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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