RF-induced heating reduction by minimizing the external portion of the partially in and partially out medical devices under MRI at 1.5 T

Purpose: To address the issue of RF-induced heating for partially in and partially out (PIPO) medical devices during 1.5 T MRI scans by proposing a method of minimizing the external portion.

Methods: A method of tightly winding the external segment of the PIPO device is proposed to minimize the overall device effective reception length during MRI scans to mitigate the RF-induced heating. Two commercially available PIPO medical devices and simplified solid wires were used to demonstrate the concept. RF heating results are compared between typical and minimized-length trajectories under the American Society for Testing and Materials (ASTM) testing procedure. In addition, 16 scaled and validated device models were used in conjuncture with human body numerical simulations within three virtual human models to estimate clinically relevant heating.

Results: The wound segments in PIPO devices functioned as a lumped element rather than a receiving antenna, reducing induced energy/heating as compared to the original PIPO devices under typical straight or loop configurations. Minimizing the lead's external portion can reduce the RF-induced heating by significant factors for all studied cases during ASTM phantom measurements and in human body simulations.

Conclusion: Our findings show a significant reduction in RF heating by minimizing the external segment, thereby enhancing patient safety during 1.5 T MRI procedures. Although limited to four devices at 1.5 T across two applications, the extent of heating reduction may vary for others. Nonetheless, tightly winding the external segment of PIPO electrodes holds promise for improving device safety under MRI.