Wireless Coils in Water and Fluorocarbon Fluid

The paper describes magnetic resonance imaging (MRI) experiments using different types of wireless coils, including solenoid, multi-turn loop, metamaterial-inspired coils (MMI), and transmission line resonators (TLR). Their performance is compared in terms of MR signal amplification inside and near the coils when placed in various mediums—air, water, and fluorocarbon (FC) fluid. Water and FC fluid serve as imaging media for constructing sensitivity maps using ¹H and ¹⁹F MRI. The sensitivity maps obtained by immersing the coils in FC fluid can be used to calculate corresponding maps for the same coils in air, as well as for coils redesigned to detect ¹H signals. It is demonstrated that a resonant circuit based on a solenoid or multi-turn loop may not require lumped capacitance when the coil is immersed in water. In such cases, the coil's self-capacitance (inter-turn capacitance) can fulfill this role, increasing by a factor of 80 upon immersion in water. Additionally, examples are provided for using wireless coils to image living organisms as well as objects that do not produce an NMR signal, employing the signal void imaging approach.