Method and apparatus for magnetic susceptibility tomography, magnetoencephalography, and taggant or contrast agent detection

A method of producing magnetic susceptibility tomographic (MST) images of an object comprising:

• providing an alternating magnetic field to a volume of the object from at least a first bias coil at a first frequency, a second bias coil at a second frequency, a third bias coil at a third frequency, and a fourth bias coil at a fourth frequency, the first, second, third, and fourth frequencies being different;
• measuring magnetic fields at a plurality of sensors disposed about the volume;
• constructing a model in memory of a processor, the model having multiple voxels representative of smaller volumes within the volume;
• relating currents of the bias coils to bias fields at each voxel represented in the model and bias fields at each sensor of the plurality of sensors;
• relating the effects of magnetic susceptibility at the voxels on a measured magnetic field at each sensor;
• deriving magnetic susceptibility information for each voxel from the modeled relationships between the bias fields, magnetic susceptibility at the voxels and measured magnetic fields;
• and
• producing an MST image indicative of magnetic susceptibility at voxels.

An apparatus for obtaining magnetic susceptibility data from an object comprising:

• at least one sensitive magnetic sensor disposed near the object, and adapted to measure magnetic fields of the object;
• a plurality of bias coils disposed near the object and adapted for providing magnetic fields within the object;
• driving circuitry coupled to the bias coils and adapted to driving the bias coils with alternating current;
• sensing circuitry coupled to read the sensitive magnetic sensors;
• digitization circuitry adapted to digitize readings of the sensitive magnetic sensors;
• a processor adapted to receive information from the digitization circuitry;
• magnetic susceptibility taggant recognition (MSTR) routines in memory of the processor, the MSTR routines comprising machine readable instructions that when executed determine differences between applied and measured field strengths of magnetic fields at each sensor, to determine a response comprising a contribution of difference between applied and measured strengths of magnetic fields at a plurality of frequencies and a frequency distribution of magnetic susceptibility, and to recognize a taggant in the object when the response meets predetermined criteria.