The flipped longitudinal polarization sequence

Abstract 

By flipping the longitudinal magnetization with a chain of 180° pulses it is possible to effectively restore the effects of relaxation so that the same longitudinal magnetization is periodically recovered. The pulse sequence for achieving this, called Flipped LOngitudinal Polarization (FLOP), can be incorporated into any pulse sequence whenever it is desired to stop the attenuation in longitudinal magnetization caused by relaxation. We illustrate its use for fast, single-shot measurements of the longitudinal relaxation time and for three-dimensional T₁ mapping.

Keywords: Longitudinal relaxation, T₁–T₂ relaxation spectra, Inversion recovery, T₁ mapping, Steady state, Spin temperature