Research MRI and networks

Question 1

T1 can show

Answer 1

gadolineum (recent lesions), sever destruction

Question 2

T2 can show

Answer 2

lesions in MS, water, the loss of membranes

Question 3

what is FLAIR?

Answer 3

a T2 with suppressed CSF. therefore the contrast is easier to see.

Question 4

what is DIR

Answer 4

FLAIR with white matter suppression, even more contrast.

Question 5

zijn deze technieken qualitative or quantitative

Answer 5

qualitative -> is there a lesion or not? zeggen niks over de severity of lesions (quantitative)

Question 6

main T… for tumors?

Answer 6

T1

Question 7

main T.. for atrophy?

Answer 7

T1

Question 8

difference imaging in clinic and research

Answer 8

in the clinic you need to make fast images, in research detail is important

Question 9

axal is… radial is…

Answer 9

lang, korte lijn

Question 10

wat meet je met een DTI (of diffused tensor imaging/diffused weighted imaging)

Answer 10

how the free weighted water moves

Question 11

bij MS en DTI:

Answer 11

bij MS is het myeline op bepaalde plekken weg. hierdoor kan het water meer freely bewegen. de patient heeft dan een lagere fractional anisotrophy.

Question 12

waardoor increased axial diffusion?

Answer 12

bc of atrophy -> more extracellular fluids and then higher axial diffusion

Question 13

increased radial diffusion because of…

Answer 13

demyelination. that leads to anisotrophic diffusion (does not move in the same direction)

Question 14

What can you measure with DTI?

Answer 14

subtle damage, quantitative in research

Question 15

what is structural connectivity

Answer 15

to quantify the number of axons between two brain regions.

Question 16

hoe kan je structural connectivity krijgen

Answer 16

dmv een DTI

Question 17

deterministic tractography

Answer 17

you measure all bundles from one axon, and then show the mean direction in which they go. you show the strongest pathway from one region to another (but then you also miss a lot).

Question 18

probabilistic tractography

Answer 18

you assign a probability that it will go in that way. you get more different pathways, and keep that information (bij deterministic vallen de zwakke pathways weg)

Question 19

BOLD response

Answer 19

more neuronal activity is more metabolism is more oxygen use

Question 20

wat voor research kan je doen met een functional mri

Answer 20

kijken naar plaatjes waarvan je dingen herkent. dan moet je ook plaatjes laten zien van andere aspecten, zodat alleen de recognition overblijft.

Question 21

functional connectivity

Answer 21

kijken of brain regions met elkaar in verbinding staan. -> correlation

Question 22

difference in centrality dynamics patients vs healthy

Answer 22

healthy kan goed switchen tussen stages of focus and default mode. bij cognitive impairment zijn deze tegelijkertijd aanwezig.

Question 23

andere naam voor connection

Answer 23

edges

Question 24

what kind of distribution does the human brain have?

Answer 24

power law distribution -> many nodes with few connections, few nodes with many connections

Question 25

weighted graph

Answer 25

number of connections, meer connections is een dikkere lijn (DTI!)

Question 26

wat is beter: lange of korte pathlenght?

Answer 26

korte

Question 27

clustering coefficient

Answer 27

• how many of my friends are friends? dus hoeveel neighbours zijn ook connected met elkaar?
• aantal connected neighbours / aantal neighbours

Question 28

small world network

Answer 28

een balans tussen korte pathways maar wel clusters

Question 29

wat is een hub?

Answer 29

heeft een high degree of connections

Question 30

twee verschillende soorten hubs

Answer 30

• een connector hub connects zijn eigen cluster aan een andere cluster.
• een provincial hub zit midden in een cluster, en is dus aan veel binnen zijn eigen cluster verbonden

Question 31

minimum spanning tree

Answer 31

the path of all higher connected hubs, that can reach all nodes

Question 32

bij MS patients is de minimum spanning tree..

Answer 32

een soort lijn, elke node is maar connected aan een andere node

Question 33

wat is hier dan het verschil?

Answer 33

de nodes zijn niet veranderd!!! maar de connections tussen de nodes wel!

Question 34

rich club

Answer 34

highly connected nodes that are also connected to each other.

Question 35

what 4 factors determine centrality?

Answer 35

• degree connectivity -> how many connections
• closeness centrality -> distance to all other nodes
• betweenness centrality -> number of shortest paths that go throught the node
• degree prestige -> how many high-quality connections?

Question 36

what is happening with the default mode network in cognitive impairment

Answer 36

more present, centrality of the default network increases.

Question 37

what happens in MS with the connections?

Answer 37

less connections, therefore simpler. it takes longer to get the information where it needs to be.

Question 38

what does DTI measure? and what kind of connectivity do you therefore measure?

Answer 38

NUMBER OF CONNECTIONS, structural connectivity

Question 39

what does functional connectivity measure

Answer 39

the degree of similarity between two signals

Question 40

small world measures

Answer 40

pathlength and connectivity

Question 41

static connectivity

Answer 41

connectivity across entire scan

Question 42

dynamic connectivity

Answer 42

connectivity varies over time