2a. Skull Bones Views and Positioning Flashcards
How many views are there for the skull
name them
3 views
AP or PA/FO or OF 20-25
Townes/FO30/30Half axial/AP axial
Lateral (HR)
what is the patients position for the FO/AP projection
in terms of patient sitting/lying down, chin position, MSP
patient seated erect/supine
chin raised to bring RBL to 20-25*
MSP perpindicular to IR
what is the central ray and centering point for the FO/AP view
CR perpindicular to IR and centered in the midline to the nasion
what are the exposure factors for the FO/AP view
mAs and kVp
70kVp and 16mAs
what is the SID for the FO/AP view
110cm
what do you want the petrous ridges position for the FO/AP view
petrous ridge in lower 1/3 of orbit
how will you position patient when their OMBL is at 90, how will you get the baseline to be 20-25
raise head up so baseline is at 20-25*
this pulls the petrous ridge down
what does it mean if the petrous ridge is too low/below the orbit
youve tilted head too far back/raised head too much
what is the image criteria for the FO/AP view in terms of rotation
Want to measure lateral border of orbit to the lateral border of skull/equidistant = no rotation
what is the image criteria for the FO/AP view in terms of structure superimposition
petrous ridge superimpose infraorbital margin and should not be sitting higher than lower 1/3 of orbit
what is the image criteria for the FO/AP view in terms of area of interest
entire cranial vault visualised
what is the image criteria for the FO/AP view in terms of exposure
sufficient exposure to visualise frontal bone without overexposing the perimeter regions of the skull
for the FO/AP view how do you adjust/detect the OMBL/RBL alignment
for superimposition of the petrous ridge and lower orbital margin:
increase OMBL by 5*
approx 5 degrees for every 1cm
for the FO/AP view how do you adjust/detect the OMBL/RBL alignment in terms of correcting the tilt
for superimposition of the petrous ridge and lower orbital margin:
increase OMBL by 10*
approx 5* for every 1cm
what is the townes projection also named as
2 names
30* Half-axial or AP axial
what 3 bones and landmarks are of import in the FO projection
frontal sinus
supraorbital rim
petrous ridge
what 4 bones and landmarks are of import in the townes projection
occipital bone
foramen magnum
petrous ridge
mastoid air cells on lateral borders
what info about the skull does the townes view give
info about the back of the skull
what is the patients position for the townes projection
in terms of patient sitting/lying down, chin position, MSP, distance between IR and ___
patient erect/supine
chin tucked down so OMBL/RBL is perp to IR
MSP perpind to IR
Equal distance between EAM and IR
what is the central ray for the townes view
CR angled 30* caudally
what are the exposure factors for the townes view
mAs and kVp
77kV, 25mAs
what is the SID for the townes view
110cm
what is the image criteria for the townes view in terms of rotation
cranium demonstrated without rotation
check rotation by distance from foramen magnum to either outer side of skull, make sure its equidistant
what is the image criteria for the townes view in terms of structural superimposition
dorsum sellae centered within the foramen magnum
