Chuanhong He

A multi-channel magnetic induction tomography measurement system for human brain model imaging

This paper proposes a multi-channel magnetic induction tomography measurement system for biological conductivity imaging in a human brain model. A hemispherical glass bowl filled with a salt solution is used as the human brain model; meanwhile, agar blocks of different conductivity are placed in the solution to simulate the intracerebral hemorrhage. The excitation and detection coils are fixed co-axially, and the axial gradiometer is used as the detection coil in order to cancel the primary field. On the outer surface of the glass bowl, 15 sensor units are arrayed in two circles as measurement parts, and a single sensor unit for cancelling the phase drift is placed beside the glass bowl. The phase sensitivity of our system is 0.204 degrees /S m(-1) with the excitation frequency of 120 kHz and the phase noise is in the range of -0.03 degrees to +0.05 degrees . Only the coaxial detection coil is available for each excitation coil; therefore, 15 phase data are collected in each measurement turn. Finally, the two-dimensional images of conductivity distribution are obtained using an interpolation algorithm. The frequency-varying experiment indicates that the imaging quality becomes better as the excitation frequency is increased.

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

To improve the lack of information and model error of twodimensional electrical impedance tomography (EIT), a three-dimensional EIT model is set up. Finite element method is used to calculate the forward problem. To compare different stimulation mode, distinguish ability and surface projection method are used. The result shows that back electrode mode has obvious advantages in detecting depth and in clinical use. The conclusion of this paper can provide reference for the study of three-dimensional EIT.

Characterization of cerebral infarction in multiple channel EEG recordings based on quantifications of time-frequency representation

In this paper, a method for characterizing cerebral infarction (CI) utilizing spontaneous electroencephalogram (EEG) is described. We obtained the time-frequency representations (TFRs) of EEG signals recorded from both normal subjects and CI patients. The corresponding characteristics were depicted by relative frequency band energy (RFBE) and Shannon entropy (SE) of TFR. Comparing with the normal subjects, the CI patients had some changes in EEG as follows: (1) delta and theta rhythms were attenuated while beta and gamma rhythms were enhanced, and the changes of delta and beta were more significant, (2) alpha was also blocked with eyes open, however the blocking action was less evident, (3) SE increase was pronounced. Consequently, the quantitative EEG methods are promising tools to provide helpful and sensitive information for the detection and diagnose of CI.

Open Electrical Impedance Tomography: Computer Simulation and System Realization

Electrical impedance tomography (EIT) is a non-invasive technique used to image the electrical conductivity and permittivity within a body from measurements taken on body’s surface. But the low spatial resolution of imaging, complicated operation and the asymmetrical placement of electrodes make the EIT cannot achieve the requirements of clinical application. In this paper, we proposed a novel idea of open electrical impedance tomography (OEIT) and a new type of electrode to provide more valuable distribution information of electrical impedance for local subsurface biological tissues than closed EIT. The OEIT system is constructed. The electromagnetic mathematical models of OEIT are presented and a method to solving the boundary value problem of half infinite calculating region is proposed for the computer simulations. Furthermore, we have realized the OEIT system, and completed the physics and the clinical experiments. Experiment results show that the OEIT system can obtain a better resolution and positioning accuracy, and is more suitable for clinical application.

A multi-channel electrical impedance measurement system using DSP

Electrical impedance tomography (EIT) is believed to be a distinctive imaging technology and have good prospect in the field of biomedical testing. A multi-channel electrical impedance measurement system using DSP is studied. It includes four modules: excitation source, electrode array, signal acquisition, and signal processing. The results in experiment demonstrate that the system can distinguish objects of different conductivity and locate it.