An on-line multi-frequency electrical resistance tomography (mfERT) device with a melt-resistive sensor and noise reduction hardware has been proposed for crystalline phase imaging in high-temperature molten oxide. The melt-resistive sensor consists of eight electrodes made of platinum-rhodium (Pt-20mass%Rh) alloy covered by non-conductive aluminum oxide (Al₂O₃) to prevent an electrical short. The noise reduction hardware has been designed by two approaches: (1) total harmonic distortion (THD) for the robust multiplexer, and (2) a current injection frequency pair: low $f^L$ and high $f^H$, for thermal noise compensation. THD is determined by a percentage evaluation of k-th harmonic distortions of ZnO at $f=0$.1~10,000 Hz. The $f^L$ and $f^H$ are determined by the thermal noise behavior estimation at different temperatures. At $f <1$00 Hz, the THD percentage is relatively high and fluctuates; otherwise, THD dramatically declines, nearly reaching zero. At the determined $f^L\ge$ 10,000 Hz and $f^H\approx$ 1,000,000 Hz, thermal noise is significantly compensated. The on-line mfERT was tested in the experiments of a non-conductive Al₂O₃ rod dipped into conductive molten zinc-borate (60ZnO-40B₂O₃) at 1000~1200 $°$C. As a result, the on-line mfERT is able to reconstruct the Al₂O₃ rod inclusion images in the high-temperature fields with low error, ${\mathsf{\varsigma }}_{f^L, T}$ = 5.99%, at 1000 $°$C, and an average error$⟨{\mathsf{\varsigma }}_{f^L}⟩$ = 9.2%.

Multi-node electrical impedance tomography ( mn EIT) throughout whole-body electrical muscle stimulation ( wb EMS) has been proposed for the simultaneous imaging of muscle compartments response. mn EIT has two characteristics which are 1) network hardware for synchronized measurement in multi-node simultaneously and 2) nodal fast Fourier transform (FFT) for cancelling time-varying noise. By mn EIT, the muscle compartments response in the upper arm and thigh of eight healthy subjects are imaged throughout wb EMS under four voltage intensity levels. According to the reconstructed images of conductivity distribution σ in prior training and throughout wb EMS, the conductivity distribution trend of the upper arm and thigh are boosted along with the rise of wb EMS voltage intensity. As the hardware error evaluation, the normalized spatial-mean impedance error ε _f of mn EIT is relatively higher in the increase of frequency while the average error 〈ε〉 is 7. 521% respectively. Here our mn EIT has the best result at ε _f <〈ε〉 which occurred at f ≤ 2500 Hz that covers the frequency selection f ₁ = 500 Hz and f ₂ = 1000 Hz to obtain the best visualization of conductivity distribution σ. Meanwhile, based on the Pearson correlation as the statistical evaluation, the mn EIT has a relatively high accuracy value at the upper arm r _arm =0.9391 and thigh r _thigh =0.894.

The comparison between breast cancer recognition by electrical impedance tomography implemented with Gaussian relaxation time distribution (EIT-GRTD) and conventional EIT has been conducted to evaluate the optimal frequency for cancer detection f ^cancer. The EIT-GRTD has two steps, which are 1) the determination of the f ^cancer and 2) the refinement of breast reconstruction through time-constant enhancement. This paper employs two-dimensional numerical simulations by a finite element method (FEM) software to replicate the process of breast cancer recognition. The simulation is constructed based on two distinct electrical properties, which are conductivity σ and permitivitty ε, inherent to two major breast tissues: adipose tissues, and breast cancer tissues. In this case, the σ and ε of breast cancer σ ^cancer, ε ^cancer are higher than adipose tissues σ ^adipose, ε ^adipose. The simulation results indicate that the most effective frequency for breast cancer detection based on EIT-GRTD is f ^cancer = 56,234 Hz. Meanwhile, conventional EIT requires more processing to determine the f ^cancer based on image results or spatial conductivity analysis. Quantitatively, both EIT-GRTD and conventional EIT can clearly show the position of the cancer in layers 1 and 2 for EIT-GRTD and only layer 1 for conventional EIT.

Local muscle quality imaging in human calf by phase angle electrical impedance tomography (ΦEIT) has been proposed to monitor the local muscle aging (MA), local muscle fat infiltration (FI), and local muscle cross-sectional area (CSA) for the daily monitoring of muscle quality. The MA is assessed by the calf-specialized phase angle Jacobian matrix ^Φ J, the FI is estimated by the phase angle distribution Φ _M , and the high-intensity binarization of phase angle cross-sectional area predicts CSA (Φ _M ). The ΦEIT is applied to 14 healthy subjects categorized into the young subject group (age ≤ 30, n =7) and middle-aged subject group (age > 30, n =7). An independent samples t-test was conducted to elucidate the statistical significance of spatial-mean phase angle <Φ> for MA assessment, spatial-mean phase angle <Φ> _M for FI estimation as compared with FI by conventional ultrasound (uFI), and phase angle cross-sectional area (Φ _M ) for CSA prediction compared to muscle area by the conventional ultrasound cross-sectional area (uCSA). The results from the independent t-test show that the ΦEIT correlates well with the subject’s age, uFI, and uCSA. The <Φ> is significantly correlated to the MA ( n =14, p < 0.001) in the young and middle-aged groups. The <Φ> _M is related substantially to FI ( n =14, p < 0.05) in the young and middle-aged groups. the Φ _M is significantly related to CSA ( n =14, p < 0.05) in the young and middle-aged subject groups.

Objectives. Phase angle muscle imaging has been proposed by phase angle electrical impedance tomography (ΦEIT) under electrical muscle stimulation (EMS) for long-term monitoring of muscle quality improvement, especially focusing on calf muscles. Approach. In the experiments, twenty-four subjects are randomly assigned either to three groups: control group (CG, n = 8), low voltage intensity of EMS training group (LG, n = 8), and optimal voltage intensity of EMS training group (OG, n = 8). Main results. From the experimental results, phase angle distribution images Ф are cleared reconstructed by ФEIT as four muscle compartments over five weeks experiments, which are called the M ₁ muscle compartments composed of gastrocnemius muscle, M ₂ muscle compartments composed of soleus muscle, M ₃ muscle compartments composed of tibialis-posterior muscle, flexor digitorum longus muscle, and flexor pollicis longus muscle, and M ₄ muscle compartment composed of the tibialis anterior muscle, extensor digitorum longus muscle, and peroneus longus muscle. Ф is inversely correlated with age, namely the Ф decreases with increasing age. A paired samples t-test was conducted to elucidate the statistical significance of spatial-mean phase angle in all domain <Ф>_Ω and in each muscle compartment <Ф> _M with reference to the conventional phase angle Ф by bioelectrical impedance analysis, muscle grey-scale G _muscle by ultrasound, and maximal dynamic strength S _Max by one-repetition maximum test. Significance. From the t-test results, <Ф>_Ω have good correlation with Ф and S _Max. In the OG, <Ф ^W5>_Ω, Ф ^W5, and (S _Max)^W5 were significantly higher than in the first week (n = 8, p < 0.05). A significant increase in the phase angle of both M ₁ and M ₄ muscle compartments is observed after five weeks in LG and OG groups. Only the OG group shows a significant increase in the phase angle of M ₂ muscle compartment after five weeks. However, no significant changes in the spatial-mean phase angle of M ₃ compartment are observed in each group. In conclusion, ФEIT satisfactorily monitors the response of each compartment in calf muscle to long-term EMS training.

Invasive ductal carcinoma (IDC) in breast specimens has been detected in the quadrant breast area: (I) upper outer, (II) upper inner, (III) lower inner, and (IV) lower outer areas by electrical impedance tomography implemented with Gaussian relaxation-time distribution (EIT-GRTD). The EIT-GRTD consists of two steps which are (1) the optimum frequency f opt selection and (2) the time constant enhancement of breast imaging reconstruction. f opt is characterized by a peak in the majority measurement pair of the relaxation-time distribution function γ , which indicates the presence of IDC. γ represents the inverse of conductivity and indicates the response of breast tissues to electrical currents across varying frequencies based on the Voigt circuit model. The EIT-GRTD is quantitatively evaluated by multi-physics simulations using a hemisphere container of mimic breast, consisting of IDC and adipose tissues as normal breast tissue under one condition with known IDC in quadrant breast area II. The simulation results show that EIT-GRTD is able to detect the IDC in four layers at f opt = 30, 170 Hz. EIT-GRTD is applied in the real breast by employed six mastectomy specimens from IDC patients. The placement of the mastectomy specimens in a hemisphere container is an important factor in the success of quadrant breast area reconstruction. In order to perform the evaluation, EIT-GRTD reconstruction images are compared to the CT scan images. The experimental results demonstrate that EIS-GRTD exhibits proficiency in the detection of the IDC in quadrant breast areas while compared qualitatively to CT scan images.