Resonant marker design and fabrication techniques for device visualization during interventional magnetic resonance imaging

Abstract

Magnetic resonance imaging (MRI) has great potential as an imaging modality for guiding minimally invasive interventions because of its superior soft tissue contrast and the possibility of arbitrary slice positioning while avoiding ionizing radiation and nephrotoxic iodine contrast agents. The major constraints are: limited patient access, the insufficient assortment of compatible instruments and the difficult device visualization compared to X-ray based techniques. For the latter, resonant MRI markers, fabricated by using the wire-winding technique, have been developed. This fabrication technique serves as a functional model but has no clinical use. Thus, the aim of this study is to illustrate a four-phase design process of resonant markers involving microsystems technologies. The planning phase comprises the definition of requirements and the simulation of electromagnetic performance of the MRI markers. The following technologies were considered for the realization phase: aerosol-deposition process, hot embossing technology and thin film technology. The subsequent evaluation phase involves several test methods regarding electrical and mechanical characterization as well as MRI visibility aspects. The degree of fulfillment of the predefined requirements is determined within the analysis phase. Furthermore, an exemplary evaluation of four realized MRI markers was conducted, focusing on the performance within the MRI environment.

Preclinical feasibility of a technology framework for MRI-guided iliac angioplasty

“…The main benefits are that resonant circuits are technically simpler compared to active tracking coils [13]. Low profile resonant circuits have the potential for integration into the commercial production of catheters [25] as no physical wire connection to the MRI scanner is required.…”

“…However, the increased stiffness and outer diameter are temporary problems relating to manually produced resonant circuits. Recently, micro systems-based technologies for producing resonant circuits have been validated [25] and fully integrated designs have been proposed [25], which would allow for complete integration under the final coating of catheters.…”

Magnetic Resonance Imaging System–Driven Medical Robotics

“…During the imaging, the wire antenna is activated to increase the signal in close proximity of the catheter. The semiactive positive contrast tracking methods are based on wireless resonators, which are designed to resonate with the MRI's excitation RF field to intensify the signal created by them . Figure c shows an example of a wireless resonator imaged by a fast field echo (FFE) sequence.…”

“…b) Catheter antenna image without sensitivity correction, where the antenna boosts the signal around the catheter . c) Aerosol deposed MRI marker image at different angles and voxel sizes . d) The artifact image of a current‐passing catheter imaged with gradient echo .…”

Interventional magnetic resonance imaging guided carotid embolectomy using a novel resonant marker catheter: demonstration of preclinical feasibility

“…Herein we pursue a tracking method consisting of MR compatible fiducial markers in isolated resonance circuits (Wendt and Wacker 2000; Zuehlsdorff et al 2004). By tuning wire coil resonant circuits to the Larmor frequency of water protons in the external magnetic field, the circuit can couple with the transmit coil and increase the B1 field intensity by enhancing the exciting angle of protons in only a localized field surrounding the marker (Kuehne et al 2003; Kaiser et al 2015). Thus water protons adjacent to the circuit experience a much higher flip angle than the more distant surroundings.…”