ACPC-coordinates

Discussions
1

Hello, is it possible to export the location of the surface- and invasive-electrode in coordinates according to ACPC-system? In the tutorials, I read that in general ACPC is somehow included in the brainstorm software, but how can I convert and export into ACPC-coordinates?

Thank you so much for your time and help!

2

Hi @ievamzi, indeed the conversion from SCS to ACPC coordinates is built in in Brainstorm.

While exporting data directly into files ACPC is not a GUI option, it is possible to do it by loading the MRI, Surface and Channel files into Matlab, as indicated below:

  1. Export MRI file as Matlab variable sMri (right-click > File > Export to Matlab)
  2. Export Surface file as Matlab variable sSurf
  3. Export Channel file as Matlab variable sChannel

Convert Surface vertices from SCS to ACPC
VerticesAcpc = cs_convert(sMri, 'SCS', 'ACPC', sSurf.Vertices);

  • Save those vertices in a format that satisfy your needs
  • See the functions out_tess_* in out_tess.m for various mesh files formats

Convert Channel locations from SCS to ACPC

ChannelAcpc = sChannel.Channel;
for iChannel = 1 : length(ChannelAcpc)
    if ~isempty(ChannelAcpc(iChannel).Loc)
        ChannelAcpc(iChannel).Loc = cs_convert(sMri, 'SCS', 'ACPC', ChannelAcpc(iChannel).Loc')';
    end
end
  • Save those channel locations in a format that satisfy your needs
  • See the functions out_channel_* in export_channel.m for various channel files formats
3

Thank you for your help!

I just wanted to clarify: the Surface file - do you mean the generated head mask or isoSurface?

4

That depends on what you need. All surfaces in Brainstorm are saved in SCS, so the procedure is the same for all of them.