Safe SAR levels in inductively powered brain implanted visual prostheses

This paper derives the health risks of an inductively powered brain implanted visual prosthesis with a CAD based head model. A high efficiency self-oscillating class E transmitter circuit operating at 5 MHz has been designed to wirelessly power the implant. The electromagnetic field inside the head model has been computed using Finite Integration Technique method. Simulations illustrate that a maximum localized SAR level averaged over 10 g attains 1.91 W/kg when the power transmission is equal to 1 W, which is just below the safe level specified at 2 W/kg. Using the same power transmitter, the temperature in the brain with and without considering bio-heat factors, such as blood flow and basal metabolic rate, increases respectively with 0.918 °C and 0.293 °C above the applied body temperature of 37 °C.