Research On Key Technologies Of Dynamic Bio-impedance Information Extraction And Processing

Bio-Impedance Measuring Technology (BIMT) is a noninvasive measuring technology, the purpose of which is to extract physiological and pathological information by detecting the electrical properties (impedance, admittance, dielectric constant) of tissues and organs. It has unique discriminability to blood, gas, body fluid and different tissue compositions, and it maintains the feature of low-cost, safety, easy-operating and wealth of information. So it has extensive application perspective in clinical diagnosis, health supervision and etc.In this thesis, the author has accomplished the tasks as follows:1. Virtual instrument based digitized multi-frequency bio-impedance measurement system is implemented according to the principles of bio-impedance measurement. Further more, the system is optimized by solving the problems of data acquisition and digital demodulation so that dynamic bio-impedance information can be detected in much wider frequency band by the system.2. Active electrodes and cable driver are applied to enhance the signal-to-noise ratio and the anti-stray-capacitance ability of the system. Meanwhile, the system error is analyzed and compensated, so the precision of the system is improved.3. Discrete Fourier Transform (DFT) based multi-frequency signal demodulation method is studied in the thesis. It presents that the energy leakage and fence effect of DFT have some affections to sine signal detection. So DFT interpolation method, virtual reference vector technique and method of DFT interpolation combined with virtual reference vector is respectively applied to compensate the measurement results. The compensation of virtual reference vector technique is validated by the experimental results.4. According to the feature of bio-impedance signal, dyadic wavelet transform is used for bio-impedance signal processing, by which the blood and gas information can be separated and the time-frequency characteristics of the bio-impedance signal can be extracted.5. Experiments of human pulmonary function detection are designed in response to some related medical background. Bio-impedance signal energy analysis method based on wavelet transform is presented to analyze the blood gas ratio when people in different physiological status.Finally, some improvement suggestions are presented at the end of the thesis.