Figure 2.

(a): A segment of a Steer-PROP sequence illustrating steering gradient design for the special case of N = 3. (b): k-Space trajectory of the sequence segment in (a). G_x and G_y are used to denote readout (or X) and phase-encoding (or Y) gradients in a conventional sequence. G_xd1, G_xd2, G_yd1 and G_yd2 are the diffusion gradients on the X and Y axes as indicated. G_pe is a phase-encoding pulse for the spin echo, G_xro1 is the readout gradient pulse corresponding to the 1^st gradient echo, G_xro2 and G_yro2 are the X and Y components corresponding to the 2^nd gradient echo, G_xro3 and G_yro3 are the X and Y components corresponding to the 3^rd gradient echo, G_xθ, G_yθ, G_x2θ, and G_y2θ are the steering gradient pulses, and G_xr and G_yr are the phase-rewinding pulses. The three k-space lines sampled by the three gradient echoes are illustrated as the white lines (denoted as b1, b2, and b3, respectively) in their respective color-coded blades. The curved arrow lines illustrate the effect of the steering gradient pulses or the rewinding gradient pulse on the k-space trajectory with the color of the lines corresponding to the same color of the gradient pulses in (a).