Fig.1:
(a) User interface for image segmentation software, (b) segmented left and right lungs with airways, (c) 3D anatomical model of human thorax.
Fig.2:
(a) Three-dimensional geometry of the ribcage enclosing the lungs and heart, with the heart located between the left and right lungs, (b) 3D geometrical model imported to FEM software showing electrodes placed on the surface of the thorax, (c) finite element mesh representation of the thoracic model.
Fig.3:
Tetrapolar electrode configuration and sweeping of electrode array along different vertical levels of the thorax (left). Lower portion of the right lung modeled as fluid buildup by assigning dielectric properties of body fluid (right).
Fig.4:
Spatial sensitivity distribution along the planes 6cm (top) and 8cm (bottom) away from the electrode plane (thorax surface). The unit of volume impedance density in the color bar is Ω/m3. Average planar volume impedance density variation with depth from the surface of the thorax (bottom).
Fig.5:
Vertical variation of transfer impedance along the thorax. (a) Left-side electrode configuration under healthy (no fluid) and fluid-accumulation conditions. (b) Right-side electrode configuration under the same conditions. (c) Relative impedance change (%ΔZ) for the left-side configuration. (d) Relative impedance change (%ΔZ) for the right-side configuration.
Fig.6:
Variation of impedance for different amounts of fluid accumulation in the lower lobes of the left and right lungs, with electrodes placed on the chest surface directly above the simulated fluid buildup.
Fig.7:
Impedance spectrum of the thorax under baseline (no fluid) and fluid-accumulation conditions.
Table S1:
Electrical conductivity and relative permittivity values assigned to the thoracic tissue domains at different frequencies.
| Tissue | Parameter | Frequency (Hz) | ||||||
|---|---|---|---|---|---|---|---|---|
| 5,000 | 10,000 | 50,000 | 100,000 | 200,000 | 500,000 | 1000,000 | ||
| Lungs | Conductivity σ (S/m) | 0.08914 | 0.093172 | 0.10265 | 0.10735 | 0.11287 | 0.12301 | 0.13609 |
| Relative Permittivity εr | 33529 | 17174 | 4272.5 | 2581.3 | 1664.1 | 1025 | 733.18 | |
| Soft tissue | Conductivity σ (S/m) | 0.18014 | 0.18233 | 0.188033 | 0.193132 | 0.204333 | 0.235367 | 0.26388 |
| Relative Permittivity εr | 27582.75 | 13497 | 5133.21 | 4091.043 | 3216.858 | 1840.93 | 931.811 | |
| Ribs | Conductivity σ (S/m) | 0.051324 | 0.051527 | 0.052032 | 0.052342 | 0.052852 | 0.054448 | 0.057376 |
| Relative Permittivity εr | 1914.26 | 1089 | 438.685 | 349.675 | 295.58 | 241.33 | 196.74 | |
| Heart | Conductivity σ (S/m) | 0.13665 | 0.15421 | 0.19543 | 0.21511 | 0.23824 | 0.28072 | 0.32753 |
| Relative Permittivity εr | 128090 | 70054 | 16982 | 9845.8 | 6001.1 | 3264.5 | 1967.3 | |
| Fluid | Conductivity σ (S/m) | 1.5 | 1.5 | 1.5 | 1.5 | 1.5001 | 1.5003 | 1.5007 |
| Relative Permittivity εr | 98.958 | 98 | 98.558 | 97.99 | 96.556 | 91.35 | 84 | |
| Electrodes | Conductivity σ (S/m) | 4.00E+06 | 4.00E+06 | 4.00E+06 | 4.00E+06 | 4.00E+06 | 4.00E+06 | 4.00E+06 |
| Relative Permittivity εr | 1 | 1 | 1 | 1 | 1 | 1 | 1 | |