Effect of the RF shield-to-coil distance on coil efficiency for a 46 mT Halbach-based point-of-care MRI system

Motivation: Inner-Shield in Halbach-array magnet effect RF coil transmit efficiency and signal-to-noise ratio(SNR). With this, finding a good trade of between magnet diameter and SNR is important. Goal(s): Find the proper magnet diameter with respect to the RF coil transmit efficiency. Approach: Simulations of the transmit efficiency of three RF coils used for neuroimaging on a 46 mT Halbach-array point-of-care MRI system have been performed in terms of analyzing the coil to RF shield distance located inside the magnet. Results: Results show that a distance of 1 cm results in a 50% lower transmit/receive efficiency than a 3 cm gap. Impact: This means that slightly larger magnets may have higher signal-to-noise even though the B0 field is lower.