Computational and experimental investigation of RF‐induced heating for multiple orthopedic implants

Abstract

Purpose: This paper investigates the RF-induced heating for multiple adjacent orthopedic implants under MRI at 1.5T and 3T exposure. When multiple implants are closely spaced to each other, the interactions between the implants may affect the RF-induced heating. Traditional RF-induced heating labeling is often only applicable to configurations of an individual implant, and is not applicable for multi-implant configurations. Therefore, the aim of this study is to evaluate the effects of multiple orthopedic implants on RF-induced heating and to propose potential appropriate instructions for safe scanning of multi-implantable orthopedic implants. Methods: Typical plate and nail implants were used as examples. The effects of implant configuration, relative positions, and number of implants were investigated.Numerical simulations were conducted using full-wave electromagnetic simulation software. Experimental measurements at 1.5 T were performed to validate the numerical results. Results: Numerical results indicate that, due to device interaction, the RF-induced heating of multiple medical implants can be significantly different from that of a single implant. The measured temperature rise for multiple devices could be 2.7 times larger than that of a single implant. Conclusion: Our results confirm that RF-induced heating of multiple implants can be quite different, and do not follow simple superposition of the results from single devices. Instructions for safe scanning of individual orthopedic devices would not be applicable to multi-implant configurations. K E Y W O R D Sfinite-difference time domain, magnetic resonance imaging, multiple orthopedic implants, radiofrequency heating

Radiofrequency‐induced heating of broken and abandoned implant leads during magnetic resonance examinations

“…For longer leads, however, capping the proximal end of an abandoned lead may result in higher deposited power at the distal end of the lead (ie, the lead‐tip) 22‐25 . An analogous situation arises in risk assessment of passive orthopedic implants, whereby fractured or adjacent metallic implants can exhibit higher RF‐induced heating by up to a factor of 10 than predicted by safety evaluations based on single implants 26,27 …”

“… 22 , 23 , 24 , 25 An analogous situation arises in risk assessment of passive orthopedic implants, whereby fractured or adjacent metallic implants can exhibit higher RF‐induced heating by up to a factor of 10 than predicted by safety evaluations based on single implants. 26 , 27 …”

“…[22][23][24][25] An analogous situation arises in risk assessment of passive orthopedic implants, whereby fractured or adjacent metallic implants can exhibit higher RF-induced heating by up to a factor of 10 than predicted by safety evaluations based on single implants. 26,27 In this study, we developed a generic AIMD with a metallic IPG and a 100-cm long lead containing 1 or 2 wires. The scaled transfer function, the deposited lead-tip power, and the RF-induced maximum local SAR near the lead-tip were derived both numerically and experimentally.…”

Wire‐based sternal closure: MRI‐related heating at 1.5 T/64 MHz and 3 T/128 MHz based on simulation and experimental phantom study

“…Based on the results from in vitro simulations, the simple wire closure always has the lower peak SAR 1g values as compared with the figure‐of‐8 and Robicsek closures. Because the element for simple wire closures has no metallic contact to its adjacent element and the adjacent elements are not close to each other, there would be no antenna effect or capacitive coupling (i.e., adjacency) effect, which are the 2 very important factors increasing the RF‐induced heating near the device . The antenna effect refers to the scenario in which the entire device can be considered as a single antenna if the construct electrical length is close to the resonant length.…”

Assessment of Human Exposure to Electromagnetic Fields: Review and Future Directions

“…PIMD and AIMD tests are performed experimentally, computationally, or a combination thereof [133]. Recent safety concerns include the safety of legacy PIMDs and AIMDs and the safety of broken and abandoned AIMD leads, which can result in a 20-fold increase in RF EMFinduced heating [134][135][136].…”