1. A method of simultaneously determining multiple parameters or a parameter distribution characterizing material properties of a volume under investigation using an inversion process of sparse measurements, said method including the step of defining an initial model of said volume and modifying said initial model by matching said multiple parameters or parameter distribution with said measurements using alternatingly an iterative inversion method and a probabilistic inversion method; and determining said multiple parameters or parameter distribution after one or more iterations of said alternating inversions.