SQUID neuromagnetometric reconstruction of brain activity

Ionic flow associated with neural activation of the brain produces a magnetic field that can be measured outside the head in a magnetically unshielded room using a highly sensitive neuromagnetometer based on a superconducting quantum interference device (SQUID). Reconstruction of images portraying the tomographic distribution of neural generators (assumed to be current dipoles) of the neuromagnetic field, a modality that we have termed "neuromagnetic imaging" or NMI, represents a powerful noninvasive method of dynamic functional imaging dependent upon brain structure and activity. Reconstruction in NMI, i.e., the inverse problem, however, has no unique solution and requires incorporation of modeling constraints for practical implementation. Results of several phantom and test-object studies and a preliminary human study to develop the method of NMI under various modeling constraints are presented.