Neither Flat Profile Nor Black Spots: A Simple Method to Achieve Acceptable CP-Like Mode Transmit B1 Pattern for Whole Brain Imaging with Transmit Arrays at 7 Tesla

Sebastian Schmitter¹, Gregor Adriany¹, Edward J. Auerbach¹, Kamil Ugurbil¹, Pierre-Francois Van de Moortele¹

At 7T the short transmit B1 (B1+) RF wavelength leads to spatial variations of |B1+| including possible B1+ nodes of fully destructive interference. RF phase shimming using multi-channel TX coils can mitigate this problem. However, a 'good starting-phase set' without B1+ nodes and with reasonably high B1+ efficiency is not necessarily known before starting a scanning session. Yet, such CP-like mode is indispensable for whole brain anatomical imaging, B0 mapping and RF power calibration. In this work we present a simple but efficient method to determine a good starting set of CP-like RF phases for multi-channel head coils at 7T.