What is an Orbit?What is an Orbit?

Cone-shapedCone-shapedBony-walledBony-walledUsually 2- one on Usually 2- one on each side of each side of midsagittal planemidsagittal planePrimarily sockets Primarily sockets for eyeballsfor eyeballs

Orbit is made up of 7 bonesOrbit is made up of 7 bones

Note that 4 Note that 4 of bones of bones are sinus are sinus containing containing

bonesbones

Typical Orbit projectionsTypical Orbit projections

Parieto-orbital-- 3 point landing (Rhese)Parieto-orbital-- 3 point landing (Rhese)

(Orbitoparietal-- reverse Rhese)(Orbitoparietal-- reverse Rhese)

Modified Waters (paritoacanthial)Modified Waters (paritoacanthial)

LateralLateral

Optic canal (foramina)Optic canal (foramina)Parieto-orbital oblique (Rhese)Parieto-orbital oblique (Rhese)

3 point landing-3 point landing-chin,cheek, nosechin,cheek, nose

center effected orbit on IR center effected orbit on IR crosshairscrosshairs

CR-no angle, perp. To IR CR-no angle, perp. To IR (Adjust flexion of neck to (Adjust flexion of neck to

place acanthomeatal line place acanthomeatal line is perp. To plane of film)is perp. To plane of film)

(Adjust rotation of head (Adjust rotation of head so midsagittal forms 53 so midsagittal forms 53 deg. Angle with plane of deg. Angle with plane of IR)IR)

Optic Foramina-Optic Foramina-Parieto-orbital obliqueParieto-orbital oblique (Rhese method)(Rhese method)

Optic CanalOptic CanalOrbitoparietal obliqueOrbitoparietal oblique (Rhese) (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 ForaminaOptic Foramina

Modified WatersModified Waters

Before MRI is performed on Before MRI is performed on anyany part of part of body, if even a suspicion patient has metal body, if even a suspicion patient has metal in eye, Waters must be takenin eye, Waters must be taken

Particulary true in regions with lots of Particulary true in regions with lots of industry and manufacturing or welders and industry and manufacturing or welders and mechanics (at UCSF, a CT scan is done)mechanics (at UCSF, a CT scan is done)

Why?Why?

Orbits -Waters projectionOrbits -Waters projection

R

Modified WatersModified Waters

Similar to Similar to Waters, but Waters, but nose and chin nose and chin touch IRtouch IR

OML 50 deg OML 50 deg angle. To IRangle. To IR

Gives better Gives better look into look into orbits-less orbits-less foreshorteningforeshortening

Modified WatersModified WatersEvaluation CriteriaEvaluation Criteria

RPetrous ridges Petrous ridges below orb. rims, below orb. rims, but not below but not below max. sinusmax. sinusOrbits Orbits symmetric, no symmetric, no rotation or tiltrotation or tilt

Lateral Orbit projection

Similar to Lateral Sinus projection

L

Parieto-orbital obliqueParieto-orbital oblique

A- Superior A- Superior orb.marginorb.margin

B- lat. Orb MarginB- lat. Orb Margin C- optic foraminC- optic foramin D-Med.orb. Marg.D-Med.orb. Marg. E- lesser wing of E- lesser wing of

sphenoidsphenoid F- ethmoidsF- ethmoids G- inferior orb. G- inferior orb.

Marg.Marg.

A

B

C

D

E

F

G

Optic Canal Parieto-orbital Evaluation Criterion

Optic foramina Optic foramina should lie in inferior should lie in inferior lateral quadrant (4 lateral quadrant (4 o’clock or 8 o’clock)o’clock or 8 o’clock)

Optic foramina Optic foramina should be seen should be seen enface at end of enface at end of sphenoid ridgesphenoid ridge

Entire orbital rim Entire orbital rim must be shown, with must be shown, with close beam close beam restrictionrestriction

R

Blowout FxBlowout Fx. . ofof Orbit Orbit

Eyeball like small Eyeball like small waterballoonwaterballoon

Fluid of eyeball will Fluid of eyeball will not compressnot compress

Eye ball capsule Eye ball capsule changes shape when changes shape when hithit

Force is transferred- Force is transferred- floor of orbit is floor of orbit is weakestweakest

Tripod Fx. Of ZygomaTripod Fx. Of Zygoma

Blow to Zygoma Blow to Zygoma (malar bone) (malar bone) breaks breaks frontalfrontal, , temporaltemporal and and

maxillarymaxillary bones.- bones.-leaving leaving Zygoma Zygoma freely floatingfreely floating

temp

frontal

max

Face is highly vascular- thus heals quicklyFace is highly vascular- thus heals quickly

GoodGood- fx. heals quickly- fx. heals quickly

BadBad- if cheekbone is depressed or out of place, - if cheekbone is depressed or out of place, heals - leaves face mis-shapen - will need to heals - leaves face mis-shapen - will need to be rebroken, and resetbe rebroken, and reset

This is both good and bad!

Name the 7 bones of OrbitName the 7 bones of Orbit

A- frontal B- sphenoid C- palatine D- zygoma E- maxillae F- ethmoid G- lacrimal

What projections?What projections?

RL

A B

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 LW8x10 LW Similar to Towne 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 Midway between TMJsbetween TMJs

3” above nasion

First closed First closed mouth, then mouth, then open if not open if not contraindicatedcontraindicated

AP Axial TMJ’s-Supine

AP Axial TMJ’sEvaluation 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 Place pt. head lateral position, position, effected side side closest to IR (like closest to IR (like lateral skull) lateral skull)

CR CR enters ½ “ ant., 2” superior to to upside EAM EAM

CR CR exits ½ anterior, , 1” inferior to EAM to EAM affected sideaffected side

CR angled 30 deg. CR angled 30 deg. CaudadCaudad

2” above2” above EAMEAM

1” below EAM1” below EAM

Temporomandibular ArticulationsAxiolateral projections

Semi-prone

Closed open

Temporomandibular Articulations

Axiolateral projectionErect

Open Closed

TMJ’s Axiolateral projections

L L

? ?

All 4 projections are performed for TMJAxiolateral Series

LEFT

RIGHT

Open

Open

Closed

Closed

Which is the Open-mouth, and which is the Closed-mouth Axiolateral TMJ projection?

A B