Dear Jeff,
I'm not sure I understand your question but I'll try. Is it the case
that you have an SPM dataset with coregistration already done and you
are trying to figure out what the MRI fiducials were? These are not
stored in the structure (unless standard fiducials were used that you
can find in D.inv{val}.mesh.fid).
You can recover them by applying a transform to native coordinates
D.inv{val}.mesh.Affine\D.inv{val}.datareg.toMNI to
D.inv{val}.datareg.fid_mri.fid.fid.pnt.
Regarding your second question, there is no support in SPM for
exporting MEEG data to BIDS, just for reading data from BIDS.
Exporting MEG data would be tricky as most of the original header
fields are not imported into SPM.
Best,
Vladimir
On Tue, May 24, 2022 at 6:13 PM Jeff Stout
<[log in to unmask]> wrote:
>
> Hi SPM Users/Devs,
>
> I am new to using SPM for MEG, but had a few questions.
>
> 1) How would I get the fiducial locations on the original nifti image imported during the coregistration.
> I have tried a few variables in the data structure:
> D.fiducials
> D.inv{2}.datareg.fid_eeg
> D.inv{2}.datareg.fid_mri.fid.pnt
>
> All of these variables are either in CTF space or head space and not MRI space. Is there a transformation matrix stored in the data structure to go from the original nifti image to the headspace mri so that I can invert and get the fiducial locations on the original MRI?
>
> 2) I have seen some operations to read bids datasets using spm - is there a bids export function for MEG datasets that are in SPM format (including the fiducials in the T1w.json)?
>
> Any help would be greatly appreciated.
>
> Thank you,
> Jeff Stout
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