Boosting Performance of 1.5T MRI using Switchable Metasurface Wraps Composed of Interconnected Rectangular Windings

Magnetic resonance imaging (MRI) is a versatile non-invasive diagnostic technique among modern radiological technologies, used to investigate a wide range of health conditions affecting human organs and tissues. Recent advancements in metasurfaces have shown potential to enhance MRI performance by improving the signal-to-noise ratio (SNR) without increasing the applied static magnetic field (B<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf>). Metasurfaces can confine and amplify magnetic fields in the region of interest during scans which makes them effective clinical accessories that can be placed between patients and transceiver arrays. Various designs of metasurfaces have been reported in the literature to enhance RF magnetic fields and improve the signal-to-noise ratio (SNR) of 1.5T MRI systems. However, while enhancing RF magnetic fields and SNR in 1.5T MRI systems, these structures interact with RF signals during transmission (Tx) and reception (Rx) phases. During Tx, this interaction may amplify RF power delivered to scanned tissues, raising safety concerns such as tissue heating and higher specific absorption rate (SAR). To address these challenges, a switchable metasurface composed of interconnected rectangular windings has been developed. This design selectively amplifies RF signals during the Rx phase while remaining inactive during Tx phase. The resonance frequency of metasurface shifts during Tx due to PIN diodes on its unit cells, detuning it from 63.8 MHz. During Rx, it resonates as a tank circuit, enhancing the received magnetic field. This approach improves the SNR by greater than five-fold in human head models during the Rx phase while minimizing patients’ safety concerns during the Tx phase by behaving as a non-interacting element for RF signals, offering a more efficient MRI imaging solution.