An electrical impedance spectro-tomography consists of a quasi-adjacent sensing method and a frequency-time difference imaging for relatively complex dielectric object monitoring has been proposed. A quasi-adjacent sensing method is designed to measure an electrical impedance spectroscopy based on four-wire measurement technique at the multi-electrodes electrical impedance tomography sensor. A frequency-time difference imaging for spatial distribution monitoring is needed, as the electrochemical reaction incur during the short time meanwhile the spatial geometry tends to be constant. An artificial set of phantoms were made and the proposed technique was capable to show the Cole-Cole parameters as a dielectric relaxation model on each measurement pair. Compare with the adjacent method, using the quasi-adjacent method show Re(Z) is two times higher, Imag(Z) is ten times higher, and a higher and homogeneous sensitivity map area are 60% wider. A negative resistance at high-frequency measurement also can be eliminated successfully by using the proposed method.

A sectorial sensitivity matrix using a K -means clustering algorithm has been proposed for electrical capacitance tomography (ECT) for accurate determination of permittivity distribution in the inclusion within the background area. The proposed sectorial sensitivity matrix clusters the pixel position of the inclusion area to minimize the soft field effect that leads to image artifacts and blurred images. The standard sensitivity matrix is nonlinear thus it is not easy to eliminate image artifacts due to the noise signal and nonlinear electric field propagation. The performance of the sectorial sensitivity matrix is evaluated through numerical simulation and experimental studies. From the results, the sectorial sensitivity matrix improves the reconstructed images with a 42.92% and 67.12% lower root mean square error RMSE, 1.66% and 16.16% higher correlation coefficient CC, and 21.37% lower image error IE values in the simulation and experimental studies respectively as compared to the standard sensitivity matrix. The sectorial sensitivity matrix has an advantage of high performance even when the signal to noise ratio in an ECT system is low. Under such conditions, the present normalization method is incapable of calculating the normalized capacitance of the inclusion due to the low ratio of permittivity of the inclusion to that of the background.

Objectives . The human skeletal muscle responds immediately under electrical muscle stimulation (EMS), and there is an immediate physiological response in human skeletal muscle. Non-invasive quantitative analysis is at the heart of our understanding of the physiological significance of human muscle changes under EMS. Response muscle areas of human calf muscles under EMS have been detected by frequency difference electrical impedance tomography ( fd -EIT). Approach . The experimental protocol consists of four parts: pre-training ( pre ), training ( tra ), post-training ( post ), and relaxation ( relax ) parts. The relaxation part has three relaxation conditions, which are massage relaxation (MR), cold pack relaxation (CR), and hot pack relaxation (HR). Main results . From the experimental results, conductivity distribution images σ ^p ( p means protocol = pre , tra , post , or relax ) are clearly reconstructed by fd -EIT as response muscle areas, which are called the M ₁ response area (composed of gastrocnemius muscle) and the M ₂ response area (composed of the tibialis anterior muscle, extensor digitorum longus muscle, and peroneus longus muscle). A paired samples t -test was conducted to elucidate the statistical significance of spatial-mean conductivities 〈 σ ^p 〉 _{M 1} and 〈 σ ^p 〉 _{M 2} in M ₁ and M ₂ with reference to the conventional extracellular water ratio β ^p by bioelectrical impedance analysis . Significance . From the t -test results, 〈 σ ^p 〉 _{M 1} and 〈 σ ^p 〉 _{M 2} have good correlation with β ^p . In the post-training part, 〈 σ ^post 〉 and β ^post were significantly higher than in the pre-training part ( n = 24, p < 0.001). The relax–pre difference ratios of spatial-mean conductivity Δ〈 σ ^relax–pre 〉 and the relax–pre difference ratios of extracellular water ratio Δ β ^relax–pre in both MR and CR were lower; on the contrary, the Δ〈 σ ^relax–pre 〉 and Δ β ^relax–pre in HR were significantly higher than those in post–pre difference ratios of spatial-mean conductivity Δ〈 σ ^post–pre 〉 ( n = 8, p < 0.05). The reason for the changes in 〈 σ ^p 〉 _{M 1} and 〈 σ ^p 〉 _{M 2} are caused by the changes in muscle extracellular volumes. In conclusion, fd -EIT satisfactorily evaluates the effectiveness of human calf muscles under EMS.

A weighted parameter vector χ _norm based on extracellular fluid resistance in the Cole impedance model is hereby proposed in order to compensate for the volatile-distributed current. The volatile-distributed current due to variance in the unknown contact impedance in an electrical impedance tomography (EIT) sensor distorts the ideality of the frequency-dependent behavior of the object of interest, leading to inaccuracy in the reconstructed images. The sources of variance in the unknown contact impedance include the use of electrodes with inconsistent impedance values, electrochemical reaction or the improper attachment of electrodes to the object of interest. χ _norm represents the current pathway lengths at zero frequency which reflects the volatile-distributed current, and it is used to determine the source of the measured impedance. The source of the unknown contact impedance can be the background object in the normal physiological condition, an inclusion object in an abnormal physiological condition or systematic error. The new reconstruction methods are derived from the frequency-difference EIT (fd-EIT) and the weighted-frequency-difference EIT (wfd-EIT) using χ _norm . The new reconstruction methods are frequency-difference electrical impedance spectro-tomography (fd-EIST) and weighted-frequency-difference electrical impedance spectro-tomography (wfd-EIST). The performance of fd-EIST and wfd-EIST was evaluated by experimental and simulation studies using biomaterials with frequency measurements from f = 500 Hz to f = 100 kHz and the results were compared with those from fd-EIT and wfd-EIT. The results showed that the use of χ _norm reduces the root mean square error, position error, ringing and shape deformation. It also increases the ideality of the frequency-dependent behavior, either for the inclusions or the background objects at different frequencies.