A Water Relaxation Atlas for Age- and Region-Specific Metabolite Concentration Correction at 3 T

Area of Science:

• Neuroimaging
• Biophysics
• Medical Physics

Background:

• Magnetic Resonance Spectroscopy (MRS) quantification typically uses water referencing, correcting for relaxation time differences.
• Standard methods often use fixed literature values for water relaxation times (T1 and T2) in different brain tissues.
• Water relaxation times vary significantly by brain location and age, introducing potential biases in current MRS studies.

Purpose of the Study:

• To develop a comprehensive water relaxometry atlas of the human brain.
• To integrate location- and age-specific water relaxation values into the MRS analysis workflow.
• To improve the accuracy of metabolite concentration estimates in MRS studies, particularly those focusing on aging.

Main Methods:

• Recruited 101 healthy volunteers across a range of adult ages (20s-60s).
• Acquired T1-weighted MPRAGE images and performed whole-brain water T1 and T2 mapping using DESPOT at 3T.
• Registered relaxation maps to the JHU MNI-SS/EVE atlas, calculated mean relaxation values per parcel, and generated age-dependent linear models to create reference atlases.

Main Results:

• Generated reference atlases for T1 and T2 relaxation times, detailing "age-30-intercept" and age-slope.
• The water relaxation aging atlas revealed significant regional and tissue-specific differences in water relaxation across adulthood.
• Integrated the atlas into the Osprey software for location- and age-appropriate water relaxation parameter calculation in MRS analysis.

Conclusions:

• The developed water relaxation aging atlas provides crucial location- and age-specific data for MRS quantification.
• Integrating these data into the MRS workflow addresses a key methodological limitation, reducing quantification biases.
• This approach is expected to enhance the reliability of metabolite concentration measurements, especially in aging research.