MRI

Question 1

Larmor frequency

Answer 1

Resonance frequency of protons, frequencies need to be the same to transport energy (63MHz)

Question 2

T1 relaxation

Answer 2

Atom going back to z-direction, speed depends on tissue (fat 260ms < white mater < grey mater)

Question 3

Reasons for protons to dephase

Answer 3

• Spin-spin interaction (using energy by spinning into eachother)
• inhomogeneities in magnetic field
• magnetic susceptibility (blood or iron interacting)
• chemical shift

Question 4

spin echo sequence

Answer 4

combination of 90 and 180 degree pulses

Question 5

Free induction decay (FID)

Answer 5

coil spins right after 90 degree signal, loses amplitude because of T2 (happens during dead time)

Question 6

TE and TR when T1 contrast is wanted (two different tissues)

Answer 6

short TE, short TR (T2 other way around)

Question 7

Slice selection (how does it work)

Answer 7

Every slice has an unique larmor frequency (spins in feet different than head)

Question 8

Selection of voxel (locating the place in a slice)

Answer 8

Row: different frequencies (x-direction), done by gradient
Collumn: different phases (y direction), turning off gradient or short sprint

Question 9

Amount of repetitions for one slice

Answer 9

number of rows (often 256), frequency encoding only done once

Question 10

K-space

Answer 10

Lower frequencies (contrast) at center, higher frequencies (details) at edges

Question 11

Material used to inject and see certain parts in MRI better

Answer 11

Gadolium (Gd), toxic so saved in molecule which is safe to infject, only dangerous for people with renal problems

Question 12

Acoustic neurinoma

Answer 12

Brughoektumor (goedaardig)

Question 13

Syndrome of rasmussen

Answer 13

inflammantory disease in one side of brain

Question 14

Grey matter

Answer 14

processes and sends information

Question 15

white matter

Answer 15

connect grey matter, interprets sensory information

Question 16

Diffusion tensor imaging DTI

Answer 16

picture of nerves inside the brain, preparation of an operation

Question 17

Functional MRI

Answer 17

see what parts of the brain are active during certain tasks, preparation of an operation

Question 18

MR-angiography

Answer 18

image of vessels by using contrast agents

Question 19

Choline peak in spectroscopy

Answer 19

tumor

Question 20

Spacial gradient field

Answer 20

how fast magnetic field is increasing

Question 21

effects of mri in humans

Answer 21

• dizziness
• metal taste

Question 22

Specific absorption rate (SAR)

Answer 22

max power to be used on a patient by law: whole body is 4W/kg (max 15 min)