A Novel Sensor Design and Fabrication for Wireless Interventional MRI Through Induction Coupling

Interventional magnetic resonance imaging (iMRI) using active MR-Catheters potentially has a great impact on the field of minimally invasive medical operations. Detector coils inside the patient act as antennas, coupled to the magnetic resonance radio frequency transmit field, thereby making the catheter visible in an MR environment. The elongated transmission conductor which is attached to the coil is coupled to the RF field as well. This coupling heats the conductor, causing dangerous tissues heating, which has hindered the clinical use of MR-catheters up to now. Transmitting the signal wirelessly through induction coupling, between the coil on the catheter’s tip and a surface coil outside the patient, is a feasible way to avoid using the conductive transmission wire. However, induction coupling still encounters problems regarding catheter orientation and frequency splitting. The purpose of this work is to present a mathematical model for the frequency splitting to facilitate the matching and tuning processes. Also, to propose a novel design of two perpendicular uncoupled coils on the catheter tip to keep coupling at all orientations. These coils were fabricated with a multilayer fabrication process for flexible electronics on the microscale.