Probing the analogy of the proton relaxation in biological tissues and porous media

Summary Experimental data are reported that show the analogy of longitudinal and transverse proton relaxation in heterogeneous systems as different as biological tissues and water-saturated rocks. Published data on the τ-dependence of the transverse-relaxation rate for biological tissues with magnetite grains, used as a contrast agent in MRI, are discussed in the light of our recent results on water-saturated porous media, and give for the liver another case of a behaviour parallel to that in rocks. There are enough similarities between NMR relaxation in tissues and in other porous media that, for work in either area, attention to the other is likely to be fruitful. Work supported by Italian CNR and MURST grants