Brain imaging Flashcards
Hypodense lesion with ring enhancement (increased radio-opacity) on contrast CT
Suggestive of abscess (central necrosis and peripheral inflammation - increased vascularisation = increased enhancement on contrast)
CT head.
a) Normal calcified structures in the brain
b) Calcified structures appear what colour on CT?
c) Acute bleed appears what colour on CT?
d) How to view a skull fracture on CT head?
a) Pineal gland, choroid plexus (in ventricles)
b) White
c) White
d) Bone window (rather than brain window)
Loss of grey-white matter differentiation.
a) typical of…?
b) which itself may be caused by…?
a) Oedema
b) Hypoxia (cardiac arrest), infarction
Interpreting CT head
blood, bone, symmetry
Blood - hyperdense (WHITE) lesions; look at shape of bleed (convex, concave, death star)
- old blood is darker
Bone - skull fracture
Symmetry - tissue ischaemia, sulcal effacement, ventricular compression / midline shift (mass effect)
Hounsfield units (HU).
a) What are they?
b) Colour on CT relative to HU value
c) Give the HU for:
- Air
- Fat
- Water
- CSF
- White matter
- Grey matter
- Fresh blood
- Old blood
- Bone/ calcification
a) Measure of radiodensity of matter (used in CT)
b) Very negative = black (e.g. air); very positive = white (e.g. bone)
c) Air = -1000, Fat = -70, Water = 0, CSF = 10, White matter = 30, Grey matter = 45, Fresh blood = 100, Old blood = 20, Bone/calcification = 1000
What would be the typical appearance of the following on CT head:
a) Acute intracerebral haemorrhage
b) Acute extradural haemorrhage
c) Subacute subdural haemorrhage
d) Acute intracerebral infarct
a) Area of high density (fresh blood - white), possibly surrounded by area of lower density (oedema - grey)
b) Convex area of high density between the skull and the cortex
c) Concave area of low-medium density between the skull and the cortex
d) May have area of low density (oedema) in the territory of a major vessel
