The spin echo pulse sequence is the most commonly used pulse sequence. The pulse sequence timing can be adjusted to give T1-weighted, Proton or spin density, and T2-weighted images.
Dual echo and multiecho sequences can be used to obtain both proton density and T2-weighted images simultaneously.
The two variables of interest in spin echo sequences is the repetition time (TR) and the echo time (TE). All spin echo sequences include a slice selective 90 degree pulse followed by one or more 180 degree refocusing pulses.