Novel frequency selective B1focusing passive Lenz resonators for substantial MRI signal-to-noise ratio amplification.

Objective: The need for increased sensitivity in magnetic resonance imaging (MRI) is crucial for its advancement as an imaging modality. The development of passive Lenz Resonators for effective RF magnetic field focusing will improve MRI sensitivity via local amplification of MRI signal, thereby leading to more efficient diagnosis and patient treatment.

Approach: While there are methods for amplifying the signal from specific nuclei in MRI, such as hyperpolarization, a general solution will be more advantageous and would work in combination with these preexisting methods. While the Lenz Lens proposed such a general solution based on Lenz's law and the reciprocity principle, it came at the cost of limited signal enhancement. In this work, the first-in-kind prototype Lenz Resonator was conceived and examined as a general frequency-selective passive flux-focusing element for significant MRI signal enhancement. A 3.0 T Philips Achieva MRI was used to compare the signal from a phantom in the presence of Lenz Lenses, Lenz Resonators, and control trials with neither component.

Main results: An MRI investigation demonstrated an experimental amplification of the signal-to-noise ratio up to 80% using an MRI insert of two coaxial Lenz Resonators due to superior B1 magnetic field focusing. The resonators displayed consistent amplification, nearly independent of their x-position within the MRI bore.

Significance: This behavior demonstrates the feasibility of imaging large objects of varying shapes without penalties for signal amplification using Lenz Resonators. The Lenz Resonators versatility in geometrical design and consistent signal amplifying abilities between pulse sequences should allow for the development of Lenz Resonators suitable for most commonly used MRI setups.