Fiber-orientation independent component of R₂* obtained from single-orientation MRI measurements in simulations and a post-mortem human optic chiasm.

ABSTRACT: The effective transverse relaxation rate (R₂*) is sensitive to the microstructure of the human brain like the g-ratio which characterises the relative myelination of axons. However, the fibre-orientation dependence of R₂* degrades its reproducibility and any microstructural derivative measure. To estimate its orientation-independent part (R_2,iso*) from single multi-echo gradient-recalled-echo (meGRE) measurements at arbitrary orientations, a second-order polynomial in time model (hereafter M2) can be used. Its linear time-dependent parameter, β₁, can be biophysically related to R_2,iso* when neglecting the myelin water (MW) signal in the hollow cylinder fibre model (HCFM). Here, we examined the performance of M2 using experimenta

SUBMITTER: Fritz FJ 

PROVIDER: S-EPMC10491021 | biostudies-literature | 2023

REPOSITORIES: biostudies-literature