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.     

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.     

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.     

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.     

Applications in Reconstructing Images of the Upper Limbs of Human Body Using Electrical Impedance Computed Tomography Techniques

Human body experiment is one of the key problems for the electrical impedance tomogryphy(EIT) in clinical meaning.In this paper an orbicular passive 32 electrode system which is suited for the upper limbs is developed,and the mathematical model for EIT to solve inverse problem is given.After testing many upper arms or forearms of persons, the author have reconstructed the images which are distinct to distinguish skeleton from muscle.     

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.     

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。     

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.     

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.     

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.     

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。     

Calculation of lumped parameter of two-port network forvolume conduction energy transfer

Skin electrode unit is a channel through which energy can be transferred to the implanted device by volume conduction. The unit can be equivalent to lumped circuit, but so far there are no appropriate calculation methods of these circuit parameters, so variable load method based on field-circuit coupled is proposed. A skin electrode unit field circuit coupled model is established to obtain the relationship of the network parameters between voltage and current at electrode port, and the amplitude and phase of the power signal is extracted by the use of all phase FFT spectrum analysis. On this basis, equivalent circuit impedance parameters of the skin electrode unit under various conditions are obtained by the application of variable load method and the validity of the method is verified. As a result, the equivalent circuit impedance parameters obtained in this way can be used for the circuit analysis and optimization of the volume conduction energy transfer system.     

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.     

Numerical analysis on the performance of spiral antennas

The surfaces of the Planar Spiral Antennas and Conical Spiral Antennas are analyzed with planar triangle. The surface currents of the antennas are solved by using the Method of Moment (MoM) based on the RWG basis function. The input impedance, directivity, gain, radiated power and radiation field of the antenna can be found. The results indicate that, in very wide frequency band, the value of the input impedance equals to the theoretical value of Self-Compensated antennas (in agreement with Babinet-booker' principle), which is,188.5 ohm , the half of the wave impedance of free space, while the directivity, gain and radiated power are stable within the frequency band. When the antenna is driven by the signal of derivative Gaussian pulse, the radiating electric field waveform is obtained by the Fourier transform. When the spiral antenna is used as the pulse radiation antenna, the waveform of the radiation electric field shows the characteristics of the Gaussian quadratic differential.     

Parameter Design for Machining Quenched Internal Helical Gears by EDM

Aiming at the problem of machining quenched internal helical gears, a method and its equipment are discussed and designed, which is used for machining quenched internal helical gears by EDM. Its characteristic and principle are proposed. The modifying design of the electrode gear and the calculating method of its modification coefficients is presented. Analyzing for the error of the machining equipment is done. The results show that this problem can be solved by EDM, the electrode gear is the modification gear of machined gear and the machining accuracy can be improved by controlling errors.     

The edge element method in the forward problem of magnetic inductiontomography with homogeneous sinusoidal magnetic excitation

The edge finite element method and the imaging visualization have been studied in the forward problem of magnetic induction tomography MIT with homogeneous sinusoidal magnetic excitation. The definite equations of the forward problem were established using the electric field intensity as the vector variable. The edge FE method for solving the definite equations was introduced in detail and realized as the MATLAB program. In order to realize the visualization of MIT in imaging the intracranial hemorrhage, a real human brain finite element model was created with the human head MRI data. On the basis of this model, we realized the 3D visualization of MIT imaging in MATLAB. The research results demonstrated the validity of the definite equations and the edge FE method in calculating the forward problem. And the 3D visualization of MIT imaging with real human brain model established a foundation for the application study of MIT in imaging intracranial hemorrhage.     

Dynamic Imaging for 3 - D Brain Hematoma

Based on disturbance method of electrical current field, numerical calculation about dynamic imaging for brain hematomas have been studied on a 3 - D sphere model. With current injected, we have found the law of the brain boundary potentials'change while the volume of brain hematoma changed. Some studies about the effect of brain skull with poor electrical conductivity to the brain boundary potentials. The results show that we can know the change of brain hematomas in terms of the measurement for the change of boundary potentials. The injected current can penetrate through the skull. These results are valuable to help doctor to accurately diagnose the brain hematoma and realize the noninvasive monitoring the brain hematoma.     

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。     

Fast circle measurement of industrial CT images based on existence probability

The general methods in reverse engineering cannot measure the inside of close parts. Traditional methods like Capture Geometrical Inside (CGI) would destroy the part. We used the industrial computer tomography (ICT) method to obtain accurate measurements of close parts. Based on the acquired computer tomography images, the size of an internal part was obtained through image measurement and subsequently edited, amended, and dimensioned in CAD software. First, the position and the pixel size of the circle were determined based on existence probability. Next, the actual size of one pixel was obtained based on the image size and the purview diameter. Finally, the actual circle size was calculated by multiplying the pixel size and the actual size of one pixel. A real part was measured using the method. The results show that the relative error of the measured circle radius and the actual size is less than 0.5% and the measuring time is several seconds.