Electric Field Probe Used for Gradient Coil-Induced Field Measurements During Medical Device Testing: Design, Calibration, and Validation

In this article, an ultralow-frequency electric field probe capable of measuring time-varying gradient coil induced electric fields in a tissue-mimicking material was constructed, calibrated, and validated. This probe consisted of a 2 cm short dipole antenna followed by an instrumentation amplifier. The designed amplifier had a gain of 100 and a cutoff frequency of 31 kHz. The probe was fabricated on a four-layer printed circuit board (PCB), FR4 of thickness 1.57 mm and a copper thickness of 35 μm. A waterproofed 3-D probe holder was used to cover the electronics and expose the dipole tip to the saline solution. To calibrate this probe in a known environment, a parallelplate conductor was used. The calibrated probe was validated by measuring the electric field in a saline-filled cylindrical phantom placed within a cylindrically symmetric test coil. In order to do the validation, simulations were performed using an in-house tool developed in MATLAB and a validated tool in Sim4Life.