  In radial fast spin-echo MRI, a set of overlapping spokes with an
inconsistent T2 weighting is acquired, which results in an averaged image
contrast when employing conventional image reconstruction techniques. This work
demonstrates that the problem may be overcome with the use of a dedicated
reconstruction method that further allows for T2 quantification by extracting
the embedded relaxation information. Thus, the proposed reconstruction method
directly yields a spin-density and relaxivity map from only a single radial
data set. The method is based on an inverse formulation of the problem and
involves a modeling of the received MRI signal. Because the solution is found
by numerical optimization, the approach exploits all data acquired. Further, it
handles multi-coil data and optionally allows for the incorporation of
additional prior knowledge. Simulations and experimental results for a phantom
and human brain in vivo demonstrate that the method yields spin-density and
relaxivity maps that are neither affected by the typical artifacts from TE
mixing, nor by streaking artifacts from the incomplete k-space coverage at
individual echo times.
