  In this work a generic model-based reconstruction for the quantification of
relaxation parameters is developed. In contrast to previous approaches that
rely on simplified models derived from the Bloch equations, this work includes
the Bloch equations directly into the reconstruction. Therefore, non-linear
calibrationless parallel imaging is combined with a generic Runge-Kutta 5(4)
based forward operator to simulate spin dynamics described by arbitrary
sequences. Gradients are determined by using a sensitivity analysis and solving
the resulting ordinary differential equations parallel to the signal
simulation. Based on this formulation an IRGNM-FISTA algorithm is used to
estimate quantitative maps for $T_1$, $T_2$, $M_0$, and the coil profiles $c_N$
from fully-sampled multi-inversion and golden-angle single-shot
inversion-recovery radial bSSFP measurement with a custom-built $T_1$-$T_2$
phantom.
