Keywords: Microstructure, Microstructure
Motivation: $$$R_2$$$ in WM is orientation dependent due to microscopic magnetic anisotropy. So far, the Standard Model of diffusion (SM) has been extended to only include isotropic $$$R_2$$$ (TEdDI).
Goal(s): Our goal is to characterize $$$R_2$$$ anisotropy of a multi-echo dMRI signal for long diffusion times and incorporate $$$R_2$$$ anisotropy into TEdDI (STEdDI).
Approach: We simulate $$$R_2$$$ of PGSE signal in magnetized cylinders using Monte-Carlo, and fit TEdDI and STEdDI on ex vivo mouse multi-echo dMRI data acquired at 16.4T.
Results: $$$R_2$$$ anisotropy outside axons are non-axially-symmetric, depends on B0 direction, gradient direction and b-value. Residuals are significantly lower with STEdDI in dMRI data.
Impact: Interplay between microscopic magnetic fields and diffusion weighting affects $$$R_2$$$ in extra-axonal space. Incorporating $$$R_2$$$ anisotropy$$$\,$$$into modeling lowered the residuals and may allow rotation-free estimation of $$$R_2$$$ anisotropy, which could be useful to gain a deeper insight into brain microstructure.
How to access this content:
For one year after publication, abstracts and videos are only open to registrants of this annual meeting. Registrants should use their existing login information. Non-registrant access can be purchased via the ISMRM E-Library.
After one year, current ISMRM & ISMRT members get free access to both the abstracts and videos. Non-members and non-registrants must purchase access via the ISMRM E-Library.
After two years, the meeting proceedings (abstracts) are opened to the public and require no login information. Videos remain behind password for access by members, registrants and E-Library customers.
Keywords