  The aim of this paper is to optimally design the set of b-values for
diffusion weighted MRI with the aim of accurate estimation of intra- voxel
incoherent motion (IVIM) parameters (f perfusion fraction, Ds slow diffusion,
Df fast diffusion) according to the model developed by Le Bihan. Previous
studies have addressed the design in a Monte Carlo fash- ion. Due to huge
computation times, this approach is feasible only for a limited number of
values of the parameters (local design): however, as the parameters of a
specific exam are not known a priori, it would be desirable to optimise
b-values over a region of parameters. In order to overcome this issue, we
propose to use a D-optimal design approach. The optimal combination of b-values
can be chosen from a candidate set of predefined values taken from the
literature. Our study has two key results: first, the optimal design does not
depend on perfusion fraction: this allow to perform a search over a 2D
parameter space instead of 3D; second, as an exhaustive search over all
possible designs would still be time consuming, we proposed an algorithm to
find an approximate solution can be found very quickly.
