Abstract
Abstract
In this study, sodium concentration in the dermis layer is imaged by the square wave open electrical impedance tomography (SW-oEIT) with spatial voltage thresholding (SVT). The SW-oEIT with SVT consists of three steps which are (1) voltage measurement, (2) spatial voltage thresholding, and (3) sodium concentration imaging. In the 1st step, the root mean square voltage
v
̃
is calculated based on the measured voltage
v
under the square wave current
I
through the planar electrodes on the skin domain Ω. In the 2nd step, the m-th measured voltage
v
is converted to a compensated voltage v
* based on the voltage electrodes distance
d
v
and threshold distance
d
Γ
in order to highlight the region of interest of the dermis layer
Ω
d
.
In the 3rd step, sodium concentration is imaged by the Gauss-Newton reconstruction method. The SW-oEIT with SVT was applied to multi-layer skin simulation and ex-vivo experiments under various dermis sodium concentrations c in the range of 5–50 mM. As an image evaluation result, the spatial mean conductivity distribution
σ
*
in
Ω
d
is successfully determined as increasing c on both simulations and experiments. The relationship between
〈
σ
*
〉
and c was evaluated by the determination coefficient R
2 and the normalized sensitivity
〈
S
〉
.
The optimized
d
Γ
with the highest evaluation values of
R
2
=
0.84 and
〈
S
〉
=
0.83 is under the condition of
d
Γ
= 2 mm. Based on the signal evaluation, the SW-oEIT with SVT has a 15.32% higher correlation coefficient CC compared to the conventional oEIT based on sinewave injection.
Cited by
3 articles.
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