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What is an Orbit?

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)

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What is an Orbit?

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  1. What is an Orbit? Cone-shaped Bony-walled Usually 2- one on each side of midsagittal plane Primarily sockets for eyeballs

  2. Orbit is made up of 7 bones Note that 4 of bones are sinus containing bones

  3. Typical Orbit projections • Parieto-orbital-- 3 point landing (Rhese) • (Orbitoparietal-- reverse Rhese) • Modified Waters (paritoacanthial) • Lateral

  4. 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)

  5. Optic Foramina-Parieto-orbital oblique (Rhese method)

  6. Optic CanalOrbitoparietal oblique (Rhese) Ifa pt. cannot be done prone Will increase object magnification Greater exposure of lens of eye Can be done upright orrecument

  7. Optic Foramina

  8. 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?

  9. Orbits -Waters projection R

  10. Modified Waters • Similar to Waters, but nose and chin touch IR • OML 50 deg angle. To IR • Gives better look into orbits-less foreshortening

  11. R Modified WatersEvaluation Criteria Petrous ridges below orb. rims, but not below max. sinus Orbits symmetric, no rotation or tilt

  12. Lateral Orbit projection L Similar to Lateral Sinus projection

  13. 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

  14. Optic Canal Parieto-orbitalEvaluation 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

  15. 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

  16. Tripod Fx. Of Zygoma • Blow to Zygoma (malar bone) breaks frontal, temporal and maxillary bones.-leaving Zygoma freely floating frontal temp max

  17. Face is highly vascular- thus heals quickly This is both good andbad! • 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

  18. Name the 7 bones of Orbit • A- frontal • B- sphenoid • C- palatine • D- zygoma • E- maxillae • F- ethmoid • G- lacrimal

  19. What projections? B A L R

  20. What is the TMJ? • Where condyle of Mandible inserts into notch in Temporal bone

  21. 2 Types of Projections in TMJ Series Axiolateral AP Axial

  22. 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!

  23. AP Axial TMJ’s • CR 35 deg. Caudad • Midway between TMJs • 3” above nasion • First closed mouth, then open if not contraindicated

  24. AP Axial TMJ’s-Supine

  25. AP Axial TMJ’sEvaluation Criteria • Condyles and TMJ below Pars Petrosa • Open mouth may be performed if not contraindict.

  26. TMJ-Axiolateral projection

  27. Temporomandibular Articulations Axiolateral projections

  28. TMJ Axiolateral projection • Place pt. head lateral position, effectedside closest to IR (like lateral skull) • CR enters½ “ ant.,2” superior to upside EAM • CR exits½ anterior, 1” inferior to EAM affected side • CR angled 30 deg. Caudad 2” above EAM 1” below EAM

  29. Temporomandibular ArticulationsAxiolateral projectionsSemi-prone Closed open

  30. Temporomandibular ArticulationsAxiolateral projectionErect Open Closed

  31. TMJ’s Axiolateral projections L L ? ?

  32. All 4 projections are performed for TMJAxiolateral Series Closed Open LEFT Closed Open RIGHT

  33. Which is the Open-mouth, and which is the Closed-mouth Axiolateral TMJ projection? B A

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