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EIDORS: Electrical Impedance Tomography and Diffuse Optical Tomography Reconstruction Software

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EIDORS fwd_models

Creating an FEM and solving a 3D forward problem

EIDORS has functions to create common FEM models.
nelec= 8; nrings= 2;
ring_vert_pos = [0.2, 0.5]; 
fmdl= ng_mk_cyl_models([1,0.3,0.05],[nelec,ring_vert_pos],[0.1,0.05,0.02]);

stim = mk_stim_patterns(nelec,nrings,[0,1],[0,1],{'meas_current'},1);
fmdl.stimulation = stim;

conduct = 1;
img = mk_image( fmdl, conduct ); 

show_fem(img);
print_convert forward_solver_3d_01a.png '-density 75'

extra={'ball','solid ball = sphere(0,0.2,0.5;0.1);'};
fmdl= ng_mk_cyl_models([1,0.3,0.05],[nelec,ring_vert_pos],[0.1,0.05,0.02], extra);
fmdl.stimulation = stim;

img= mk_image(fmdl, conduct);
img.elem_data(fmdl.mat_idx{2}) = 0.1;

show_fem(img);
print_convert forward_solver_3d_02a.png '-density 75'


Figure: A 3D finite element model (left) and an insulating inclusion (right)
Solving voltage pattern with and without inclusion
img.fwd_solve.get_all_meas = 1;
img.elem_data(fmdl.mat_idx{2}) = conduct; % Homogenous
vh = fwd_solve(img);

img.elem_data(fmdl.mat_idx{2}) = 0.95*conduct; %Non-conductive inclusion
vi = fwd_solve(img);

plot([vh.meas, 100*(vh.meas-vi.meas)])
axis tight
print_convert forward_solver_3d_03a.png '-density 77'


Figure: Measured voltages pattern from adjacent stimulation
img_v = rmfield(img, 'elem_data');
img_v.node_data = vh.volt(:,1);

show_slices(img_v,[0.2;0.3;0.4]*[inf,inf,1])
print_convert forward_solver_3d_04a.png '-density 75'

img_v.node_data = vh.volt(:,1) - vi.volt(:,1);
show_slices(img_v,[0.2;0.3;0.4]*[inf,inf,1])
print_convert forward_solver_3d_04b.png '-density 75'


Figure: The voltage pattern in three vertical slices of medium from adjacent stimulation. (left) voltage pattern. (right) pattern due to a change in conductivity.
img.fwd_model.electrode([2,13]) = img.fwd_model.electrode([13,2]); % flip electrodes

img.elem_data(fmdl.mat_idx{2}) = conduct; % Homogenous
vh = fwd_solve(img);

img.elem_data(fmdl.mat_idx{2}) = 0.95*conduct; %Non-conductive inclusion
vi = fwd_solve(img);

img_v.node_data = vh.volt(:,1);

show_slices(img_v,[0.25;0.35;0.45]*[inf,inf,1])
print_convert forward_solver_3d_05a.png '-density 75'

img_v.node_data = vh.volt(:,1) - vi.volt(:,1);
show_slices(img_v,[0.25;0.35;0.45]*[inf,inf,1])
print_convert forward_solver_3d_05b.png '-density 75'


Figure: The voltage pattern in three vertical slices of medium from opposity stimulation (across two electrode rings). (left) voltage pattern. (right) pattern due to a change in conductivity.

Last Modified: $Date: 2017-02-28 13:12:08 -0500 (Tue, 28 Feb 2017) $ by $Author: aadler $