磁感应断层成像中的一种高精度同步相位测量方法

Precise synchronous phase measurement method in magnetic induction tomography

磁感应断层成像(magnetic induction tomography,MIT)是一种新兴的非接触医学成像方法,在脑部病变连续动态检测方面具有良好的应用前景。测量过程中的相位漂移是影响MIT系统检测精度的主要因素。为了提高检测精度,实现了一种实用的MIT相位测量方法,可以快速进行相位测量而且可以长时间保持稳定,具有很低的相位漂移水平。该方法实现了激励信号、检测信号、参考信号、本振信号以及采样时钟之间的完全同步,并引入了正交序列解调算法,提高了解调的速度。实验结果表明:单次相位测量时间小于1 ms,1 min内的最大相位漂移小于0.005°,1 h内的最大相位漂移小于0.008°。基于该相位测量方法建立了一个16通道MIT系统,并获得了初步的低电导率(0.84 S/m和1.26 S/m)物理模型成像结果。

Magnetic induction tomography （MIT） is a new noncontact medical imaging method. It is promising in the continuous and dynamic inspection of brain diseases. The phase drifts in measurement is main limitation of MIT system precision. In order to improve the precision, a practical phase measurement method is developed, which can run a fast and stable phase measurement with a very low level of phase drifts. The method implements a full synchronization among exciting signal, receiving signal, local oscillation signal and sampling clock. The orthogonal sequential demodulation is applied to compute the phase and increase the demodulation speed. Experimental results show that the phase measurement method can run a single measurement in 1 ms, phase drift in one minute is less than 0. 005°, and the phase drift in one hour is less than 0. 008°. A 16-channel MIT system is set up and the preliminary imaging results on phantoms with low conductivity （0.84 S/m and 1.26 S/m） is obtained.