A new head phantom with realistic shape and spatially varying skull resistivity distribution.

Brain electrical impedance tomography (EIT) is an emerging method for monitoring brain injuries. To effectively evaluate brain EIT systems and reconstruction algorithms, we have developed a novel head phantom that features realistic anatomy and spatially varying skull resistivity. The head phantom was created with three layers, representing scalp, skull, and brain tissues. The fabrication process entailed 3-D printing of the anatomical geometry for mold creation followed by casting to ensure high geometrical precision and accuracy of the resistivity distribution. We evaluated the accuracy and stability of the phantom. Results showed that the head phantom achieved high geometric accuracy, accurate skull resistivity values, and good stability over time and in the frequency domain. Experimental impedance reconstructions performed using the head phantom and computer simulations were found to be consistent for the same perturbation object. In conclusion, this new phantom could provide a more accurate test platform for brain EIT research.

[Gentiana veitchiorum particles inhibited LPS induced pulmonary alveolar macrophages (AM) TNF-α production and the underlying mechanism].

AIM: To investigate the effect of Gentiana veitchiorum particles on the expression of TNF-α in pulmonary alveolar macrophages (AM) which induced by LPS, to explain the mechanism about anti-inflammatory action of Gentiana veitchiorum particles. METHODS: Purification of rat AM, TNF-α level in AM culture supernatant was detected by ELISA. Western blot method for detecting the expression of TNF-α and pERK in the AM. While application of ERK antagonist (PD98059) in rat AM and the expression of TNF-α was observed by Western blot. RESULTS: Gentiana veitchiorum particles can reduce the LPS induced AM TNF-α increase in dose dependent manner. Gentiana veitchiorum particles (100 mg/L) can significantly reduce the LPS induced pERK and TNF-α protein expression in AM. compared with LPS stimulation group, we found that ERK inhibitor (PD98059 30 mol/L), Gentiana veitchiorum particles intervention and Gentiana veitchiorum particles+PD98059 groups' TNF-α expression were significantly reduced in rat AM. CONCLUSION: Gentiana veitchiorum particles can inhibit the LPS induced pulmonary AM TNF-α expression, one of the possible mechanism is to inhibit the extracellular signal transduction pathway.

[A simulation study of electrical impedance scan-imaging based on a phantom].

OBJECTIVE: To testify the feasibility of electrical impedance scanning (EIS) imaging and to classify the factors influencing EIS imaging at the early stage of electrical impedance scanning breast imaging study. METHOD: Based on the EIS experiment workplace, a phantom to simulate the distribution of breast tissue was designed. Using NaCl solution and agar block with different conductance, three kinds of electric fields disturbances were simulated. RESULT: Different electric fields disturbance induced by different conductance distributions bring different imaging effects. CONCLUSION: The imaging based on the theory of EIS is feasible. Initiative factors influencing EIS imaging are confirmed.

Induced current electrical impedance tomography system: experimental results and numerical simulations.

In electrical impedance tomography (EIT), measurements of developed surface potentials due to applied currents are used for the reconstruction of the conductivity distribution. Practical implementation of EIT systems is known to be problematic due to the high sensitivity to noise of such systems, leading to a poor imaging quality. In the present study, the performance of an induced current EIT (ICEIT) system, where eddy current is applied using magnetic induction, was studied by comparing the voltage measurements to simulated data, and examining the imaging quality with respect to simulated reconstructions for several phantom configurations. A 3-coil, 32-electrode ICEIT system was built, and an iterative modified Newton-Raphson algorithm was developed for the solution of the inverse problem. The RMS norm between the simulated and the experimental voltages was found to be 0.08 +/- 0.05 mV (<3%). Two regularization methods were implemented and compared: the Marquardt regularization and the Laplacian regularization (a bounded second-derivative regularization). While the Laplacian regularization method was found to be preferred for simulated data, it resulted in distinctive spatial artifacts for measured data. The experimental reconstructed images were found to be indicative of the angular positioning of the conductivity perturbations, though the radial sensitivity was low, especially when using the Marquardt regularization method.