Comparison of the relative r₀₁ differences for models that can (right) and cannot (left) be used for a meaningful inversion. The relative differences above 0.5 are discarded because they are not appropriate for the linear formalism of the inversion. (a) Model LM1 of target 2, well fitted r₀₁ ratios that are not suited for an inversion. (b) Model LM of target 2, relative r₀₁ differences suited for an inversion.