[FieldTrip] EEG electrode coordinate system transformation

[Paolo Belardinelli]

Dear all,
we are recording EEG electrode positions using the LOCALITE TMS navigator
acquisition software. We dispose over MRI data in DICOM format.
The electrode positions are stored in the (LPS) coordinate system. Unity
measures are mm.
We load the electrode positions in Fieldtrip by means of ft_read_sens. We
use the elec structure to prepare the layout with ft_prepare_layout.
Attached are the obtained layout (localite_layout) and the layout obtained
using standard electrode positions (standard_layout).
Appearantly, besides an inversion of both X and Y axes, we have to deal
with a Z offset we don't know how to exactly calculate ( a simple inversion
of axes does not provide correct results, see attached
inverted_localite_layout).
Is there a way to address this issue in Fieldtrip or with some mathematical
manipulation?

Thank you in advance,

Paolo

-- 
--
Paolo Belardinelli, PhD
Neurology Department
University Hospital Tuebingen
Eberhard Karls University Tuebingen
Hoppe-Seyler Str. 3
D-72076 Tuebingen
Tel: +49 7071 / 29 80478
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