saturationrecovery

Saturation recovery is a magnetic resonance technique used to measure the longitudinal relaxation time, T1, of a material. The method involves saturating the longitudinal magnetization with a radiofrequency pulse train so that Mz is brought near zero, followed by a variable delay and a signal readout that probes the recovering magnetization.

The signal recovery is governed by Mz(t) = M0(1 − exp(−t/T1)) for a single-component system, allowing T1 to be extracted by fitting the recovery curve to the observed data. In practice, the initial saturation may be achieved with a train of hard or composite 90-degree pulses, or with partial saturation.

Compared with inversion-recovery methods that invert magnetization and begin from −M0, saturation recovery starts from approximately zero, making it less sensitive to imperfect refocusing and certain pulse errors. It is widely used to generate T1 maps in MRI and to quantify changes in relaxation during contrast-enhanced studies.

Limitations include sensitivity to B1 and B0 inhomogeneities, multi-component tissues where a single T1 is insufficient, and systematic errors in saturation efficiency. Nonetheless, saturation-recovery remains a simple and robust option for rapid T1 assessment and for validating other quantitative MRI techniques.