Flashcards in Lecture 5 - CT Deck (22):
What is CT?
A radiological technique based on x-ray, which measures the density of tissue. It shoots an array of beams at many angles of the brain.
It cannot generate a 3D image.
Problems with CT?
- exposure to radiation
- not good at distinguishing between white and grey matter.
Describe the colours seen in CT.
bone/hard substances = white
black = air
What is the stripy look in CT?
Advantages of CT?
" Quick - 5 to 10 minutes
" Cost effective
" Superior for visualising fresh haemorrhage.
" Preferred technique for patients with head trauma or suspecter intracranial haemorrhage
" Used in emergency settings
How much csf is in the body?
What are the 5 ways mass effect can be seen, and can show up on a CT?
Blood can be very bad.
What brain structure is inside a pocket in the skull?
it rips out if you take the brain out
What are cisterms
" Cisterns are areas in the subarachnoid space which widen to form larger CSF collections.
What are the 4 cisterns from sagittal view
- Suprasellar Cistern
- Quadrigeminal Cistern
- Peripontine Cistern
- Infrapontine Cistern
What are the cisterns when viewed at high midbrain level
- sylvian cystern
- quadrigeminal cistern
- interhemispheric cistern
Describe the flow of CSF in production
lateral ventricle choroid plexus --> intraventricular foramen (foramen monro) --> 3rd ventricle --> cerebral aqueduct --> 4th ventricle --> median and lateral aperature --> down into subdural space to lumbar system --> back up to 4th ventricle --> draining by the superior sagittal sinuses (arachnoid villi)
How does blood appear on CT?
dense = acute, once it clots. = white.
isodense at 1 week
hypodense (less dense, darker) at 2 weeks
What is an epidural haematoma
- due to haemorrhage between dura and skull.
- lens shaped due to sutures
- tear to meningeal artery
Describe a subdural haematoma
- crosses sutures, but not the midline.
- acute subdural haematoma marker for severe head injury
- chronically, it is slow venous bleed and well tolerated
Describe a subaranoid haemorrhage
- usually due to the bursting of an aneurysm - an outpouching of of the vessel wall
- usually occurs in the circle of willis
"worst headache ever"
- blood in cisterns and cortical gyral surface
Describe CT for subarachnoid haemorrhage
clearest the sooner it is to the event
best 0-12 hrs.
90-95% - 24 hours
80% - 3 days
50% - 1 week
30% - 2 weeks
What is an intraventricular/intraparenchymal haemorrhage
bleeding within the brain parenchyma
What are the four main cisterns
What are the two key questions when looking at cisterns?
- is there blood
- are they open?
Why is intracranial air bad?
it is effectively a lesion, because it can't get out.