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Simulations of RF Probes for Endovascular MRI using the Finite Element Method

  • Author(s): Poulin, Nathan Daniel
  • Advisor(s): Hetts, Steven W.
  • Zhang, Xiaoliang
  • et al.
Abstract

The positioning of surface receiver coils limits the signal-to-noise ratio (SNR) of MRI. Endovascular RF imaging coils placed at or near the region of interest can image at greatly enhanced SNR compared with surface coils. Treatment protocols for neurovascular and cardiovascular diseases and conditions would benefit from better image quality.

A series of numerical simulations using the Finite Element Method (FEM) of the electric and magnetic fields of endovascular RF probes of the looped and loopless (antenna) kinds were performed in order to assess their imaging performances and to improve their designs at the imaging strength of 3T. Safety of the probes was also considered. Emphasis is placed on simulations of a loopless coil, with and without the addition of an extremely high dielectric coating. A new design concept for actively tracking the distal end of a loopless coil is proposed, where signal dropout normally prevents its visualization and localization. This would be one of the few available multi-functional coils which could be used for imaging and tracking. The design consists of a corkscrew shaped inductive loop placed at the end of the loopless coil (maintaining an open circuit), with its axis oriented in the xy plane, allowing for signal gain in the axis of the loop. Electric and magnetic fields were mapped and preliminary SNRs and Specific Absorption Rates (SARs) are presented, showing the corkscrew's viability as a potential active tracking mechanism.

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