B1 Inhomogeneity Mitigation in the Human Brain at 7T with Selective Pulses by using Average Hamiltonian Theory

Nicolas Boulant¹, Martijn Cloos¹, Alexis Amadon¹

The design of the strongly modulating pulses, developed by the same authors and initially non-selective, has been adjusted to create selective pulses by using average Hamiltonian theory. Such a theory formulates an approximate analytical expression of the dynamics which allows navigating quickly in some pulse parameter space. Once a pulse is found to perform sufficiently well using that approximation, it can be modified with a few iterations by calculating more accurately the spin evolution. Using that technique, in-vivo results are reported which show good mitigation of the B1 inhomogeneity problem over an axial slice in the human brain at 7T.