What is an Orbit? 4 5 2014

Cone-shapedBony-walledUsually 2- one on each side of midsagittal planePrimarily 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 eyeCan 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 WatersEvaluation Criteria

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

R

Lateral Orbit projection

Similar to Lateral Sinus projection

L

Parieto-orbital oblique

• 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.

A

B

C

D

E

F

G

Optic Canal Parieto-orbital Evaluation Criterion

• 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

R

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

• Blow to Zygoma (malar bone) breaks frontal, temporal and maxillary bones.-leaving Zygoma freely floating

temp

frontal

max

Face is highly vascular- thus heals quickly

• 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

This is both good and bad!

Name the 7 bones of Orbit

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

What projections?

R L

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 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’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 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

2” above2” above EAMEAM

1” below EAM1” below EAM

Temporomandibular ArticulationsAxiolateral projections

Semi-prone

Closed open

Temporomandibular ArticulationsAxiolateral projection

Erect

Open Closed

TMJ’s Axiolateral projections

L L

? ?

All 4 projections are performed for TMJ Axiolateral Series

LEFT

RIGHT

Open

Open

Closed

Closed