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Wireless Resonant Circuits Printed Using Aerosol Jet Deposition for MRI Catheter Tracking

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Each year, nearly three-quarters of a million people in the US suffer from an ischemic stroke, caused by a blood clot in the vessels that feed the brain. Magnetic Resonance Imaging (MRI) provides the gold standard in determining whether it is safe to restore blood flow via a thrombectomy procedure, which removes the clot under X-ray guidance. Interventional MRI could allow for diagnosis and immediate treatment; however, the magnetic fields in the MRI scanner create a challenging environment for medical devices. The devices for clot removal include catheters, which are long tubes often built from a mixture of polymer and metal, and have an outer diameter in the millimeter range. Markers are needed on the catheter to track it under image guidance, typically X-ray. To track the catheter under MRI, electronic markers have previously been built, but the standard methods of microfabrication are too rigid and bulky for the neurovascular vessels.

Here, we report a new approach that uses aerosol jet deposition to 3D print an inductively coupled RF coil marker on a polymer catheter. Our approach enables lightweight, conforming markers on polymer catheters and these low-profile markers allow the catheter to be more safely navigated in small vessels. Prototype markers with an inductor with the geometry of a double helix are incorporated on catheters for in vitro studies, and we show that these markers exhibit good signal amplification. We provide material properties and electromagnetic simulation performance analysis. We report temperature measurements, and finally demonstrate feasibility in a preliminary in vivo experiment. This work presents fully aerosol jet-deposited and functional wireless resonant markers on polymer catheters for use in 3T clinical scanners.

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