RAD 233 Orbits

How many bones make up the orbit

7

what are the bones that make up the orbits

frontal

sphenoid

ethmoid

maxilla

zygoma

lacrimal

palatine

The orbit primarily serves as what?

the bony socket for the eyeball

what shape are the orbits

cone shaped

what does orbits contain

blood vessels and nerves

The walls of the orbits are really thin which are subject to what?

fracture

what bone forms the roof and lateral wall of the orbit?

Sphenoid bone

what bone forms the lateral wall and floor of orbit

zygomatic

what bone forms the roof of the orbit?

Frontal

what bone forms the floor and medial wall of orbit?

Maxilla

Is the cleft between the greater and lesser wings of the
sphenoid bone

The superior orbital fissure

Is the narrow cleft extending from the lower anterolateral aspect of the sphenoidal body anteriorly and laterally
between the floor and lateral wall of the orbit

Inferior orbital fissure

Which projection is used for blowout fractures?

parieto-acanthial projection (Waters Method)

What exams are the most common for the orbits?

Ultrasound + CT

Why is MRI not used for the orbits?

Due to the movement of foreign object may lead to hemorrhage or other serious complication

The quadrilateral shaped anterior circumference, easily palpable

Base of orbit

Each orbit has a…

Roof, a medial wall, lateral wall and a floor

The long axis of each orbit is directed obliquely, posteriorly and medially at an average angle of… to the MSP

37 degrees

The orbits lie superiorly about… from the IOML

30 degrees

To produce a better image of the orbits what most be done?

Increase SID

Decrease OID

Focal spot smaller

Close collimation

Elimate motion

why is a smaller focal spot used?

reduce penumbra

Why is close collimation used ?

Reduce scatter

Where is the IR centered to for the LAT orbits?

outer canthus of affected eye

How is the MSP and IPL positioned for the LAT orbits?

MSP→ Parallel

IPL→ Perpendicular

How is the IOML positioned to the front edge of the IR for the LAT orbits?

Perpendicular

CR for LAT orbits

Perpendicular through the outer canthus

What are some instructions given to the PT for the LAT orbits?

Look straight ahead for the exposure

PT position for the PA Axial orbits?

Upright w/ forehead and nose on IR

Where is the IR centered for the Caldwell of the orbits?

¾ inch (1.9 cm) distal to the nasion

How is the MSP and OML for the Caldwell orbits?

perpendicular

CR for Caldwell orbits

Directed through the center of the orbits at a caudal angulation of 30 degrees

What’s the purpose of using a 30 degree angulation for the Caldwell of the orbits?

project the petrous portions of the temporal bones below the inferior margin of the orbits

What are some instructions given to the PT for the Caldwell and Modified Waters orbits?

close the eyes and to concentrate on holding them still for the exposure

For the Modified waters the IR is centered where

level of the center of the orbits

What of the PT is against the IR for the modified waters?

Chin

How is the MSP for the modified waters?

Perpendicular

For the modified waters the OML should form how much of an angle from the plane of IR

50 degrees

CR for modified waters

Perpendicular through the mid-orbits

What is recommended to do to reduce magnification and eliminate possible artifacts from radiographic table or grid for the Orbit projections?

A nongrid (very high resolution) technique

The exposed eyeball is covered by a thin mucous membrane called the

conjunctiva (Also lines the inner surface of the eyelids)

Produce tears that Keep the eye moist, Prevent drying, Reduce friction during blinking and eye movement

Lacrimal Glands

Used to visualize the optic foramen, optic canal, and superior orbital fissure, primarily to evaluate for tumors or Trauma?

Rhese method

What has to be against the IR for the Rhese method?

Cheek, Chin and Nose

How do you know you positioned properly for the orbits???

The superior orbital margin and inferior orbit margin is included