# EUROISMAR 2019

25-30 August 2019
Henry Ford Building
Europe/Berlin timezone

## Double micro-resonators for orientation-free MR-catheter tracking during interventional MRI, enabled by inductive coupling

Not scheduled
4h
Harnack House and Henry Ford Building

Board: 328
Poster

### Speaker

Mr Omar Nassar (Institute of Microstructure Technology, Karlsruhe Institute of Technology (KIT))

### Description

Accurate geometrical tracking of the tip of a catheter during minimal invasive surgery using intervention MRI provides a surgeon with orientation relative to the body. The tip can be visualized in the MR environment by locating a micro-resonator at this position. If the resonator is tuned to the Larmor frequency of abundant nuclei, and subject to a radio frequency excitation pulse, it's motion can be tracked under direct image guidance. The conductive cable connecting the detector to the spectrometer, for signal transfer and matching and tuning, cause dangerous tissue heating and has prevented this technology to find widespread use. An alternative is to couple the resonator wirelessly through inductive coupling to a wired resonator outside of the body. Tuning and matching is then confined to the external resonator. However, as the catheter orientation changes, the coupling between the detector and the external coil will also change, which leads to a change in the visibility of the catheter. Visibility can be totally lost if the wireless resonator and external coil's $B_1$ fields are orthogonal. Also, when the coupling changes, the entire system will need to be re-matched and tuned. Here we present a novel detector design based on two perpendicular miniaturized saddle coils that maintain constant coupling strength between the MR-catheter detector and the external coil, for all axial orientations. We also present a multilayer fabrication process for the conductive structure of the resonator, on a flexible and low aspect ratio substrate that is suitable for wrapping around catheters without significantly modifying either its stiffness or diameter. A setup is presented for characterizing the coupling strength of the two coils for all possible orientations. The results for two different detectors (single and double saddle coil) were, compared showing significant enhancement in the coupling in the case of the proposed double coil.

### Primary authors

Mr Omar Nassar (Institute of Microstructure Technology, Karlsruhe Institute of Technology (KIT)) Dr Dario Mager (Institute of Microstructure Technology, Karlsruhe Institute of Technology (KIT)) Prof. Jan Korvink (Institute of Microstructure Technology, Karlsruhe Institute of Technology (KIT))

### Presentation Materials

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