[FieldTrip] Pruning

[Carsten Wolters]

Hi John,

I would assume it is the pruning for the "Venant condition", i.e., that 
all dipole positions are close to a vertex
whose neighbors are all in grey matter, because they get the monopolar 
weights that approximate best
the given dipolar moment. Check e.g. this one
https://urldefense.com/v3/__https://www.sciencedirect.com/science/article/abs/pii/S1053811919306202?via*3Dihub__;JQ!!HJOPV4FYYWzcc1jazlU!4DOkcvTkP8Z9h_Yzt9uN57aiBPGOzIlZdiq7PXavgWu2nBGVh0tRGmOObbdzcvD0VPSgLcWYRDApReSO059VXIwT8NHMCMF2xSWo_A$ 

@Johannes: Did you implement the "ft_inside_headmodel.m" and do you agree?

We are now investigating a new FEM source model, the "localized 
subtraction approach"
https://urldefense.com/v3/__http://www.sci.utah.edu/*wolters/PaperWolters/2022/HoeltershinkenEtAl_Biosignale2022.pdf__;fg!!HJOPV4FYYWzcc1jazlU!4DOkcvTkP8Z9h_Yzt9uN57aiBPGOzIlZdiq7PXavgWu2nBGVh0tRGmOObbdzcvD0VPSgLcWYRDApReSO059VXIwT8NHMCMHvhmzaGw$ 
where this "pruning" might be alliviated or not be needed at all, as 
long as the source is in GM.

Best regards
     Carsten

-- 
Prof. Dr.rer.nat. Carsten H. Wolters
University of Münster
Institute for Biomagnetism and Biosignalanalysis
Malmedyweg 15
48149 Münster, Germany

Phone:
+49 (0)251 83 56904
+49 (0)251 83 56865 (secr.)

Fax:
+49 (0)251 83 56874

Email: carsten.wolters at uni-muenster.de
Web: https://urldefense.com/v3/__https://campus.uni-muenster.de/biomag/das-institut/mitarbeiter/carsten-wolters/__;!!HJOPV4FYYWzcc1jazlU!4DOkcvTkP8Z9h_Yzt9uN57aiBPGOzIlZdiq7PXavgWu2nBGVh0tRGmOObbdzcvD0VPSgLcWYRDApReSO059VXIwT8NHMCMGyB_9iWw$ 



Am 13.02.23 um 19:52 schrieb Richards, John via fieldtrip:
>
> In on of the source analysis modules, likely for the simbio lead field 
> computation, I get the message below about pruning elements of the 
> head model.  Does anyone know what this means?  I don’t think I have 
> seen it before.
>
> John
>
> creating sourcemodel based on user specified 3D grid
>
> using electrodes specified in the configuration
>
> selecting dipole positions inside the 'gm' tissue
>
> pruning headmodel volume elements from 1572480 to 450494 (29%)
>
> pruning headmodel vertices from 262013 to 159509 (61%)
>
> pruning dipole positions from 1887681 to 1759824 (93%)
>
> This is in the ft_inside_headmodel, both inverse and forward
>
> ./inverse/private/ft_inside_headmodel.m: fprintf('pruning headmodel 
> volume elements from %d to %d (%d%%)\n', numhex, sum(insidehex), 
> round(100*sum(insidehex)/numhex));
>
> ./inverse/private/ft_inside_headmodel.m: fprintf('pruning headmodel 
> vertices from %d to %d (%d%%)\n', numpos, sum(insidepos), 
> round(100*sum(insidepos)/numpos));
>
> ./inverse/private/ft_inside_headmodel.m: fprintf('pruning dipole 
> positions from %d to %d (%d%%)\n', numdip, sum(insidedip), 
> round(100*sum(insidedip)/numdip));
>
> ./forward/ft_inside_headmodel.m: fprintf('pruning headmodel volume 
> elements from %d to %d (%d%%)\n', numhex, sum(insidehex), 
> round(100*sum(insidehex)/numhex));
>
> ./forward/ft_inside_headmodel.m: fprintf('pruning headmodel vertices 
> from %d to %d (%d%%)\n', numpos, sum(insidepos), 
> round(100*sum(insidepos)/numpos));
>
> ./forward/ft_inside_headmodel.m: fprintf('pruning dipole positions 
> from %d to %d (%d%%)\n', numdip, sum(insidedip), 
> round(100*sum(insidedip)/numdip));
>
> ***********************************************
> John E. Richards
> Carolina Distinguished Professor
> Department of Psychology
> University of South Carolina
> Columbia, SC  29208
> Dept Phone: 803 777 2079
> Fax: 803 777 9558
> Email: richards-john at sc.edu <mailto:richards-john at sc.edu>_
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