EVALUATION OF MYELINATION BY MEANS OF THE T-2 VALUE ON MAGNETIC-RESONANCE IMAGINE

The progress of myelination in the cerebrum was evaluated by visual in spection, and magnetic resonance (MR) imaging and the transverse relax ation time (T-2) was calculated from double echo images. Twenty-three pediatric cases, who did not show intracranial organic changes on MR e xamination, were included. The T-2 values in the corpus callosum (CC), frontal deep white matter (FWM), occipital deep white matter (OWM) an d centrum semiovale (CS) were calculated, and the changes in these val ues with age were followed. During the first year of life, a rapid dec rease in the T-2 value was seen, followed by a more gradual decrease. The T-2 value seemed to reach the adult level between 2 and 3 years of life in all areas examined. The T-2 values between 2 and 16 years in CC, FWM, OWM and CS were 59.7 +/-3.6, 64.5 +/- 5.2, 69.8 +/- 4.8 and 6 6.3 +/- 3.3 ms (mean+/-S.D.), respectively. The T-2 values in patients with clinically diagnosed Pelizaeus-Merzbacher disease (PMD) and late onset Krabbe disease were also calculated. In PMD, non-progressive pr olongation of the T-2 value was observed in all areas. In late onset K rabbe disease, on the other hand, progressive prolongation of the T-2 values was mainly demonstrated in OWM and the posterior part of CS. Th ese results suggest that the T-2 value in the cerebral white matter al lows more objective judgement than visual inspection, and makes it pos sible to clarify the mechanism underlying abnormal myelination, i.e. p rogressive or not.