The present invention relates to a magnetic resonance imaging system (1)
comprising a plurality of RF coils (4) forming a multi-coil array and
furthermore to a magnetic resonance imaging method for such a system. In
order to provide an MR imaging system and method in which a desired
excitation pattern is achieved in a simple way, it is suggested to
utilize an analytical procedure how to combine the single coil elements
to obtain the most homogeneous B1 excitation possible with a given coil
array. In other words, the homogeneity of the B1 field is improved in a
very simple way. The sensitivity of each RF coil (4) of the coil array is
scaled or weighted by a complex factor, i.e. phase and amplitude of each
coil drive signal is adjusted accordingly. These complex factors are
determined analytically utilizing the sensitivities S(8) of the coil
elements (4) and the desired excitation pattern P (IO, 11). The invention
allows an optimized control of the field distribution (RF shimming) for
arbitrary RF coil arrays. With the invention a fast and easy independent
phase and amplitude control of the coil elements (4) is provided for
reducing body-induced RF non-uniformities, which appear in high field MR
systems.