1. IMAGING IN ORBIT

2. IMAGING TECHNIQUES
X-RAY
ULTRASONOGRPHY
CT SCAN
MRI
MRA

3. X RAY Not commonly used now a days because
A three-dimensional structure is seen in two dimensional plane, giving rise to disturbing superimposition.
Moreover, its sensitivity to small differences in the attenuation is low
, i.e., its contrast resolution is poor.

4. X-RAY
WATERS VIEW
CALDWELL’S VIEW
LATERAL VIEW
SUBMENTOVERTEX VIEW
RHESE VIEW

5. WATERS VIEW: Waters projection is created by placing the chin of the patient on the x-ray cassette with the canthomeatal line (the line that connects the lateral canthus and the external auditory meatus) at 37 degrees to 45 degrees

6. (a, frontal sinus; b, medial orbital wall; c, innominate line; d, inferior orbital rim; e, orbital floor; f, maxillary antrum; g)superior orbital fissure; h, zygomatic-frontal suture; i, zygomatic arch) 

7. CALDWELL’S VIEW: The patient is positioned with both the nose and forehead against the x-ray cassette while the x-ray beam is directed downward 15 degrees to 23 degrees to the canthomeatal line.

8. (a, frontal sinus; b, innominate line; c, inferior orbital rim; d, posterior orbital floor; e, superior orbital fissure; f, greater wing of sphenoid;g, ethmoid sinus; h, medial orbital wall; i, petrous ridge; j, zygomatic-frontal suture; k, foramen rotundum) 

9. LATERAL VIEW: lateral projection (Fig
LATERAL VIEW: lateral projection (Fig. 4) is created by placing the patient's head against the x-ray cassette and centering the cassette on the lateral canthus. The x-ray beam is directed perpendicularly to the midpoint of the cassette and enters the patient's head at the lateral canthus remote from the cassette

10. Radiograph of a lateral projection
Radiograph of a lateral projection. (a, orbital roof; b, frontal sinus; c, ethmoid sinus; d, anterior clinoid process; e, sella turcica; f, planum sphenoidale)

11. SUBMENTOVERTEX VIEW :this projection is obtained with the patient's neck extended either in the supine or upright position. The top of the head is placed so that the infraorbitomeatal line is parallel with the x-ray cassette. The x-ray beam is directed at right angles to the infraorbitomeatal line

12. (a, zygomatic arch; b, orbit; c, lateral orbital wall; d, posterior wall of maxillary sinus; e, pterygoid plate; f, sphenoid sinus

13. RHESE VIEW: The zygoma, nose, and chin should touch the cassette
RHESE VIEW: The zygoma, nose, and chin should touch the cassette. The x-ray beam is directed posterior-anteriorly at 40 degrees to the midsagittal plane

14. Radiograph of an oblique apical projection
 Radiograph of an oblique apical projection. (a, right optic canal; b, optic strut; c, superior orbital fissure; d, ethmoid sinus; e, planum sphenoidale; f, greater wing of sphenoid) 

15. PROJECTION STRUCTURE PATHOLOGY RHESE VIEW OPTIC CANAL
WATERS VIEW
ORBITAL FLOOR ANT 2/3
BLOW OUT#
CALDWELL’S VIEW
INNOMINATE LINE,ORBITAL FLOOR POST.1/3
MEDIAL, LATERAL WALL#
LATERAL VIEW
ORBITAL ROOF
ORBITAL ROOF #
SUBMENTO VERTEX
LATERAL WALL OF ORBIT
LATERAL WALL#
RHESE VIEW
OPTIC CANAL
OPTIC NERVE TUMORS

16. X-RAY SIGNS OF ORBITAL DISEASES
SIZE OF ORBIT
CHANGE IN BONE DENSITY
CHANGE IN ORBITAL SHAPE
DEHISCENCE OF ORBITAL BONES
INTRAORBITAL CALCIFICATION
ENLARGEMENT OF SUP. ORBITAL FISSURE
CHANGE IN OPTIC CANAL

17. SIZE OF THE ORBIT
SYMMETRICAL ENLARGMENT observed in intraconal lesions
e.g ; optic nerve glioma, hemangioma
ASYMETRICAL ENLARGEMENT observed in extraconal lesions e.g; rhabdomyosarcoma, dermoid cyst

18. CHANGE IN BONE DENSITY
Localised decreased density/indentation of the orbital wall Benign tumors like, dermoid, mixed cell lacrimal gland tumor
Diffuse bony destruction malignant tumors like, lacrimal gland carcinoma

19. SUP.WALL DESTRUCTION IN RHABDOMYOSARCOMA

20. CHANGE IN ORBITAL SHAPE
As a result of local expansion of the orbital wall
Orbital dermoids
Encapsulated lacrimal gland tumors

21. Intraorbital calcification
Retinoblastoma
Orbital varix
Optic nerve sheath meningioma
Phthisical eye

24. Enlargement of Sup.Orbital fissure
Infraclinod carotid aneurysm
Extraseller extension of pitutary tumors

26. Changes in Optic Canal Normal dimensions: Vertical 6mm Horizontal 5mm
Abnormal when ,
Asymmetry greater than 1mm,
Vertical dimension greater than 6.5mm

27. Optic canal enlargement
Seen in,
Regular enlargement
Optic nerve glioma
Aneurysm of ophthalmic artery
Irregular enlargement
Retinoblastoma
Optic nerve sheath meningioma

28. OPTIC CANAL ENLARGEMENTIN OPTIC NERVE GLIOMA

29. Optic canal compression
Seen in
Fibrous dysplasia
Paget’s disease
Hyperostosis secondary to meningioma
Microphthalmos

30. OPTIC CANAL COMPRESSION IN FIBROUS DYSPLASIA

31. X-RAY IN ORBITAL WALL/RIM FRACTRURES
TRIPOD FRACTURE
BLOW OUT FRACTURE

32. TRIPOD FRACTURE

33. ORBITAL FLOOR FRACTURE

34. Intraorbital foreign body

35. Intra ocular foreign body

36. CT SCAN OF ORBIT ADVANTAGE: BONY DETAILS /CALCIFICATION
SPACE OCCUPYING LESION CAN BE VISUALISED IN THREE DIMENSIONS BY COBINATION OF CCT AND CAT
STRUCTURES LIKE GLOBE ,EOM, OPTIC NERVE CAN BE VISUALISED
IN ORBITAL TRAUMA FOR DETECTING SMALL ORBITAL WALL #
IOFB
HERNIATION OF EOM

37. DISADVANTAGE
INABILITY TO DISTINGUISH BETWEEN PATHOLOGICAL SOFT TISSUE MASS WHICH ARE RADIOLOGICALLY ISODENSE
RADIATION INDUCED CATARACT

38. CT scan is most informative,
when the ophthalmologist seeks active participation of the radiologist in the diagnostic work-up.
The clinical information supplied by the referring ophthalmologist is used by the radiologist .

39. Major consideration while requesting a CT Scan
Slice thickness
Imaging plane
Tissue window
Contrast enhancement
Modification of CT procedure
Orbit with brain CT

40. Slice thickness Spatial resolution of a CT depends on slice thickness.
The thinner the slice, the higher the resolution.
Usually, 2mm cuts are optimal for the eye and orbit.
In special situations (like evaluation of the orbital apex), thinner slices of 1mm can be more informative.

41. Imaging plane Routine CT scan involves axial& coronal views .
Saggital view: along the axis of the inferior rectus muscle is important in evaluation of orbital floor blow-out fractures.

42. A spiral CT is Preferable when reformatted sagittal cuts are required.
The plane inclined at 30° to the orbito-meatal line  best depicts the optic canal and the entire anterior visual pathway.

43. Tissue window
Each tissue window has a specific window width and window level.
Soft-tissue window  is best for evaluating orbital soft tissue lesions,
Fractures and bony details are better seen with bone window settings .

45. Contrast enhancement
Evaluation of optic chiasma, perisellar region and extra-orbital extensions of orbital tumours.
Helps to define vascular and cystic lesions as well as optic nerve lesions, particularly meningioma and glioma.

47. Modification of CT procedure
Certain cases may require special modifications during the scanning procedure to aid diagnosis.
In a case of orbital venous varix, it is important to request for special scans (with contrast) while the patient performs a Valsalva maneuver.

48. Simultaneous brain CT
Suspected neurocysticercosis with orbital involvement.
Head injury with orbital trauma
Optic nerve meningiomas

49. Components of CT scan
Patient data This includes the name, age, gender of the patient as well as the date of the CT scan .
Type of CT scan
Plain CT scan
Contrast enhancement
It will be printed next to each image whether the scan is plain or contrast enhanced.

50. Laterality
The best way to confirm laterality is to look for the "R" or "L" mark which represents right or left respectively .

51. Axial scan orientation
Each axial slice is always displayed with the anterior (ventral) end facing up.
As we move from inferior to superior, the prominence of the nose flattens out anteriorly, and increasingly more brain parenchyma appears posteriorly.

53. Coronal scan orientation
Maximum globe diameter roughly represents the equator of the eyeball.
The cross-sectional size of the orbital cavity reduces as we move to the posterior. 

55. Systemic evaluation of ocular and orbital structures on CT scan
Orbital dimensions:
Vertical and horizontal should be measured on coronal scans
Medial ,lateral wall, sup.orbital fissure, optic canal evaluated on axial scan.
Orbital roof and floor on coronal scan.

56. The eyeball
The sclera, choroid and retina together form a well defined ring that enhances with contrast.
The lens appears white, and the vitreous black.

57. Extraocular muscles On axial cuts only the horizontal recti are seen.
The superior rectus and the levator palpebrae superioris are seen as a single soft tissue shadow on high axial scans  and coronal scans .
The superior oblique is best seen in the coronal view lying supero-medial to the superior rectus .
The inferior oblique is the least defined muscle on CT scan.

58. Size
 There is an excellent symmetry between the extra-ocular muscles of both the orbits, and they are thus comparable in all respects.
enlargement
maximum : tumors,cysts
moderate : thyroid ophthalmopathy, vascular lesions, and myositis. ,
decreased muscle diameter suggests atrophy from denervation or myopathy.

59. Shape:
 Diffuse enlargement inflammation, venous congestion or infiltration,
focal enlargement
neoplasm or cyst.
Tendon involvement suggests myositis.

60. Muscle margin Healthy extra-ocular muscles have sharp margins.
Uniform configuration with distinct margins is seen in Graves' myopathy and vascular engorgement.
Irregular enlargement with indistinct borders :diffuse infiltration by metastatic disease .

61. Contrast enhancement
 Normal muscles have moderate contrast enhancement,
Marked enhancement is seen in thyroid ophthalmopathy or myositis.
Variable in arterio-venous fistulas and neoplasms.

62. Extraconal tissues
The lids, conjunctiva, and the orbital septum which on axial scans is seen to extend from the pre-equatorial part of the globe to the lateral and medial orbital margins 
The lacrimal gland lies within its fossa supero-temporally, and can be seen on high-axial as well as anterior coronal scans .

63. Intrconal tissue
The two most important structures optic nerve and the superior ophthalmic vein (SOV).
CT evaluation of optic nerve lesions is facilitated by 1.5 mm axial scans.

64. Gliomas
have fusiform enlargement with sharp delineation from the surrounding tissue .
They are isodense with the optic nerve, and
show variable enhancement with contrast.

66. Optic nerve meningioma
They tend to be hyperdense to the optic nerve,
More consistent contrast enhancement.
Calcification within the optic nerve shadow

67. Optic nerve meningioma

68. Orbital diseases and CT presentation
Vascular disorders
orbital venous varices,
arteriovenous malformations,
carotid cavernous fistulas, and
aneurysms.

69. Orbital varix Fusiform and globular density
It has smooth, well-defined margins, and shows bright contrast enhancement.
Increase in size during Valsalva maneuvre almost always confirms the diagnosis.

71. carotid cavernous fistulas
  ipsilateral enlargement of the cavernous sinus, superior ophthalmic vein and extraocular muscles, causing proptosis.
Arterio-venous malformations : Irregular tortuosities with marked contrast enhancement, and intracranial component

73. Orbital neoplasia Assessment of proptosis: Hilal &Trokel.
 Using a mid-orbital axial scan, a straight line is drawn between the anterior margins of the zygomatic processes.
Normally it intersects the globe at or behind the equator.
The distance between the anterior cornea and the inter-zygomatic line is normally 21mm or less.
Asymmetry >2mm or value > 21mm indicates proptosis.

75. Size of the tumour:  Measured with the geometric protractor at its widest dimensions
Circumscription of the tumour: Whether well delineated or diffuse Shape of the tumour: Whether it conforms to the shape of adjacent structures.

76. Shape of the tumour, and whether it conforms to the shape of adjacent structures. Margin of the tumour: whether smooth (benign lesion), or irregular (malignant lesion). Effect on surrounding structures: displacement (benign lesion) or infiltration (malignant neoplasm). Internal consistency: homogenous (benign lesion) or heterogenous (malignant lesion). .

77. Surrounding bone: fossa formation (benign lesion), erosion (malignant lesion), or hyperostosis
Exact location:extrconal/intraconal
Relationship with the adjacent vital structures such as the optic nerve, extra ocular muscles, proximity to superior orbital fissure and optic foramen, and its posterior extent helps to plan the surgical approach.
Extraorbital extension of the tumour.

78. Vascular tumours
Cavernous haemangioma: well demarcated contrast enhancing intraconal mass.
Lymphangiomas : poorly defined masses with heterogeneous tumour density. irregular margins, little or no contrast enhancement.
Capillary haemangioma: well demarcated, homogenous, contrast enhancing, extraconal mass .

80. Pleomorphic adenomas
Nodular well delineated lesions with moderate contrast enhancement.
smooth and well defined margins,
local bony fossa formation is common.

82. Malignant neoplasm of lacrimal gland
Mass with poorly defined margins and
Intralesional calcification,
Surrounding bone destruction
Neoplastic lesions generally tend to extend posteriorly, and may cross the vertical midline of the orbital cavity.

84. Dermoid cysts Well delineated may show calcification of the cyst rim.
Well delineated may show calcification of the cyst rim.
Lucent internal consistency

86. Orbital inflammatory diseases
 Orbital cellulitis
Small stippled densities appear within the orbital fat
Secondary thickening of extra-ocular muscles, especially the medial rectus
A frank orbital subperiosteal abscess  shows a typical ring enhancement on contrast study.

88. Orbital pseudotumour Wide range of CT findings.
A well-defined mass, or mimic a malignancy.
May show an enlarged lacrimal gland.
Thickening of the posterior scleral rim, with surrounding soft tissue involvement.
Muscle thickening.

90. Myositis
Usually involves a diffuse (occasionally irregular) enlargement of one or more muscles
There are usually no bony changes, and involvement of tendinous insertionis common

92. Graves' ophthalmopathy
Graves ophthalmopathy typically shows unilateral or bilateral involvement of single or multiple muscles.
CT shows fusiform muscle enlargement with smooth muscle borders, especially posteriorly.
The tendons are usually not involved and orbital fat is normal, but pre-septal oedema may be seen.

94. Orbital trauma
Evaluation of fractures: their number, location, degree and direction of fracture fragment displacement, and demonstration of detached bony fragments in the orbital or intracranial cavity. Evaluation of soft tissue injury: Muscle entrapment, haematoma, emphysema, etc.

95. CT in retained foreign body
determines its location (extraocular or intraocular), and its relationship to the surrounding ocular structures.
Metal foreign bodies up to 0.5 mm can be detected,
stone, plastic or wood less than 1.5 mm size are usually not visualised.

97. Orbital floor fractures
Bony discontinuity, and displacement of fragments into the maxillary sinus
Prolapse of orbital fat or inferior rectus, as well as opacification of maxillary sinus with or without fluid level may be seen.
In medial wall fractures, orbital emphysema & bony discontinuity.

99. Ocular lesions
A retinoblastoma is seen as a well-defined high density mass with calcification.
To differentiate between extrascleral extension of the tumour and orbital cellulitis secondary to tumour necrosis.
The former shows a well-defined soft tissue density in continuity with the globe, and the latter shows a diffuse orbital haze.

101. MAGNETIC RESONANCE IMAGING

102. BASIC IMAGE SEQUENCES
T1- weighted (T1W) images - Tissues with shorter T1-relaxation times like fat appear brighter than those with longer T1-relaxation like water/vitreous/CSF.
T2- weighted (T2W)mages -
Tissues with longer T2-relaxation like water/vitreous/CSF, appear brighter than tissues with shorter T2-relaxation like blood products.

104. Fluid attenuation inversion recovery (FLAIR)
Signal from fluid can be suppressed using the FLAIR sequence.
FLAIR is especially useful in demyelinating conditions where the white matter hyperintensities on T2W images are better appreciated when the bright signal from the adjacent CSF in the ventricles is nulled.

106. Postcontrast images
Gadolinium CAUSES shortening of T1-relaxation times, which results in brighter areas on T1W images. Therefore postcontrast images are always obtained with T1 weighting.
The optic nerve does not normally enhance.

108. Fat-suppressed images
Bright signal from intraorbital fat can mask the signal and enhancement of pathology.
This problem can be overcome by suppressing the signal of fat by special fat suppression sequences.  

110. Heavily T2W images
This sequence helps in better visualization and tracing the course of the cisternal portions of the cranial nerves (useful in cases of suspected 3 rd nerve palsy).

111. Magnetic resonance angiography (MRA)
the intracranial vessels and aneurysms alone can be demonstrated after subtracting the images of the brain parenchyma with or without injecting GADOLINIUM

112. Magnetic resonanace venography (MRV):
Similar to MRA, images of the dural venous sinuses can be obtained with or without injecting gadolinium.

113.  Imaging Protocol
 Routine imaging of the orbit should include: Thin section (3 mm or less) axial and coronal T2W images of the orbit.
Thin section fat saturated pre and postgadolinium axial and coronal images.
The cavernous sinuses should be included in all the sequences

114. Disadvantages: Advantages of MRI Excellent soft tissue details
Entire course of optic nerve well studied
No exposure to radiation
Disadvantages:
Less sensitive for detecting bony abn. And calcification.
Fat saturation artifacts can mimic pathology, C/I in metallic IOFB,longer time

115. Contraindication Of MRI
Suspected metallic intraocular foreign bodies:
Cardiac pacemaker and implanted cardiac defibrillator:
MRI incompatible aneurysm clip.
Implants: Cochlear, otologic, or ear implant. 
Lid gold implants  and metallic orbital floor implants .

116. Imaging plane

117. T2W Axial section with fat supression through mid orbit

118. T2W axial scan through sup.orbit

119. T2W axial scan through inf. orbit

120. T2W coronal section through ant. orbit

121. T2w coronal section through globe

122. T2W coronal section post to globe

123. MRI in retinoblastoma &cavernous hemangioma

124. MRI in orbital varix in supine position and prone position

125. Ultrasonography
Non invasive
Well tolerated
Safe technique

126. USG
D/D is based on
Patterns of sound reflectivity at the surface of the mass.
Transmission characteristics of the sound wave as it passes through the lesions.

127. Normal echo pattern Scan through the plane of the optic nerve
Normal echo pattern appers as W shaped acoustially opaque area.

128. Echo pattern in mass lesions
Cystic swellings:
mucocele ,dermoid cyst
Shrpely defined round border,good sound transmission

129. Solid tumors Like, optic nerve glioma Well outlined border
Poor sound transmission

130. Spongy lesions of orbit
Like, Hemangioma
Irregular shape ,good sound transmission, strong internal echoes

131. Infiltrating orbital lesion
Like, pseudotumors, lymphangioma, metastatic carcinoma
Variable shape,
Poor sound transmission

132. USG in grave’s ophthalmopathy
Thickening of extra ocular muscle
MR is the first muscle to enlarge
Accentuation of retrobulbar fat
Perineural inflammation of optic nerve

133. THANK YOU