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NMR in Biomedicine - 2020 - Lundell - Cytosolic diffusivity and microscopic anisotropy of N%E2%80%90acetyl aspartate in human white.pdf (2.05 MB)

Cytosolic diffusivity and microscopic anisotropy of N-acetyl aspartate in human white matter with diffusion-weighted MRS at 7 T

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posted on 2023-06-15, 20:39 authored by Henrik Lundell, Carson Ingo, Tim B Dyrby, Itamar RonenItamar Ronen
Metabolite diffusion measurable in humans in vivo with diffusion-weighted spectroscopy (DW-MRS) provides a window into the intracellular morphology and state of specific cell types. Anisotropic diffusion in white matter is governed by the microscopic properties of the individual cell types and their structural units (axons, soma, dendrites). However, anisotropy is also markedly affected by the macroscopic orientational distribution over the imaging voxel, particularly in DW-MRS, where the dimensions of the volume of interest (VOI) are much larger than those typically used in diffusion-weighted imaging. One way to address the confound of macroscopic structural features is to average the measurements acquired with uniformly distributed gradient directions to mimic a situation where fibers present in the VOI are orientationally uniformly distributed. This situation allows the extraction of relevant microstructural features such as transverse and longitudinal diffusivities within axons and the related microscopic fractional anisotropy. We present human DW-MRS data acquired at 7 T in two different white matter regions, processed and analyzed as described above, and find that intra-axonal diffusion of the neuronal metabolite N-acetyl aspartate is in good correspondence to simple model interpretations, such as multi-Gaussian diffusion from disperse fibers where the transverse diffusivity can be neglected. We also discuss the implications of our approach for current and future applications of DW-MRS for cell-specific measurements.

History

Publication status

  • Published

File Version

  • Published version

Journal

NMR in Biomedicine

ISSN

0952-3480

Publisher

Wiley

Issue

5

Volume

34

Article number

e4304

Event location

England

Department affiliated with

  • BSMS Neuroscience Publications

Full text available

  • Yes

Peer reviewed?

  • Yes

Legacy Posted Date

2022-06-14

First Open Access (FOA) Date

2022-06-14

First Compliant Deposit (FCD) Date

2022-06-13