Sodium concentration imaging in dermis layer by square-wave open electrical impedance tomography (SW-oEIT) with spatial voltage thresholding (SVT)

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 R2 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.

Skin layer classification by feedforward neural network in bioelectrical impedance spectroscopy

“…One potential reason for the misclassifications could be the similarity between the dermis and epidermis layers in terms of their electrical properties [ 26 ]. Future studies could consider incorporating additional features [ 33 ] or imaging techniques [ 34 ], highlighting the importance of continuing to refine the model and improving the accuracy of the classification for these layers. Overall, the confusion matrix results demonstrate the potential of the FNN in accurately classifying skin layers but also highlight the need for further optimization and refinement of the model.…”

Free and bound sodium identification by skin dielectric properties separation algorithm of bioelectrical impedance spectroscopy (spa-BIS) in human skin model

“…For further skin phantom development, the multilayered phantoms [26] with the planar electrode's concept [27] for sodium-ion concentration measurement are important approaches to mimic the real clinical diagnostic on the human body for evaluating multilayer tissues such as skin. Therefore, 2D imaging [28] or 3D imaging [29] noninvasive modalities are interesting in assessing sodium-ion concentration in a certain layer of the skin model [30].…”

Detection of invasive ductal carcinoma in quadrant breast areas by electrical impedance tomography implemented with gaussian relaxation-time distribution (EIT-GRTD)

“…In order to reconstruct the conductivity distribution in the breast specimen, Gauss-Newton image reconstruction is utilized, which is expressed by [18,25].…”

“…In order to solve the drawbacks of the conventional modalities, electrical impedance tomography (EIT) is an alternative to detect whole breast cancer [8,9] which is non-invasive [10] and provides realtime information that utilizes electrical current to measure conductivity changes, breast tissues crosssectional [11,12]. EIT explores electrical conductivity at various frequencies to monitor the human body [13] such as arm [14] and calf [15] compartments, gastric shape [16], albumin accumulation [17], and sodium imaging [18]. However, conventional EIT for breast cancer detection has shortcomings related to spatial resolution.…”