skull positioning Flashcards
CR angle for AP Axial (Towne)
30 caudad to OML ~or~ 37 caudad to IOML
CR centering for AP Axial (Towne)
2.5 inches above the glabella
Part position for AP Axial (Towne)
OML perpendicular to IR ~or~ IOML if patient is unable to flex
Image analysis for AP Axial (Towne)
-petrous ridges should be symmetric (indicating no rotation)
-under-angulation of CR/insufficient flexion of neck = dorsum sellae superior to foramen magnum
-over-angulation of CR/excessive neck flexion = posterior arch of C1 over dorsum sellae within the foramen magnum and foreshortening of dorsum sellae
Correct CR angle and proper neck flexing in the Towne Method are indicated by __________ visualized in the ___________
Dorsum sellae and posterior clinic processes, foremen magnum
With AP Axial (Towne) images, under-angulation of CR/insufficient flexion of neck puts ___________________
dorsum sellae superior to the foramen magnum
With AP Axial (Towne) images, over-angulation of CR/excessive flexion of neck puts ___________________
posterior arch of C1 over the dorsum sellae within the foramen magnum and produces foreshortening of the dorsum sellae
With AP Axial (Towne) method, the petrous ridges will appear ______ in the direction of rotation
narrowed
CR angle for Lateral Skull
perpendicular to IR
CR centering for Lateral Skull
2 inches superior to EAM ~or~ halfway between glabella and inion for other types of skull morphologies
Part position for Lateral Skull
-MSP parallel to IR with no rotation or tilt
-IPL perpendicular to IR
-IOML perpendicular to front edge of IR
_____________ is only position to see air/fluid level in trauma for a lateral skull
horizontal beam (cross table beam)
rotation in a lateral skull image is evident by ______________
anterior and posterior separation of symmetric vertical bilateral structures (such as mandibular rami, greater wings of sphenoid)
tilt in a lateral skull is evident by ____________________
superior and inferior separation of symmetric horizontal structures (such as orbital plates and greater wings of sphenoid bone)
anatomy demonstrated in a lateral skull
-entire cranium
-superimposed __________
-entire sella turcica including ____________________
-_________________ demonstrated in profile
-parietal bones
-anterior/posterior clinoid processes and dorsum sellae
-sella turcica and clivus
*okay to not have entire mandible
Part position for PA Axial (Caldwell)
OML perpendicular to IR, MSP perpendicular to IR
CR angle for PA Axial (Caldwell)
15 caudad (to exit at nasion)
CR centering for PA Axial (Caldwell) 15 degrees caudad
exit at nasion
How to tell the difference between a PA Caldwell and AP Caldwell
Orbits will be magnified on an AP (due to OID magnification)
Part position for PA Skull
OML perpendicular to IR, MSP perpendicular to IR
CR angle for PA skull
0 (perpendicular)
CR centering for PA skull
exit at glabella
Patient position for SMV
hyperextend neck to get IOML parallel to the IR, rest head on vertex, MSP perpendicular to CR
CR angle for SMV
perpendicular to IOML
CR centering for SMV
1 ½ inch below mandibular symphysis ~or~ midway between gonions (approx. 2/4 inch anterior to level of EAM)
Example of AP Axial (Towne) rotation: left petrous ridges narrowed means the head was rotated towards the _______
left, as petrous ridges appear narrowed in the direction of rotation
In an AP Axial (Towne) image, unequal petrous ridges is indicative of (tilt/rotation)
rotation
In an AP Axial (Towne) image, shifting of the anterior or posterior clinoid processes laterally within foramen magnum is indicative of (tilt/rotation)
tilt
in a lateral skull, do you need to have the entire mandible on the x-ray?
no
clinical indications for AP Axial (Towne)
skull fractures (medial and lateral displacement), neoplastic processes, Paget disease
clinical indications for lateral skull
skull fractures, neoplastic processes, Paget disease
clinical indications for PA Axial (Caldwell) skull
skull fractures, neoplastic processes, Paget disease
clinical indications for PA (straight) skull
skull fractures (medial and lateral displacement), neoplastic processes, Paget disease
visualizes frontal bone with minimal distortion
anatomy demonstrated for PA Axial (Caldwell)
frontal bone, greater and lesser sphenoid wings, superior orbital fissures, frontal and anterior ethmoid sinuses, supraorbital margins, crista galli
PA Axial (Caldwell) image will result in the petrous ridges in what part of the orbits?
lower 1/3 of orbits
PA (straight) skull mage will result in the petrous ridges in what part of the orbits?
filling the orbits
where does a 25-30 degree Caldwell exit?
also at nasion
what does a 25-30 degree Caldwell demonstrate?
in addition to typical Caldwell:
foramen rotundum adjacent to each IOM, superior orbital fissures within the orbits
A 25-30 Caldwell will demonstrate ___________________ better than a typical Caldwell will
superior orbital fissures, foramen rotundum, inferior orbital rim
what impacts the location of petrous ridges within the orbits for Caldwell exams?
CR angle and OML alignment
Unequal distance from mid-lateral orbital margins to lateral cortex of cranium on a Caldwell exam is indicative of (tilt/rotation)
rotation
Example of PA Axial (Caldwell) rotation: if the distance between the lateral orbit and lateral cranial cortex is greater than the left side, the face is rotated ______
toward the left side
Correct positioning for a PA Axial (Caldwell) exam will show petrous ridges in the __________ of orbits and the _____________ visualized without superimposition
lower 1/3 of orbits, supraorbital orbital margins
PA Axial (Caldwell) 25-30 degrees will result in the petrous ridges in what part of the orbit?
at or just below the IOM to allow visualization of entire orbital base
clinical indications for SMV
advanced bony pathology of inner temporal bone structures (skull base), possible basal skull fracture
correct extension of neck and relationship between IOML and CR are indicated by the ___________ being ___________
mandibular mentum being anterior to the ethmoid sinuses
in an SMV, unequal distances between mandibular ramus and lateral cranial cortex is indicative of (tilt/rotation)
tilt
Example of SMV tilt: if the distance on the left side between the ramus and lateral cranium is greater on the L than the R, the cranial vertex is tilted to the ____
left
anatomy demonstrated on SMV
-foramen _____________
-mandible
-_________________ sinuses
-______ process
-petrous ridges
-hard palate
-foramen _______
-_______ bone
-foramen ovale and spinonum
-mandible
-sphenoid and posterior ethmoid sinuses
-mastoid
-petrous ridges
-hard palate
-foramen magnum
-occipital bone
*need PA straight skull added
