On the Feasibility of a High-Sensitivity Imaging System for Biomedical Applications Based on Low-Frequency Magnetic Field

In this article, the theoretical and experimental feasibility analyses of a high-sensitivity imaging system for non-invasive detection of pathological inclusions within biological tissues are presented. The radiating system, exploiting a low frequency magnetic field operating at 3 MHz, consists of an inner resonant spiral sensor, inductively coupled to an unloaded external planar probe loop. The proposed configuration produces a focused magnetic field distribution, therefore a high-sensitivity imaging with respect to the wavelength can be accomplished (detecting inclusions with size in the order of λ/10000, i.e., 1 cm). In particular, the inclusion detection is carried out by observing the amplitude shift of the external probe loop input impedance while scanning the region of interest, leading to a non-invasive and contactless imaging procedure. In addition, we demonstrate the possibility to detect an inclusion, placed within the investigated tissue, either with or without the use of a ferromagnetic contrast medium. To evaluate the proposed imaging system effectiveness, we first perform full-wave numerical simulations. Then, we report the experimental measurements acquired over a fabricated prototype interacting with a representative biological phantom, observing a very good agreement with the numerical simulations. The results confirm the potential for an innovative near-field imaging system to be employed for non-invasive detection of malignant inclusions, expanding the adoption of low RF frequencies in biomedical applications.