Metasolenoid resonator for controlling magnetic field in 3T MRI.

Motivation: Passive resonators have proven effective for focusing radiofrequency fields (RF) and improve breast and wrist imaging in 1.5T MRI systems. Goal(s): Assess the performance of such resonators for 3T MRI for which transmit efficiency must be critically improved to reduce specific absorption rate. Approach: A metasolenoid was fabricated and tuned. Flip angle maps were acquired on phantom at 3T. Results: The metasolenoid improved the transmit efficiency within a targeted region. A three-fold increase was obtained with a quadrature driven birdcage and a five-fold increase was achieved with a linear driven birdcage. Impact: This study validates experimentally a metasolenoid resonator for focusing radiofrequency fields in 3T MRI, initially applied at 1.5T for breast and wrist imaging. Our resonator reduces RF input power and could be useful for specific 3T MRI applications.