try something like
to3d -time:zt 30 180 0 alt+z *.ima
where you will have to replace "30" and "180" by the correct number of slices and repetitions, respectively. If this doesn't give the correct TR, you'll also have to put the correct TR in place of "0", as in "2.5s" for 2.5 seconds, or "2500" for 2500 milliseconds.
bob cox