Fig 1. Pulse sequence diagram for a diffusion-weighted acquisition shows that 2 diffusion-sensitizing gradients (dark gray) are added to a spin-echo sequence, 1 before and 1 after the 180° refocusing pulse. The diffusion-weighting factor b depends on the amplitude of the diffusion gradient (G), the duration of each diffusion gradient (), and the interval between the onset of the diffusion gradient before the refocusing pulse and that following the refocusing pulse (). RF indicates radiofrequency pulses; Gz, gradient pulses.