Head and NeckLive data

CT Orbits

CT of the orbits provides rapid, high-resolution assessment of the bony orbit, globe, extraocular muscles, optic nerve and retrobulbar fat. It is the first-line modality for orbital trauma and is also used for proptosis, infection and mass evaluation, with contrast reserved for inflammatory and neoplastic indications.

Indications

Orbital trauma with suspected fracture, globe injury or retrobulbar haemorrhage
Suspected metallic or radiodense intraorbital foreign body
Proptosis and orbital mass characterisation
Orbital or preseptal cellulitis and suspected subperiosteal or orbital abscess
Suspected optic nerve or extraocular muscle pathology (e.g. thyroid eye disease)

Contraindications & Cautions

Standard iodinated contrast contraindications for enhanced protocols
MRI preferred for optic nerve, intracranial extension and detailed soft-tissue characterisation
Weigh radiation dose to the lens, particularly in children and repeated imaging

Patient Preparation

Remove metallic eyewear, jewellery and facial hardware where possible
Instruct the patient to keep the eyes still or gently closed during acquisition
Screen for iodinated contrast allergy and renal function if enhancement planned
Clarify mechanism of trauma or clinical concern to tailor windows and contrast use

Technique & Parameters

Thin-section axial acquisition (≤1 mm collimation) covering the orbital rims to orbital apex
Direct or reformatted coronal images, essential for orbital floor and roof assessment
Sagittal reformats to profile the orbital floor and herniated contents
Bone and soft-tissue window review; avoid gantry angulation through the lenses where feasible
Intravenous contrast for suspected infection, inflammation or neoplasm

Systematic Review

Inspect all four orbital walls (floor, medial, roof, lateral) for fracture
Assess extraocular muscles for entrapment, enlargement or displacement
Evaluate the globe for contour, hyphaema, lens dislocation and open-globe signs
Review the retrobulbar fat and optic nerve for haemorrhage, mass or tenting
Check paranasal sinuses and intracranial structures for associated injury or extension

Key Findings & Significance

Orbital floor (blowout) fracture with herniation of fat/inferior rectus and the trapdoor pattern in children
Medial wall (lamina papyracea) fracture with orbital emphysema
Extraocular muscle entrapment causing restricted motility
Retrobulbar haemorrhage with proptosis and posterior globe tenting (compartment syndrome)
Subperiosteal or orbital abscess with rim enhancement adjacent to sinus disease

Differential Considerations

Blowout fracture versus congenital orbital wall dehiscence
Orbital cellulitis versus preseptal cellulitis (relationship to orbital septum)
Thyroid eye disease (fusiform muscle enlargement sparing tendons) versus orbital myositis
Cavernous venous malformation versus optic nerve sheath meningioma versus schwannoma
Retrobulbar haemorrhage versus orbital mass or vascular lesion

Pearls & Pitfalls

Paediatric trapdoor fractures may show minimal bony displacement but entrap muscle (white-eyed blowout)
Posterior globe tenting and a taut optic nerve indicate sight-threatening orbital compartment syndrome
Coronal reformats are indispensable for orbital floor and roof fractures
Distinguishing preseptal from postseptal (orbital) infection is critical for management and drainage decisions

Structured Report

Specify fractured wall(s), degree of displacement and any herniated contents
State presence or absence of extraocular muscle entrapment
Report globe integrity, lens position, hyphaema and signs of open globe
Describe retrobulbar haemorrhage, proptosis and optic nerve tenting if present
For infection, localise abscess relative to the orbital septum and note sinus source

References

ACR-ASNR-SPR Practice Parameter for the Performance of CT of the Extracranial Head and Neck
Radiographics: Winegar BA et al. Spectrum of Critical Imaging Findings in Orbital Trauma
ACR Appropriateness Criteria: Orbits, Vision and Visual Loss
Radiographics: LeBedis CA, Sakai O. Nontraumatic Orbital Conditions

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.

CT Orbits

📋 Indications

⛔ Contraindications & Cautions

🧑‍⚕️ Patient Preparation

⚙️ Technique & Parameters

🔎 Systematic Review

🩻 Key Findings & Significance

🧠 Differential Considerations

💡 Pearls & Pitfalls

📝 Structured Report

📚 References