Capacitively-Loaded Spiral Array based RF Metasurfaces for Boosting the Performance of 1.5T MRI

The narrow-band resonance in metamaterial is exploited in magnetic resonance imaging (MRI) to facilitate boosting of magnetic field and signal-to-noise ratio (SNR). However, most of the reported metamaterials for 1. 5T MRI applications focus on three-dimensional structures, which are unsuitable for practical implementations since they are electrically large and bulky. Here, we demonstrate a spiral-array based ultra-thin metasurface, which can be used as an ‘add-on’ for enhancing the performance of 1. 5 T MRI. The metasurface is integrated with phantom and bio-model mimicking human properties to enhance the magnetic field inside the region-of-interest (ROI) of specimens undergoing scan. Inductive coupling between these capacitively-loaded closely spaced spirals causes an enhancement of the signal-to-noise ratio by ~3. 5 times for 1. 5T MRI while maintaining the specific absorption ratio (SAR) well below the safety limit. The proposed structure can be easily integrated in the available tight space (of thickness ≤ 2 mm) of clinical MRI scanners where the placement of any bulky additional structure is challenging.