A state of balance that exists between two opposing forces or divergent forms of influence.

In fast imaging sequences driven equilibrium sensitizes the sequence to variations in T2. This MRI technique turns transverse magnetization Mxy to the longitudinal axis using a pulse rather than waiting for T1 relaxation.
The first two pulses form a spin echo and, at the peak of the echo, a second 90° pulse returns the magnetization to the z-axis in preparation for a fresh sequence. In the absence of T2 relaxation, then all the magnetization can be returned to the z-axis. Otherwise, T2 signal loss during the sequence will reduce the final z-magnetization.
The advantage of this sequence type is, that both longitudinal and also transverse magnetization are back to equilibrium in a shorter amount of time. Therefore, contrast and signal can be increased while using a shorter TR. This pulse type can be applied to other sequences like FSE, GE or IR.

Sequences with driven equilibrium:
Driven Equilibrium Fast Gradient Recalled acquisition in the steady state - DE FGR,
Driven Equilibrium Fourier Transformation - DEFT,
Driven Equilibrium magnetization preparation - DE prep,
Driven Equilibrium Fast Spin Echo - DE FSE.

A state in which all parts of a system are at the same effective temperature, in particular where the relative alignment of the spins with the magnetic field is determined solely by the thermal energy of the system (in which case the relative numbers of spins with different alignments will be given by the Boltzmann distribution).

(DE FSE) A fast spin echo sequence with application of a pulse, which sensitizes the sequence to variations in T2.

(DEFT) This sequence enhances fluid signal by using a 'tip-up' pulse following a spin echo train.
See Driven Equilibrium and Fourier Transformation Imaging.