MRI 4

Question 1

Slice selection

Answer 1

The combined use of a spatial magnetic field gradient and an electromagnetic pulse to excite spins within a slice.

Question 2

Spatial gradient (G)

Answer 2

A magnetic field whose strength varies systematically over space.

Question 3

Frequency encoding gradient (Gx)

Answer 3

A gradient that is applied during the data acquisition period, so that the spin precession frequencies change over space.

Question 4

Phase encoding gradient (Gy)

Answer 4

A gradient that is applied before the data acquisition period, so that spins accumulate differential phase offsets over space.

Question 5

k-space

Answer 5

A notation scheme used to describe MRI data acquisition. The use of k-space provides a mathematical and conceptual advantages for describing the acquired MR signal in image form.

Question 6

Fourier transform (FT)

Answer 6

A mathematical technique for converting a signal (i.e. changes of intensity over time) into the frequencies that make it up.