Neuro Imaging Flashcards
what are the useful landmarks for imaging the brain
Lateral fissure
Central sulcus
Parietal-occipital fissure
Tentorium cerebelli
what does the frontal lobe do
executing behaviour
Motor cortex- direct control of voluntary muscles via the brainstem and cord
Pre frontal cortex executive function;planning and executing complex behaviour
what two cortex are in the frontal lobe
motor cortex
pre-frontal cortex
what does the motor cortex contain
homunculus
what’s the difference between pre-central gyrus and post central gyrus
pre central gyrus – has the primary motor cortex
Post central gyrus – has the primary somatosensory cortex
what does the parietal lobe do
Integration of sensory information
Primary somatosensory cortex post central gyrus and
Visuospatial processing
Complex sensory processing
what are the black spaces in the Brian
CSF
what happens if you have a lesions anteriorly
effects motor function
what happens if you have a lesions posteriorly
effects sensory function
what does the temporal lobe do
Auditory perception,
language, speech, memory, emotional response
what does the occipital lobe do
Primary visual cortex
describe an MRI photo of the optic pathway
MRI scan through the orbits
Can see the globes and lens – lens is dark - doesn’t contain so much free water
Coming of the back of the globe you can see the optic nerev can see the CSF nerve sheath around it
Goes through a bony canal
Can see optic chiasm
Can see the optic radiations that it gives of
where is the corpus callosum
it sits on top of the lateral ventricle
what does the cerebellum do
Motor control
Coordination
Posture/balance
Equilibrium
what does the brainstem have in it
cranial nerve nuclei 3-12 and the white matter tracts
what is the largest cranial nerve (not the longest)
trigeminal nerve
what are the imaging options
Skull x ray
computerised tomography
MRI
when is a Skull X ray used
Obsolete
Depressed skull # or penetrating injury only
when is CT used
Mainstay in acute situation
Perfusion information
When is MRI used
Occasionally acutely
Functional applicn/perfusion/spectroscopy
How does CT image
Whole body t 20-30 seconds
Produces over 1000 slices in this time frame
Can image soft tissue
when is absorbed in a CT
bone is absorbed therefore it is white whereas air is not
describe colours on a CT scan
Air
- 1000
very black
Fat -100 black
Water 0 dark grey
Brain +40 grey
Blood +90 white
I Contrast +100 white
Bone +1000 very white
what scan can you see an haemorrhage on
CT
what vessels does the subarachnoid space contain
Intracerebral
how do you identify an anyerusm
use a CT angiography
how does an angiography work
Feel the blood vessels with contrast medium that contains iodine so they show up on the CT scan
100mls of contrast
Wait for it to go up the brain into the aorta and carotid artery
Gets a picture of the arteries and not the veins
Get a picture of the circle of willis
Anneruysms form where the areas branch of
what is stroke
Loss of arterial supply-
what is ischaemia
irreversible infarction of brain tissue
How do you treat aneurysms
Treat aneurysms – clip or coil - put a femoral cather in the groin and then a thin wire and then pack the aneryrms with coils until the whole thing is packed with coils and then there is no blood flow to that area
what are the advantages of CT
Excellent bone detail
Good for blood + Ca +
Limited soft tissue detail
Vascular/perfusion-3D
what are the disadvantages of CT
X-ray dose
Limited soft tissue resolution
How does an MRI machine work
1.5 Tesla static magnetic field
Apply an RF pulse via a coil - all H+ spin, stop the RF pulse
- Relaxation of H+
Apply magnetic gradients allows for spatial resolution
what are the possible RF pulse sequences
T1 and T2
H+ behave differently depending on…
H+ behave differently depending on their surroundings
=tissue characterisation
what cannot go in the scanner
any magnetic materials
what is the difference between T1 and T2
T2 weighted – CSF is white
T1 WEIGHTED – CSF is black
what is T2 sensitivity to
T2 sensitive to pathology
tumours inflammation infection ischaemia scarring
High sensitivity
Low specificity
what is T1 sensitive to and describe T1
better anatomy
less sensitive to pathology
Sensitive to haemorrhage
(not hyperacute)
Identify fat
Useful with contrast agent
GADOLINIUM
what does gadolinium IV do
Gadolinium-IV alters the T1
Relax time
Does not cross an intact
blood brain barrier
Infection
Infarction
Tumour
Inflammation- acute
what can infect the brain
Bacterial meningitis usually not seen on imaging
TB meningitis - severe inflammation / thickening of meninges around the basal cisterns
what does DWI do
Shows areas of restricted water motion
- Dying cells- cytotoxic oedema- infarction
- Abscesses containing pus ( not TB)
what does tractogrpahy - MR do
- follows the white matter tracts of the brain
what are the advantages of MRI
- Excellent characterisation of lesions
- Imaging in any plane (axial, coronal, sagittal)
- No radiation
what are the disadvantages of MRI
- Prolonged scanning time
- Strong magnetic field -1.5 T or 3T
Compare CT to MRI
CT Quick Easily available 1st line Acute trauma & stroke and blood Radiation Perfusion
MRI Time consuming Multiplanar Resolution better Strong Magnetic field No radiation Functional Spectroscopic
