Simulation analysis on stimulation patterns of three-dimension electrical impedance tomography

To solve the lack of information and the error in forward and inverse problem caused by the approximation of actual three-dimensional field from two-dimensional field in electrical impedance tomography (EIT), this article presents a new EIT system. This system improves one-dimensional electrode array to two-dimensional array, and extends the solution domain to the entire three-dimensional field in order to increase the information quantity and eliminate the model error. Based on several current stimulation patterns in EIT which might yield the best sensitiveness for 3-D field, we calculate the forward problem by finite element method and the distinguishability and surface projection image method. The results show that the back electrode pattern has obvious advantages in detecting depth and precision, and has convenience in clinical application. The conclusion of this article can provide reference for the study of 3-D EIT.     

High speed, high precision digital phase sensitive detector design for electrical impedance tomography

Electrical impedance tomography (EIT) system must have the properties of high precision and speed, thus the digital phase sensitive detector (DPSD) based on the field programmable gate array(FPGA) is developed for data collection of EIT. Based on the principle of DPSD, the relationship between signal to noise ratio (SNR) and sample resolution as well as total number of samples is deduced. An implementation scheme of this system and a method of designing analog to digital converter (ADC) clock based on direct digital synthesis (DDS) technology are provided. The system adopts high speed multi channel ADC and low jitter clock conditioner for ADC. Real time DPSD is implemented with FPGA. The experiments show that the measurement accuracy reaches 0.03% and the SNR reaches 85 dB. The agar phantom experiments prove that the performance of the DPSD meet the designing requirement for EIT.     

A STUDY ON THE IMAGE RECONSTRUCTION AIGORITHM FOR ELECTRICAL IMPEDANCE CT

A new image reconstruction method fur electrical impedance CT is derived rigorously. The Jacobi Matrix is made sparse by analysing each narrow region which is detrmined by equipotential lines seperately. Both storage and computation can be deduced. The method is realized by using first order square FEM and some computer model is reconstructed. The relaxed version of Hildreth's method for interval convex programing is applied, which can hold the sparsity of the Jacobi Matrix and overcome the ill-condition of the matrix.     

Modeling and simulation based on open electrical impedance tomography

In order to improve the error in image reconstruction caused by changeable positions of the electrodes in closed electrical impedance tomography, we propose an open electrical impedance tomography (OEIT) model using fixed electrode array. The problem was approximately assumed to be a virtual field by defining certain local sensitive area instead of solving the boundary problem in the whole electromagnetic field strictly. Modeling and simulation of OEIT have been conducted to define reasonable boundary parameters and electrode array structure. The finite element method is used for forward computation while Newton one step error reconstructor is used for image reconstruction. The target position, area and conductivity change can be reflected by the relative change of the boundary voltage and the reconstructed image is clear. Better resolution and positioning accuracy can be obtained in the shallower surface of the body by OEIT, so it is valuable in clinical applications.     

Electrical Impedance Technology Applied to Examining Brain Edema

Biological electrical impedance is a physical quantity to reflect electricity character of biological tissue, apparatus, cell or whole organism, which is a kind of new method developed recently to analyze component of body. This technology is unhurt examining method which obtains certain biomedicine information about human body according to electrical character and change of biological tissue or apparatus, has unhurt, cheap, safe, innocuity, operator simple and abundant information etc., is prone to be accepted by doctors and patients. Now unhurt brain electrical impedance double channel examining system and brain electrical impedance topographic mapping system have entered clinical experiment moment, and contactless magnetic induction tomography(CMIT) is taken notice of widely as a more effective examining method.     

Examining brain oedema through brain electrical impedance topographic mapping

Change of Brain Electrical Impedance has great relations with brain oedema and brain block, a new method of Examining Brain Oedema through Brain Electrical Impedance Topographic Mapping(BEITM)is reviewed. Network topology structure that used in BEITM are also presented. According to topology, we discuss the drawing algorithm that based on triangle element. Some patients have been measured to make clinical data, according to this data Brain Electrical Impedance topographic come into being by computer at last, functional imaging has been implemented. Clinical case analysis compared with change state of an illness and repeatability of steady patient's data has proved the method is feasible.     

Optimization of regularization parameters for electricalimpedance tomography

The image quality and computation speed are bounded up with regularization parameters. To improve the ill-posed property of the inverse problem of electrical impedance tomography (EIT), a novel approach, which is based on the product of the residual norm and the solution norm(PRS), is presented to optimize the Tikhonov regularization parameters of EIT. To verify the feasibility and effectiveness of the proposed method, five simulations of image reconstruction, together with a tank experiment, have been carried out with considering different sizes, locations, conductivity distributions and numbers of the target areas as well as the scenarios of the data with noises. The encouraging results demonstrate that the proposed optimization approach can identify the relatively optimal regularization parameter quickly and has better noise immunity, and it also enhances the quality of the reconstructed images significantly compared with the conventional L-curve method.     

宰后牛骨骼肌肉生物电阻抗特性初探

用四电极法在多频(5-200kHz)条件下对宰后牛骨骼肌肉的电阻抗特性进行了初步的研究。发现牛骨骼肌生物电阻抗与肌肉纤维方向、电流信号频率和宰后肌肉所经历的阶段有关。横向电阻(沿垂直于骨骼肌纤维方向)大于纵向电阻(沿骨骼肌纤维方向),而且受电流信号频率的影响较明显,尤其是在5￣100kHz范围内。牛宰后生物电阻抗的变化与pH值的变化有一定的相关性。     

The Open Software System for Electrical Impedance Computed Tomography

The components of open software system for Electrical Impedance Computed Tomography and their functions under Windows environment are introduced, and the ways to extend system's functions are given.     

Analysis of cross-plane electrode arrays for electrical impedance tomography

A cross-plane electrical impedance tomography system is constructed to solve the problem of the conventional planar electrode array. This system consists of four planar and eight axial cross imaging planes composing from 65 electrodes. The Tikhonov regularization algorithm is adopted for image reconstruction in simulation and flume experiment. Comparison between the reconstruction result and the original object shows that the cross-plane reconstruction method in three-dimensional space provides higher spatial resolution and position accuracy. In addition, it effectively reduces the amount of computation, and reveals great prospect for the application of clinical examination and monitoring.     

An Application of Continuation Method for Electrical Impedance Tomography in Brain Hematoma Case

It is a significative attempt in medical diagnosis that Electrical Impedance Tomography is used to hematoma monitoring. Since there is great difference in physiological parameters among different persons, among varieties of ill cases, and different tissues, it is important to loosen the limits of initial values of reconstruction algorithm. A new approach named Continuation method is proposed in Electrical Impedance Tomography. In addition, simulating calculation results are given to validate the approach effective.     

Three-dimensional reconstruction of electrical impedance tomography based on corresponding points matching interpolation

An interpolation algorithm with corresponding point matching is presented for interpolating two-dimensional reconstructed images of electrical impedance tomography(EIT）to realize three-dimensional reconstruction. The calculation methods of the gradient and its orientation angle have been adjusted according to the characteristic of the EIT data, and the interpolated slice shows good quality. The experimental model is a 2.1 S/m cylinder agar block immersed in a cylindrical water tank. The comparisons of the presented algorithm to the linear interpolation and the shape-based interpolation are made. The results show that corresponding point matching algorithm can ensure both accuracy and computational efficiency, thus the algorithm satisfies the requirements of the real-time EIT monitoring.     

电阻抗图谱法与电导法测定枣树枝条抗寒性的相关性

选育抗寒性强的品种是避免枣树受到低温气候伤害的最有效方法,因而,探寻测定枣树抗寒性的合适方法非常重要。以7个品种枣树1年生枝条为材料,利用电导率(EL)法和电阻抗图谱(EIS)法测定其抗寒性。研究了低温胁迫下枣树枝条EIS参数（单分布电路元素电阻率r、r₁;胞外电阻率r_e;胞内电阻率r_i;弛豫时间τ;弛豫时间分布系数ψ）的变化,并对比分析了2种方法测定枣树抗寒性结果的相关性,以期确定快速测定枣树抗寒性的最佳参数。结果表明：在低温胁迫下,随着处理温度的降低,枣树枝条的各EIS参数均减小。通过EIS参数胞外电阻率r_e和弛豫时间τ拟合估算的抗寒性与EL法测定的抗寒性呈显著正相关,相关系数分别为0.840和0.879。结果表明冷冻处理后EIS参数r_e和τ可以作为测定枣树抗寒性的参数。采用EIS法测定抗寒性省时、不需要温育、不破坏植株,具有更大的优越性。     

Open-electrical impedance tomography with variation regularization algorithm

Open electrical impedance tomography (OEIT) with fixed electrode row is proposed to overcome the clinical application problems in closed electrical impedance tomography such as poor model adaptability, electrode position error, and inflexibility. Variation regularization algorithm (VRA) using variations function as regularization penalty term is proposed to save the more serious ill-posed inverse problem of OEIT. Simulation and experiment results show that the inverse problem of OEIT can be efficiently solved by VRA. The position, size and the relative value of conductivity of target at shallower position below electrodes can be clearly reflected by the restored image. OEIT is more potentially practical and effective in clinical applications.     

Image reconstruction of electrical impedance tomography based on particle swarm optimization algorithm

Electrical impedance tomography (EIT) has many advantages in practical application,but image reconstruction of EIT is a highly ill-posed, non-linear inverse problem. Newton-Raphson algorithms are widely used in EIT, which have to calculate the Jacobian matrix and use regularization techniques. So this kind of algorithms is complex and less stable. To address the problem, a new static image reconstruction method for EIT is proposed based on particle swarm optimization (PSO) algorithm. PSO is a population-based, adaptive search optimization technique. It is simple in concept, few in parameters, quick in convergence and easy in implementation. The model of EIT forward problem is given and some appropriate improvements in PSO are made to accommodate the solution of EIT. Compared with Newton-Raphson(MNR) algorithms, PSO only uses an iterative processing to get the best solution instead of using a complicated Jacobian matrix. The experimental results indicate that using PSO-based algorithm to solve image reconstruction of EIT, the position of mutation region is more accurate and graphics space resolution is much higher.     

Designing a microstrip bandpass filter with multi coupling stepped impedance resonators

A compact multi coupling microstrip bandpass filter based on microstrip stepped impedance resonator (SIR) characteristics was presented. The principle of second harmonic suppression with a proper impedance ratio was introduced, which improved the rejection at the stopband of the bandpass filter. A microstrip multi coupling SIR bandpass filter with 3.65 GHz center frequency and 3.5% fractional bandwidth was designed and fabricated. The result of simulating the filter showed -10 dB attenuation at the first harmonic center frequency, making the upper skirt deeper and the bandpass response more symmetric than filters without microstrip SIR. The experimental filter was measured and had -3.2 dB insert loss at the central frequency and a bandwidth of approximately 120 MHz. The measured result was consistent with the simulated one.     

Relationship Between Electrical Property and Microstructure of Mineral Admixtures-Cement Paste

The electrical properties of fly ash, slag and limestone powder-cement paste were studied by the methods of Cyclic Voltammetry and AC Impedance Spectroscopy. The results of electrical test were fitted by equivalent circuit. The correlations between electrical parameters of paste and unevaporable water content, pore structure by mercury porosimetry were compared. The results show that there is a positive relation between the unevaporable water content and the electrical resistivity of paste. If the unevaporable water content is higher, the hydration degree is higher and the electrical resistivity of paste is higher. The electrical resistivity of paste is increased with fly ash and slag, and it is unaffected with limestone powder of 5% dosage. The resistance Rs of pore solution of paste is increased with the prolongation of hydration, and the changes of resistance Rs and the electrical resistivity are unanimous. The resistance Rp and electrical capacitance C of gel are related to C-S-H content, and there is a negative relation between the resistance Rp and electrical capacitance C of gel. The complexity of pore structure of paste is increased with the prolongation of hydration. The constant phase angle exponent P by AC Impedance Spectroscopy is decreased and the value of fractal dimension by mercury porosimetry is increased.     

盐碱地区不同观赏树种电阻抗图谱参数和电导率的变化

在盐碱地区对4-6月生长期的两种不同观赏树种垂榆（Ulmus pumila var. pendula）和女贞（Ligustrum lucidum）进行电导率及电阻抗测定,分析春季和初夏生长期间在盐碱地区这两种不同观赏树种电导率和电阻抗图谱参数的变化。结果表明：在自然的盐碱环境条件下生长的垂榆和女贞,随着生长期的延长其电导率和电阻抗图谱参数均出现规律性变化,垂榆和女贞的叶片电导率均表现为先增加、后减小的变化趋势,茎均表现为先减小、后增加的变化趋势;两种观赏树种叶片的胞外电阻率表现为先增加、后减小的变化趋势,茎的胞外电阻率和弛豫时间表现为不断增加或先增加、后减小的变化趋势。相关分析表明应用电阻抗图谱参数可以表征观赏树种受盐胁迫的程度,为垂榆和女贞耐盐碱程度的电阻抗诊断提供初步的参数。     

苹果砧木实生后代枝条电阻抗参数与抗寒性的相关性

以苹果砧木实生后代单株为试材,研究低温胁迫下苹果砧木实生后代枝条电阻抗（EIS）参数（胞外电阻率re、胞内电阻率ri、电阻率r1和弛豫时间τ）的变化,并分析电阻抗图谱法和常规的电导法测定的苹果砧木抗寒性的相关性。结果表明,随着温度降低,苹果砧木枝条的胞外电阻率re、胞内电阻率ri、电阻率r1和弛豫时间τ均减小。以苹果砧木枝条的EIS参数电阻率r1、胞外电阻率re、胞内电阻率ri求得的抗寒性与EL法测定的抗寒性呈显著性正相关（r=0.838～0.906）。r1测定的苹果砧木枝条的抗寒性与EL法测定的抗寒性相差10℃,不适合用于测定苹果砧木枝条的抗寒性。表明经低温胁迫后的苹果砧木枝条用re和ri可以测定苹果砧木枝条的抗寒性。     

Post-process of Finite Element Method in Electrical Impedance Tomography

In the research of electrical impedance tomography (EIT), each calculation may produce a large amount of data(such as conductance , resistance etc.). The rule of these data is not clear and is hard to understand. How to express the calculation result by means of image in order that such parameters as conductance and resistance can be grasped from the image is significant in analyzing and understanding the calculation result and is helpful to the doctor. This paper has discussed the realization of the post-process of finite element method in electrical impedance tomography and we have developed the software of the post-process of finite element method using Visual C++ .NET and OpenGL. Some problems in drawing the contour line and color contour band have been solved properly.