The uptake of Gd-chelates in tissues causes T1, and to a lesser extent T2, to shorten dramatically; this makes lesions with Gd-chelate uptake bright on T1-weighted sequences because with shorter T1 values have higher signal.
Unlike T2, the stronger B0, the longer T1.
The spin-echo pulse sequence consists of a 90 Pulse followed by a 180 Pulse followed an equal time later by signal collection.
The two user selectable delay times in spin-echo imaging are the sequence repetition time, TR, and the echo time, TE.
TR controls the T1-weihting, while TE controls the T2-weighting of the spin-echo pulse sequence.
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