2. Systemic Approach to head CT
Symmetry
Midline
Cross-sectional anatomy
o Brain tissue
o CSF space
o Skull and soft tissues
Subdural space
Bone windows
12. Normal CT of Brain
• Sulci are symmetrical on both
sides
• Midline is straight
• Grey-white distinction is clear
• Ventricles are normal sized
• Skull is intact with no scalp
edema.
28. Ischemic stroke can be further classified on the basis of the time from the onset of
symptoms as
■ hyperacute
■ acute
■ subacute
■ chronic
29. the goals of CT in an acute setting are:
1. exclude ICH
2. look for early features of ischemia
3. exclude other IC pathologies that may mimic the stroke
30. Immediate change
• The earliest CT sign visible is the
hyperdense segment of a vessel,
representing the intravascular thrombus
or emboli.
• Its most often observed in the MCA:
MCA Dot sign/ hyperdense MCA sign
31. Acute stroke
• Loss of grey-white matter
differentiation .
• Cortical hypodensity with associated
parenchymal swelling with resultant
gyral effacement
• Insular ribbon sign
• There will be significant mass effects
also due to the swelling
32. Subacute stroke
• The swelling starts to subside and small
amounts of cortical petechial
hemorrhages may appear.
• This is known as CT fogging
phenomenon.
• Can be misleading as the affected
cortex may appear normal.
33. Chronic infarct
• Here the residual swelling passes and
gliosis sets in.
• Finally it appears as a region of low
density with negative mass effect.
• Sometimes, cortical mineralisation can
be seen as hyperdense areas.
34. CT perfusion
■ Allows to identify both the core of infarct and the penumbra.
■ The following parameters are used for its identification:
Cerebral blood volume(CBV)
Cerebral blood flow(CBF)
Mean transit time(MTT)
Time to peak (TTP)