Importing captrak files

[Raymundo.Cassani]

@bakerdon

Is it best practice to refine the CapTrak positions using head points, and when do I know that I need to do this? I thought we said above that we should not have to refine CapTrak data using head points, as the NAS/LPA/RPA are defined for CapTrak during the data collection.

The refinement using head points is could help in the case that the alignment with fiducials is not enough. This happens for example, if the fiducials in the MRI and the fiducials in the CapTrak system were not placed in exact same place on the head. If they were the same the refinement using head points will not change the position of electrodes at all.

https://neuroimage.usc.edu/brainstorm/CoordinateSystems#Subject_Coordinate_System_.28SCS_.2F_CTF.29

@bakerdon

Does converting the MRI to MNI space for some of our patients (but not all, such as in the case of those with MRI and CapTrak data) affect computations or their results later? I feel that if we were to convert some of the MRIs to MNI space, but not all, there may introduce some bias.

By MNI normalization, I meant to compute the transformation between the individual's anatomy and the ICBM152 anatomy. This will not affect any computation later. And it is necessary if at some point you plan to do group analysis.