Synopsis

Relaxation time constant T1, T2, and T1rho are important parameters to characterize tissue properties. The spatial and temporary variation of the magnetic field due to dipolar coupling and molecular tumbling is a main source of the observed relaxation effect. Relaxation can also be affected by chemical exchange and magnetization transfer effect. These physical processes reflect the metabolites and macromolecules content in tissues. Thus, imaging methods based on the measurements of relaxation time can be used to probe the biochemical properties of tissues.