fwd_bem_model.h File Reference

Boundary Element Method (BEM) volume-conductor model — layered triangulated surfaces, conductivities, IP-approach matrix and potential-solution matrix. More...

#include "fwd_global.h"
#include "fwd_coil_set.h"
#include <fiff/fiff_coord_trans.h>
#include <fiff/fiff_dir_node.h>
#include <fiff/fiff_tag.h>
#include <fiff/fiff_named_matrix.h>
#include <memory>
#include <vector>
#include <Eigen/Core>
#include <QString>

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Classes
class	FWDLIB::FwdBemModel
	Layered triangulated volume-conductor model (scalp/skull/inner-skull surfaces, per-compartment conductivities, IP-approach data and dense potential-solution matrix) used by the linear-collocation BEM forward solver. More...

Namespaces
namespace	FWDLIB
	Forward modelling — BEM solver, spherical models, sensor/coil definitions and the lead-field assembly that links current dipoles to MEG/EEG sensor readings.
namespace	MNELIB
	Core MNE data structures (source spaces, source estimates, hemispheres).
namespace	FIFFLIB
	FIFF file I/O, in-memory data structures and high-level readers/writers.

Variables
constexpr int	FWDLIB::FWD_BEM_UNKNOWN = -1
constexpr int	FWDLIB::FWD_BEM_CONSTANT_COLL = 1
constexpr int	FWDLIB::FWD_BEM_LINEAR_COLL = 2
constexpr double	FWDLIB::FWD_BEM_IP_APPROACH_LIMIT = 0.1
constexpr int	FWDLIB::FWD_BEM_LIN_FIELD_SIMPLE = 1
constexpr int	FWDLIB::FWD_BEM_LIN_FIELD_FERGUSON = 2
constexpr int	FWDLIB::FWD_BEM_LIN_FIELD_URANKAR = 3

Detailed Description

Boundary Element Method (BEM) volume-conductor model — layered triangulated surfaces, conductivities, IP-approach matrix and potential-solution matrix.

SPDX-License-Identifier: BSD-3-Clause Copyright (c) 2017-2026 MNE-CPP Authors

Author

Christoph Dinh chris.nosp@m.toph.nosp@m..dinh.nosp@m.@mne.nosp@m.-cpp..nosp@m.org; Lorenz Esch loren.nosp@m.z.es.nosp@m.ch@tu.nosp@m.-ilm.nosp@m.enau..nosp@m.de; Ruben Doerfel doerf.nosp@m.elru.nosp@m.ben@a.nosp@m.ol.c.nosp@m.om; Juan GPC jgarc.nosp@m.iapr.nosp@m.ieto@.nosp@m.mgh..nosp@m.harva.nosp@m.rd.e.nosp@m.du; Gabriel Motta gabri.nosp@m.elbe.nosp@m.nmott.nosp@m.a@gm.nosp@m.ail.c.nosp@m.om

Since

0.1.0

Date

March 2017

The BEM reformulates the EEG/MEG forward problem from a 3-D PDE on the head volume into a 2-D integral equation on the boundaries between compartments of piecewise-constant conductivity (typically scalp, outer skull, inner skull). Hamalainen & Sarvas (1989) discretise that equation by linear collocation on a triangulated surface, giving a dense linear system whose inverse — stored here as solution — maps the infinite-medium potential at every node to the true bounded-medium potential. From that node potential, electrode voltages follow by linear interpolation and MEG fields follow from the Geselowitz formula.

Because the scalp/skull conductivity ratio (≈50–1) makes the system ill-conditioned, the Isolated Skull Approach (IP) of Meijs et al. pre-conditions the inner-skull block; FWD_BEM_IP_APPROACH_LIMIT and ip_approach_limit guard that step. Constants FWD_BEM_LINEAR_COLL and FWD_BEM_CONSTANT_COLL select the linear- or constant-potential basis, and FWD_BEM_LIN_FIELD_* selects the analytic integral used for the MEG primary-current term (Simple / Ferguson / Urankar).

Refactored from the MNE-C fwdBemModelRec struct in fwd_types.h and the solver routines in fwd_bem_linear_collocation.c.

Definition in file fwd_bem_model.h.