and deep from vertex to base
Dolichocephalic skull
For a Dolichocephalic skull
how do the petrous pyramids project ?
Petrous pyramids project anteriorly and medially at 40-degree angle from MSP
Name some landmarks of the skull:
Glabella
Inner canthus
Outer canthus
Nasion
Infraorbital margin
Acanthion
Gonion
Mental point
EAM
Auricular point
Top of ear attachment (TEA)
where is your glabella
in between eyebrows
where is your inner and outer canthus
corners of eyes
where is your nasion
bridge of nose
where is your acanthion ?
right below nose
where is your Gonion
angle of your mandible
where is your mental point
chin
where is your EAM
hole in your ear
Where is your TEA (top of ear attachment)
where ear actually attches
Line from outer canthus to EAM
Orbitomeatal line (OML)
line from From infraorbital margin to EAM
Infraorbitomeatal line (IOML)
line From glabella to EAM
Glabellomeatal line (GML)
what is the difference between IOML and OML
7 degrees
line from From acanthion to EAM
Acanthiomeatal line (AML)
Perpendicular line between pupils of eyes
(EAM to acanthion)
Interpupillary line (IPL)
why do hyposthenic /asthenic patients usually need support to chest ?
To elevate cervical spine which helps prevent downward tilt of MSP
why do hypersthenic patients require radiolucent support at the head
helps prevent upward tilt of MSP
Essential projections of the Cranium:
Lateral
-Right and left lateral positions
-Dorsal decubitus position
Posteroanterior (PA)
PA axial (Caldwell method)
Anteroposterior (AP)
AP axial
AP axial (Towne method)
PA axial (Haas method)
Submentovertical (SMV)
-For cranial base
How is the MSP of the head in the lateral projection of the skull?
MSP of head parallel to image receptor (IR)
how is the IPL in the lateral projection of the skull
IPL perpendicular
how is the IOML in the lateral projection of the skull
IOML parallel to transverse axis of cassette
CR for lateral projection of the skull
Perpendicular to center of IR
Enters 2 inches (5 cm) superior to EAM
what is in profile in the lateral skull
Sella Turcica
CR for lateral projection (dorsal decubitus ) for the skull
Horizontal and perpendicular to center of IR
Enters 2 inches (5 cm) superior to EAM
criteria for lateral projection of lateral skull
Entire cranium without rotation or tilt
Superimposed orbital roofs, mastoid region and EAM
Superimposed TMJs
Sella turcica in profile
No overlap of cervical spine by mandible
patient position for PA projection of the skull
Seated erect or prone
MSP centered to midline
Forehead and nose resting on table or upright Bucky
how is the OML for the PA projection of the skull
perp to the IR plane
How is the MSP in the PA projection of the skull
MSP perpendicular to IR
what is the IR centered to in the PA projection of the skull
nasion
how are the petrous ridges in the PA skull
Petrous pyramids fill the orbits with 0 degree CR angulation
CR for PA projection of the skull
Perpendicular
Exits nasion
CR for the PA axial Skull (Caldwell)
Angled 15 degrees caudad
Exits nasion
how are the petrous ridges in the PA Axial Skull (Caldwell)
Petrous pyramids lying in lower third of orbit with a caudal CR angulation of 15 degrees
CR for AP Axial (skull)
Perpendicular or 15 degrees cephalad for AP axial projection
Enters nasion
how is the MSP and OML for the AP/AP Axial projection?
MSP centered to midline
MSP and OML perpendicular to IR
is the orbits more magnified in the PA skull or AP?
AP
what is seen on the PA skull
posterior ethmoidal air cells
Posterior ethmoidal air cells
Crista galli
Frontal bone and sinuses
Dorsum sellae
Petous ridges filling the orbits
what is seen on the pa axial skull
Anterior and side walls of cranium
Anterior ethmoidal air cells and frontal sinuses
Petous ridges in lower third of orbits
what does the angel do to the petrous ridges in the PA axial?
Angle pushes petrous ridges down
how is the MSP for AP Axial (Towne Method)
MSP centered to midline
MSP perpendicular
how is the OML and IOML for the AP Axial (Twone Method)
OML or IOML perpendicular
CR for AP Axial (Towne Method)
CR enters 2 ½ inches above glabella
where is the IR center for the AP Axial (Towne Method)
IR center at or near foramen magnum
IR top border level with skull vertex
CR for AP Axial Towne Method (OML)
Directed through foramen magnum
OML – 30 degrees caudal
CR for AP Axial Towne Method (IOML)
Directed through foramen magnum
IOML – 37 degrees caudal
What should be seen on the AP axial Townes
Occipital bone
Posterior portion of parietal bones
Petrous pyramids
Foramen Magnum
Dorsum sellae and posterior clinoids within foramen magnum
what is within the foramen magnum in the AP AXIAL TOWNES for skull
Dorsum sellae and posterior clinoids within foramen magnum
what is the best view for the parietal bone?
Lateral
For trauma what degree would you use for the AP AXIAL Townes
Trauma use IOML at 37˚
Patient position for PA Axial (HAAS method)
Prone or seated upright
MSP centered to midline
Shoulders in same horizontal plane
Forehead and nose on table
how is the MSP and OML in the PA Axial (Haas Method)
MSP perpendicular
OML perpendicular to IR
CR for the PA axial (Haas Method)
Directed cephalad at 25-degree angle to OML
Enters at a point 1½ inches (3.8 cm) below external occipital protuberance
Exits 1½ inches (3.8 cm) superior to nasion
how is the MSP for the SMV
MSP centered to midline
MSP perpendicular to IR
how is the IOML for the SMV
IOML parallel with IR
CR for SMV
Through sella turcica perpendicular to IOML
Enters MSP of throat between angles of mandible
Passes through a point ¾ inch (1.9 cm) anterior to level of EAM
Center IR to CR
What should be seen in SMV
Base of cranium demonstrating petrosal
Zygomatic arches
Bony nasal septum
Foramina ovale & spinosum, mastoids
Sphenoid & ethmoid sinuses
Mandible
Dens
Occipital bone
criteria for SMV
Equal distance from lateral border of skull to mandibular condyles on both sides
Superimposition of mental protuberance over anterior frontal bone
Mandibular condyles anterior to petrous pyramids
Symmetric petrosae
What is the CR angle and direction for the PA axial (Caldwell) of the cranium?
15 degrees caudad
Which baseline is positioned perpendicular to the IR on the lateral projection of the cranium?
Interpupillary
If IOML is positioned perpendicular to the IR for the AP axial (Towne) projection of the cranium, what is the CR orientation?
37 degrees
