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Medicine > Neuroimaging > Flashcards

Neuroimaging Flashcards

1
Q

what uses of brain imaging are there

A

locating cysts and tumours
oedema, haemorrhage
identify stroke effects

some show structure, function, or both

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2
Q

what factors should you consider when choosing neuroimaging

A

availability
cost
practicality
side effects

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3
Q

what does ct stand for

A

computerised tomography

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4
Q

how does ct work

A

uses x-ray and a computer

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5
Q

advantages and disadv of ct

A

adv:
fast (0.3 seconds to image, up to 64 slices per rotation/ second)
widely available

disadv:
ionising radiation- damage nucleus and bone

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6
Q

what is radiation measured in

A

Sievert (Sv)
therefore can calculate radiation risk

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7
Q

what is radiation risk factor

A

total lifetime risk of radiation-induced fatal cancer for the general population

0.05% per mSv

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8
Q

what is good about photon-counting ct

A

reduce radiation
better resolution
safer

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9
Q

what planes can ct be used
what is the view

A

only in axial plane, oblique
can be reconstructed- supraorbitomeatal plane
it is caudal

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10
Q

what is the scale of ct

A

grey scale- white to black
bone - white +1000
air- black -1000
generated by ABSORPTION
poor differentiation for soft tissues

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11
Q

what is MRI reliant on

A

hydrogen atoms- they have a single proton in its atom
they are found in abundance in the body

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12
Q

how does mri work

A

uses a combo of magnetic field and radio waves to produce images
Rf pulse (radio frequency) used in MRI is non-ionising, may cause heating effect

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13
Q

why can’t you scan eyes only in MRI

A

because of the heating effect, dangerous

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14
Q

what does the Rf pulse do in MRI

A

applied to hydrogen nuclei of patient, which flips them to a higher energy state
nuclei return to their resting state when Rf off
receiver measures time and energy until nuclei return to original orientation

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15
Q

what planes can mri do

A

saggital
coronal- LOOKING AT FACE OF PT
axial- FOOT OF THE BED
oblique
ANY PLANE

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16
Q

What three properties of tissues affect contrast

A

T1 time (t1 recovery)
T2 time (t2 decay)
Proton density (pd)

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17
Q

what is a pulse sequence

A

series of RF and magnetic field applications to create contrast

18
Q

what is t-1 weighted image good for

A

anatomy and contrast
- water is dark, grey matter is dark grey, white matter is off-white, fat is white

number 1 priority for radiologist is anatomy

19
Q

what is t2 wighted image good for

A

identifying pathology, inflammtion and oedema
MORE SENSTIVE TO WATER

water is white, white matter is darker than grey matter

WW2 Water is White of t2 images

20
Q

what is magnetic resonance angiography

A

make vessels visible
with or without contrast agent
can over-exaggerate stenoses

21
Q

when to not use contrast agent

A

if allergies
kidney disease might be hard to eliminate the contrast

22
Q

which angiographies do not require contrast agent

A

inflow angiography
phase-contrast angiogprahy

23
Q

what are contrast agents

A

liquid injected into vessels to make them visible
plus oedema

24
Q

what happens in a healthy person vs person w tumour when contrast agent is added

A

healthy- light up vessels
tumour- BBB damaged so contrast seep through , highlight oedema

25
Q

what do positive contrast agents do, give an example

A

produce increase in signal intensity
gadolinium BUT may build up in the body

26
Q

what do negative contrast agents do

A

produce a decrease in signal intensity in affected tissue
contain iron oxide

27
Q

what is diffusion weighted imaging DWI dependant on

A

diffusion of water molecules
it is the standard when you suspect stroke, early detection of ischaemia, infarct, stroke, differentiation of brain tumours and intracranial infections

28
Q

how do DWI work with regards to water molecules

A

if there is a disruption to the blood flow, brain cells run out of atp therefore na/k pump stops functioning and interstitial fluid rushes in and cell swells
then interstitial space narrows, so water molecules have difficulty diffusing
lower diffusion, brighter the image (increased signal intensity).– infarct black

29
Q

what is the apparent diffusion coefficient ADC

A

measure of the magnitude of diffusion of water molecules within tissue

determine age of infarct

it is the OPPOSITE of DWI

30
Q

what is tractography

A

makes white matter tracts, axons visible
see if pathways are going through tumour or tumour is invading tract

31
Q

what is fMRI

A

obtain info on function and structure by visualising cortical activity
DETECTS SUBTLE ALTERATION IN BLOOD FLOOW/OXYGENATION IN RESPONSE TO STIMULI/ ACTIONS

there are limitations

32
Q

what are the disadv of mri

A

cant use for everyone:
-pacemakers, cochlear implants, non-mri compatible heart valves, stents
-foreign bodies (shrapnel)
-claustrophobia
less available as ct, more expensive, need better facilities

v good for soft tissues

33
Q

what is SPECT and PET

A

intravenous contrast agents
show metabolic and biochem function by measuring radiotracer uptakes (glucose) by the tissues- cancer, infection, coronary artery disease, brain disorder
PET offers better spatial resolution, higher diagnostic accuracy, lower patient dosimetry than SPECT but EXPENSIVE

34
Q

What is the system for interpreting scans

A

ABC’S

35
Q

What are the ABCs

A

A- adequacy, alignment, artefact
B- bones, blood, brain
C- CSF-filled spaces (cisterns and ventricles)
S- subcutaneous and surfaces, symmetry

36
Q

can you see bones on mri

A

not directly as need h+ ions, no water in bone
shows other structures around bones, so creates a silhouette

37
Q

what does a subdural heamatoma look like

A

crescentric
semi-lunar

blood collection between dura and arachnoid matter
tear in bridging veins
alcoholics and elderly are prone

38
Q

what does an epidural hematoma look like

A

lens shape
blood between dura and skull
tearing of MIDDLE MENINGEAL ARTERY
adolescents and young adults affected (trauma)

39
Q

what doe s a subarachnoid hemorrhage look luke

A

blood in circle of willis, cisterns, fissures
rupture of BERRY ANEURYSM
polycystic kidney disease is a risk factor

40
Q

what does intracerebral hemorrhage look like

A

blood in parenchyma and ventricles
hypertensive vasculopathy
territory of PENETRATOR ARTERIES

41
Q

pay more attention to bones or soft tissue in ct scans

A

BONES

Medicine (54 decks)

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