Transcript
BASICS
What is CT or Computed Tomography..?
• It employs X rays which pass through body and reach a detector , image is reconstructed using computer.
Where to use CT..?
• At present main use of CT is in• Suspected trauma.• Foreign body.• Evaluation of orbital infections/
abscesses.• Evaluation of extraocular muscles.• Not so useful in optic nerve
disease / demyelinations.
How to read CT…?
CT scan is bascially a densitometer. Fluid filled structures like globe , fat are dark , dense structures like bone are dense
Any thing to be cautious while asking for CT..
• CT is associated with radiation. There is a small increased risk of cancer with CT examination.
• A CT head delivers 2-3 mSv of radiation dose.• Repeated CTs are also associated with rising
incidence of cataract.
What is MRI ..?
• MRI employs a powerful magnet , radio waves and movement of protons inside our body to produce images.
• High soft tissue resolution.• MRI is used in• In particular useful in optic nerve pathology ,
demyelination and cranial nerve assessment.• Less useful in trauma. Fractures not well depicted.
Caution about MRI
• MRI should not be done in a patient suspected of metallic foreign body without doing CT. if a ferromagnetic particle is present , it can have missile effect and damage orbital structures.
• Should be cautious while doing MRI in patients with pacemakers , protruding metallic objects.
I hear so many terms like T1,T2 in MRI what are they..?
• MRI is an unique diagnostic technique in the sense that one can see pathology in many colors. We label these as T1,T2 and other names.
Another commonly done sequence is called STIR sequence , this sequence suppresses fat to highlight
pathology.
ANATOMY CORONAL
Anatomy in Axial
Showing vessels
Anatomy of foramina
Cases..
Case 1
• Loss of vision right eye…
STIR sequence shows enlarged right optic nerve with hyperintensity.
Coronal images showing periventricular hyperintensity.
Diagnosis -
• Demyelination with optic neuritis• MRI is the best imaging modality to diagnose
optic neuritis and brain demyelination.• STIR sequence in MRI is useful in diagnosing
optic neuritis.
Case 2
• Proptosis for evaluation
Enlarged superior ophthalmic vein right side.
Dynamic angio
Dynamic angio
Visualization of cavernous sinus on arterial phase
Enlarged sup oph vein
DSA showing carotico cavernous fistula
Enlarged Superior ophthalmic vein
Contrast filling of cavernous sinus on arterial phase.
Carotid-cavernous fistula
• CCF (carotid-cavernous fistula )represents high flow communication between cavernous internal carotid artery and cavernous sinus.
• Remember that on MRI , only sign may be enlargement of Superior ophthalmic vein , hence easily missed.
• Type A CCF- direct communication between internal carotid artery and cavernous sinus.
• Type B-D – various types of indirect communication between ICA and cavernous sinus.
• Endovascular management of CCF is the preferred treatment.
• Treated by appropriately placing detachable balloons or detachable coils.
• Covered Stent placement is a new technique.
CCF pre procedure
CCF post procedure
PROPTOSIS DEFINITION
• A line connects bony lateral margins.
• Distance form this line to anterior surface of cornea is measured.
• Normal less than 18-20 mm.• Difference of more than 2
mm between two eyes is abnormal.
Case 3
• 2 year old child with eyelid swelling
T2 axial
T1 coronalCoronal STIR
Parasitic cyst in eyelid
• Parasites like Dirofilaria preferentially involve eye.
• In differential diagnosis of cystic lesions in orbit , this needs to be given.
• High resolution USG is characteristic , it can show live larva.
Smitha M, Rajendran VR, Devarajan E, Anitha PM. Case report: Orbital dirofilariasis. Indian J Radiol Imaging 2008;18:60-2
Case 4
• History of trauma to face left side.
2
2
Fluid level in left maxillary sinus and soft tissue tear drop caused
by blow out fracture
Case 5
• 12 year old boy hit by a tree while travelling.
Plain CTContrast CT
T2
Contrast MRI
Lucent areas seen within left orbit.Remember that wood also can cause similar appearance.
Enhancement suggests orbital cellulitis.
Final diagnosis
• Wood particles (foreign body) in orbit with granuloma.
Imaging in orbital trauma
• CT is modality of choice.• Take minimum 3 mm axial
sections with coronal reformations.
• Pay particular attention to fractures of optic canal / orbital apex fractures.
• Look for foreign body. Small FBs can be missed.
Right orbital apex fracture
Case 6..
• Severe periorbital pain right side and right 3rd nerve palsy
T2 images showing subtle mass at superior orbital fissure
Plain MRI Contrast MRI showing a mass at SOF region.
Diagnosis --Tolosa Hunt syndrome. It is an idiopathic inflammatory condition involving orbital apex and cavernous sinus.In active phase enhancing tissue is seen.
Case 7
• Pain and proptosis right orbit.
Enlarged lateral rectus muscle involvement of belly and tendinous insertion is seen which is classical of myositic form of pseudotumor.
Diagnosis– pseudotumor.It is an idiopathic inflammatory condition. Can involve many parts of orbit.Hence can be Myositic type.Involve lacrimal gland.Intraconal mass involving sclera.
Hence is one of common differential diagnosis.Difficult to separate from lymphoma.Follow up is advised always.
Thyroid associated ophthalmopathy is differential of pseudotumor. `` coke bottle `` appearance seen sparing anterior tendon.Pneumonic- IMSLOW
Case 8
A Spotter
Bilateral retinoblastoma.
Intraocular mass with calcifications.90% show calcifications.40% bilateral.
What`s new …
• With high resolution imaging , it is possible to see cranial nerves on MRI .
6th nerve
Arrows showing 3rd nerves
Arrows showing 5th nerve
What`s new ..?
• Functional MRI of visual pathway..• Newer MRI can map brain activity , by giving a
visual stimulus we can which areas of brain are getting activated.
Demonstration of visual cortex.
What`s new
• Fiber tracking of visual pathway using diffusion tensor imaging.
Common ocular lesionsRetinal detachmentRetinoblastomaChoroidal detachmentMelanomatrauma
Common intraconal lesionsOptic nerve gliomaOptic neuritisVascular malformations
Common conal lesionsPseudotumorThyroid ophthalmopathy
Common extraconal lesionsSubperiosteal abscess.Fibrous dysplasia.Lacrimal gland lesions
30 year old with headache and pain in left eye.? Caroticocavernous fistula/ vascular malformation
Case 9
Axial T2
Axial T1
STIR COR
Normal angiogram
T1 post contrast
Diagnosis
• ? Myositic pseudotumor• ? Vascular malformation
I said
Ophthalmologist said..Please see again , can not be pseudotumor
Before valsalva
Aftervalsalva
Diagnosis
• Orbital varix.
Rule out superior oblique pathology .History of trauma
CASE 10
Normal superior oblique
Question from ophthalmologist? Blow out fracture
A small blow out fracture was missed on initial look..
Commonly missed orbital lesions inmy experience on MRI and CT
• Blow out fracture if proper coronal not taken.• Carotico-cavernous fistula– due to dynamic
nature.• Worm granuloma- may need to high
resolution USG.• Small orbital varix- may need valsalva .
Thank you for viewing this presentation.Hope it was useful.
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