Approach to CT Head Imaging
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Approach to CT Head Imaging
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Approach to CT Head Imaging
- 1. Approach to CT Head Dr Fan Zhang
- 2. Overview • Common indications • Basic anatomy • Emergency CT checklist • Trauma • Intracranial Haemorrhage • Stroke • Tumours • Cases
- 3. CT Head – Common Indications • Non-Contrast • Trauma • Stroke (± angiogram, perfusion) • Intracranial haemorrhage • Acute headache (eg. Thunderclap) • Hypoxia • Quick, easily accessible • Low dose (~2.3 mSv) • Post-Contrast Angiogram • Stroke/TIA workup (including CT perfusion) • Vascular workup (eg. Aneurysm, vascular malformation) • Post-Contrast • Neoplasms • Abscesses
- 4. CT Head anatomy • Grey matter • = Neurons • denser so overall higher density (37-42HU) • White matter • = Axons • have myelin (fatty), so overall lower density (20-30 HU) • Gyri & Sulci arranged in various lobes • CSF spaces – ventricles, basal cisterns • Misc – pituitary gland, pineal gland, choroid plexus • Intra-axial vs extra-axial
- 6. Emergency CT Checklist • Midline structures • Suprasellar region • Pineal region • Base of skull • Symmetry • Basal cisterns • Ventricles • 3rd & 4th ventricles in midline • Lateral ventricles not enlarged
- 8. Trauma • Blunt trauma >> penetrating trauma • Skull is much harder than brain; CSF acts as a cushion • Skull fracture – often subtle, can merge with cranial sutures • Subgaleal haematoma – indicates site of trauma • Coup / contre-coup injury pattern • Brain contusion – often inferior frontal lobe • Diffuse axonal injury
- 9. Intracranial blood • Patterns of intracranial bleeding: • Extra-axial • Epidural – blood between skull & dura • Subdural – blood between dura & pia mater • Blood along the falx is always SDH • Subarachnoid – blood between pia & arachnoid mater • Check the basal cisterns • Intra-axial • Intraventricular • Parenchyma – basal ganglia, lobar, grey/white matter junction • Lesional – eg. Neoplasm, haemorrhagic transformation of ischaemic infarct
- 10. Ischaemic Stroke • Key features: • Loss of grey/white matter differentiation • Insular ribbon sign • Dense vessel sign • Has to be appropriate & fit the clinical picture • CT angiogram – assess arteries • CT perfusion – assess salvageability
- 11. Tumours • Intra-axial vs Extra-axial • Primary vs Secondary • Primary • Glial series tumours / Glioblastoma • CNS lymphoma – hyperattenuating • Secondary • Metastases – multiple lesions
- 12. Cases…
Notas do Editor
- Suprasellar region – Sella turcica, pituitary gland, Circle of Willis (terminal ICAs, MCA, ACA, ACOM, PCOM), optic chiasm, anterior 3rd ventricle, mammillary bodies, anterior interhemispheric fissure, tip of basilar artery, PCAs, ACAs, carotid siphons, PComm, optic nerve and tracts. Pineal region – Midbrain, tegmentum, aqueduct of Sylvius, pineal gland, superior cerebellar vermis, superior vermian cistern. Craniocervical junction – Anterior arch C1, odontoid process, cervical occipital ligaments, clivus, cerebellar tonsils (</=5mm below anterior and posterior lips of foramen magnum), obex (above foramen magnum). Any soft tissue other than the cervico-medullary junction and a small portion of the cerebellar tonsil in the foramen magnum is pathologic.