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The GCA Subcortical Segmentation Atlas Volume Format

The .gca (Gaussian Classifier Atlas) file format encodes voxel label information based on probabilistic information estimated from a training set. The GCA format is proprietary, defined by the NMR Center (at Massachusetts General Hospital). Below is an informal specification of the format, extracted from the code snippets below:

The .gca file is composed of three volumes, which can be extracted like this:

mri_convert atlas.gca -nth 0 means.mgz
mri_convert atlas.gca -nth 1 labels.mgz
mri_convert atlas.gca -nth 2 priors.mgz


See also the script rebuild_gca_atlas.csh in the Freesurfer distribution for info on how the gca is built.


FsTutorial/GcaFormat (last edited 2012-04-18 14:20:10 by NickSchmansky)