TR and T1-weighting
If TR is short and if tissue A has a longer T1 than tissue B, the longitudinal magnetization of tissue A will recover less than the longitudinal magnetization of tissue B.
Thus, the transverse magnetization amplitude of tissue B will be higher after the next excitation.
In the graphs below :
- The first part of the following curves corresponds to the longitudinal magnetization recovery after the first excitation.
- TR is the delay between excitations.
- The second part corresponds to the transverse magnetization decay after the second excitation.
- The MR signal is acquired at time TE after excitation.
By setting the TR to short values, tissue contrast will depend on differences in longitudinal magnetization recovery (T1).