Pocket Electrical Impedance Tomography (p-EIT) System With Wide Impedance Range Buffer- Mirrored Current Source (BMCS) With Assist of Filter-Trained Quasi-3-D Method for Functional Gastric-Shape Imaging

Abstract

In this study, a functional gastric-shape imaging method based on a pocket electrical impedance tomography (p-EIT) system is proposed, which consists of the development of 1) a buffer-mirrored current source (BMCS) as a wide impedance range circuit and 2) a filter-trained quasi-3-D method as an image reconstruction algorithm. The BMCS provides a wide impedance range of constant current $I_{c}$ with a high signal-to-noise ratio SNR. The filter-trained quasi-3-D method iteratively trains the threshold $\alpha $ to obtain the most sensitive impedance $Z$ pair from a multilayer sensor. Using simulations and experiments, the performance of BMCS is validated by comparison with the conventional impedance circuit which is based on an enhanced Howland current source (EHCS). With the p-EIT system, gastric-shaped objects are imaged under the various content conductivity ${\Delta \sigma }_{c}$ , different levels of gas–liquid ratio ${\Delta \sigma }_{l}$ , and different gastric volume ${\Delta \sigma }_{V}$ . Based on simulations and experiments, the BMCS successfully provides $I_{c}$ 1 mA on 1–27.54 $\text{k}\Omega $ of $Z$ range, meanwhile, it provides 1–10 $\text{k}\Omega $ in a practical test. By SNR over than 80 dB, the BMCS is proper to be examined for several cases. In $\Delta \sigma _{c}$ , using the BMCS and filter-trained quasi-3-D method on the p-EIT system improves the accuracy of filtered images $\sigma ^ \ast $ which has a 24.18% higher cross correlation (CC), 23.11% lower image error image area error (IAE), and 41.03% lower root-mean-square error (RMSE). In $\Delta \sigma _{l}$ and $\Delta \mathrm {\sigma }_{V}$ , the quasi-3-D conductivity distribution of numerical simulation $\Theta _{\mathrm {sim}}$ and experiment $\Theta _{\mathrm {exp}}$ studies are evaluated by volumetric content estimation on liquid storage $\varphi _{V}$ emptying $\varphi _{l}$ process. From the results, in $\Delta \sigma _{V}$ , $\varphi _{V\mathrm {, sim}}$ increases from 5.87 to 9.62 cm3 and $\varphi _{V\mathrm {, exp}}$ increases from 3.29 to 10.23 cm3. Also, in $\Delta \sigma _{l}$ , show that $\varphi _{l\mathrm {, sim}}$ decreases from 13.26 to 2.28 cm3 and $\varphi _{l\mathrm {, exp}}$ decreases from 12.11 to 2.93 cm3. The developed p-EIT system reaches average volumetric improvement $\langle \Delta \varphi _{l} \rangle = 57.71$ % in the case of $\Delta \varphi _{l}$ and 12.30% in the case of $\Delta \varphi _{V}$ . Both of $\Delta \varphi _{\mathrm {sim}}$ and $\Delta \varphi _{\mathrm {exp}}$ have a similarity pattern close to $\Delta \varphi _{\mathrm {true}}$ .