Can't import MEG data!

KaterinaGialopsou · July 4, 2019, 10:30am

Hi All,

I want to use Brainstorm to analyze my MEG data but as I am using a different kind of magnetometers (not SQUIDs) I don't use any of the available MEG systems.
Some details about the MEG measurements:
All the measurements can be either in Voltage (and then convert them to the magnetic field) or simply, magnetic field. Each file represents one sensor and contains and the measurements and the time.
The above format is different than any other and I couldn't find the exact format of other MEG systems.
Could you please tell me the required format for MEG data, so I can import them?
Or any other possible solution would be great!

PS: I searched some of the previous posts but I couldn't find something similar.

Thank you in advance.
Cheers,
Katerina

Francois · July 5, 2019, 2:09pm

Hi Katerina,

MEG file formats are all proprietary, there is no standard that you could convert your data to.
Which MEG system is it? Is it a new commercial system that is not supported yet in Brainstorm, or are these some internal developments that you lead at your lab?

If this is a stable system with a fully described file format, we could help you adding the native support for it in Brainstorm. We would need:

A Matlab function to read the file headers (eg. similar to in_fopen_ctf.m)
A Matlab function to read a block of recordings in a continuous file or MEG recordings (eg. in_fread_ctf.m)
Some example files
Links to online documentation of this file format
The description of the geometry of your MEG sensors added to the file coil_def.dat:
https://github.com/brainstorm-tools/brainstorm3/blob/master/toolbox/io/private/coil_def.dat
https://martinos.org/mne/stable/manual/source_localization/coil_geometries.html

If this is a system that is under development, you'd need to figure out how to import your files to the database by yourself. For testing purposes, the simplest option is to create a channel_...mat and and one or more data_...mat file in a folder of the database, and then right-click on the folder in the Brainstorm database explorer > Reload.
https://neuroimage.usc.edu/brainstorm/Tutorials/ChannelFile#On_the_hard_drive
https://neuroimage.usc.edu/brainstorm/Tutorials/Epoching#On_the_hard_drive

If you want to work on a more formal integration, you could write your own your own in_fopen and in_fread functions. Let me know if you are interested, I could give you additional details on all the functions to modify.