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ORBIT ANATOMY vish.pptx
- 1. ORBIT-RADIOLOGICAL ANATOMY Dr VISHNU DUTT E
- 2. RADIOGRAPH ULTRASOUND CT MRI
- 3. ORBIT The orbit is a conical-to-pyramidal–shaped recess that contains the globe, extraocular muscles, blood vessels, nerves(cranial nerves II, III, IV, V, and VI, and sympathetic and parasympatheticnerves), adipose and connective tissues, and mostof the lacrimal apparatus.
- 4. Periostium of the orbit is seperated from the globe by tenons capsule. Anteriorly are the orbital septum and the lids. The orbital apex is directed posteromedially and the orbital opening is directed anterolaterally
- 5. Its bony walls of orbit is related to Superiorly-anterior cranial fossa Medially-the ethmoid air cells, sphenoid sinus, and nasal cavity Inferiorly –the maxillary sinus Laterally and posteriorly –the lateral face and temporal fossa
- 8. LATERAL WALL OF ORBIT
- 10. SUPERIOR WALL OF ORBIT
- 11. MEDIAL WALL OF ORBIT
- 12. PASSAGES OF BONY ORBIT 1.Superior orbital fissure Just inferolateral to the optic canal and separated from it by the optic strut is the superior orbital fissure, located between the greater and lesser wings of the sphenoid bone
- 17. The superior orbital fissure communicates with the middle cranial fossa. Transmits the oculomotor, trochlear,and abducens nerves and the terminal branches of the ophthalmic nerve (V1) and the ophthalmic veins. The lacrimal, frontal,and trochlear nerves traverse the narrow lateral part of the fissure, which also transmits the meningeal branch of the lacrimal artery.
- 18. Optic nerve in optic canal Superior orbital fissure Inferior orbital fissure and pterygopalatine fossa
- 20. 2.Inferior orbital fissure. At the posterior aspect of the orbit, the inferior and lateral walls of the orbit are separated by the inferior orbital fissure. The fissure lies just below the superior orbital fissure and is bounded above by the greater wing of the sphenoid,below by the maxilla and the orbital process of the palatine bone, and laterally by the zygomatic bone.
- 22. Inferior orbital fissure transmits zygomatic nerve,inferior ophthalmic vein and infraorbital nerves and vessels.Parasympathetic nerves to lacrimal gland.
- 23. IOF commincates with the pterygopalatine fossa The PPF communicates posterosuperiorly to the middle cranial fossa via F of Rotundum. PPF communicates medially with the nasal cavity via sphenopalatine foramen PPF communicates laterally with the infratemporal fossa via pterygomaxillary fissure.
- 25. 3.Optic canal The optic canal, having virtually no length at birth, becomes 4 mm long by 1 year of age and is up to 9 mm long in adults. The optic canal is directed forward, laterally (approximately 45 degrees from the midsagittal plane and has orbital and intracranial openings)
- 26. Optic nerve,ophthalmic artery and sympathetic nerves pass through optic canal.
- 29. SURGICAL SPACES AROUND ORBIT
- 30. The arterial supply is mainly from the ophthalmic artery, which arises from the internal carotid artery. Its main branches are the central retinal artery. The major venous drainage occurs through the superior ophthalmic vein , which drains to cavernous sinus
- 31. RADIOGRAPH OF ORBIT VIEWS WATERS VIEW CALDWELL’S VIEW LATERAL VIEW RHESE VIEW
- 32. WATERS VIEW The most important view for sinus problems and injury involving the maxilla or orbits. Waters or occipitomental view is an angled PA radiograph of the skull with patient gazing slightly upwards.
- 34. Ethmoid sinus Zygoma Frontal sinus Floor of orbit
- 35. CALDWELL view It is a caudally angled radiograph with PA xray beam directed 15 to 23 degree downward to the canthomeatal line. Useful for evaluating superior orbital rims.
- 37. Frontal sinus Medial wall of orbit Greater wing of sphenoid Zygomatico- frontal suture Innominate line Inferior orbital rim
- 38. Inominate line Caused by the Xray beam hitting the Greater wing of sphenoid in a tangent. Its seen in occipitofrontal projection.
- 40. Sphenoid sinus Maxillary sinus Frontal sinus Orbital roof Ethmoid sinus
- 41. RHEESE VIEW(Postero-anterior oblique view) The x ray beam is projected postero-anteriorly at 40 degree to the midsagittal plane
- 43. PROJECTION STRUCTURE PATHOLOGY WATERS VIEW ORBITAL FLOOR ANTERIOR 2/3 BLOW OUT# CALDWELL’S VIEW INNOMINATE LINE,ORBITALFLOOR POSTERIOR 1/3 MEDIAL, LATERAL WALL# LATERAL VIEW ORBITAL ROOF ORBITAL ROOF # RHESE VIEW OPTIC CANAL OPTIC NERVE TUMORS
- 46. Normal ocular ultrasound.-A normal eye will maintain its shape with a round cornea, anterior chamber, iris, lens, and posterior chamber. Adjust the depth to visualize the entire globe and optic nerve. In adults, the normal anteroposterior ocular globe diameter is 22–25 mm.
- 48. ONSD measurment-Measure diameter 3mm posterior to optic disc.
- 49. ONSD measurment is useful in the assessment of papilledema in patients with raised ICT. In USG normal value is 4 mm in infants,4.5 mm in children and 5 mm in adults.More than 5 mm corresponds to a raised ICT of more than 20 mmhg. In CT normal value is 4.8 to 6.2 mm when measured from 3 mm posterior to the disc.
- 50. CT Technique For intraocular lesions 1.5 to 3 mm thick axial sections globe is taken. For all foreign bodies at 6 and 12’O clock an additional direct 3 to 5mm coronal sections are obtained. Additional post contrast axial sections (1.5,3, or 5 mm). In cases of suspected retinoblastoma and uveal melanoma,additional 5 to 10 mm axial sections of the head-To see intracrainal abnormality.
- 52. CT is useful in cases FBs,Intraocular calcifiactions,bony lesions and orbital fractures. NCCT CECT FBs Osteogenic or Uncomplicated orbital # chondrogenic sarcoma Uncomplicated thyroid ophthalmopathy Metastatic boneds. Dermoid cyct Osteoma,osteoid osteoma Fibrous dysplasia,Pagets disease
- 58. MR Protocol 1 ) T1-AXIAL with FOV for orbits + CORONAL (from chiasm through orbits ) +/- SAGITTAL Purpose-For anatomical overview 2) T2 Fat suppressed-AXIAL Purpose-Highlight inflammatory changes. 3) STIR-CORONAL Purpose-Highlight inflammatory changes.
- 59. MR IMAGING 3 to 5 mm thick sections with no gap or a 0.6 to 1.5 mm interslice gap using head coil-FOV 16 X 16. Orbital suraface coil-improves spatial resolution. For optic nerve and retrobulbar invasion head coil is preferred.
- 60. 4)Post contrast T1 fat suppressed-AXIAL and CORONAL (Orbit and head) Purpose-Assessing the abnormal enhancement in characterization of tumors,inflammatory and infective conditions. 5)DWI-AXIAL Purpose-To look for stroke and active demyelination.
- 61. For optic nerve lesions additional parasagittal images are obtained using head coil. MR is C/I in traumatized eye and in cases of suspected ferromgnetic foreign bodies. Post contrast (Gd) sequences are obtained in cases of suspected Orbital abscesses Tumors and orbtal masses Pseudotumors ON lesions (Optic neuritis)
- 62. MRI-T1 Axial LENS Optic nerve Lacrimal gland LR MR
- 63. Axial T2 AC PC ON Medial palpaberal ligament LENS Lacrimal gland
- 64. NLD and saccule Inferior orbital fissure Orbicularis oculi IR
- 68. T1 FS C+
- 70. Extraocular muscles Well visualised in CT and MR and unifomly enhances in post contrast images. EOM tendon insertions normally taper anteriorly- Thickening can be seen in pseudotumor or lymphoma. Superior muscle bundle-SR+LPS] LR appear thicker than it is as a result of volume averaging of its oblique orientation.
- 71. Trochlea of SO is a pulley like cartilagenous structure situated in the superior nasal aspect of frontal bone seen in axial and coronal sections.It is occasionally physiologically calcified. Most common cause of enlarged EOM is thyroid associated orbitopathy.
- 74. SO
- 75. Coronal T1
- 76. Lacrimal gland Prominent structure readily identified in the superolateral extraconal space. It is seperated from the globe by LR muscle. Palpebral (superficial) lobe is seperated from orbital(deep) by lateral horn of levator muscle aponeurosis.
- 78. Lacrimal gland
- 80. Vascular and Neural structures Opthalmic artery seen in the apex of the orbit on the inferior aspect of ON then pass lateral to it before looping over ON to lie in the superior medial aspect. Superior ophthalmic vein originates in the extraconal space in the anteromedial aspect of orbit pass through the muscle cone beneath SR muscle and above ON.It exits the intraconal space through superior orbital fissure.
- 81. Optic nerve The optic nerve arises from the ganglionic layer of the retina and consists of coarse myelinated fibers, like the white matterof the central nervous system. The orbital segment of the optic nerve is 3 to 4 mm in diameter and 20 to 30 mm long. From its insertion on the posterior globe, it courses posteriorly, medially, and superiorly to exit the orbit at the optic canal.
- 82. The optic nerve is covered by layers of pia, subarachnoid membrane, and dura mater. The optic nerves join in the suprasellar cistern to form the optic chiasm. The subarachnoid space around the optic nerve sheath has a low density on CT and can be imaged during the course of iodinated contrast cisternography. The meningeal layers of the optic nerve show enhancement on postcontrast CT.
- 83. On coronal scans, immediately posterior to the globe, a small central density within the nerve represents the central retinal artery and vein. The optic nerve and sheath measure 3 to 5 mm in the axial plane and 6 mm in the coronal plane. optic nerve has signal intensities similar to those of normal white matter.
- 84. ON
- 85. T1 coronal FS C+ Optic chiasm
- 88. Globe The three ocular coats (sclera, choroid, and retina) form a well-defined single line on CT that enhances with IV contrast. On MR imaging the ocular coats appear as a hypointense ring. The lens is normally hyperdense on CT and has low T1- weighted and very low T2-weighted signal intensities. The vitreous appears hypodense on CT and has signal intensities similar to those of CSF on MR imaging. The vitreous does not enhance
- 89. The globe is unique in that it contains both the most (vitreous) and least (lens) water-laden soft tissues in the body On MR imaging the normal lens is characteristically darker than the surrounding fluid-laden tissue on T2- weighted pulse sequences, predominately because of the dominance of its ultrashort T2 relaxation time and its crystalline-like structure.
- 90. The anterior chamber is crescent shaped,is just anterior to the lens, and is almost isointense to the vitreous humor on both T1-weighted and T2-weighted MR images. The ciliary body may be seen on T2-weighted MR images as a hypointense area running from the edge of the lens to the wall of the globe
- 91. Thank you