Apr 20, 2018

Data-driven experimental evaluation method for the safety assessment of implants with respect to RF-induced heating during MRI

Aiping Yao, Earl Zastrow, and Niels Kuster, Radio Science, online 20 April 2018, DOI: 10.1029/2017RS006433

Small (mm size) distal electrodes of active medical implants can cause localized radio frequency (RF)-induced power deposition with extreme spatial gradient (5–6 dB/mm). We propose a method that aims to improve the accuracy of the traditional experimental evaluation, which relies solely on hardware instrumentation. A numerically derived local deposition distribution is used to assist the estimation of power deposition. The method was successfully validated against numerical simulations, considering three different generic implants with a single electrode. The estimation of deposited power in the region surrounding the implant electrodes by means of the proposed method was validated, with less than 1 dB (30%) of uncertainty.

The scientific and technical impact of the study can be summarized as follows:

  • A novel approach for assessing total deposited power at implant hotspots with reduced uncertainty by correlating near-field measurements to numerically derived distributions is described.
  • The approach has been validated with three generic implant designs, and an uncertainty budget has been established.
  • Further investigation is needed to determine whether the proposed method can be extended to devices with multiple electrodes and a wider variety of exposure conditions.