The coregistration of data sets is an important prerequisite for analyzing and visualizing functional data in 3D space, i.e. in a standard reference system such as Talairach space. This section describes the two most important alignment problems of fMRI data analysis:
The coregistration of functional (FMR) and 3D anatomical (VMR) data sets is necessary to convert the original slice-based functional data into a series of volumes in a known 3D space. The transformed functional data files are called "volume-time-course files" or simply VTC files. These files contain the proper time courses "behind" the voxels of the subject's VMR data set. In combination with additional spatial transformation files, VTC files can be created in standard Talairach space, which is, for example, necessary to run Talairach-based group analyses.
The coregistration of two 3D (VMR) data sets is very helpful if the same subject has been recorded in multiple scanning sessions. If the VMR data set of scanning session 1 has been transformed in ACPC and Talairach space, the creation of VTC files in Talairach space can be performed automatically for session 2, if the VMR data of scanning session 2 can be coregistered properly with the (ACPC transformed) VMR data from scanning session 1.
Note: Coregistration assumes that 3D data sets are available in a standard, sagittal orientation, for details see the topic "Standardization of 3D data sets".