Acute CT Brain Imaging: We Depend on You!
February 21, 2015
Kaiser Symposium
Suzie M. El‐Saden, MD
Chief, Imaging Service GLA VA Professor and Vice Chair of Radiology, UCLA
CT Imaging on the rise
Use of CT scans in emergency rooms increased 330% in 12 years
WHY? • Fast • Still the 1st imaging choice for trauma and mental status changes
• Sensitive to blood
• Inexpensive (vs. MRI)
• No contraindications (vs. MRI)
• Downside: ‐radiation exposure
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Too much white or too much black?
• Polychromatic beam shades of gray
• Appearance of intracranial hemorrhage
• Appearance and types of brain edema
• Quiz 
Intracranial Hemorrhage (too much white)
• Subarachnoid Hemorrhage (SAH) • Epidural Hematoma (EDH)
• Subdural Hematoma (SDH)
• Parenchymal Hemorrhage
• Location & anatomy determine the appearance of blood on CT
• Why is Blood white on CT?
Why is Blood white on CT?
Clot retraction leads to increased density
• 30 min s/p head trauma
• Density = 49 HU
• 100 min s/p head trauma
• Density = 67 HU
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Intraparenchymal hematoma As clot retracts, serum protein expelled & vasogenic edema forms = Halo
Meninges ‐ Outside to Inside
• Dura Mater‐ 2 layers, insertion at sutures
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Outer layer = periosteum of inner table of skull = Endosteum
Inner layer reflects to form Falx and Tentorium Subdural space is deep to both layers
Epidural space‐ superficial to both layers (between dura and skull)
Layers only separate for venous sinuses
Dura and Venous Sinuses
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Meninges‐ anatomy cont.
• Dura Mater
– 2 layers only separate for venous sinuses
• Arachnoid Membrane
– Sub arachnoid space contains CSF and Arteries (Circle of Willis)
• Pia Mater: surface of the brain
– “Nothing comes between the brain and its pia”
70 yo comatose s/p fall
Subdural Hematoma SDH
Shape: CRESCENTIC
‐Deep to both layers of dura
‐Reflects at dural reflections
‐Cannot cross midline
‐May travel along tentorium
• Source: Venous bleeding (bridging veins)
• Acuity: usually slowly progressive/self limited
• Surgical evacuation‐often elective
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Anatomy review
Torn bridging
Torn bridging vein with associated SDH
Age of hematoma affects density
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Tentorial SDH
Tentorial SDH
28 yo boy s/p bike accident
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Epidural Hematoma EDH
• Shape: Lens, lenticular, biconvex
– Confined by dural insertions at sutures
– Superficial to both layers of dura
– Can cross midline
• Etiology usually trauma
• Often has associated fracture & laceration of middle meningeal artery
• Acuity: Rapidly progressive arterial bleeding • Surgical emergency or close observation & serial CT follow up
44 yo male found down with loss of consciousness
MMA Arteriogram
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Fractures can be hard to see (check scout image)
SDH VS. EDH
67 yo presents with acute H/A
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Subarachnoid Hemorrhage (SAH) Ruptured aneurysm
SAH from Aneurysm
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Head CT for acute blood
Then angiogram (CTA or Conventional)
50% die before arrival
Risk of rerupture in 1st 24 h high
Branch points off of the Circle of Willis
85% anterior circulation 15% posterior circulation 20% incidence of multiple aneurysms
SAH
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Angiogram
CTA
Catheter Angiogram
80 yo male with Rt weakness
Hypertensive Hemorrhage
• 10‐20% of strokes
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Putamen
Thalamus
Pons
Cerebellum
Lobar
• MRI to R/O underlying lesion (Vascular Malformation, Metastasis)
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Is it Blood?
Edema (too much black)
• Cytotoxic
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Cell injury with loss of homeostasis
Gray matter involved
Most commonly due to arterial occlusion
Contrast not helpful
• Vasogenic
– Involves white matter sparing gray matter
– Leaky capillaries
• Underlying etiology: Infxn, Tumor
– Give Contrast
MCA Embolic Occlusion
Hypoxemia (lack of blood flow)
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“Stroke”: Embolic Arterial Occlusion
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ATP depletion
Na+/K+ pump failure
Na+ and H20 in
Cellular swelling
Shift of water from interstitium to intracelluar
Early MCA Stroke on CT
Cytotoxic Edema‐DWI within 4h
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4 days post stroke
• Cytotoxic and Vasogenic Edema
• Edema peaks 3‐5 days
• Bland infarct
• No thromolytic intervention Vasogenic Edema
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Leaky Capillaries
BBB breakdown
Finger like extension
Spares gray matter
Give contrast!!
Vasogenic Edema
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Review
Quiz Time…
Quiz #1
Quiz #2
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Quiz #3
Quiz #4
Quiz #4 with contrast
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Quiz #5
Quiz #8
Thank you!
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