Metabolite T₁ relaxation times decrease across the adult lifespan

Area of Science:

• Neuroimaging
• Biophysics
• Gerontology

Background:

• Quantifying brain metabolites using in vivo magnetic resonance spectroscopy (MRS) requires accurate relaxation correction.
• Current MRS quantification often assumes constant T1 relaxation across all ages, potentially introducing inaccuracies.
• Evidence suggests that aging may alter T1 relaxation rates, similar to observed changes in T2 relaxation.

Purpose of the Study:

• To investigate the age-dependent changes in T1 relaxation times of key brain metabolites.
• To assess whether T1 relaxation varies between gray and white matter with increasing age.
• To establish the necessity of age-normed metabolite T1 values for precise MRS quantification in aging research.

Main Methods:

• Utilized a large, publicly available dataset of 3 Tesla (3T) MRS data from 102 healthy volunteers (aged 20-69).
• Analyzed metabolite-nulled and full metabolite spectra from posterior cingulate cortex (PCC) and centrum semiovale (CSO) using Osprey software.
• Calculated T1 relaxation times for N-acetyl aspartate (tNAA) and creatine (tCr) using a single inversion recovery method and evaluated age correlations.

Main Results:

• Significant negative correlations were found between age and T1 relaxation times for tNAA and tCr in the white-matter-rich CSO.
• A less pronounced, but significant, negative correlation was observed for tNAA in the gray-matter-rich PCC.
• T1 relaxation times for tCr in the PCC did not show a significant age-related decrease.

Conclusions:

• Metabolite T1 relaxation times exhibit age-dependent changes, particularly in white matter.
• The assumption of constant T1 relaxation across age is not universally valid for MRS quantification.
• Further research is crucial to develop and implement age-normed T1 values for accurate metabolite quantification in aging studies.