Recursively-applied Scanning Algorithms for Inverse Analyses of Gastrointestinal Biomagnetic Fields

A. Irimia (USA)


Biomagnetic fields, gastric propagation, inverse algorithms.


The process of identifying dipolar sources of bioelectric current in the gastrointestinal (GI) tract is of great importance to the future of medical diagnosis. Superconducting QUantum Interference Device (SQUID) magnetometers measure the minute magnetic fields associated with electrical control activity (ECA) from GI smooth muscle. The phenomenology of abnormal ECA current propagation can offer important insights into the early identification and treatment of many diseases, including gastroparesis and ischemia. In order to identify these gastrointestinal sources of current, a biomagnetic field reconstruction program has been developed in which the abdomen is modeled using a set of dipoles that are distributed so as to produce an anatomically realistic simulation. A numerical algorithm for solving the inverse biomagnetic problem was developed, in which a novel dipole localization procedure was implemented in order to identify dipole sources of current based on magnetic field values recorded using SQUID magnetometers. This computational inverse reconstruction was tested with excellent results on simulated data sets containing 1, 3, and 190 dipoles. In all cases, dipoles were identified at correct locations, consistent with propagating GI electrical activity, and with dipole moments that oscillated with frequencies accurately corresponding to the known ECA frequencies. These results are very promising for future studies of abnormal gastrointestinal propagation phenomena, and for the development of noninvasive medical diagnosis procedures for the stomach and intestine.

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