# Age-related changes in myelin and myelin water quantified with short-TR adiabatic inversion-recovery (STAIR) sequences

## TL;DR

This study uses MRI techniques to measure age-related changes in brain myelin and myelin water, showing significant differences between young and old volunteers.

## Contribution

The study introduces STAIR-UTE and STAIR-STE as reliable methods to quantify myelin and myelin water fractions in aging brains.

## Key findings

- MPF and MWF values were significantly higher in young compared to old volunteers.
- Most WM/GM regions showed linear and quadratic relationships between MPF/MWF and age.
- MPF and MWF were significantly correlated in the majority of brain regions.

## Abstract

•STAIR-UTE maps myelin and STAIR-STE maps myelin water in young and old volunteers.•High ICC values demonstrate excellent inter-reader reliability of the protocol.•MPF and MWF maps showed significant differences between young and old volunteers.•Most WM/GM regions show significant quadratic and linear relationships with age.•WM and GM regions demonstrate significant correlations between MPF and MWF.

STAIR-UTE maps myelin and STAIR-STE maps myelin water in young and old volunteers.

High ICC values demonstrate excellent inter-reader reliability of the protocol.

MPF and MWF maps showed significant differences between young and old volunteers.

Most WM/GM regions show significant quadratic and linear relationships with age.

WM and GM regions demonstrate significant correlations between MPF and MWF.

Myelin proton density fraction (MPDF) and myelin water fraction (MWF) measured with short-TR adiabatic inversion-recovery (STAIR) sequences are potential biomarkers of aging and neurodegeneration, but the effects of aging on MPDF/MWF remain unknown. This study aims to assess relationships between age and MPDF/MWF using the 3D STAIR ultrashort echo time (STAIR-UTE) and STAIR short echo time (STAIR-STE) sequences, respectively. 42 volunteers (29 young (<55y), 13 old (>55y)), were recruited for MPDF and MWF mapping for white matter (WM) and gray matter (GM) on a 3 T scanner. Excellent inter-reader reliability was demonstrated for MPDF and MWF measurements with ICC values of 0.97 and 0.98, respectively, between two readers. In the young group, WM MPDF and MWF range from 8-13 % and 6–13 %, respectively, while GM MPDF and MWF range from 5-7 % and 3–5 %, respectively. In the old group, WM MPDF and MWF range from 6-12 % and 5–13 %, and GM MPDF and MWF range from 3-6 % and 2–5 %, respectively. The young group’s MPDF/MWF values were significantly higher than those of the old group. Altogether, the 42 volunteers display linear and quadratic associations of MPDF/MWF with age. MPDF demonstrated significant correlations with MWF in the majority of brain regions. This study demonstrates the capability of two myelin imaging biomarkers, STAIR-UTE measured MPDF and STAIR-STE measured MWF to map brain myelin and MW. These biomarkers hold the potential to differentiate normal aging from neuroinflammatory/neurodegenerative diseases.