基于SQUID梯度计的心磁图仪标定及通道差异性研究

Calibration and Channel Difference of Magnetocardiography Based on SQUID Gradiometer

在基于超导量子干涉器(SQUID)的多通道心磁图(MCG)系统中,由于各通道硬件系统之间不可避免地存在差异性,因此精确标定每个SQUID的磁场-电压传输系数(VCAL/BCAL)对心磁信号测量及心磁图像反演至关重要。基于九通道MCG系统工作原理,利用杜瓦底部的限位环阵列结构固定九通道梯度计位置,根据标定圆盘内激励线圈与限位环阵列的一致性实现对SQUID的快速标定,每个通道单独标定结果的准确性由九通道差异性验证。实验表明,九通道的标定结果为1.49 mV/pT~1.76 mV/pT,该结果对应的通道差异性为4.5%,符合MCG系统差异性小于5%的经验值。所述标定方法及差异性计算方法可靠且准确度高,可用于MCG系统传输能力的快速评估。

The multi-channel magnetocordiography(MCG)system is based on superconducting quantum interference devices(SQUID).Due to the differences between the hardware systems of each channel of the MCG,it is very important to accurately calibrate the magnet-ic field-to-voltage transfer coefficient(VCAL/BCAL)of each SQUID for the measurement of magnetic heart signal and the inversion of the magnetic heart image.According to the working principle of the nine-channel MCG system,the limiting ring array at the bottom of the Dwar is used to fix the nine-channel gradiometer.The rapid calibration of the SQUID is realized according to the consistency of the posi-tion of the excitation coil and the limit ring array.The accuracy of the single-channel calibration is verified by the nine-channel differ-ence calculation.Experiments show that the calibration results of nine channels are 1.49 mV/pT-1.76 mV/pT,and the channel differ-ence is 4.5%.The MCG system can work normally when the difference is less than 5%.The calibration method and the difference veri-fication are reliable and accurate,and can be used for rapid evaluation of the transmission capability of the MCG system.