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Static imaging of the electrical impedance tomography can obtain the absolute electrical conductivity distribution at one section of the subject. The test is performed on a cylinder physical phantom in which slim rectangle, hollow cylinder, small rectangle or three cylinders are selected to simulate complex conductivity perturbation objects. The measurement data is obtained by a data acquisition system with 32 compound electrodes. A group of static images of conductivity distribution in the cylinder phantom are reconstructed by the modified Newton-Raphson algorithm with two kinds of regularization methods. The results show correct position, size, conductivity difference, and similar shape of the perturbation objects in the images. [ABSTRACT FROM AUTHOR]

Thus far, the measurement of dielectric properties of biological tissues has been achieved on the assumption that the biological tissues are homogeneous. In fact, most tissues should be heterogeneous because there are many small structures included in these tissues, such as blood vessel, nerve fiber and so on. When the dielectric properties of these tissues are measured by conventional sensor, the results are not the dielectric properties of tissues but the effective dielectric properties of the mixture. In this paper, the influence of the inclusion in tissues on the measurement of dielectric properties of heterogeneous biological tissues is studied and the analysis of the effective dielectric properties of heterogeneous tissues based on the mixing rule is proposed. When the coaxial probe is used to measure the dielectric properties of tissue, the results are relative to the dielectric properties of inclusion, dielectric properties of background tissue and the effective volume fraction of inclusion. Therefore, the dielectric properties of inclusion could be calculated according to mixing rule, after the effective dielectric properties are measured and the effective volume fraction of inclusion is estimated. [ABSTRACT FROM AUTHOR]

The synergistic effect of nucleating agents and plasticizers on the thermal and mechanical performance of PLA nanocomposites was investigated with the objective of increasing the crystallinity and balancing the stiffness and toughness of PLA mechanical properties. Calcium carbonate, halloysite nanotubes, talc and LAK (sulfates) were compared with each other as heterogeneous nucleating agents. Both the DSC isothermal and non-isothermal studies indicated that talc and LAK were the more effective nucleating agents among the selected fillers. Poly(D-lactic acid) (PDLA) acted also as a nucleating agent due to the formation of the PLA stereocomplex. The half crystallization time was reduced by the addition of talc to about 2 min from 37.5 min of pure PLA by the isothermal crystallization study. The dynamic mechanical thermal study (DMTA) indicated that nanofillers acted as both reinforcement fillers and nucleating agents in relation to the higher storage modulus. The plasticized PLA studied by DMTA indicated a decreasing glass transition temperature with the increasing of the PEG content. The addition of nanofiller increased the Young's modulus. PEG had the plasticization effect of increasing the break deformation, while sharply decreasing the stiffness and strength of PLA. The synergistic effect of nanofillers and plasticizer achieved the balance between stiffness and toughness with well-controlled crystallization. [ABSTRACT FROM AUTHOR]

In this paper, a convenient and noninvasive scanning imaging method using microwave frequency band for abnormal subepidermal tissues detection is proposed in the aim to improve diagnosis and prognosis in clinical environments. This method is based on the reflective detection technology with coaxial probe that is used to measure the dielectric properties of tissues. An improved equivalent circuit and simulated annealing algorithm (SA) were used in this work to analyze the dielectric properties of tissues. Computational simulations incorporating a simplified model of subcutaneous hemorrhage described in this work were used to evaluate this method. The dielectric properties data of tissues in the model of simulation is derived from the literature. The simulation results demonstrated the potential of this method to detect abnormal subepidermal tissues conveniently and expose them in the image accurately. [ABSTRACT FROM AUTHOR]

The dielectric properties of human liver were determined by characterization of tissue absorption and coupling of electromagnetic energy in the electromagnetic field. In this study the ex-vivo dielectric properties of human hepatocellular carcinoma (well and moderately differentiated), liver hemangioma, hepatic fibrosis (stages S1 and S2), and normal liver tissue were measured and analyzed over the frequency range of 10 Hz to 100 MHz. The dielectric properties over the frequency range can reflect tissue information including biological macromolecules, vesicles, and cellular membrane; these information aids in distinguishing different physiological states and lesions. The ex-vivo conductivity, permittivity, resistivity, as well as the characteristic parameters between the lesions and normal liver were analyzed and their differences were also verified. The data can contribute to developing bioelectric applications for tissue diagnostics and creating more accurate computer models for medical applications. [ABSTRACT FROM AUTHOR]

Stroke has a high mortality and disability rate and should be rapidly diagnosed to improve prognosis. Diagnosing stroke is not a problem for hospitals with CT, MRI, and other imaging devices but is difficult for community hospitals without these devices. Based on the mechanism that the electrical impedance of the two hemispheres of a normal human head is basically symmetrical and a stroke can alter this symmetry, a fast electrical impedance imaging method called symmetrical electrical impedance tomography (SEIT) is proposed. In this technique, electrical impedance tomography (EIT) data measured from the undamaged craniocerebral hemisphere (CCH) is regarded as reference data for the remaining EIT data measured from the other CCH for difference imaging to identify the differences in resistivity distribution between the two CCHs. The results of SEIT imaging based on simulation data fromthe 2Dhuman head finite elementmodel and that fromthe physical phantomof human head verified thismethod in detection of unilateral stroke. [ABSTRACT FROM AUTHOR]

A simulative study was performed to measure the dielectric properties of anisotropic tissue using several in vivo and in vitro probes. COMSOL Multiphysics was selected to carry out the simulation. Five traditional probes and a newly designed probe were used in this study. One of these probes was an in vitro measurement probe and the other five were in vivo. The simulations were performed in terms of the minimal tissue volume for in vivo measurements, the calibration of a probe constant, the measurement performed on isotropic tissue and the measurement performed on anisotropic tissue. Results showed that the in vitro probe can be used to measure the in-cell dielectric properties of isotropic and anisotropic tissues. When measured with the five in vivo probes, the dielectric properties of isotropic tissue were all measured accurately. For the measurements performed on anisotropic tissue, large errors were observed when the four traditional in vivo probes were used, but only a small error was observed when the new in vivo probe was used. This newly designed five-electrode in vivo probe may indicate the dielectric properties of anisotropic tissue more accurately than these four traditional in vivo probes. [ABSTRACT FROM AUTHOR]

In this study, the in vivoand in vitroosteogenesis was successfully induced in situby the controlled release of alendronate (AL) and dexamethasone (Dex) from the poly(lactic-co-glycolic acid) (PLGA)/hydroxyapatite (HA) sintering microsphere scaffold (SMS). This microspherically based controlled release system is constructed with two-levels of structure: AL attached HA particles and a Dex-PLGA matrix. Bone marrow mesenchymal stem cells (BMSCs) cultured on AL loaded PLGA/HA sintering microsphere scaffold (PLGA/HA-AL-SMS) and AL-Dex loaded PLGA/HA sintering microsphere scaffold (PLGA/HA-Com-SMS) displayed a strong osteogenic commitment locally in vitro. The osteogenic commitment of BMSCs on the scaffolds were verified by an alkaline phosphatase (ALP) activity assay, real time-PCR and immunohistochemistry analysis. The results demonstrated that BMSCs cultured on PLGA/HA-AL-SMS and PLGA/HA-Com-SMS exhibited superior osteogenic differentiation owing to significantly high gene expression of typical osteogenic genes–osteocalcin (OC), type I collagen, BMP-2, and also protein secretion of type I collagen. In addition, BMSCs laden with PLGA/HA-AL-SMS and PLGA/HA-Com-SMS were also implanted into the back subcutis of mice and bone defects surgically created on rabbit femurs. The histology and immunohistochemistry results indicated that the scaffolds promoted BMSCs osteogenic commitment and also the new bone formation in vivo. In conclusion, this controlled release system is promising for implanted biomedical devices to improve bone reparation and regeneration. [ABSTRACT FROM AUTHOR]

A series of experimental precipitated calcium carbonates (PCCs) coated with commercial stearic acid (stearin), with the coating amount of stearin added to the PCC particles ranging from 3 to 13.5 wt %, were prepared in aqueous medium and characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). FTIR and TGA results indicated that only calcium stearate is present without any free stearic acid left on the surface of the produced PCCs. It was also found that the calcium stearate formed on the coated surface is partially chemisorbed and partially physisorbed. Interestingly, the surface coverage of the chemisorbed stearate, determined by the DSC technique in about 3.25 wt %, was much lower than the theoretical full monolayer coverage (4.17 wt %) for the same set of particles. This result was confirmed by determining the amount necessary to cover the filler with a full monolayer of surfactant by means of a dissolution method where the amount of dissolved surface agent, after the coating reaction, was measured by gas chromatography (GC). In other words, a complete chemisorbed monolayer on the surface cannot be reached, even in the presence of an amount of stearate ions far in excess compared to those required by the stoichiometry. This can be explained by considering that the coating in aqueous medium is quite different from solvent or dry coating, since the process is controlled by micelle adsorption, followed by the collapse of micelles into double or multiple layers during the drying stage. [ABSTRACT FROM AUTHOR]

Low, uniform, and stable electrode–skin impedance is required to achieve good performance of the electrode–skin interface for electrical impedance scanning (EIS) examination. This can be used to measure the real impedance distribution of breast tissue beneath the skin. In this study, the gel interface, the cotton fine grid thin layer (CFGTL) interface, and the hydrogel interface were compared. Experiments were conducted to assess the influence of each interface on the multi-frequency EIS data and their capacity to retain moisture. Results showed that the CFGTL and hydrogel interfaces decreased contact impedance and made the impedance between the electrodes and the breast skin more even and stable. The Cole–Cole model was also used to fit the multi-frequency EIS data. The results demonstrated that the CFGTL and hydrogel interfaces were advantageous for measuring the impedance of the breast tissue under the gel interface. In general, the CFGTL and hydrogel interfaces had good contact with the skin, and both interfaces were proper choices for EIS examination at present. The hydrogel interface was a better choice for our new EIS system. [ABSTRACT FROM AUTHOR]

In vitro osteogenesis was successfully achieved with synovium-derived mesenchymal stem cells (SMSCs), which intrinsically have a strong chondrogenic tendency, by in situ release of alendronate (AL) and dexamethasone (Dex) from poly(lactic-co-glycolic acid) (PLGA)/hydroxyapatite (HA) sintered microspherical scaffold (PLGA/HA-SMS). Cumulative release profiles of AL and Dex from PLGA/HA-SMS and the influence on SMSCs osteogenic commitment were investigated. SMSCs seeded in Al-/Dex-loaded PLGA/HA-SMS (PLGA/HA-Com-SMS) exhibited significant osteogenic differentiation, as indicated by high yields of alkaline phosphatase (ALP) and bone calcification. In addition, mechanical properties (compressional) of PLGA/HA-Com-SMSs were also evaluated and approved. In conclusion, by promoting osteogenic commitment of SMSCs in vitro, this newly designed controlled-release system opens a new door to bone reparation and regeneration. [ABSTRACT FROM AUTHOR]

A novel material hexagonal mesoporous silica-hydroxyapatite (HMS-HA) has been developed based on self-assembly of nanohydroxyapatite in mesoporous silica in situ. The structural and textural properties of the materials are, respectively, characterized via X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N2 adsorption, thermogravimetic analysis, and high-resolution transmission electron spectroscopy (HRTEM). Variable crystallinity of HA involved in the mesopores yields from different sintering temperature, and correspondingly determines different degradation manners. This biocompatible new material hybridized nanoporosity to well acknowledge biofunctional scaffold (HA). It promises a high potential for application in drug and gene delivery. [ABSTRACT FROM AUTHOR]

Electrical impedance scanning (EIS) is a kind of potential bio-impedance measurement technology, especially aiding the diagnosis of breast cancer in women. By changing the frequency of the driving signal in turn while keeping the other conditions stable, multi-frequency measurement results on the object can be obtained. According to the least square method and circuit theory, the parameters in two models are deduced when measured with data at multiple driving frequencies. The arcs, in the real and imaginary parts of a trans-admittance coordinate, made by the evaluated parameters fit well the realistic data measured by our EIS device on female subjects. The Cole-Cole model in the form of admittance is closer to the measured data than the three-element model. Based on the evaluation of the multi-frequency parameters, we presented parameter mapping of EIS using two kinds of circuit model: one is the three-element model in the form of admittance and the other is the Cole-Cole model in the form of admittance. Comparing with classical admittance mapping at a single frequency, the multi-frequency parameter mapping will provide a novel vision to study EIS. The multi-frequency approach can provide the mappings of four parameters, which is helpful to identify different diseases with a similar characteristic in classical EIS mapping. From plots of the real and imaginary parts of the admittance, it is easy to make sure whether there exists abnormal tissue. [ABSTRACT FROM AUTHOR]

We proposed a new method based on total relative change (TRC) from measured boundary voltages to quantify the volume changes of fluid during electrical impedance tomography (EIT) monitoring. The results showed that TRC linearly correlated with the volume of infused saline solution into a phantom, and the slope of TRC changes was approximately linear with the infusion speed. A inserted copper tube at different positions did not affect TRC significantly. The linear relationship between TRC and volume change indicates that TRC could be a good quantitative index for dynamic MT. [ABSTRACT FROM AUTHOR]

Since the need for vascular networks to supply oxygen and nutrients while expelling metabolic waste, most cells can only survive within 200 µm of blood vessels; thus, the construction of well-developed blood vessel networks is essential for the manufacture of artificial tissues and organs. Three-dimensional (denoted as 3D) printing is a scalable, reproducible and high-precision manufacturing technology. In the past several years, there have been many breakthroughs in building various vascularized tissues, greatly promoting the development of biological tissue engineering. This paper highlights the latest progress of 3D printed vascularized tissues and organs, including the heart, liver, lung, kidney, and penis. We also discuss the application status and potential of the above printed tissues, and prospect the further requirement of 3D printing technology for manufacturing clinically useable vascularized tissues. [ABSTRACT FROM AUTHOR]

Dielectric properties are vital biophysical features of biological tissues, and biological activity is an index to ascertain the active state of tissues. This study investigated the potential correlation between the dielectric properties and biological activities of human hepatic tissue with prolonged ex vivo time through correlation and regression analyses. The dielectric properties of 26 cases of normal human hepatic tissue at 10 Hz to 100 MHz were measured from 15 min after isolation to 24 h at 37 °C with 90% humidity. Cell morphologies, including nucleus area (NA) and alteration rate of intercellular area (ICAR), were analyzed as indicators of biological activities. Conductivity, complex resistivity, and NA exhibited opposing changes 1 h after isolation. Relative permittivity and ex vivo time were not closely correlated (p > 0.05). The dielectric properties measured at low frequencies (i.e. <1 MHz) were more sensitive than those measured at high frequencies in reflecting the biological activity of ex vivo tissue. Highly significant correlations were found between conductivity, resistivity and the ex vivo time (p < 0.05) as well as conductivity and the cell morphology (p < 0.05). The findings indicated that establishing the correlation between the dielectric properties and biological activities of human hepatic tissue is of great significance for promoting the role of dielectric properties in biological science, particularly in human biology. [ABSTRACT FROM AUTHOR]

Silica nanotubes have been extensively applied in the biomedical field. However, very little attention has been paid to the fabrication and application of micropatterned silica nanotubes. In the present study, microgrooved silica nanotube membranes were fabricated in situ by microgrooving silica-coated collagen hybrid fibril hydrogels in a Teflon microfluidic chip followed by calcination for removal of collagen fibrils. Scanning electron microscopy images showed that the resulting silica nanotube membranes displayed a typical microgroove/ridge surface topography with ~50 μm microgroove width and ~120 μm ridge width. They supported adsorption of bone morphogenetic protein 2 (BMP-2) and exhibited a sustained release behavior for BMP-2. After culturing with osteoblast MC3T3-E1 cells, they induced an enhanced osteoblast differentiation due to the release of biologically active BMP-2 and a strong contact guidance ability to directly align and elongate osteoblasts due to the presence of microgrooved surface topography, indicating their potential application as a multi-functional cell-supporting matrix for tissue generation.

To seek a single source drive pattern that is more suitable for brain electrical impedance tomography (EIT), a comparison between adjacent, cross, polar and newly proposed quasi-polar drive patterns was made in aspects of boundary voltages dynamic range, independent measurement number, Total boundary voltage changes and anti-noise performance based on an equivalent circuit of the brain resistivity distribution consisting of 7300-odd resistors. The results demonstrate that quasi-polar drive pattern is optimal in all the aspects except dynamic range. Polar and cross drive patterns come next, and adjacent drive pattern is the worst. Therefore, the quasi-polar drive pattern should be chosen for brain EIT.

Electrical impedance scanning (EIS) is a new adjunctive diagnostic method for women breast cancer examination. In clinic research, we found some influencing factors which can induce a bad EIS imaging results. In order to analyze the influencing factors on EIS imaging and find the solutions, we set up an EIS workbench which can simulate the influencing factors that may happen in a clinic. We studied the influencing factors from size, depth of the target; the influence from the poor contact; the influence from the unparallel current field. The experiment results show that the detectability of EIS system is a function of the depth, the size and the area of electrodes; a good contact between the probe and the skin can decrease the artificial imaging; using the imaging algorithm can calibrate the imaging induced by unparallel current field.

A 16-channel magnetic induction imaging system is introduced briefly. Highly precise phase and magnitude detecting method is applied to the information acquisition. The resolution of phase detecting is 0.003deg. The results of magnitude detecting also provide us with useful information. The characteristic curves are smoother than that of our previous system. One dimension results in different positions of the measurement region demonstrate the trend of variation of the detected signals. The positions of the object affect the results greatly and the trend of variation is regular.

An image monitoring system using electrical impedance tomography (EIT) for intraperitoneal bleeding was designed (FMMU V3.5). It consists of a constant current driving source with frequency of 50 KHz, a high accuracy measurement module, a driving and measuring mode program-controlled circuits, a data acquisition card, an optoelectronic isolated digital I/O board, and a custom-specified linear power supply units. The system applied equal-potential back projection algorithm to reconstruct dynamic images. The relative accuracy of the system is 0.1%, the RTI noise is 11.1 mu V (bandwidth 100 Hz). Based on physical phantom, images reconstructed by the system showed that it can image dynamically to the infused saline solution, and by infusing more solution the gray changed area of the image also enlarged accordingly. For stomach filling model in vivo, the dynamic imaging processes showed that the system can clearly and sensitively monitoring the saline solution drinking into the stomach for 50 ml each time, and by drinking more saline solution the conductivity changed area of the dynamic image also enlarged accordingly.

To establish a high precision data acquisition system for multi-frequency electrical impedance tomography (EIT), a series of methods were introduced. Those methods include building a driving signal with up to four frequency components to diminish the effect of the dynamic change of tissues resistivity, extracting the impedance information by a digital demodulator that can improve the SNR by 8 times. The system that established can work at a wide range from 1.6kHz to 380kHz. Its CMRR is 74dB at 100kHz. The output impedance of current source is 2M&#937; at that frequency. And measurement precision on a 100ohm resistor is better than -80dB in full bandwidth. Both the quasi-static and the dynamic imaging results based on a saline tank can reflect the resistivity changes inside the phantom clearly. Therefore, the system was competent in multifrequency EIT research work.