Lecture 5 - CT Flashcards Preview

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Flashcards in Lecture 5 - CT Deck (22):
1

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.

2

Problems with CT?

- exposure to radiation
- not good at distinguishing between white and grey matter.

3

Describe the colours seen in CT.

bone/hard substances = white

black = air

4

What is the stripy look in CT?

movement artefact

5

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

6

How much csf is in the body?

120 ml

7

What are the 5 ways mass effect can be seen, and can show up on a CT?

Blood can be very bad.

Blood
Cisterns
Brain
Ventricles
Bone

8

What brain structure is inside a pocket in the skull?

Pituitary gland.

it rips out if you take the brain out


anterior

9

What are cisterms

" Cisterns are areas in the subarachnoid space which widen to form larger CSF collections.

10

What are the 4 cisterns from sagittal view

- Suprasellar Cistern
- Quadrigeminal Cistern
- Peripontine Cistern
- Infrapontine Cistern

11

What are the cisterns when viewed at high midbrain level

- sylvian cystern
- quadrigeminal cistern
- interhemispheric cistern

12

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)

13

How does blood appear on CT?

dense = acute, once it clots. = white.
isodense at 1 week
hypodense (less dense, darker) at 2 weeks

14

What is an epidural haematoma

- due to haemorrhage between dura and skull.
- lens shaped due to sutures
- tear to meningeal artery

15

Describe a subdural haematoma

- sickle-shaped
- crosses sutures, but not the midline.
- acute subdural haematoma marker for severe head injury
- chronically, it is slow venous bleed and well tolerated
-

16

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

17

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

18

What is an intraventricular/intraparenchymal haemorrhage

bleeding within the brain parenchyma

19

What are the four main cisterns

- circummesencephalic
-suprasellar
-quadrigeminal
-sylvian

20

What are the two key questions when looking at cisterns?

- is there blood
- are they open?

21

Why is intracranial air bad?

it is effectively a lesion, because it can't get out.

22

What is the ex-vacuo phenmenon?

also known as compensatory enlargement of the CSF spaces, is a term used to describe the increase in the volume of CSF, characterised on images as an enlargement of cerebral ventricles and subarachnoid spaces, caused by encephalic volume loss.