The characteristics of the tissues determines the contrast and brightness of each sequences. The easiest way to differentiate a T1-weighted and T2-weighted image is to look at the CSF. On a T1 image the CSF is dark, while on a T2 image the CSF is bright.
FLAIR sequences can be helpful to visualise inflammation from infections or demyelination as these tissues are bright, however normal CSF fluid is attenuated and remains dark.
Routine structural sequences include: