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Magnetic Resonance Materials in Physics, Biology and Medicine
Published in: Magnetic Resonance Materials in Physics, Biology and Medicine 3/2020

Open Access 01-06-2020 | Research Article

Modeling radiofrequency responses of realistic multi-electrode leads containing helical and straight wires

Authors: Mikhail Kozlov, Marc Horner, Wolfgang Kainz

Published in: Magnetic Resonance Materials in Physics, Biology and Medicine | Issue 3/2020

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Abstract

Purpose

To present a modeling workflow for the evaluation of a lead electromagnetic model (LEM) consisting of a transfer function (TF) and a calibration factor. The LEM represents an analytical relationship between the RF response of a lead and the incident electromagnetic field. The study also highlights the importance of including key geometric details of the lead and the electrode when modeling multi-electrode leads.

Methods

The electrical and thermal responses of multi-electrode leads with helical and straight wires were investigated using 3D electromagnetic (EM) and thermal co-simulations. The net dissipated power (P) around each lead electrode and the net temperature increase at the electrodes (ΔT) were obtained for a set of incident EM fields with different spatial distributions. A reciprocity approach was used to determine a TF for each electrode based on the results of the computational model. The evaluation of the calibration factors and the TF validation were performed using the linear regression of P versus the LEM predictions.

Results

P and ΔT were investigated for four multi-electrode leads and four single-electrode leads containing either helical or straight wires. All electrodes of the multi-electrode lead were found to be points of high power deposition and temperature rise. The LEMs for the individual electrodes varied substantially. A significant dependence of the calibration factors on the surrounding tissue medium was also found. Finally, the model showed that the TF, the calibration factor, P and ΔT for multi-electrode leads differ significantly from those for single-electrode leads.

Conclusion

These results highlight the need to evaluate a LEM for each electrode of a multi-electrode lead as well as for each possible surrounding medium. It is also shown that the results derived from simulations based on simplified single-electrode leads can significantly mislead multi-electrode lead analyses.
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Metadata
Title
Modeling radiofrequency responses of realistic multi-electrode leads containing helical and straight wires
Authors
Mikhail Kozlov
Marc Horner
Wolfgang Kainz
Publication date
01-06-2020
Publisher
Springer International Publishing
Published in
Magnetic Resonance Materials in Physics, Biology and Medicine / Issue 3/2020
Print ISSN: 0968-5243
Electronic ISSN: 1352-8661
DOI
https://doi.org/10.1007/s10334-019-00793-9

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