The amplitude of the gradient field (measured in mT/m).

One of three linear magnetization waveforms superimposed on the main magnetic field at specific times within a pulse sequence to select the imaging region or provide necessary spatial localization information. A magnetic gradient is defined as the amount and direction of the linear rate of change of the magnetic field in space.

Magnetic field gradient pulse used to create spatial variation of phase of transverse magnetization. For example, it may be applied prior to signal detection in the presence of a magnetic field gradient with opposite polarity (or of the same polarity if separated by a refocusing RF pulse) so that the resulting gradient echo signal will represent a more complete sampling of the Fourier transformation of the desired image.

See also Spoiler Gradient Pulse.

In MRI systems, the gradient amplifier increases the energy of the signal before it reaches the gradient coils, in a way, that the field strength is intense enough to produce the variations in the main magnetic field for localization of the later received signal. Three gradient coils normally require three gradient amplifiers. As all amplifiers, gradient amplifiers produce heat, which requires cooling.

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Magnetic field gradient pulse applied to reverse the spatial variation of phase of transverse magnetization caused by a dephasing gradient. For example, in selective excitation, it is a magnetic field gradient applied for a brief period after a selective excitation pulse, in the opposite direction to the gradient used for the selective excitation. The result of the gradient reversal is a rephasing of the spins (which will have gotten out of phase with each other along the direction of the selection gradient), forming a gradient echo and improving the sensitivity of imaging after the selective excitation process.