Maybe add something for ``slice_order`` like:

     where the values represent the spatial position of the scans along the slice axis, and the element number in the array [0, 1, ...] represents  
     the order in time.  For example, for an interleaved sequence with 10 slices, where we acquired slice 0 (in space)  first, then slice 2 (in 
     space) etc, this array would  be [0, 5, 1, 6, 2, 7, 3, 8, 4, 9]