基于数字处理的频差电阻抗成像系统设计

Design of frequency difference electrical impedance imaging system based on digital processing

电阻抗成像(EIT)作为一种功能医学影像技术,可以反映组织功能的变化。在已有研究的基础上,开发一种体积小、功耗低、高速、频带宽、具有扫频和混频2种激励方式的电阻抗成像系统,应用于人体胸腹部疾病的早期筛查。该系统采用8×8电极阵列,用高性能FPGA为核心,使得激励源控制、数字频率合成、信号预处理、高速相敏检波、快速傅里叶变换解调测量信号等功能集成在单一的芯片中,减小了系统的复杂性,提高了可靠性和可移植性。在图像重构中,使用可靠性较高的正则化算法抑制电阻抗成像逆问题解的振荡,从而重建过程趋于稳定,提高了目标空间分辨率和成像深度。

Electrical impedance tomography （EIT）, as a medical imaging method, reflects functional changes in tissue. For the application of early detection of breast disease, a EIT system with sweep and mixing frequency excitation modes is developed, which can realize small size, low power consumption, high-speed and wide bandwidth. The complexity of the system is reduced and the reliability is improved, which is based on high-performance FPGA as the core, the excitation source control, digital frequency synthesis, signal preprocessing, high-speed phase sensitive detector, and fast Fourier transform demodulation measurement integrated in a single chip. For the image reconstruction, the high reliability regularization based arithmetic is used to suppress the concussion arising from inverse problem solution,which results in stability of the reconstruction and improvement in the spatial resolution and imaging depth.