Development of T2-relaxation values in regional brain sites during adolescence

Abstract

Brain tissue changes accompany multiple neurodegenerative and developmental conditions in adolescents. Complex processes that occur in the developing brain with disease can be evaluated accurately only against normal aging processes. Normal developmental changes in different brain areas alter tissue water content, which can be assessed by magnetic resonance (MR) T2 relaxometry. We acquired proton-density (PD) and T2-weighted images from 31 subjects (mean age±S.D., 17.4±4.9 years; 18 male), using a 3.0-T MR imaging scanner. Voxel-by-voxel T2-relaxation values were calculated, and whole-brain T2-relaxation maps constructed and normalized to a common space template. We created a set of regions of interest (ROIs) over cortical gray and white matter, basal ganglia, amygdala, thalamic, hypothalamic, pontine and cerebellar sites, with sizes of ROIs varying from 12 to 243 mm(3); regional T2-relaxation values were determined from these ROIs and normalized T2-relaxation maps. Correlations between R2 (1/T2) values in these sites and age were assessed with Pearson's correlation procedures, and gender differences in regional T2-relaxation values were evaluated with independent-samples t tests. Several brain regions, but not all, showed principally positive correlations between R2 values and age; negative correlations emerged in the cerebellar peduncles. No significant differences in T2-relaxation values emerged between males and females for those areas, except for the mid pons and left occipital white matter; males showed higher T2-relaxation values over females. The findings indicate that T2-relaxation values vary with development between brain structures, and emphasize the need to correct for such age-related effects during any determination of potential changes from control values.

Copyright © 2011 Elsevier Inc. All rights reserved.

Figures

Figure 1

Brain regions showing regions of interest (ROIs) on mean background images, with ROIs represented by rectangles proportional to volumes collected and used for T2-relaxation calculations. ROIs are overlaid onto mean background images, derived from normalized T2-weighted images; for clarity, only left-sided ROIs are displayed. 1, frontal white matter; 2, caudate nucleus; 3, putamen; 4, globus pallidus; 5, anterior insula; 6, mid insula; 7, posterior insula; 8, superior temporal white matter; 9, midline occipital gray matter; 10, anterior cingulate; 11, anterior thalamus; 12, mid thalamus; 13, posterior thalamus; 14, occipital white matter; 15, frontal cortex; 16, inferior hippocampus; 17, mid hippocampus; 18, superior hippocampus; 19, amygdala; 20, inferior temporal white matter; 21, mid temporal white matter; 22, anterior corpus callosum; 23, mid corpus callosum; 24, posterior corpus callosum; 25, superior pons; 26, mid pons; 27, inferior pons; 28, mid cingulate; 29, posterior cingulate; 30, hypothalamus; 31, superior cerebellar peduncle; 32, mid cerebellar peduncle; 33, inferior cerebellar peduncle; 34 cerebellar deep nuclei; 35, rostral cerebellar cortex; 36, caudal cerebellar cortex.

Figure 2

Brain regions within the rostral brain (telencephalon), including the amygdala, caudate, putamen, globus pallidus, hippocampus, and temporal white matter showing significant correlations between R2 values and age. Solid lines show best fit lines for the data, and dotted lines above and below the best fit line show 95% mean confidence intervals.

Figure 3

Brain areas within the cingulate, insula, and hippocampus showing significant correlations between R2 values and age. Figure conventions are the same as in Figure 2.

Figure 4

Brain sites within the thalamus showing significant correlations between regional R2 values and age. Figure conventions are the same as in Figure 2.

Figure 5

Multiple brain areas in the cerebellar peduncles and deep nuclei that show significant correlations between R2 values and age. Figure conventions are the same as in Figure 2.