Age‐related regional brain T2‐relaxation changes in healthy adults

Abstract

Purpose: To determine normal T2-relaxation values from different brain areas in healthy adults, assess age-related T2-relaxation changes in those sites, and evaluate potential gender-related T2-relaxation value differences. Materials and Methods:We performed proton-density and T2-weighted imaging in 60 healthy adults (male: 38, age range ¼ 31-64 years, mean age 6 SD ¼ 46.1 6 9.3 years; female: 22, age range ¼ 37-66 years, mean age 6 SD ¼ 49.5 6 8.3 years), using a 3.0 Tesla MRI scanner. T2-relaxation values were calculated voxel-by-voxel from proton-density and T2-weighted images, and whole-brain T2-relaxation maps were constructed and normalized to a common space. A set of regions-of-interest were outlined within the basal ganglia, limbic, frontal, parietal, temporal, occipital, thalamic, hypothalamic, cerebellar, and pontine regions using mean background images derived from normalized and averaged T2-weighted images of all individuals, and regional T2-relaxation values were determined from these regions-of-interest and normalized T2-relaxation maps. Pearson's correlations were calculated between T2-relaxation values and age, and male-female differences evaluated with independent-samples t-tests.Results: T2-relaxation values typically increased with age in multiple brain sites; only a few regions showed declines, including the putamen and ventral pons. Sexrelated differences in T2-relaxation values appeared in basal ganglia, frontal, temporal, occipital, and cerebellar regions; males showed higher values over females in these sites.Conclusion: Establishment of normative adult T2-relaxation values over different brain areas, with age and sex as co-factors, offers baseline values against which diseaserelated tissue changes can be assessed. NONINVASIVE ASSESSMENT OF adult human brain changes resulting from neurologic, neuropsychological, and neurocognitive pathologies against normal age-related changes remains difficult (1-3). Myelin and neurons undergo slow degradation with age in adults (4,5), and these normative changes, as well as neurodegenerative processes inducing myelin and neuronal loss (6,7), increase free tissue water content. However, certain deep brain structures, including the basal ganglia, are known to show iron deposition with age in adult subjects (8), which can alter indications of normal progression of tissue changes in these sites. Pathological and treatment-related brain tissue alterations can be assessed accurately, but only after controlling for age-related changes, which mandates determination of normative values from gray and white matter regions over wide-spread brain areas.MR T2-relaxometry provides a quantitative surrogate marker of brain tissue changes in both health and disease by assessing free tissue water content (9) in the absence of diamagnetic and paramagnetic substances, which differs during pediatric development over normal patterns of aging in adult controls (5,10), and increases with disease processes (11). T2-relaxation values increase with increased free tissue water cont...

Detection of Normal Aging Effects on Human Brain Metabolite Concentrations and Microstructure with Whole-Brain MR Spectroscopic Imaging and Quantitative MR Imaging

“…The metabolite concentrations determined in this study agree in general with those reported by using single voxel spectroscopy (SVS), with NAA being the largest component in cerebrum and tCr the largest component in cerebellum, while the Cho concentration is the smallest in both regions 14, 15 , though in this study the measurements were obtained in multiple regions using only a single MRSI acquisition. The T2 and T2′ values found in this study are also comparable with those previously published, with T2′ being shortest in supratentorial deep gray matter, and T2 longest in cerebellum 6, 16 . With combined wbMRSI and qMRI measurements this study determined for the first time simultaneously the age-related metabolite concentrations and tissue transverse relaxation times at multiple supratentorial and infratentorial structures in healthy human brain, which has the potential to provide a reference basis for future studies to identify pathological alterations in patients.…”

Brain development and aging: Overlapping and unique patterns of change

“…An important task for further research is to disentangle to what degree common mechanisms may be responsible for brain maturation in childhood and degenerative changes in aging (Nikolaev et al, 2009; Wines-Samuelson and Shen 2005), and to what degree distinct processes are causing the observed macrostructural changes. Longitudinal studies should utilize multimodal and multidimensional data to explore the relationships between morphometric measures, water diffusivity and signal intensity and tissue contrast in development and aging (Brown and Jernigan In press; Groves et al, 2012; Kumar et al, 2012; Salat et al, 2009; Westlye et al, 2010a; Westlye et al, 2009), as this could indirectly inform us on the underlying specific biological processes that give rise to the imaging effects. Intriguingly, a recent cross-sectional study (Brown et al, 2012)found that different imaging modalities contribute most strongly to predicting age over the course of development, indicating a dynamic cascade of changes with different features dominating at different points.…”

The BOLD cerebrovascular reactivity response to progressive hypercapnia in young and elderly

“…T 2 * information can provide a useful proxy for examining changes in baseline BOLD signals, and interpreting the related BOLD-CVR signal with age. However, intrinsic, tissues T 2 values can also vary due to age-related physical changes (Siemonsen et al, 2008;Kumar et al, 2012). Separating hemodynamic/oxygenation state from intrinsic tissue properties will remain challenging as both extravascular T 2 ′and T 2 values are affected by the blood oxygenation level, especially around small vessels (Siero et al, 2013).…”