Imaging of gastric acidity scale by integration of pH-conversion model (pH-CM) into 3D-gastro electrical impedance tomography (3D-g-EIT)

Abstract

The gastric acidity scale has been imaged by integration of the pH-conversion model (pH-CM) into 3D-gastro electrical impedance tomography (3D-g-EIT) under the influence of spatial mean hydrogen-specific conductivity σH+. The pH-CM uses Debye-Hückel-Onsager (DHO) interionic equation, molar conductivity ratio, ωH+, viscosity ηstate(k) and relative permittivity εstate(k) in order to convert the imaged conductivity distribution σ to the pH distribution pH*. With the proposed integration, phantoms of empty (S1), liquid storage (S2-S4), and solid meal storage (S5) states are measured to reflect the dilution state. In the case of empty (S1), the artificial gastric juice is made based on 99.50% of H2O and 0.50% solution consisting of HCl (1.4263 g/L), KCl (0.8647 g/L), and NaCl (2.8559 g/L). In the case of the liquid storage (S2-S4) state, 200 mL of H2O is added three times as a dilution of artificial gastric juice in each S2, S3, and S4. In the solid meal storage (S5) state, an acid solid meal is blended into the artificial gastric content. The modified constants, α, and β are calculated based on the variation of viscosity ηstate(k) and permittivity εstate(k) of each state. The conductivity of gastric-shape models in five states is studied in the simulation. In the experiments, the simulated models were measured as gastric phantoms. Integrating pH-CM into 3D-g-EIT successfully images the pH* in the simulations and experiments. As a result, the estimated acidity scale 〈pH〉 is inversely proportional to σH+ with mean pH error evaluation of simulations eˆpH(sim) and experiments eˆpH(sim) are 15.8% and 8.5%, respectively.