Magnetic field sensitivity at 7‐T using dual‐helmholtz transmit‐only coil and 12‐channel receive‐only bended coil. Issue 6 (19th January 2016) - Kim, Kyoung‐Nam
Summary: The purpose of this study was to combine a dual‐Helmholtz (DH) transmit (Tx)‐only coil and 12‐channel receive (Rx)‐only bended phased array (PA) coil to improve the magnetic flux (|B1 |) sensitivity in the superior‐to‐inferior (S‐I) direction during human brain magnetic resonance imaging (MRI) at 7‐T. The proposed coil combination was primarily implemented by electromagnetic (EM) simulation and compared with the 16‐leg birdcage coil and 8‐channel PA coil, which are generally used for the Tx‐ and Rx‐only modes, respectively. The optimal coil combinations for the proposed structure were determined by |B1 | field calculations using the |BT + | and |BR − | fields, which are respectively the transmit and receive components of the |B1 | field. The coil performance was then evaluated by a bench test and 7‐T MRI experiment. The results of the computational calculations indicated that the |BT + | field of the DH coil was distributed similarly to that of the 16‐leg birdcage coil despite the fewer conducting legs of the former. However, the 12‐channel Rx‐only bended PA coil had clearly higher |BR − | profiles compared to the 8‐channel PA coil. The results of the 7‐T in vivo experiment showed that the proposed combination of the DH Tx‐only coil and 12‐channel Rx‐only bended PA coil had better |B1 | field homogeneity in the sagittal slice as well as higher |B1 | field sensitivity during human brain MRI compared to an 8‐channel Rx‐only PA coil. SCANNING 38:515–524, © 2015 Wiley Periodicals, Inc.