1st week: 1 Flashcards
Two types of neuroimaging? Used for?
Structural and functional. Structural used for brain anatomy, functional for living, functioning, dynamic brain imaging.
In general, how long does it take to take a functional images? Therefore: … temporal resolution. How detailed are structural imaging techniques? Therefore: … spatial resolution
seconds or fraction of a second High temporal resolution Low spatial resolution
In general, how long does it take to take a structural image? Therefore: … temporal resolution. How detailed are structural imaging techniques? Therefore: … spatial resolution
minutes Low temporal resolution. High spatial resolution.
Phileas Cage is an example of … studies of brain anatomy/function.
Lesional study
Angelo Mosso
Italian physiologist 19th century, tried to weigh brain activity.
Wilhelm Röntgen discovered x-ray 1895.
Why is x-ray difficult to use for brain imaging?
Lack of contarast inside the scull.
Walter Dandy
Ventriculography (/ pneumoencephalography)?
Discovered 1919, used until when?
Safety?
radiography of the ventricles of the brain with the cerebral fluid replaced by air or radiopaque material or labelled with a radionuclide.
Used until 1970s
Risky!!
What was the first real time brain measuring tool?
Discovered recorded human EEG by… , year…?
EEG
Electroencephalogrphy
Hans Berger (DE)
1924
Milestones of EEG:
1934
1953
Nowdays often ombined with fMRI, why?
1934 Epileptic spikes
1953 different stages of sleep
Combined with fMRI to be able to identify whole networks and brain regions involved.
Godfrey Hounsfield 1967 - first commercial ….?
CT - computer tomography
[tomos: slice, section]
CAT
How does it work?
CAT - computer axial tomography
X-ray CT
X-rays from many directions to reconstruct the volume of interest in slices
Active molecule tagged with radioactive tracer. Injected into the body.
What method?
What is emitted from the radioactive substance?
What makes this method expensive?
Positron Emission Tomography PET
GAMMA rays.
Needs a cyclotron close by making the radioactive molecules. (Radioactivity lasts only for ~30 sec.)
Current best technology for structure imaging?
What is diffusion tension imaging?
Magnetic Resonance Imaging MRI
DTI type of MRI, looking at microstructural changes
Arrived mid 90s
Measures changes every couple of sec.
Used often comparing brain activity in rest / task
functional MRI
resting state fMRI / task-based fMRI
Combination of different imaging techniques (like MRI, fMRI and EEG) is called:?
Often includes several … and a few …
(MRI, fMRI)
Multimodulling imaging
Often includes several MRI and a few fMRI
What technique?
Spatial resolution: lowest
Temproral resolution: highest
Tolerance needed: 1/3 low
[Practicality: portable
Price: cheap]
Explain
EEG
Activity measured on a millisecond scale on the surface of the scalp.
Non-invasive
multiple electrodes
Portable and cheap (hat&gel&computer)
What technique?
Spatial resolution: lowest
Temporal resolution: highest
Tolerance needed: 2/3 medium
[Practicality: helmet, helium used for cooling
Price: medium]
Explain
MEG - Magnetoencephalography
Measures magnetic fields
Head in a MEG helmet
Low spatial resolution-doesn’t reach to deep brain areas
High temporal, millisecond-level
tolerance, sticking ones head to a massive helmet-like machine, don’t move
What technique?
Spatial resolution: 3/4 high
Temporal resolution: 1/4 lowest
Tolerance needed: 3/3 highest
Price: most expensive
Measuring based on what brain function?
Explain
PET - Positron Emission Tomography
Measures glucose metabolism
Glucose tagged using radiopharmaceuticals (tolerance highest)
fluorine - 18 (F-18)
fluorodeoxyglucose (FDG)
10-20 sec, mid temporal
whole brain mm scan good spatial
fNIRS?
Based on what?
Spatial resolution: ?
Temporal resolution: ?
Tolerance needed: ?
[Practicality: works well for…
Price: cheapish]
Explain
functional near-infrared spectoscopy
BOLD
Difference between oxy-deoxyhaemoglobin (in colour)
Measures both oxygenation level and blood volume (excess of oxygenated blood after use/brain activity)
Spatial resolution: 2/4 low (surface 5 cm, small amount of sensors)
Temporal resolution: 3/4 high
Tolerance needed: low, suitable for babys
Works well for babies with their thin scull
BOLD?
Used in which techniques?
Based on what?
Blood
Level
Oxygenation
Most used imaging technique.
Based on BOLD
spatial 4/4 highest
temporal 2/4 low
tolerance needed 2/3
fMRI - functional magnetic resonance image
Difference between oxy-deoxyhaemoglobin (in colour)
Measures both oxygenation level and blood volume (excess of oxygenated blood after use/brain activity)
Gives very detailed image
every few seconds, low temporal
tolerance needed medium, noisy
Give examples of indirect brain imaging
Indirect:
fMRI - based on BOLD, magnetic differences between oxy-deoxyhaemoglobin. Oxygenated blood flooding after use.
fNIRS - also based on BOLD colour difference
Direct:
EEG
find the pairs:
diamagnetic
deoxyhaemoglobin (Hhb)
strong magnetic field
weak magnetic field
paramagnetic
oxyhaemoglobin (O2HB)
strong magnetic field:
deoxyhaemoglobin (Hhb) - paramagnetic
close to nothing magnetic field:
oxyhaemoglobin (O2Hb) - diamagnetic
What technique:
1.5 or 3 Tesla [machine]
uses magnetic: ? x earth’s magnetic field
fMRI
30 000 (strong enough to lift up a car)
To check that someone is MR compatible?
Why is this important?
MR - magnetic resonance
Wearing no metal in clothing or body.
Magnetic used in MRI scan is 30 000 stronger than earth’s magnetic field.
What is typically tested using fMRI?
Comparing different stimuli -> activation in different brain areas.
Based on BOLD.
BOLD
Does paramagnetic (magnetic) deoxyhaemoglobin cause the image to get darker or brighter?
Explain
Darker.
Brain activity sips first oxygen in from the nearby environment -> lots of deoxyhaemoglobing, more magnetic perturbation -> initial dip (dark picture)
Followed by overflow of diamagnetic oxyhaemoglobin –> less deoxyhaemoglobin than at rest -> less magnetic perturbation than at rest –> bright colour than t rest
Put in the right order:
raw data
preprocessing
group-level analysis
single subject analysis
raw data
preprocessing
(‘clean up’: remove head movements, breathing, cardiac pulsation etc. increase the signal to noise to ratio)
single subject analysis
(general linear model GLM, fix head size etc to the template, where is the individual brain activity compared to experiment model)
group-level analysis
(compare groups, patients/healthy controls)
