Implant Safety: Novel Mechanistic Model and Approach for Safety Assessment at WPT Frequencies

Safety assessment of active implants at frequencies used in wireless power transfer (WPT) is not yet defined by the current guidelines. A mechanistic model for elongated implants at magnetic resonance imaging (MRI) frequencies (typically 64/128 MHz) has been postulated and used as a basis for safety guidelines. However, this mechanistic model is inconsistent with the behavior observed at WPT frequencies. In this study, we propose a new mechanistic model applicable to a wide range of frequencies. Based on this model, the problem of assessing implant safety can be decomposed into separate, approachable steps. To validate the approach, predictions of the mechanistic model were compared to results of numerical simulations. The impact of parameters such as tissue properties, tip shape, and insulation thickness was studied. The findings may be applicable to the formulation of safety standards for implant wearers exposed to electromagnetic fields (EMF) at WPT frequencies.