Dear Stuart,
I am not sure what you mean by there being two rows per volume. The eddy_movement_rms/eddy_restricted_movement_rms files only have one row per volume.
Are you by any chance referring to already processed data from the HCP? If so, in the HCP each diffusion direction was acquired twice with opposing PE-directions and after running topup/eddy/etc the volumes with the same diffusion direction were averaged. This was done to save space and processing time for the subsequent processing steps (bedpost etc). But that means that there will be twice as many RMS values, estimates of motion, of EC etc as there are volumes in the finished data set.
Jesper
> On 16 Mar 2018, at 04:00, Stuart Oldham <[log in to unmask]> wrote:
>
> Hi all,
>
> In the eddy_movement_rms/eddy_restricted_movement_rms output files from eddy, it appears that each volume has two rows associated with it. The documentation describes why there are two columns, but why are there two rows per volume? Is there a further subtlety in how the RMS value is calculated beyond comparing to the first/previous volume?
>
> Kind regards,
>
> Stuart
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