Electromagnetic Inversion for Noninvasive Specific Absorption Rate Characterization

The inverse source framework, which comprises a subset of electromagnetic inversion, is applied to the noninvasive specific absorption rate (SAR) characterization problem. An algorithm is developed and presented which takes field measurements external to the phantom and provides the electromagnetic sources required to obtain the SAR distribution. The unique aspect of this inverse source algorithm is that it casts the problem as the simultaneous inversion (SI) of two sets of equivalent currents: one for the device under test (DUT), and the other for the phantom. The dependency of these two sets of currents is then incorporated as an explicit regularization term in the resulting algorithm. The method is proposed to be relatively robust in terms of measurement noise. A simplified two-dimensional problem is presented to support this proposition.