Research And Development Of A Portable Bio-impedance Spectroscopy System For Breast Detection

The incidence of breast cancer has ranked first among female malignancies,but there is no complete early clinical diagnosis method.Bio-impedance spectroscopy(BIS)is a detection technique of using electrical impedance characteristics of biological tissues to extract corresponding pathological information,which has great application prospects in biological tissue detection because of its small system interference,comprehensive process information,and reliable results.However,most measurement devices are limited to the application of bio-impedance spectroscopy in daily breast health testing due to its large size and high price.Therefore,this project is to develop a portable,low-cost BIS system for breast detection,the specific content are as follows:Firstly,a portable BIS detection system for impedance spectroscopy is developed,consisting of program interface and the device of measurement.The device based on FPGA cooperates with DAC module for a frequency sweep signal generation and ADC module for signal acquisition,then perform FFT transformation and parameter calculation on acquired signal.The program interface running on PC is designed through the GUI function of MATLAB,which sends control commands to FPGA,and receives data for processing while the measurement is completed.Secondly,a BIS parameter extraction method based on equivalent circuit fitting is proposed,which is realized by a mixed algorithm combining genetic algorithm and nonlinear least squares algorithm.The genetic algorithm provides excellent original values as initial values of non-linear least squares solution,which makes fitting function iteratively converge to final result.The experimental results show that mixed algorithm can effectively extract the BIS parameters.Finally,an experimental platform is built for experimental verification and breast detection application of developed system.(1)The measurements of electrical equivalent circuit by BIS system is compared with high-precision commercial impedance analyzer ZX70 A,maximum relative error of amplitude and maximum absolute error of phase are 2.42% and 0.936° respectively;(2)The BIS system is used to measure impedance change during egg heating and equivalent circuit fitting is performed on measurement results.(3)The impedance spectrum under different fat and muscle ratios is measured,and target is detected based on equivalent mass of pork fat tissue and muscle tissue to simulate breast detection.The experimental results show that developed BIS system enables low-cost,portable,high-precision measurement of biological tissues,which is applicable to breast detection.