Glossary Terms  Home

L

Laboratory Frame

The normal reference frame that is aligned with the magnetic field of the scanner.

Larmor Frequency

The resonant frequency of a spin within a magnetic field of a given strength. It defines the frequency of electromagnetic radiation needed during excitation to make spins change to a high-energy state, as well as the frequency emitted by spins when they return to the low-energy state.

Least-Squares Error

A commonly used cost function, the sum of the squared residuals.

Localization of Function

The idea that the brain may have distinct regions that support particular mental processes.

Longitudinal

Parallel to the main magnetic field, or z-direction, of the scanner (into the bore).

Longitudinal relaxation (or spin-lattice relaxation)

The recovery of the net magnetization along the longitudinal direction as spins return to the parallel state.