Neuroimaging

Question 1

what uses of brain imaging are there

Answer 1

locating cysts and tumours
oedema, haemorrhage
identify stroke effects

some show structure, function, or both

Question 2

what factors should you consider when choosing neuroimaging

Answer 2

availability
cost
practicality
side effects

Question 3

what does ct stand for

Answer 3

computerised tomography

Question 4

how does ct work

Answer 4

uses x-ray and a computer

Question 5

advantages and disadv of ct

Answer 5

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

disadv:
ionising radiation- damage nucleus and bone

Question 6

what is radiation measured in

Answer 6

Sievert (Sv)
therefore can calculate radiation risk

Question 7

what is radiation risk factor

Answer 7

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

0.05% per mSv

Question 8

what is good about photon-counting ct

Answer 8

reduce radiation
better resolution
safer

Question 9

what planes can ct be used
what is the view

Answer 9

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

Question 10

what is the scale of ct

Answer 10

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

Question 11

what is MRI reliant on

Answer 11

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

Question 12

how does mri work

Answer 12

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

Question 13

why can’t you scan eyes only in MRI

Answer 13

because of the heating effect, dangerous

Question 14

what does the Rf pulse do in MRI

Answer 14

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

Question 15

what planes can mri do

Answer 15

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

Question 16

What three properties of tissues affect contrast

Answer 16

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

Question 17

what is a pulse sequence

Answer 17

series of RF and magnetic field applications to create contrast

Question 18

what is t-1 weighted image good for

Answer 18

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

Question 19

what is t2 wighted image good for

Answer 19

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

Question 20

what is magnetic resonance angiography

Answer 20

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

Question 21

when to not use contrast agent

Answer 21

if allergies
kidney disease might be hard to eliminate the contrast

Question 22

which angiographies do not require contrast agent

Answer 22

inflow angiography
phase-contrast angiogprahy

Question 23

what are contrast agents

Answer 23

liquid injected into vessels to make them visible
plus oedema

Question 24

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

Answer 24

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

Question 25

what do positive contrast agents do, give an example

Answer 25

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

Question 26

what do negative contrast agents do

Answer 26

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

Question 27

what is diffusion weighted imaging DWI dependant on

Answer 27

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

Question 28

how do DWI work with regards to water molecules

Answer 28

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

Question 29

what is the apparent diffusion coefficient ADC

Answer 29

measure of the magnitude of diffusion of water molecules within tissue determine age of infarct it is the OPPOSITE of DWI

Question 30

what is tractography

Answer 30

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

Question 31

what is fMRI

Answer 31

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

Question 32

what are the disadv of mri

Answer 32

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

Question 33

what is SPECT and PET

Answer 33

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

Question 34

What is the system for interpreting scans

Answer 34

ABC'S

Question 35

What are the ABCs

Answer 35

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

Question 36

can you see bones on mri

Answer 36

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

Question 37

what does a subdural heamatoma look like

Answer 37

crescentric semi-lunar blood collection between dura and arachnoid matter tear in bridging veins alcoholics and elderly are prone

Question 38

what does an epidural hematoma look like

Answer 38

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

Question 39

what doe s a subarachnoid hemorrhage look luke

Answer 39

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

Question 40

what does intracerebral hemorrhage look like

Answer 40

blood in parenchyma and ventricles hypertensive vasculopathy territory of PENETRATOR ARTERIES

Question 41

pay more attention to bones or soft tissue in ct scans

Answer 41

BONES