Integrated RF/shim coil array for parallel reception and localized B0 shimming in the human brain

The purpose of this work was to develop a novel integrated radiofrequency and shim (RF/shim) coil array that can perform parallel reception and localized B-0 shimming in the human brain with the same coils, thereby maximizing both the signal-to-noise ratio and shimming efficiency. A 32-channel receive-only head coil array was modified to enable both RF currents (for signal reception) and direct currents (for B-0 shimming) to flow in individual coil elements. Its in vivo performance was assessed in the frontal brain region, which is affected by large susceptibility-induced B-0 inhomogeneities. The coil modifications did not reduce their quality factor or signal-to-noise ratio. Axial B-0 maps and echo-planar images acquired in vivo with direct currents optimized to shim specific slices showed substantially reduced B-0 inhomogeneities and image distortions in the frontal brain region. The B-0 root-mean-square error in the anterior half of the brain was reduced by 60.3% as compared to that obtained with second-order spherical harmonic shimming. These results demonstrate that the integrated RF/shim coil array can perform parallel reception and localized B-0 shimming in the human brain and provide a much more effective shimming than conventional spherical harmonic shimming alone, without taking up additional space in the magnet bore and without compromising the signal-to-noise ratio or shimming performance. (C) 2014 Elsevier Inc. All rights reserved.