[Mne_analysis] Error running make_forward_solution: Head<-->sensor transform not found

[Eric Larson]

Can you simplify the script to use a minimal number of files and lines to
reproduce the error (e.g., hopefully it doesn't depend on bad channels at
all), and upload the necessary files and script somewhere? I guess that
error could happen if you only have sensors in head coordinates to start
with -- we can probably work around it.

It shouldn't be too difficult to add that digitization information without
having to resort to MNE-C tools. Feel free to open an mne-python issue
about this stuff so we can hash out a solution, then we can report back to
this thread.

Eric


On Tue, Nov 17, 2015 at 10:13 PM, Hari Bharadwaj <hari at nmr.mgh.harvard.edu>
wrote:

> Hi Emily,
>    Perhaps you could try converting the digitization data to one of the
> formats (e.g., .hpts) accepted by mne.channels.read_montage(.) using
> the C-version of mne_convert_dig_data (if they are already not
> available in one of those formats). Once you do that and read it into
> python as a Montage object using mne.channels.read_montage(.), you
> could supply it as to the montage argument in
> mne.io.read_raw_brainvision(.).
>
> Also, the digitization data should contain cardinal points (like nasion,
> LPA, RAP) for the head along with the EEG sensor locations.. That way,
> "head coordinated" and "sensor coordinates" can be matched in the Montage.
>
> HTH,
> Hari
>
>
> On Tue, November 17, 2015 7:07 pm, Emily Stephen wrote:
> > Hi All,
> >
> > I'm getting an error when I run mne.make_forward_solution, but only if I
> > try to save the result.
> >
> > That is, if I set fname=None then the whole thing runs fine, but if I set
> > fname=<filename>, it fails in the call to write_forward_solution with the
> > error:
> > Head<-->sensor transform not found
> >
> > Seems like write_forward_solution is expecting values in info under
> > dev_head_t or ctf_head_t, which never got set.
> >
> > I think it may be related to the fact that I'm loading (just EEG) data
> > from
> > a brainvision file using mne.io.read_raw_brainvision.
> >
> > I've been struggling to figure out how to include the digitizer
> > information
> > in the preprocessed data. My digitizer info is in a .fif file that
> > otherwise doesn't contain any measurement data (I can't even figure out
> > how
> > to load it using the python MNE). So far the only thing I've done with
> > that
> > file is to use it to update the channel locations with a call to the C
> > implementation:
> >     call(['mne_check_eeg_locations',
> >           '--file', fname,
> >           '--dig', op.join(subjects_dir,subject,subject + '.fif'),
> >           '--fix'])
> >
> > I'm new to all of this (including python) so any help would be much
> > appreciated! I've attached the code (apologies for the mess).
> >
> > Thanks,
> > Emily
> > _______________________________________________
> > Mne_analysis mailing list
> > Mne_analysis at nmr.mgh.harvard.edu
> > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/mne_analysis
>
>
> --
> Hari Bharadwaj
> Research Fellow
> Martinos Center for Biomedical Imaging,
> Massachusetts General Hospital
> 149 Thirteenth Street,
> Charlestown, MA 02129
>
> hari at nmr.mgh.harvard.edu
> Ph: 734-883-5954
> www.haribharadwaj.com
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