RF shimming strategy for an open 60-channel RF transmit 7T head coil for routine use on the single transmit mode

Purpose To develop an RF shimming approach for operating the 2 nd Generation Tic Tac Toe RF Coil System (60 transmit channels integrated with 32-channel receive insert) for routine use in 7T neuro MRI on the single transmit mode. Methods RF simulations were performed and used to develop non-subject-specific RF shim cases over three anatomically detailed head models: adult male, adult female, and child female. Multi-ROI shimming strategies were developed and implemented. B 1 + maps and in-vivo images were acquired on the single transmit mode of a 7T scanner using the RF shim cases derived from the computer simulations. Results The availability of 60 transmit channels enables more control over RF power efficiency, SAR efficiency, and B 1 + homogeneity using RF shimming. On the single transmit mode, the 2 nd Generation Tic Tac Toe RF Coil System consistently provides homogeneous B 1 + field distribution with extended coverage into the temporal lobes, cerebellum, reaching all the way to C5-C6. Safe levels of SAR are also achieved. Conclusion By using a non-subject specific RF shimming approach derived from computer simulations, the 2 nd Generation Tic Tac Toe RF Coil System allows for robust, routine neuroimaging (> 1750 in-vivo scanning sessions over the past 28 months) at 7T in single transmit mode.