A combined 32-channel receive-loops/8-channel transmit-dipoles coil array for whole-brain MR imaging at 7T

Abstract

Purpose: Multichannel receive arrays provide high SNR and parallel-imaging capabilities, while transmit-only dipole arrays have been shown to achieve a large coverage of the whole-brain including the cerebellum. The aim of this study was to develop and characterize the performances of a 32-channel receive-only loop array combined with an 8-channel dipole coil array at 7T for the first time. Methods: The 8Tx-dipoles/32Rx-loops coil array was characterized by the SNR, g-factors, noise correlation matrix, accelerated image quality, and B+1 maps, and compared with a commercial 1Tx-birdcage/32Rx-loops array. Simulated and measured B+1 maps were shown for the 8Tx-dipoles/32Rx-loops coil array and compared with the 8Tx/Rx dipole array. Results: The in-house built 32-channel receive coil demonstrated a large longitudinal coverage of the brain, particularly the upper neck area. G-factors and accelerated MR acquisitions demonstrated robust performances up to R = 4 in 2D, and R = 8 (4 × 2) in 3D. A 83% increase in SNR was measured over the cerebellum with the in-house built 8Tx/32Rx coil array compared to the commercial 1Tx/32Rx, while similar performances were obtained in the cerebral cortex. Conclusions: The combined 32-channel receive/8-channel transmit coil array demonstrated high transmit-receive performances compared to the commercial receive array at 7T, notably in the cerebellum. We conclude that in combination with parallel transmit capabilities, this coil is particularly suitable for whole-brain MR studies at 7T.