Apply corregistration to other files

FranLop89 · April 24, 2020, 9:36pm

Hello,

I am performing corregistration between MRI and EEG/MEG channel positions, and I there is an option at the end to apply the same changes to all channel files within the subject. However, some files in my subject have slight changes in MEG channel positions and therefore the transformation is not applied to them, which I would like to. Besides manually corregister these additional files myself, is there any brainstorm function that may allow me to apply the same transformation to other files using code?

Many thanks in advance,

Fran

Francois · April 27, 2020, 8:46am

This is not easy to do, and prone to manipulation errors. I wouldn't recommend you try doing this, unless you are confident with your Matlab coding skills and your understanding of 3D geometry and spatial transformations (4x4 rotation-translations in homogeneous coordinates).

The successive transformations applied to the electrode coordinates are available in the channel file, in the fields TransfEeg and TransfMeg:
https://neuroimage.usc.edu/brainstorm/Tutorials/ChannelFile#On_the_hard_drive

To apply a transformation an other channel file, check out the function channel_apply_transf.m:

github.com

brainstorm-tools/brainstorm3/blob/master/toolbox/sensors/channel_apply_transf.m

function ChannelMats = channel_apply_transf(ChannelFiles, Transf, iChannels, isHeadPoints)
% CHANNEL_APPLY_TRANSF: Apply a transformation matrix to a list of channel files.
% 
% USAGE:  ChannelMats = channel_apply_transf(ChannelFiles, Transf, iChannels=[all], isHeadPoints=1)
%         ChannelMats = channel_apply_transf(ChannelMats,  Transf, iChannels=[all], isHeadPoints=1)
%
% INPUT:
%     - ChannelFiles : List of channel files to process (string or cell array of strings)
%     - Transf       : [4x4] transformation matrix to apply to the sensors
%     - iChannels    : List of sensor indices to update
%     - isHeadPoints : Update the digitized head points

% @=============================================================================
% This function is part of the Brainstorm software:
% https://neuroimage.usc.edu/brainstorm
% 
% Copyright (c)2000-2020 University of Southern California & McGill University
% This software is distributed under the terms of the GNU General Public License
% as published by the Free Software Foundation. Further details on the GPLv3
% license can be found at http://www.gnu.org/copyleft/gpl.html.

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