Ch2 - MRI Scanners

Question 1

field uniformity

Answer 1

in MRI: uniform magnetic field that has constant strength throughout a wide region near the center of the scanner

Question 2

homogeneity

Answer 2

uniformity over space

Question 3

field strenght

Answer 3

magnitude of the static magnetic field generated by a scanner (in Teslas)

Question 4

superconducting electromagnets

Answer 4

set of wires made of metal alloys that have no resistance to electricity at very low temperatures
- cooling electromagnet to near absolute 0 allows to generate strong magnetic field with minimal electrical power

Question 5

cryogens

Answer 5

cooling agents used to reduce the temp. of the electromagnetic coils in MRI scanner

Question 6

radiofrequency coils

Answer 6

electromagnetic coils used to generate and receive energy at the sample’s resonant frequency
- in MRI typically radiofrequency

Question 7

excitation

Answer 7

process of sending electromagnetic energy to a sample at its resonant frequency
- application of excitation pulse to spin system causes some of the spins to change from low energy state to high energy state

Question 8

reception

Answer 8

process of receiving electromagnetic energy emitted by a sample at its resonant frequency ( = detection)
- nuclei return to low energy state following the cessation of the excitation pulse

Question 9

MR signal

Answer 9

current measured in a detector coil following excitatin and reception