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<p>Hello,</p>
<p><br>
</p>
<p>SimNIBS 3 offers two ways of getting 10/10 EEG positions out of
the box.</p>
<p><br>
</p>
<p>1) Use the eeg positions calculated using MNI transformations,
which are stored in
m2m_{SubID}/eeg_positions/EEG10-10_UI_Jurak_2007.csv. Those can
also be accessed in the <a moz-do-not-send="true"
href="https://simnibs.github.io/simnibs/build/html/tutorial/gui.html">GUI</a>,
which loads it automatically, or in scripts (<a
moz-do-not-send="true"
href="https://github.com/simnibs/simnibs/blob/v3.1.2/simnibs/examples/simulations/TMS.m">MATLAB
example</a>)</p>
<p><br>
</p>
<p>2) Using the <a moz-do-not-send="true"
href="https://simnibs.github.io/simnibs/build/html/documentation/command_line/eeg_positions.html">eeg_positions</a>
command line tool with the Nz, LPA, RPA and Iz as an input</p>
<p><br>
</p>
<p>Those two were compared and validated <a moz-do-not-send="true"
href="https://link.springer.com/chapter/10.1007/978-3-030-21293-3_1">here</a>.</p>
<p> <br>
</p>
<p>I'm not sure why it is not working in your case though, might be
due to head size, as you are moving by constant amounts?</p>
<p><br>
</p>
<p>Best Regards,</p>
<p>Guilherme<br>
</p>
<p><br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 09/07/2020 19.48, Mccalley, Daniel
wrote:<br>
</div>
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Hi all, </div>
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<br>
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Our lab targets the FP1 with TMS. We use a simple measurement
system (<a href="http://clinicalresearcher.org/F3/"
moz-do-not-send="true">http://clinicalresearcher.org/F3/</a>)
to locate exactly where we want to place the coil for each
subject. Typically, we measure the subject's head, and then,
starting from nasion, we'll move up Y mm and left X mm (where X
and Y are determined from each subject's given head size).</div>
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<br>
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Ideally, we'd like to create an electric field model for each
subject that accounts for the TMS parameters as well as the
exact location used. To implement this in SIMNIBS, I've tried
the following: </div>
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<br>
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1) Open a subjects m2m file and find the coordinates for nasion
(say, for example, that these coordinates are X= -2.78, Y=
117.59, Z= -20.63).</div>
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<br>
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2) Determine Y and X used to locate FP1 for the given subject
(say, for example, that starting from nasion, we moved 37 mm in
the Y direction, and over 32 mm in the X direction). </div>
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<br>
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3) Subtract the displacements in the Y and X directions from the
original nasion coordinates, resulting in X= -34.78 and Y=80.69</div>
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<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
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4) Add a new position wherein the reference coordinates match
the original nasion coordinates (and the Define Reference
Coordinates box is checked) and the coordinates calculated in
step 3 are input in the position fields (Z is left blank for
SIMNIBs to calculate) </div>
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<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
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5) Adjust for coil orientation and TMS parameters</div>
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<br>
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This seems to have worked well for 90-95% of our subjects,
however there are a few subjects in which the resulting coil
placement appears to be over the eye (Note: Ordinarily I'd
attach examples of the working and not-working subjects, but I'm
not sure if the skin reconstruction of our participants falls
under PHI). <br>
<br>
</div>
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Am I going about this the wrong way? Could this reflect a
problem with segmentation/meshing? Or maybe a problem with the
experimenter measurements of the subjects head? Any advice would
be greatly appreciated. Thank you all so much!</div>
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<br>
</div>
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Best,</div>
<div>
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<br>
</div>
<div id="Signature">
<div>
<div style="font-family:Tahoma; font-size:13px">Dan McCalley
<div>Medical University of South Carolina</div>
<div>College of Graduate Studies, Neuroscience</div>
<div><br>
</div>
</div>
</div>
</div>
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<br>
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