Sequential changes in MR water proton relaxation time detect the process of rat brain myelination during maturation

For better understanding of the behavior of water molecules in the animal b rain, changes in magnetic resonance water proton relaxation processes were studied in the rat during maturation. Midbrains of male Wistar rats were re moved at various time points ranging from 2 to 70 days after birth. Changes in relaxation time (water proton longitudinal relaxation time by the inver sion recovery, and water proton transverse relaxation time by the spin echo and the Carr-Purcell-Meiboom-Gill pulse sequence (CPMG)) and water content were then determined for various stages of brain development. During matur ation both water proton longitudinal relaxation time and water proton trans verse relaxation time values decreased and this finding paralleled the decl ine in water content. Using the CPMG pulse sequence, the transverse relaxat ion time values were observed to separate into two components after 21 days . Morphologically, the most prominent change at the matured stage of midbra in development in the rat is myelination. Water proton relaxation time, whi ch can be estimated using the CPMG pulse sequence, showed a close correlati on with myelination in the central nervous system. (C) 2001 Elsevier Scienc e Ireland Ltd. All rights reserved.