Transcript Orbits and Optics

What is an Orbit?
4 5 2014
Cone-shaped
Bony-walled
Usually 2- one on
each side of
midsagittal plane
Primarily sockets
for eyeballs
Orbit is made up of 7 bones
Note that 4
of bones
are sinus
containing
bones
Typical Orbit projections
• Parieto-orbital-- 3 point landing (Rhese)
• (Orbitoparietal-- reverse Rhese)
• Modified Waters (paritoacanthial)
• Lateral
Optic canal (foramina)
Parieto-orbital oblique (Rhese)
• 3 point landing-chin,cheek,
nose
• center effected orbit on IR
crosshairs
• CR-no angle, perp. To IR
• (Adjust flexion of neck to
place acanthomeatal line is
perp. To plane of film)
• (Adjust rotation of head so
midsagittal forms 53 deg.
Angle with plane of IR)
Optic Foramina-Parieto-orbital oblique (Rhese method)
Optic Canal
Orbitoparietal oblique (Rhese)
If a pt. cannot be done
prone
Will increase object
magnification
Greater exposure of
lens of eye
Can be done upright
or recument
Optic Foramina
Modified Waters
• Before MRI is performed on any part of body, if even a
suspicion patient has metal in eye, Waters must be taken
• Particulary true in regions with lots of industry and
manufacturing or welders and mechanics (at UCSF, a CT scan
is done)
• Why?
Orbits -Waters projection
R
Modified Waters
• Similar to
Waters, but
nose and chin
touch IR
• OML 50 deg
angle. To IR
• Gives better
look into
orbits-less
foreshortening
Modified Waters
Evaluation Criteria
R
Petrous ridges
below orb. rims,
but not below
max. sinus
Orbits
symmetric, no
rotation or tilt
Lateral Orbit projection
L
Similar to
Lateral Sinus
projection
Parieto-orbital oblique
A
B
C
D
E
F
G
• A- Superior
orb.margin
• B- lat. Orb Margin
• C- optic foramin
• D-Med.orb. Marg.
• E- lesser wing of
sphenoid
• F- ethmoids
• G- inferior orb.
Marg.
Optic Canal Parieto-orbital
Evaluation Criterion
R
• Optic foramina should
lie in inferior lateral
quadrant (4 o’clock or 8
o’clock)
• Optic foramina should
be seen enface at end
of sphenoid ridge
• Entire orbital rim must
be shown, with close
beam restriction
Blowout Fx. of Orbit
• Eyeball like small
waterballoon
• Fluid of eyeball will not
compress
• Eye ball capsule changes
shape when hit
• Force is transferred- floor
of orbit is weakest
Tripod Fx. Of Zygoma
frontal
temp
max
• Blow to Zygoma
(malar bone) breaks
frontal, temporal
and maxillary
bones.-leaving
Zygoma freely
floating
Face is highly vascular- thus heals quickly
This is both good and bad!
• Good- fx. heals quickly
• Bad- if cheekbone is depressed or out of place,
heals - leaves face mis-shapen - will need to be
rebroken, and reset
Name the 7 bones of Orbit
•
•
•
•
•
•
•
A- frontal
B- sphenoid
C- palatine
D- zygoma
E- maxillae
F- ethmoid
G- lacrimal
What projections?
A
R
B
L
What is the TMJ?
• Where
condyle of
Mandible
inserts into
notch in
Temporal
bone
2 Types of Projections in TMJ Series
AP Axial
Axiolateral
AP Axial TMJ’s
• 8x10 LW
• Similar to Towne (which is
30 deg to OML, 2 ½ “ above glabella how’s that different from 3” above
Nasion?)
• Demonstrates condyles
of mandible and
mandibular fossa of
temporal bone
• Collimate in!
AP Axial TMJ’s
• CR 35 deg.
Caudad
• Midway
between TMJs
• 3” above nasion
• First closed
mouth, then
open if not
contraindicated
AP Axial TMJ’sSupine
AP Axial TMJ’s
Evaluation Criteria
• No rotation of head
• Minimal
superimposition of
petrosa on condyle in
closed mouth exam
• Open mouth may be
performed if not
contraindict.
• Condyle and
temporomandibular
articulation below pars
petrose
TMJ-Axiolateral projection
Temporomandibular Articulations Axiolateral
projections
TMJ Axiolateral projection
2” above
EAM
1” below EAM
• Place pt. head lateral
position, effected side
closest to IR (like lateral
skull)
• CR enters ½ “ ant., 2”
superior to upside EAM
• CR exits ½ anterior, 1”
inferior to EAM affected
side
• CR angled 30 deg.
Caudad
Temporomandibular Articulations
Axiolateral projections
Semi-prone
Closed
open
Temporomandibular Articulations
Axiolateral projection
Erect
Open
Closed
TMJ’s Axiolateral projections
L
?
L
?
All 4 projections are performed for TMJ Axiolateral Series
Closed
Open
LEFT
Open
Closed
RIGHT