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Hello,
Hope you are fine and in good health,
I would like to start from your example about the OPM-MEG data to solve our problem, kindly let me ask some questions:
1) How can I modify or generate the sensors file (size, distance, ....) to fit it to our sensors?
We have some input information for generating this location file.
All OPM will be placed in a radial orientation over the scalp surface as shown on the figure below,
but each OPM will do measurement along X, Y an Z axis. Just, we applied a 90? rotation of each OPM in order to maximize the distance between High Frequency coils of the sensors, as shown below. Ths reduced the cross talk noise in our experimental setup. But placed over the scalp, due to the curvature of the scalp surface, these HF coils will be naturally distanced.
[cid:5a3fc822-d26f-42ad-9e1c-dbfa1b9c91af]
The size of OPM basis is 2 cm x 2cm (with its packaging) but the glass cell containing He atoms which are used to do the measurement is a circular glass cell of 1 cm diameter. The sensing volume has to be computed for the glass cell. The space between two OPM should be 5 mm. The distance between the OPM and the scalp can be set to 1 mm.
For our simulations, we will have to consider both cases :
* the case ? 4 OPM ? (The 5th OPM is used for background noise measuremnt) over the scalp (these 4 OPM will be placed in an overhead position with respect the dipole location)
* for the case of a whole head OPM array and for this case, it can be derived from the SQUID
arrays by projecting the sensor locations to the scalp
2) We want to do simulation considering simple cases: radial dipole, tangential dipole + intermediate orientations, more or less deep dipole,...etc
, is it possible to do the simulation in MNE python? if not I think we can do it in brainstorm, do you have tips how can we import this dataset of opm
brainstorm?. In fact I started to open it in fieldtrip (fiff_setup_read_raw) successfully open the raw file, but I did not successed to open the forward_sample.fiff, do you have an idea? which function I should used. Beacuse I need to see the data, so that I can understand it and do the simulations.
3) Do you know what method is used to compute the forward model of the opm dataset you have? because as you know we are dealing here with free axis measurement, I asked in brainstorm discussion if we can use openmeeg to generate the leadfield in this case, but still searching for confirmation if we can use openmeeg in this case,
Thank you
Best regards
Saeed