Water-Tunable Highly Sub-Wavelength Spiral Resonator for Magnetic Field Enhancement of MRI Coils at 1.5 T

IEEE Access

Srikumar Sandeep¹  Elizaveta Motovilova¹  Shao Ying Huang¹  Michinao Hashimoto¹ 

[1] Singapore University of Technology and Design, Singapore;

关键词: MRI;    resonator;    RF lens;    RF coil;    spiral;   

DOI  :  10.1109/ACCESS.2019.2927359

来源: DOAJ

【 摘 要 】

In magnetic resonance imaging (MRI), several studies have demonstrated that the metamaterial-based structures can effectively improve the sensitivity, and thus the signal-to-noise ratio (SNR), of receiving radio-frequency (RF) coils. However, the use of metamaterials for this type of the MRI application is often limited due to the bulkiness of the metamaterial structure at RF wavelengths and a lack of frequency tunability of the final design. In this work, we propose a planar compact sub-wavelength (<; λ/50) spiral resonator to increase the sensitivity of a receive coil with frequency tunability for the 1.5 T MRI. Its double-layered spiral design with a cavity embedded in the substrate between the two spirals allows water deposition for frequency tuning. At the resonance frequency of 64 MHz, the spiral resonator shows a 24% improvement in terms of the B₁^- field at the depth of 30mm into a load experimentally. Even at a penetration depth as much as 60 mm (deep brain in the case of head imaging), an enhancement of 9% was observed. Moreover, the magnetic field enhancement comes with a decrease (10%) in specific absorption rate (SAR). In terms of tuning, by controlling the water level in the cavity, the proposed spiral resonator shows a wide tuning range of 35MHz, centered around 64 MHz, with high tunability sensitivity (2.4-0.75 MHz/ml or 15-4.8 MHz/mm), which is due to the fact that the tuning cavity is located between the two spirals, where the fields are highly confined.

【 授权许可】

Unknown