Spin-echo: What is the main purpose of the 180° RF pulse in a spin-echo sequence?

Spin-echo: The time taken to rephase after the 180° RF rephasing pulse equals the time to dephase when the 90° RF excitation pulse is withdrawn. This time is called :

 GRE pulse sequences part II:What distinguishes SE-EPI from GE-EPI?

 Spin-echo :What parameter directly influences how many echoes are collected per TR in TSE?

Spin-echo pulse sequences: What additional benefit does triple IR provide over double IR?

GRE weightings:What is the purpose of using a short TE in T1-weighted GRE imaging?

GRE pulse sequences part II:Why is TR considered infinite in single-shot EPI?

Critical Thinking: Which parameter is used to define the time between the initial 180-degree pulse and the excitation pulse in an inversion recovery sequence?

GRE pulse sequences part II:Why does phase-direction chemical shift appear in EPI?

 GRE pulse sequences part I:Why is SNR lower in 2D coherent GRE sequences?