[Simnibs-discuss] Multiple tDCS simulations employing Lead-field

Axel Thielscher axelt at drcmr.dk
Fri Apr 15 13:46:06 CEST 2022


you can easily calculate the fields created by any combination of 
electrode currents using a linear combination of the lead fields. The 
only constraint is that electrode currents sum up to zero. The 
leadfields are all calcuated relative to a common reference electrode 
for a unit current. The field between, e.g. for a current flow of 2 mA 
between electrodes 1 and 2 is then:

EF(El2 to El1, 2mA) = 2mA*( EF(El2 to El_ref) - EF(El1 to El_ref) ) = 
2mA*(leadfield_El2 - leadfield_El1).

Hope this helps.



On 14-04-2022 17:15, Jaimie Jobson (jj3g17) wrote:
> Hello,
> I’m an Msc student working on creating a neural network that is 
> capable of predicting the magnitude of electric field at a given 
> position/positions in the brain (tDCS). For this I’m using a 19 
> electrode cap. I need to be able to quickly and automatically find the 
> electric field at a given position for a large combination of 
> electrodes and positions. For example to predict the e field at a 
> position created when two electrodes are switched on from the 19 
> electrode cap. However to accomplish this I need to be able to 
> simulate hundreds if not thousands of combinations (depending on how 
> many electrodes are switched on). Doing this by undertaking thousands 
> of simulation would be extremely time consuming, however from my 
> understanding I could very quickly find the E field at certain 
> positions for many hundreds of electrode combinations by using the 
> Lead-field of a head model. All information related to Lead-fields 
> refers to optimization, however can it be used to predict the outcome 
> of many simulations. If so how would I go about programming this.
> Thanks
> Jaimie Jobson
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> Simnibs-discuss mailing list
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Dr. Axel Thielscher
Professor of Neurophysics and Neuroimaging
Danish Research Center for Magnetic Resonance
Copenhagen University Hospital Hvidovre
DK-2650 Hvidovre, Denmark
Department of Health Technology
Technical University of Denmark
DK-2800 Kgs. Lyngby
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