Download Orbits and Optics

What is an Orbit?
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
 Optic foramina
R
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 transferredfloor 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
 Place pt. head lateral
2” above
EAM
1” below EAM
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
Which is the Open-mouth, and which is the
Closed-mouth Axiolateral TMJ projection?
A
B