...
Parametric Mapping is a way to measure relaxation time for longitudinal and transverse relaxation time along with extracellular volume. The Native T1 mapping or longitudinal (T1) relaxation time is the time constant which determines the rate at which excited protons return to equilibrium. It is a measure of the time taken for spinning protons to realign with the external magnetic field. The Native T2 mapping or transverse (T2) relaxation time constant which determines the rate at which excited protons reach equilibrium or go out of phase with each other. It is a measure of the time taken for spinning protons to lose phase coherence among the nuclei spinning perpendicular to the main field. The term "native" means contrast niave in this context. the T2 measurement is only done prior to contrast.
...