A Near-Field Cloaking Study to Reduce MRI RF-Artefacts in Presence of Elongated Prostheses

The objective of this paper is to analyze a near-field electromagnetic cloaking to reduce the radiofrequency (RF) magnetic field inhomogeneities (responsible for the RF-artefacts onset) in magnetic resonance imaging (MRI) in the presence of an elongated metallic hardware. A lumped circuit is considered to explain the role that a dielectric coat has on hiding ametallic cylinder to the RF antenna. The theoretical assumptions are proved by means of full-wave simulations that are also applied to a realistic hip prosthesis considering a frequency equal to 64 and 128 MHz. The numerical results confirm the theoretical assumptions. Both the theoretical analysis and the numerical simulations highlight the different role that the coat thickness and electric permittivity have in the definition of a proper dielectric coat. A particular cloaking approach leads to a dielectric coat whose constitutive electrical parameters may be simple enough to fit the considered application reducing the interaction between an elongated prosthesis and the RF antenna. Furthermore, results obtained at 64 MHz suggest the possibility to employ an existing biocompatible material to achieve the envisaged purposes.