I need to define an ROI in a whole brain volume to be used as a mask in PyMVPA. That means having a whole brain .nii file with '1' within the ROI and '0' in every other voxel.

Is there a way to define a functional ROI in a whole brain volume, in a similar way to what I get when running funcroi with an annotation from aparc for a specific hemi? Or alternatively, is there a way to convert the aparc based ROI for a single hemi surface into a whole brain volume?