改进型MIT系统软件鉴相单元设计与实验

Design and Experiments of Improved MIT Software Phase Detection Unit

目的:为了提高脑磁感应成像(MIT)系统中相位差检测精度,在课题组原有研究基础上改进并实现了MIT软件鉴相单元。方法:软件部分采用LabVIEW2009,相位差检测选用FFT鉴相算法;硬件部分选用NI PXI 5122采集卡对数据进行100 Mbit/s的实时采样,选用考虑电磁安全性的增益放大模块实现对微弱小信号的功率放大。结果:构建了一套采样精度更高、增益放大可调、基于FFT算法的软件鉴相单元。结论:在模拟脑出血实验中进行相位差检测,随着出血量的增加相位差相应增大,呈线性关系;鉴相精度在原课题组0.01°基础上提高到0.001°;鉴相效果优于SR844锁相放大器,能够更好地反映MIT系统中组织电导率的变化。

Objective To improve and implement high-precision software MIT phase detection unit based on the original in order to improve brain magnetic induction tomography（MIT） in the phase detection accuracy of the system.Methods Part of the design of software systems was used LabVIEW2009 as development tools and FFT algorithm implementation phase platform;Experimental hardware used NI PXI 5122 data acquisition card to perform 100Mbit/s real-time sampling.The study chose the module which considered the gain of amplification of electromagnetic security on the weak small-signal power amplifier.Results The study constructed a higher sampling accuracy,gained adjustable magnification,the software algorithm based on FFT phase unit.Conclusion Cerebral hemorrhage in the simulation experiments conducts testing phase.The phase difference accords with the corresponding increase in the amount of bleeding increases linearly.Phase accuracy of 0.01 degrees in the original research group raises up to 0.001 degrees,and results are better than the SR844 lock-in amplifier,which better reflects the MIT system changes in tissue conductivity.