Fig. 4
a Conventional line fitting of a synthetic kidney spectrum with three fitted pHe compartments indicated by coloured markers (compartment 1: red stars, compartment 2: green diamonds, compartment 3: blue triangles) and comparison of calculated pHe values and ground truth data is shown as inset resulting in good agreement. b Conventional line fitting on a noisy spectrum and low compartment intensities of the medulla and the ureter. Three compartments can only be partially detected and agreement with ground truth is rather poor