T1 and T2 relaxation time estimates in the normal human brain.

Magnetic resonance (MR) relaxation time constants T1 and T2 were estimated in frontal and occipital white matter, the caudate nucleus, and the thalamus nucleus in 79 healthy subjects aged 19-85 years. The in vivo estimates were obtained with 0.02-T and 0.8-MHz MR imaging. T1 values were estimated from a series of inversion-recovery images and T2 values from spin-echo images with a single-section, single-echo technique. Although estimates were obtained from only one section, the investigated regions were distinguished from each other by the T1 values. With a polynomial regression test, the T1 data fit a cradle-shaped relation to age, with minimal values at ages 40-45 years. Sex and laterality did not influence the age-dependency results, but differences in the age-dependence curves for men and women were seen. The inclusion of 10 individuals with somatic disorders did not alter the findings.