Research On Coil Array Optimization And Measurement Methods For Biomagnetic Induction Imaging

As a new non-contract biological tissues imaging technology,Magnetic Induction Tomography(MIT)is one of the most advanced topics in the field of nondestructive examination(NDE)for today’s biomedical engineering.Based on this,aiming at the problem that the effective signal is difficult to extract under the strong background signal in the biological detection,this paper focuses on the optimization and measurement method of the biological magnetic induction imaging coil array to improve the accuracy of the measurement signal.According to the electromagnetic induction coupling theory,the impedance characteristics of the bio-EMT detection system coil sensor and the measured biological tissue circuit model have been simulated and analyzed respectively.And the resonant energy coupling model of bio-electromagnetic induction tomography is established by the equivalent circuit method.Based on the numerical analysis of Matlab,the influences of the coil quality factor,the coupling coefficient,the number of sensors and the positions of the sensors on the coupled model are obtained,and the quality factor of the exciting coil is determined as the key controlling factor for the influence of sensor and the output of measurement system.Aiming at the interference between the detection coil and the excitation coil,a four-channel bio-EMT detection model for the space array is proposed,and the characteristics of the detection model are analyzed and studied empirically.According to the existing excitation sensor parameters,the excitation sensor parameters are simulated and optimized.Based on the correlation analysis method,the selection and matching of detection coil sensor are studied experimentally,for high-frequency imaging system,which is vulnerable to external noise interference,the shielding technology is introduced.The key parameters of the shielding were simulated and experimentally researched,and the sensor array carrier structure design and material selection are completed.The detection circuit of biological EMT detection device designed and the phase detection method is determined.The simulation analyzes the phase precision and the relationship between sample rate and noise-signal ratio of FFT and other phase detection algorithmsin the high frequency condition.Moreover,the superposed noise characteristics of the detection coil under the openstope test are analyzed,showing that the mixed denoising method using wavelet denoising and median filtering can effectively suppress the Gaussian and pulse interference.The influence of spatial position changes of low-conductivity salt solution,the changes of electrical conductivity and the foreign matter interference on the output signal of the detection system has been studied at the experiment.The experimental results show that the lower limit of the linear interval,which is based on the orthogonal difference and on the condition of reducing the coupling effect between the coils,decreased to 0.25S/m,and has relatively high linearization at the range from 0.60S/m to 1.40S/m.In addition,the rotation measurement method has been optimized for the long measurement period caused by rotation measurement of spatial array.And the multi-channel coil combination measurement to reduce data redundancy has been studied and experimentally analyzed.