The relaxation profile of 40% w/w of BSA in water at 263 K shows for instance the occurrence of three quadrupolar peaks (see Figure ), which can be nicely analyzed with Eq. 4. These relaxation peaks are placed on the top of a relaxation decrease, which can be reproduced assuming contributions from dipole-dipole interactions modulated with a distribution of correlation times (Eq. 2). Relaxation profiles have been measured also for healthy muscles and tumour tissues. In these cases, the water proton relaxation rates are of the order of few tens of s -1 at 0.01 MHz, due to the relatively large amount of water molecules present in the extracellular space and in exchange with those present in the intracellular compartment. The relaxation rates decrease with increasing the magnetic field, usually quite fast at low fields and more slowly at high fields (see Figure ). The overall shape of the relaxation profiles should be related to the dynamics of the water molecules in the two different compartments, where they are subjected to a restricted mobility. The relaxation profiles can be fitted with a sum of Lorentzian functions (Eq. 2) or with including contributions from two-dimensional translational diffusion (Eq. 3).