// Then I order the slices according to the value "dist". Finally, once
// I've read in all the slices, I calculate the z-spacing as the difference
// between the "dist" values for the first two slices.
// Then I order the slices according to the value "dist". Finally, once
// I've read in all the slices, I calculate the z-spacing as the difference
// between the "dist" values for the first two slices.