Quantitative susceptibility mapping and R1 measurement : Determination of the myelin volume fraction in the aging ex vivo rat corpus callosum

© 2021 John Wiley & Sons, Ltd..

In studies of the white matter (WM) in aging brains, both quantitative susceptibility mapping (QSM) and direct R1 measurement offer potentially useful ex vivo MRI tools that allow volumetric characterization of myelin content changes. Despite the technical importance of such MRI methods in numerous age-related diseases, the supposed linear relationship between the estimates of either the QSM or R1 method and age-affected myelin contents has not been validated. In this study, the absolute myelin volume fraction (MVF) was determined by transmission electron microscopy (TEM) as a gold standard measure for comparison with the values obtained by the aforementioned MR methods. To theoretically evaluate and understand the MR signal characteristics, QSM simulations were performed using the finite perturber method (FPM). Specifically, the simulation geometry modeling was based on TEM-derived structures aligned orthogonally to the main magnetic field, the construct of which was used to estimate the magnetic field shift (ΔB) changes arising from the conjectured myelin structures. Experimentally, ex vivo corpus callosum (CC) samples from rat brains obtained at 6 weeks (n = 3), 4 months (n = 3), and 20 months (n = 3) after birth were used to establish the relationship between changes quantified by either QSM or R1 with the absolute MVF by TEM. From the ex vivo brain samples, the scatterplot of mean MVF versus R1 was fitted to a linear equation, where R1mean  = 0.7948 × MVFmean  + 0.8118 (Pearson's correlation coefficient r = 0.9138; p < 0.01), while the scatterplot of mean MVF versus MRI-derived magnetic susceptibility (χ) was also fitted to a line where χmeasured,mean  = -0.1218 × MVFmean  - 0.006345 (r = -0.8435; p < 0.01). As a result of the FPM-based QSM simulations, a linearly proportional relationship between the simulated magnetic susceptibility, χsimulated,mean , and MVF (r = -0.9648; p < 0.01) was established. Such a statistically significant linear correlation between MRI-derived values by the QSM (or R1 ) method and MVF demonstrated that variable myelin contents in the WM (i.e., CC) can be quantified across multiple stages of aging. These findings further support that both techniques based on QSM and R1 provide an efficient means of studying the brain-aging process with accurate volumetric quantification of the myelin content in WM.

Medienart:

E-Artikel

Erscheinungsjahr:

2022

Erschienen:

2022

Enthalten in:

Zur Gesamtaufnahme - volume:35

Enthalten in:

NMR in biomedicine - 35(2022), 3 vom: 19. März, Seite e4645

Sprache:

Englisch

Beteiligte Personen:

Cho, Hwapyeong [VerfasserIn]
Lee, Hansol [VerfasserIn]
Gong, Yelim [VerfasserIn]
Kim, Young Ro [VerfasserIn]
Cho, Junghun [VerfasserIn]
Cho, Hyung Joon [VerfasserIn]

Links:

Volltext

Themen:

Ex vivo MR longitudinal relaxation
Ex vivo QSM
Journal Article
Myelin volume fraction
Research Support, Non-U.S. Gov't
TEM

Anmerkungen:

Date Completed 28.03.2022

Date Revised 28.03.2022

published: Print-Electronic

Citation Status MEDLINE

doi:

10.1002/nbm.4645

funding:

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

NLM332772233