A proton NMR relaxation evaluation of a model of brain oedema fluid

Using CSF/protein solutions as models of vasogenic extracellular fluid, the concentration dependences of longitudinal and transverse proton relaxation rates have been measured at 37 degrees C and 100 MHz for the serum proteins, albumin, IgG, a 2.8:1 mixture of albumin and IgG and human serum itself. These measurements have been used to determine the sensitivity of proton relaxation rates to the amount and the type of the protein in oedema fluid, and to establish the significance of both of these factors in relation to a separation of vasogenic from cytotoxic oedema. An extension of the two-environment rapid-exchange model of solvent relaxation is presented, which accounts for the measurements on protein mixtures and which enables estimates to be made of the number and the transverse relaxation rate of water protons associated with the protein surface.