fMRIPrep accepts datasets that are in BIDS format. According to BIDS:
| Key name | Requirement level | Data type | Description |
|---|---|---|---|
| SliceTiming | RECOMMENDED, but REQUIRED for sparse sequences that do not have the DelayTime field set, and Arterial Spin Labeling with MRAcquisitionType set on 2D. |
array of numbers | The time at which each slice was acquired within each volume (frame) of the acquisition. Slice timing is not slice order – rather, it is a list of times containing the time (in seconds) of each slice acquisition in relation to the beginning of volume acquisition. The list goes through the slices along the slice axis in the slice encoding dimension (see below). Note that to ensure the proper interpretation of the SliceTiming field, it is important to check if the OPTIONAL SliceEncodingDirection exists. In particular, if SliceEncodingDirection is negative, the entries in SliceTiming are defined in reverse order with respect to the slice axis, such that the final entry in the SliceTiming list is the time of acquisition of slice 0. Without this parameter slice time correction will not be possible. |
So you’ll want your times to be something like [1, 3, 5...31, 0, 2, 4...30] / TR.