Skull Flashcards
What are the three skull types?
- Mesocephalic (average)
- Dolichocephalic
- Brachycephalic
angle between petrous ridges and MSP for mesocephalic skull?
47
angle between petrous ridges and MSP for brachycephalic skull?
54
angle between petrous ridges and MSP for dolichocephalic skull?
40
what is the cephalic index?
width (parietal eminences)/length (frontal eminence to inion x100
*Cephalic ranges for the skull types?
Mesocephalic - 75 to 80
Dolichocephalic <75
Brachycephalic >80
Landmarks slides 9-12
IPL - interpupillary line
MSP
Glabella
Naison
Acanthion
Mental Point
Gonion
TEA
SOM - supraorbital margin
EAM
IOM - infraorbital margin
what part of the eye does the outer acanthus represent?
the middle
Slide 13
MML - mentomeatal line
LML - lips-meatal line
AML - Acanthiomeatal line
GML - Glabellomeatal line
OML - orbitomeatal line
IOML - Infraorbitomeatal line - reids base line
GAL - glabelloalveolar line
*what is the difference between the GML and OML?
8 degrees
- what is the difference between the OML and IOML?
7 degrees
positioning considerations of the skull?
- Indications – pathology vs trauma
- Skull type or body habitus
- CLEAN BUCKY , IR or TABLE FIRST (must be witnessed by patient)
- Wash your hands
- Always sit your patient
- Radiation Protection - PA
breathing instructions for all skull views?
“breathe in, hold your breath, don’t breathe, don’t move”
What are you protecting in skull imaging doing the image PA?
the patients eyes
patient prep - remove?
Remove necklace, earrings, piercings, GLASSES
- hair - no ponytails
Lateral Skull
- Lateral Projection (typically Left Lateral position)
- MSP is parallel to IR - Oblique shoulders so the head is against the bucky (NOT like doing a lateral c-spine)
- Interpupillary line (IPL) is perpendicular to bucky
- IOML is parallel to the ground or perpendicular to front edge of the IR
- Main goal is to make the top of the head parallel to the top of the IR
CP 2” or 5 cm superior to EAM
Collimate
TEA is a good landmark for?
top of petrous ridges
Lateral image criteria
- Orbital plates are superimposed
- TM Joints (mandibular condyles) are in the same vertical plane
- EAMs’ are in the same vertical plane
- Sella Turcica is in profile
Lateral positioning fault - tilt
- IPL is not perpendicular to the IR or bucky
- Orbital plates will not be superimposed
Lateral Positioning fault - rotation
- MSP is not parallel to IR or bucky
- TM joints or mandibular condyles will not be superimposed posteriorly
- EAMs’ will not be in the same vertical plane
PA Projection - Ruggles method
- Forehead & nose on upright bucky
- OML Perpendicular
- Midsagittal Plane (MSP) perpendicular
- CR - perpendicular
- CP - Halfway between vertex and base of skull
- Top of the petrous ridges must be at the top of the orbits - Petrous ridges fill orbits - BEST demonstrates IAC’s - Interauditory Cannals
PA Axial Projection - Caldwell Method
- Forehead & nose on bucky
- OML Perpendicular
- MSP perpendicular
- CR – 15° caudad
- CP - Halfway between vertex and base of skull
Petrous ridges in lower third of orbits
Demonstrates superior orbital fissure
AP Axial Projection - Towne method
- MSP perpendicular
- OML perpendicular
- Chin tucked – will need a sponge behind the head if the head is not touching the bucky
- CP – passes through 2” above (5 cm) EAMs
- CR - 30° caudad
- Dorsum sellae and posterior clinoid processes demonstrated within the foramen magnum
What angle is required if the IOML was perpendicular (rather than OML) for the Towne method?
37 caudad
If you see the posterior arch of C1 what positioning fault has been made?
too much caudad angle or if the OML is pointed inferior instead of being perpendicular to the Bucky
Submentovertical Projection (SMV)Basal View or Schüller Method
- IOML parallel with plane of IR
- MSP perpendicular
- CP passes through EAM’s
- Do this image last
why do you need to check if the patient has had a neck injury for a SMV?
not for trauma patients or patients with a neck injury
Submentovertical Projection (SMV)Basal View or Schüller Method positioning criteria
- Odontoid process is demonstrated within the foramen magnum
- Equal distance between mandibular condyles and edges of skull - TILT
- Mandibular condyles anterior to petrous ridges
- Mental protuberance superimposed on frontal bone
what are Ruggles/Caldwell/Towne usually repeated for?
rotation and extension
What are laterals usually repeated for?
rotation and tilt
What are SMV’s usually repeated for?
Extension and tilt
