Cited by 134Advanced Neuroimaging Techniques and ApplicationsAdvanced MRI Techniques and ApplicationsNMR spectroscopy and applications

The DOI matches its Crossref record; 37 of the 37 references it cites were found in a registry or an index; 13 of the 29 sources its claims cite were checked for support.

Quantifying white matter tract diffusion parameters in the presence of increased extra-fiber cellularity and vasogenic edema

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Abstract

The effect of extra-fiber structural and pathological components confounding diffusion tensor imaging (DTI) computation was quantitatively investigated using data generated by both Monte-Carlo simulations and tissue phantoms. Increased extent of vasogenic edema, by addition of various amount of gel to fixed normal mouse trigeminal nerves or by increasing non-restricted isotropic diffusion tensor components in Monte-Carlo simulations, significantly decreased fractional anisotropy (FA) and increased radial diffusivity, while less significantly increased axial diffusivity derived by DTI. Increased cellularity, mimicked by graded increase of the restricted isotropic diffusion tensor component in Monte-Carlo simulations, significantly decreased FA and axial diffusivity with limited impact on radial diffusivity derived by DTI. The MC simulation and tissue phantom data were also analyzed by the recently developed diffusion basis spectrum imaging (DBSI) to simultaneously distinguish and quantify the axon/myelin integrity and extra-fiber diffusion components. Results showed that increased cellularity or vasogenic edema did not affect the DBSI-derived fiber FA, axial or radial diffusivity. Importantly, the extent of extra-fiber cellularity and edema estimated by DBSI correlated with experimentally added gel and Monte-Carlo simulations. We also examined the feasibility of applying 25-direction diffusion encoding scheme for DBSI analysis on coherent white matter tracts. Results from both phantom experiments and simulations suggested that the 25-direction diffusion scheme provided comparable DBSI estimation of both fiber diffusion parameters and extra-fiber cellularity/edema extent as those by 99-direction scheme. An in vivo 25-direction DBSI analysis was performed on experimental autoimmune encephalomyelitis (EAE, an animal model of human multiple sclerosis) optic nerve as an example to examine the validity of derived DBSI parameters with post-imaging immunohistochemistry verification. Results support that in vivo DBSI using 25-direction diffusion scheme correctly reflect the underlying axonal injury, demyelination, and inflammation of optic nerves in EAE mice.

Overview

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Written from the paper’s full text.

TL;DR

This study shows that increased extra-fiber cellularity and vasogenic edema confound conventional DTI-derived white matter metrics, whereas diffusion basis spectrum imaging (DBSI) separates and quantifies these components. A 25-direction DBSI scheme performed comparably to 99-direction DBSI for coherent tracts and detected axonal injury, demyelination, and inflammation in EAE mouse optic nerve with immunohistochemical validation.

Key findings

  • In fixed normal mouse trigeminal nerve phantoms, DTI gave λ∥ = 0.77 ± 0.05 μm²/ms, λ⊥ = 0.18 ± 0.02 μm²/ms, and FA = 0.72 ± 0.04, while DBSI gave λ∥ = 1.09 ± 0.06 μm²/ms, λ⊥ = 0.15 ± 0.02 μm²/ms, and FA = 0.84 ± 0.02; DBSI estimated axonal fiber fraction 67 ± 3%, cellularity 14 ± 2%, and extra-axonal/extracellular space 20 ± 3%.
  • Added 2% agar gel and Monte-Carlo simulations of vasogenic edema significantly decreased DTI FA and increased DTI radial diffusivity, with less consistent axial diffusivity effects, but did not affect DBSI-derived fiber FA, λ∥, or λ⊥. Increased simulated cellularity significantly decreased DTI FA and λ∥ with limited impact on λ⊥, while DBSI fiber parameters were largely unaffected.
  • DBSI estimates from 25- vs. 99-direction schemes were comparable in simulation: axial diffusivity 1.80 ± 0.03 vs. 1.81 ± 0.05 μm²/ms, radial diffusivity 0.05 ± 0.01 vs. 0.04 ± 0.01 μm²/ms, and FA 0.96 ± 0.01 vs. 0.97 ± 0.01.
  • In EAE vs. sham optic nerve, DBSI showed decreased λ∥ (1.73 ± 0.22 vs. 2.10 ± 0.04 μm²/ms, p = 0.020), increased λ⊥ (0.15 ± 0.03 vs. 0.11 ± 0.01 μm²/ms, p = 0.047), increased restricted isotropic fraction (0.10 ± 0.09 vs. 0.03 ± 0.01, p = 0.022), and increased non-restricted isotropic fraction (0.15 ± 0.03 vs. 0.03 ± 0.01, p < 0.0001); DAPI-positive nuclei correlated with DBSI cellularity (r = 0.65, p = 0.042).

Methods

  • Monte-Carlo simulations and fixed mouse trigeminal nerve phantoms were used: 20 nerves, including single nerve only (n = 7) and nerve with varying amounts of 2% agar gel to mimic vasogenic edema (n = 13); simulations modeled axons, cells, and extra-axonal/extracellular space with varying fractions.
  • Diffusion-weighted data were acquired with 99- and 25-direction encoding schemes and analyzed by conventional single-tensor DTI and DBSI, which fits anisotropic diffusion tensors plus a spectrum of isotropic diffusion tensors using nonnegative least-squares; restricted isotropic fraction was defined as ADC 0–0.3 μm²/ms and non-restricted as ADC > 0.3–3 μm²/ms.
  • In vivo validation used five EAE mice at onset of acute optic neuritis and five age-matched sham controls, imaged at 4.7 T with a 25-direction scheme, followed by immunohistochemistry for SMI-31, MBP, and DAPI; statistical comparisons used t-tests, repeated-measures linear regression, Wilcoxon signed-rank tests, and Spearman correlations.

Limitations

  • Stated: DBSI in its current form does not consider water exchange between intracellular and extracellular space, which may affect accuracy, especially under pathological conditions with altered membrane permeability.
  • Stated: DBSI was developed for white matter tracts, and further generalization is needed for gray matter pathology in CNS disorders.
  • Evident from the text: Monte-Carlo simulations neglected T1 and T2 decay; cellularity was difficult to control experimentally in fixed nerve phantoms, so simulations were used; sample sizes were small (n = 7 nerve-only, n = 13 gel phantoms, 5 EAE vs. 5 sham); and 25-direction DBSI metrics showed SNR-dependent bias, with restricted diffusion fraction overestimated at SNR ≤ 30 and non-restricted fraction underestimated at SNR = 20.

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Integrity signals

Registry

Crossref · 10.1016/j.neuroimage.2014.06.064

Cites

37 of 37 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

50 Own result · 15 Own interpretation · 7 Supported · 5 Partly supported · 3 No full text of the sources · 3 Not checked yet · 3 Own method · 3 No basis given · 1 Couldn’t confirm · 1 Sources not found · accuracy not yet measured

Show all 66 claims

  • Probably not a substantial claim. 8
  • It may state two separate claims as one. 18
  • The quote only partly states this claim. 1
25 of 25
  • The paper relies on this without support.

    The impact of increased cellularity on diffusion anisotropy was unclear at the time of the study.

    “However, its impact on diffusion anisotropy remains unclear.”
  • The authors state this as an assumption.

    DTI assumes that diffusion of water molecules in CNS white matter follows mono-exponential diffusion-weighted signal decay and can be modeled by a single anisotropic tensor.

    “DTI assumes that diffusion of water molecules in the CNS white matter follows mono-exponential diffusion weighted signal decay (typically at b-value < 1000 s/mm2), and was modeled by a single anisotropic tensor.”
  • The authors state this as an assumption.

    The boundaries of axon and cell components in the Monte-Carlo simulation are impermeable.

    “The boundaries of the axon and cell components were assumed to be impermeable.”
  • The authors state this as an assumption.

    T1 and T2 decay effects for all spin trajectories in the Monte-Carlo simulation can be neglected.

    “The effect of T1 and T2 decay for all spin trajectories were neglected (Liu et al., 2004).”
  • The authors state this as an assumption.

    Intracellular water can be modeled as restricted isotropic diffusion due to hindrance of cell membranes and sub-cellular structures.

    “To the first approximation, the intracellular water may be modeled as restricted isotropic diffusion due to the hindrance of cell membranes and sub-cellular structures.”
  • The paper relies on this without support.

    A more comprehensive study was needed to investigate the effect of increased cellularity and vasogenic edema associated with inflammation.

    “Although the effect of increased cell infiltration and edema on DTI-derived indices has been demonstrated previously using cuprizone treated mouse model and mouse trigeminal nerve phantoms (Wang, 2011), a more comprehensive study was needed to investigate the effect of increased cellularity and vasogenic edema associated with inflammation.”
  • The authors state this as an assumption.

    Water spins in the Monte-Carlo simulation can move in or out of the imaging voxel without constraints, reflecting the real physical condition.

    “During the simulation, water spins were allowed to walk in or out of the imaging voxel without constrains to reflect the real physical condition (Liu et al., 2004).”
  • The paper relies on this without support.

    The non-restricted isotropic diffusion fraction measured by DBSI corresponds to vasogenic edema.

    “The non-restricted isotropic diffusion fraction (i.e., the putative vasogenic edema) was also significantly higher in EAE optic nerves than that of the control (0.15 ± 0.03 vs. 0.03 ± 0.01, p < 0.0001).”
  • The paper relies on this without support.

    The Monte-Carlo simulation models using spheres and extra-axonal space accurately represent cellularity and vasogenic edema in tissue.

    “Since cellularity is difficult to change experimentally using the fixed nerve, MC simulation was performed with various extents of extra-fiber cells (i.e., spheres, restricted isotropic diffusion component) to mimic cellularity changes.”
  • The paper relies on this without support.

    The fixed trigeminal nerve phantom with 2% agar gel is a valid model of vasogenic edema.

    “With the addition of 2% agar gel, DTI derived λ⊥ or FA was significantly affected while DBSI derived parameters remained unchanged (Fig. 2A).”
  • The paper relies on this without support.

    The EAE mouse model at the onset of optic neuritis is representative of human optic neuritis and CNS inflammation.

    “In Vivo DBSI of EAE Mice at the Onset of Optic Neuritis”
  • The paper relies on this without support.

    DAPI-positive nuclear counts represent cellularity.

    “DAPI-positive nuclear counts correlated with DBSI estimated cellularity (r = 0.65, p = 0.042; Fig. 7E).”
  • The paper relies on this without support.

    Current MRI methods do not assess specific elements of CNS pathology.

    “MRI greatly aids CNS disease diagnosis, but current methods do not assess specific elements of CNS pathology.”
  • The paper relies on this without support.

    Gd+ MRI is not sensitive to small inflammatory lesions or inflammation behind the intact blood-CNS barrier.

    “However, Gd+ MRI is not sensitive to small inflammatory lesions or inflammation behind the intact BBB, underscoring the need to improve imaging sensitivity and specificity to identify new beneficial therapies.”
  • The paper relies on this without support.

    99-direction human whole brain DBSI scans can be performed within 15 minutes on 3.0 T clinical scanners with fast diffusion-weighted EPI.

    “With fast diffusion-weighted EPI sequence available on 3.0 T clinical scanners, 99-direction human whole brain DBSI scans can be performed within 15 minutes, making DBSI protocol feasible for routine clinical scanning of patients.”
15 of 15

Citations

Cites

Show all 37 references

Research works printed but not linked: 2

  1. Chiang, 2011, Acute visual function impairment in EAE is primarily caused by optic nerve inflammation as assessed by DBSI, Proc. Int. Soc. Magn. Reson. Med., 20, 3085
  2. Tu, 2010, Using absorption-mode images to improve in vivo DTI quality, Proc. Int. Soc. Magn. Reson. Med., 18, 4001

Cited by

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Items 101–134 of 134

Metadata

Authors
Chiang, C.-W., Wang, Y., Sun, P., Lin, T.-H., Trinkaus, K., Cross, A. H., & Song, S.-K.
Affiliations
Washington University in St. Louis (US)
Corresponding author
Song, Sheng-Kwei
Venue
NeuroImage
Publisher
Elsevier BV
Published
2014-11
Volume
101
Pages
310-319
ISSN
1053-8119 (ISSN-L)
OpenAlex
W2027270401
Cited by
134
References
37
Citations by year
2026: 13 · 2025: 8 · 2024: 12 · 2023: 13 · 2022: 8 · 2021: 16 · 2020: 13 · 2019: 10 · 2018: 12 · 2017: 7 · 2016: 10 · 2015: 10 · 2014: 2
FWCI
6.97
Type
journal article
Language
en
Open access
Locations
  • NeuroImage (publishedVersion)
  • PubMed (publishedVersion)
  • Europe PMC (PubMed Central) (submittedVersion)
  • PubMed Central (submittedVersion)
Funders
  • National Institute of Health (R01-NS047592, P01-NS059560)
  • National Multiple Sclerosis Society (NMSS) (RG 4549A4/1)
  • Department of Defense Ideal Award (W81XWH-12-1-0457)
Topics
  • Health Sciences › Medicine › Radiology, Nuclear Medicine and Imaging › Advanced Neuroimaging Techniques and Applications
  • Health Sciences › Medicine › Radiology, Nuclear Medicine and Imaging › Advanced MRI Techniques and Applications
  • Physical Sciences › Chemistry › Spectroscopy › NMR spectroscopy and applications
Keywords
diffusion basis spectrum imaging, vasogenic edema, white matter tracts, fractional anisotropy, axial and radial diffusivity, Monte Carlo simulation, tissue phantoms, experimental autoimmune encephalomyelitis, optic nerve, multiple sclerosis, demyelination, axonal injury, inflammation
MeSH terms
Animals, Computer Simulation, Edema, Female, Mice, Inbred C57BL, Monte Carlo Method, Nerve Fibers, Myelinated, Neuritis, Autoimmune, Experimental, Optic Nerve, Trigeminal Nerve, Phantoms, Imaging, Mice, Diffusion Tensor Imaging, White Matter

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