Abstract
We pursue research and development on the detection of the weak magnetic field generated by the neural propagation along the spinal cord and the investigation of non-invasive diagnosis of spinal cord function based on the analysis of the detected magnetic signals. So far, we have reported the developed prototype of the SQUID spinal cord evoked magnetic field (SCEF) measurement system applicable to patients with spinal cord disorder in actual hospitals. We have also reported the development of the visualization of the current distribution along the spinal cord by magnetic source analysis. In this paper, the improvement of the dynamic range by the newly designed multiple feedback FLL (flux locked loop) and the noise reduction using reference magnetic flux sensors are described. These features enabled to prevent saturation of the SQUID electronics and to detect separately not only the fast SCEF component reported previously but also the slow SCEF component simultaneously even in the presence of large low-frequency noise.
