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Skull Positioning
Radiology Skull Positioning
99
Health Care
Undergraduate 1
07/13/2009
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Term
Which projection of the skull will demonstrate the petrous ridges in the orbits, the ethmoid and frontal sinuses, and the crista galli?
 Definition
PA Skull but the petrous ridges will be in the lower third of the orbits.
Term
Which sinus is located immediately inferior to the sella turcica?
 Definition
Sphenoid sinus
Term
Where does the CR enter for lateral facial bones?
 Definition
Central ray enters the zygomatic bone halfway between outer canthus & EAM
Term
Which bones contain air sinuses?
 Definition
frontal, ethmoidal, sphenoidal and maxillary sinuses.
Term
Which skull suture is found between the frontal and parietal bones?
 Definition
The coronal suture
Term
Where does the CR enter for lateral skull bones?
 Definition
Perpendicular, entering 2 inches superior to the EAM
Term
Which radiographic line is perpendicular to the film for a Caldwell projection of the skull?
 Definition
OML; Orbitomeatal line
Term
Where is the maxillary sinus located?
 Definition
In the body of each maxilla, lateral to the nose
Term
Which bone in the skull has condyles that articulate with the atlas of the cervical spine?
 Definition
Occipital bone
Term
Which structures should always be radiographed in the upright position?
 Definition
Sinuses, to show any fluid levels that may be present.
Term
Where is the CR directed for lateral sinus?
 Definition
The CR is directed horizontally, entering the patient’s head ½ to 1” posterior to the outer canthus.
Term
How many bones make up the cranium?
 Definition
There are 8 cranial bones. 2 parietal, 1 frontal, 2 temporal, 1 ethmoid, and 1 sphenoid, and 1 Occipital.
Term
Where are the parietal bones located?
 Definition
Parietal bones form a large portion of the sides of the cranium. By their articulation with each other at the sagittal suture in the MSP, they also form the posterior portion of the cranial roof.
Term
Where in the orbit does the optic foramen appear in a properly positioned Rhese’s view of the orbit?
 Definition
The optic canal and foramen should be visible at the end of the end of the sphenoid ridge in the inferolateral (inferior and lateral) quadrant of the orbit.
Term
Which facial bones articulate with every other facial bone except the mandible?
 Definition
The maxillary bones.
Term
Where are the inferior nasal conchae located?
 Definition
The inferior nasal conchae extend diagonally and inferiorly from the lateral walls of the nasal cavity, at approximately its lower 1/3.
Term
Which bones form the posterior portion of the cranial roof?
 Definition
The parietal bones form the posterior portion of the cranial roof by their articulation with each other at the sagittal suture in the MSP, as well as the occipital bone.
Term
What is a brachycephalic skull?
 Definition
This refers to a skull that is short from front to back, broad from side to side and shallow from vertex to base. The petrous pyramids lie at an average angle of 54 degrees with the MSP.
Term
What is the CR angulation for the AP Axial Towne’s projection?
 Definition
The CR is directed through the foramen magnum at a caudal angle of 30 degrees to the OML or 37 degrees to the IOML.
Term
What is the centering point for lateral skull projection?
 Definition
Using a perpendicular beam, the centering point Enters 2 inches superior to the EAM.
Term
Which bones comprise the bridge of the nose?
 Definition
The nasal bones
Term
How many bones are in the face?
 Definition
14 facial bones. 2 nasal, 2 lacrimal, 2 maxillary, 2 zygomatic, 2 palatine, 2 inferior nasal conchae, the vomer, the mandible.
Term
Where should petrous ridges be seen on Water’s view?
 Definition
Petrous ridges projected immediately below maxillary sinuses.
Term
What is the smallest facial bone?
 Definition
The 2 lacrimal bones are the smallest in the skull.
Term
Which bone contains the dorsum sellae?
 Definition
Sphenoid
Term
Which bone contains the mental protuberance?
 Definition
Mandible
Term
What projection of the mandible demonstrates the symphysis free of superimposition of the spine?
 Definition
Left and right axiolateral oblique projection of the mandible
Term
What is the function of the petrous portion of the temporal bone?
 Definition
The petrous portion of the temporal bone houses the auditory organs
Term
Which bone in the skull contains the auditory organs?
 Definition
Both left and right temporal bones contain the auditory organs.
Term
What should be superimposed on a lateral projection of the skull?
 Definition
TMJ, EAM, mastoid, sella turcica should be superimposed on a lateral projection of the skull.
Term
What is the anterior process of the mandibular ramus called?
 Definition
The Coronoid process
Term
Which projection of the sinuses demonstrates all four sinus groups?
 Definition
The lateral sinus view
Term
Where does CR enter for lateral sinus?
 Definition
1" posterior to outer canthus of eye farthest from film.
Term
What bones make up the calvaria?
 Definition
4 bones, the frontal, 2 parietal, occipital.
Term
What are the smallest bones in the skull?
 Definition
Lacrimal bones located inside the orbital region.
Term
Which suture is located between the occipital and parietal bones?
 Definition
The lambdoidal suture.
Term
Where is the glabella located?
 Definition
The glabella is located on the frontal bone and is the smooth elevation located between the superciliary arches (eyebrows).
Term
What does the sella turcica house?
 Definition
The sella turcica houses the pituitary gland.
Term
The zygomatic arches are a part of which bone?
 Definition
The temporal process of the zygomatic bone and the zygomatic process of the temporal bone unite to form the zygomatic arch.
Term
Where is the maxilla located?
 Definition
The maxillary bones form part of the lateral walls and most of the floor of the nasal cavity, part of the floor of the orbital cavities and ¾ of the roof of the mouth.is the largest of the immovable bones of the face.
Term
Orbitomeatal line forms an angle of 37º with plane of the film. Which position is this?
 Definition
This position is the Parietoacanthial Waters Projection
Term
Which landmark is at the base of the nasal spine?
 Definition
The landmark is called the anterior nasal spine or acanthion.
Term
Where is the sphenoid sinus located?
 Definition
: It is located posterior and inferior to the sella turcica, medial to the maxillary sinuses. It is the most posterior sinus in the skull.
Term
What are the areas of incomplete ossification in an infants skull called?
 Definition
Fontanels
Term
What is the reverse Water’s projection of the facial bones?
 Definition
(OML @ 37-degree angle to the cassette, but taken AP)
Term
Where is the acanthion located?
 Definition
It is located on the tip of the anterior nasal spine.
Term
What angle with the plane of the film, does the mid sagittal plane form on the Rhese’s position of the orbit?
 Definition
53 degrees
Term
When do the fontanels in an infant skull close?
 Definition
They are fully hardened by 12 years.
Term
Which topographic line extends from the outer canthus to the EAM?
 Definition
Orbitomeatal line (OML)
Term
Which projection of the skull has the CR angled 37º caudad and IOML perpendicular to film?
 Definition
AP axial Towne’s Method
Term
Where is the glabella located?
 Definition
It is located on the frontal bone between the eye brows, anatomically called the supercillary arches.
Term
Which skull type is considered average in size and shape?
 Definition
Mesocephalic
Term
Where does the CR exit on PA skull projection?
 Definition
nasion
Term
How many bones make up the skull?
 Definition
22 Bones in the skull, 8 cranial, 14 facial.
Term
Where is the widest portion of the skull?
 Definition
The parietal eminences are located at the widest portion of the skull and it is here that the width of the head is measured.
Term
Which projection of the facial bones would best demonstrate a “blow out” fracture of the orbit?
 Definition
Parietoacanthial Waters View
Term
What are the two oval prominences on each side of the foramen magnum called?
 Definition
The occipital condyles which articulate with the atlas of the cervical spine.
Term
Which bone has the greater and lesser wings?
 Definition
The sphenoid bone
Term
Which is the largest sinus?
 Definition
The frontal sinus
Term
What is the CR angle for PA Axial Caldwell projection of the skull?
 Definition
A 15 degree caudal angle
Term
What is another term for the zygomatic bone?
 Definition
zygoma
Term
Where is the Infraorbitomeatal line?
 Definition
A line connecting the inferior margin of the orbital cavity and the EAM.
Term
Where is the ramus of the mandible located?
 Definition
The Rami (ramus) projects superiorly at an obtuse angle to the body of the mandible, and their broad surface form an angle of approximately 110-120 degrees.
Term
Where is the foramen magnum located?
 Definition
Foramen magnum is located on the occipital bone.
Term
Where is the temporal bone located?
 Definition
The temporal bone is located on each side of the base of the cranium between the greater wings of the sphenoid bone and the occipital bone.
Term
What other term refers to the OML?
 Definition
radiographic base line OML (orbitomeatal line) = canthomeatal line: A line connecting the outer canthus of the eye with EAM.
Term
Where are the petrous ridges projected in the Caldwell’s skull?
 Definition
The petrous ridges are projected into the lower third of the orbits in the Caldwell’s Axial Skull, they fill the orbits in non axial view.
Term
Which bone houses the sella turcica?
 Definition
Sphenoid bone.
Term
Which projection of the facial bones has the mentomeatal line approximately perpendicular to the film?
 Definition
The Parietoacanthial (Waters) View
Term
Which facial bone forms the inferior portion of the nasal septum?
 Definition
The Vomer.
Term
Where is the alveolar border located?
 Definition
The superior border of the body of the mandible is called the alveolar border. It is a spongy bone that supports the roots of the teeth.
Term
What is the clivus?
 Definition
The clivus is the sloping surface of a junction between the dorsum sellae of the sphenoid bond and the basilar portion of the occipital bone.
Term
For lateral nasal bones, what line in perpendicular to the table top?
 Definition
Interpupillary line
Term
What line is the CR perpendicular to for the SMV?
 Definition
IOML
Term
Where is the junction known as bregma located?
 Definition
Junction of the coronal and sagittal sutures.
Term
What angle does CR form with the film for a Water’s view?
 Definition
90 degrees
Term
Why is it important to place patients head on a sponge for the cross-table lateral skull?
 Definition
To get the posterior part of the skull on the film
Term
Which bone contains the olfactory nerves?
 Definition
ETHMOID
Term
Where is the hyoid bone located?
 Definition
The hyoid bone is situated at the base of the tongue.
Term
How many sinus groups are there?
 Definition
There are 4: frontal, maxillary, ethmoidal and sphenoidal sinuses.
Term
How many bones comprise the orbit?
 Definition
7 bones comprise the orbits: lacrimal, ethmoid, sphenoid, palatine, frontal, zygoma, maxilla
Term
Which two lines/planes are perpendicular to the film for a PA skull?
 Definition
The OML and the MSP
Term
Which sinus group is best demonstrated with Water’s view?
 Definition
The Maxillary sinus
Term
Where is the posterior fossa located?
 Definition
It is a deep depression, posterior to the petrous ridges, which protects the cerebellum, pons, and medulla oblongata.
Term
What is the function of the mastoid air cells?
 Definition
A protective buffer and drainage for the tympanic cavity.
Term
Which radiographic line is used when positioning for tangential nasal bones?
 Definition
the MSP needs to be parallel with the IR. Also, IPL is perpendicular to IR. IOML is parallel with the transverse axis with the IR.
Term
Which radiographic line is utilized for the lateral skull projection?
 Definition
IPL is perpendicular to the IR, and the MSP is parallel.
Term
Where does the CR exit for PA mandible projection?
 Definition
Lips
Term
Which sinuses are better demonstrated on SMV?
 Definition
The sphenoidal sinus and ethmoidal air cells are shown.
Term
Which bone contains the cribiform plate?
 Definition
Ethmoid Bone.
Term
What is diploe?
 Definition
Diploe is the two plates of compact tissue separated by an inner layer of spongy tissue
Term
What is the largest and densest facial bone?
 Definition
The Mandible
Term
Which projection of the skull uses either 30º or 37º caudad angle depending upon which radiographed line is used?
 Definition
AP axial projection, Towne’s method.
Term
Which projection of the zygomatic arches utilizes both rotation and tilt?
 Definition
The tangential projection of the zygomatic arches. MSP of head 15 degrees toward the side of interest. Top of head 15 degrees away from side of interest.
Term
Where is the gonion located?
 Definition
The gonions are located on the angles of the mandible.
Term
Which bone contains a foramen thru which the tear ducts pass?
 Definition
The left and right lacrimal bones contain a foramen thru which the tear ducts pass.
Term
If you cannot get IOML parallel to the film for SMV projection, what can you do?
 Definition
You can angle the x ray beam and the IR.
Term
What is a mesocephalic skull?
 Definition
Typical shaped skull (47 degree angle on petrous pyramids).
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