Neuroradiology

Question 1

what would indicate the need for brain imaging?

Answer 1

headache / raised ICP
seizure
weakness
stroke
trauma
LOC / neurological deficit 
post op monitoring

Question 2

what are the advantages of CT scans?

Answer 2

excellent bony details / spatial resolution
fast
compatible with emergency / ICU equipment

Question 3

what are the disadvantages of CT scans?

Answer 3

only sensitive to blood early in acute injury
poor soft tissue detail
grey and white matter show little difference in density
high radiation dose

Question 4

what shows up bright and what shows up dark on CT imaging?

Answer 4

bright = more dense (bone, any metal implants)

dark = less dense (air)

Question 5

what are the advantages of MRI scanning?

Answer 5

excellent contrast / soft tissue resolution
excellent depiction of anatomy
good for visualising marrow and cord pathologies
multiplanar

Question 6

what are the disadvantages of MRI scanning?

Answer 6

less bony detail / spatial resolution
not compatible with pacemakers and many implants (magnet)
not compatible with ICU / emergency equipments
not as quick as CT
patient co-operation required

Question 7

why are different MRI sequences used and give some examples of commonly used sequences?

Answer 7

multiple sets of MRI images are taken at the one time (eg T1, T2 etc)

different sequences use different combinations of technical parameters
each sequence is unique and gives different information

Question 8

what components of the brain enhance as “hyperintense” on T1-weighted MRI imaging?

Answer 8

3Fs and 4Ms

• fat
• slow flow (eg partially blocked vessel)
• fluid (containing protein)
• melanin
• methaemoglobin (blood)
• mineralisation (Ca / Mg etc)
• magnevist (gadolinium contrast)

Question 9

what components of the brain appear as “hypointense” on T1-weighted MRI imaging?

Answer 9

water 
high flow (eg arteries)

Question 10

what shows up as hyperintense on T2-weighted MRI imaging?

Answer 10

water or any fluid collections - oedema, demyelination, gliosis, some tumours

fat (this can be suppressed by design)

Question 11

what shows up as hypointense on T2-weighted imaging?

Answer 11

some blood products (subacute haematoma)
mineral deposition
high flow (eg arteries)

Question 12

what are some of the basic sequences used in MRI and why are they used?

Answer 12

spin echo: T1, T2, FLAIR (type of T2 where free water = suppressed eg ventricles)

T2* (gradient echo) = highlights blood

T1 (3D) = volumetric

contrast enhancement = increases density of objects needing to be visualised

Question 13

any structure within the blood-brain barrier resists contrast - true or false?

Answer 13

true

Question 14

why is gadolinium used as MRI contrast?

Answer 14

patients not allergic to it like iodine CT contrast

has many unpaired electrons which cause an MRI signal to be picked up

Question 15

what pathologies would you expect to see on brain imaging?

Answer 15

infarcts
haemorrhage
vascular anomalies

Question 16

describe how a thrombus in a blood vessel of the brain will appear on CT?

Answer 16

bright

Question 17

why is MRI more sensitive to diagnosing stroke?

Answer 17

grey and white matter differentiation on CT not good enough to outline small infarcts

Question 18

why is CT completed first over MRI on presentation of stroke?

Answer 18

faster

gives indication of infarct vs haemorrhage and whether pt should receive thrombolysis

Question 19

an intraparenchymal bleed can break through to the ventricles - true or false?

Answer 19

true

Question 20

what is a susceptibility weighted imagine (SWI) MRI sequence used to look for?

Answer 20

sensitive to venous blood

especially old venous blood that cannot be picked up on CT (looking for haemorrhage and iron storage)

Question 21

what usually causes a subarachnoid haemorrhage?

Answer 21

aneurysm

Question 22

how long after an IV injection of CT contrast does it show up in arteries?

Answer 22

8-10s

Question 23

in what type of imaging is CT contrast used?

Answer 23

CT angiogram

Question 24

why are arteries and veins easy to distinguish in the brain?

Answer 24

separated anatomically so are distinct from each other in imaging

Question 25

what imaging modality is used for aneurysm follow up?

Answer 25

MRI

Question 26

describe how a cavernoma (type of vascular anomaly) appears on imaging?

Answer 26

popcorn appearance | Ca2+ present

Question 27

MRI is more sensitive than CT for small aneurysms - true or false?

Answer 27

false - CT more sensitive due to use of contrast, MRI angiography often doesnt use contrast

Question 28

x-rays are still routinely completed in trauma cases - true or false?

Answer 28

false

Question 29

what modality of imaging is sensitive for bone injury and acute bleeding in trauma?

Answer 29

CT

Question 30

what structures in the brain are rather immobile if a bleed occurs and compresses them?

Answer 30

falx cerebri - quite stiff and wont initially move much with internal bleed

Question 31

what is a brain contusion and where does it usually occur?

Answer 31

part of many traumatic brain injuries bruise of the brain tissue associated with multiple microhaemorrhages usually occurs on underside of frontal lobe

Question 32

describe the difference between the appearance of an extradural and subdural haematoma on imaging?

Answer 32

extradural - biconvex, lemon-shaped and do not cross sutures subdural - concave, banana-shaped, crescentic, can cross sutures

Question 33

what is the difference in location between intra and extra-axial neoplastic processes?

Answer 33

extra-axial = outwith brain parenchyma intra-axial = within brain parenchyma

Question 34

intra-axial neoplastic processes are more likely to be benign - true or false?

Answer 34

false extra-axial = more often benign intra-axial = mostly malignant

Question 35

give examples of benign extra-axial tumours?

Answer 35

meningioma pituitary adenoma dermoid / epidermoid acoustic schwannoma

Question 36

give examples of intra-axial tumours?

Answer 36

glioma glioblastoma metastases

Question 37

what is a chiari malformation?

Answer 37

congenital problem lowest part of the back of the brain extends into spinal canal can put pressure on brainstem, spinal cord and obstruct the flow of fluid

Question 38

what is cortical dysplasia?

Answer 38

migration of sensory and motor information to the outer cortex during development is impaired grey and white matter seem "blurred" in the dysplastic areas

Question 39

what is polymicrogyria?

Answer 39

the brain developed too many folds (gyri and sulci) | the folds are unusually small

Question 40

what is schizencephaly, how does it look on radiology and what can this cause?

Answer 40

slits across grey and white matter from outer cerebral cortex clefts in both hemispheres commonly have developmental delays, delays in speech and language, seizures and problems with brain-spinal cord communication

Question 41

how does demyelination usually affect the brain?

Answer 41

occurs in white matter surrounding small veins | demyelination occurs perpendicular to corpus callosum

Question 42

what type of MRI imaging would you use to visualise demyelination of white matter?

Answer 42

T2 and FLAIR

Question 43

where in the brain does herpes encephalitis normally occur and what does it cause in these areas?

Answer 43

temporal lobe and limbic system swollen neurones seen

Question 44

what is CJD and what are the symptoms?

Answer 44

spongiform encephalopathy of brain - degenerative early symptoms = memory problems, behavioural changes, poor co-ordination, visual disturbances later symptoms = dementia, involuntary movements, coma