中文摘要：

目的：实现脑磁感应成像系统中的单通道高精度相位差检测功能。材料与方法：基于高精度鉴相器射频锁定放大器SR844建立了相位差检测单元，对磁感应信号进行放大、滤波处理，检测频率为1MHz；通过培养SD大鼠的大脑皮质神经细胞，获得脑正常神经细胞模型和水肿神经细胞模型；使用不同激励线圈，并在激励线圈与检测线圈之间距离不同时，分别对两种细胞模型产生的相位差进行检测实验。结果：设计的检测单元的技术指标为：检测处理的最小信号为7mV，放大倍数为3．52dB-49dB，相位差分辨率为0．02°,3dB带宽约为1．5kHz；细胞实验结果显示SD大鼠脑水肿神经细胞模型产生的相位差小于其正常神经细胞模型产生的相位差。当两线圈相距20cm，且使用圆形聚焦激励线圈时，检测得两种模型产生的相位差之间的最大差值为0．206°；当两线圈相距10cm，且使用方形聚焦激励线圈时，检测得两种模型产生的相位差之间的最小差值为0．079°。结论：设计的相位差检测单元满足高精度相位差检测要求．能检测出水肿神经细胞模型与正常神经细胞模型的相位差别。从细胞层面上对脑水肿进行了实验研究。得出了有效的实验结果．为进一步的脑水肿检测打下了良好的基础。

英文摘要：

Objective： To implement the function of detecting phase changes at a high precision in MIT system. Methods： A phase-change detection unit based on RF Lock-in amplifier SR844 was designed at the frequency of 1 MHz, consisting of pre-amplifier and narrow bandwidth filter. And an experiment with neuron cell model from SD rat cortex was to detect phase change produced by oedema neuron cell model and normal neuron cell model. In the experiment, different excitation coils were used, while the excitation coil and sensing coil were put at two different positions. Results： The unit designed was able to deal with the signal of 7mV at the smallest and provided a gain range of 3.52 dB-49 dB, phase resolution of 0.02° and 3 dB bandwidth of nearly 1.5 kHz. The results of the experiment showed that the phase change produced by oedema neuron cell model were smaller than that by normal neuron cell model. The biggest difference between the two models＇ phase change was 0.206° , when the round focused excitation coil was used and the distance of the two coils was 20cm. The smallest difference between the two models＇ phase changes was 0.079° , when the square focused excitation coil was used and the distance of the two coils was 10cm Conclusions： The unit designed had high precision of detecting phase change and had the capability of detecting the phase change of oedema neuron cell model and normal neuron cell modeleffectively. The cells experiment started the research of the cerebral edema on the point of cell. These may be of great help for further cerebral edema-detecting work.