A unified circular-polarization metamaterial-inspired resonator for increasing SNR in breast MRI

Magnetic Resonance Imaging (MRI) is crucial for population breast cancer screening. Since almost all MRI machines are equipped with transmit-receive body coils, this configuration of equipment makes MRI readily accessible to breast cancer screening. However, the signal-to-noise ratio (SNR) of breast images is limited by the low sensitivity of the body coil reception and high noise from surrounding tissues. To increase the SNR, we propose a unified circular-polarization metamaterial-inspired resonator (CPMR) for breast MRI at 1.5 T. Most MRI systems utilize birdcage coils as body coils, which produce circularly polarized magnetic fields, but the state-of-the-art resonators can only achieve magnetic field enhancement for linearly polarized fields, or enhance the two linearly polarized components of a circularly polarized magnetic field by using two separate resonators. The proposed CPMR can simultaneously enhance the two orthogonal linearly polarized components of a circularly polarized magnetic field, which will be accomplished by a single integrated resonator. The unified metamaterial-inspired resonator is easier to manufacture and position in an MRI system. The phantom imaging results indicate that, compared with using only the birdcage coil, when performing unilateral and bilateral imaging, the use of CPMR increases the SNR in the region of interest (ROI) by at least 18.4 times and 10.6 times respectively. Compared with using a dedicated breast coil, the SNR in the ROI is increased by at least 48 %.