Orbital imaging (X-RAY,CT SCAN,AND MRI)

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. 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. (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. The x-ray beam is directed posterior-
anteriorly at 40 degrees to the midsagittal plane

14. 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
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 1mmcan 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 linebest 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 windowis 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 rectusand the levator
palpebrae superiorisare seen as a single soft
tissue shadow on high axial scansand coronal
scans.
•The superior oblique is best seen in the
coronal view lying supero-medial to the
superior rectus.
•The inferior obliqueis 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 isodensewith the optic nerve,
and
•show variable enhancement with contrast.

66. Optic nerve meningioma
•They tend to be hyperdenseto 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.
•Lucent internal consistency

86. Orbital inflammatory
diseases
•Orbital cellulitis
•Small stippled densitiesappear within the
orbital fat
•Secondary thickening of extra-ocular
muscles, especially the medial rectus
•A frank orbital subperiosteal
abscessshows 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 conditionswhere 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. •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 implantsand 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