Can Diffusion MRI Reveal Stroke-Induced Microstructural Changes in GM?

IntroductionREM sleep behaviour disorder (RBD) is associated with psychiatric symptoms, such as anxiety and depression. RBD is characterized by loss of normal skeletal muscle atonia during rapid eye movement (REM) sleep with prominent motor activity and dreaming and is a usual symptom of the early stages of Parkinson's disease (PD). Diffusion MRI connectometry was used to carry out group analysis between age and gender matched PD patients with RBD in with and without depression to characterize possible depression-related white matter microstructural changes in the Parkinson patients with RBD.MethodDWI images were obtained for 15 PD-RBD with depression and 27 PD-RBD without depression. This dataset was acquired on a 3 Tesla Siemens scanner, producing 64 DWI at b = 1000 s/mm2 and one b0 image. Diffusion MRI data were corrected for subject motion, eddy current distortions, and susceptibility artefacts due to the magnetic field inhomogeneity. Diffusion MRI connectometry was conducted in a total of 27 subjects using percentage measurement.ResultsPD-RBD Patients with depressive symptoms showed decreased anisotropy (FDR < 0.05) in the fornix bilaterally, right cingulum, inferior longitudinal fasciculus bilaterally, right corticospinal tract and Genu of corpus callosum compared to PD-RBD patients without depression.ConclusionSince RBD is considered to be an early symptom of PD and also a marker of progression to PD, these results might PD-RBD patients with depression may progress dementing processes and visuospatial dysfunction earlier since fornix, cingulum and ILF have proven to be associated with these cognitive dysfunctions respectively.Disclosure of interestThe authors have not supplied their declaration of competing interest.

Download Full-text

The spatiotemporal profile of diffusion MRI based measures of microstructural changes in white matter evoked by learning novel visual scenes

Journal of Vision ◽

10.1167/19.10.205c ◽

2019 ◽

Vol 19 (10) ◽

pp. 205c

Author(s):

Cibu P Thomas ◽

Mitchell Moyer ◽

Brian Coleman ◽

Philip Browning ◽

Frank Ye ◽

...

Keyword(s):

White Matter ◽

Diffusion Mri ◽

Microstructural Changes ◽

Visual Scenes

Download Full-text

Microstructural changes and internet addiction behaviour: A preliminary diffusion MRI study

Addictive Behaviors ◽

10.1016/j.addbeh.2019.106039 ◽

2019 ◽

Vol 98 ◽

pp. 106039

Author(s):

Farzaneh Rahmani ◽

Hossein Sanjari Moghaddam ◽

Mohammad Hadi Aarabi

Keyword(s):

Internet Addiction ◽

Diffusion Mri ◽

Microstructural Changes ◽

Mri Study

Download Full-text

Time‐dependent diffusion MRI as a probe of microstructural changes in a mouse model of Duchenne muscular dystrophy

NMR in Biomedicine ◽

10.1002/nbm.4276 ◽

2020 ◽

Vol 33 (5) ◽

Cited By ~ 2

Author(s):

Paola Porcari ◽

Matt G. Hall ◽

Chris A. Clark ◽

Elizabeth Greally ◽

Volker Straub ◽

...

Keyword(s):

Duchenne Muscular Dystrophy ◽

Muscular Dystrophy ◽

Mouse Model ◽

Diffusion Mri ◽

Time Dependent ◽

Microstructural Changes

Download Full-text

Test-retest reproducibility of in vivo oscillating gradient and microscopic anisotropy diffusion MRI in mice at 9.4 Tesla

PLoS ONE ◽

10.1371/journal.pone.0255711 ◽

2021 ◽

Vol 16 (11) ◽

pp. e0255711

Author(s):

Naila Rahman ◽

Kathy Xu ◽

Mohammad Omer ◽

Matthew D. Budde ◽

Arthur Brown ◽

...

Keyword(s):

Diffusion Mri ◽

Spin Echo ◽

Spatial Scales ◽

Mean Diffusivity ◽

Sample Sizes ◽

High Reproducibility ◽

Linear Diffusion ◽

Microstructural Changes ◽

Diffusion Kurtosis

Background and purpose Microstructure imaging with advanced diffusion MRI (dMRI) techniques have shown increased sensitivity and specificity to microstructural changes in various disease and injury models. Oscillating gradient spin echo (OGSE) dMRI, implemented by varying the oscillating gradient frequency, and microscopic anisotropy (μA) dMRI, implemented via tensor valued diffusion encoding, may provide additional insight by increasing sensitivity to smaller spatial scales and disentangling fiber orientation dispersion from true microstructural changes, respectively. The aims of this study were to characterize the test-retest reproducibility of in vivo OGSE and μA dMRI metrics in the mouse brain at 9.4 Tesla and provide estimates of required sample sizes for future investigations. Methods Twelve adult C57Bl/6 mice were scanned twice (5 days apart). Each imaging session consisted of multifrequency OGSE and μA dMRI protocols. Metrics investigated included μA, linear diffusion kurtosis, isotropic diffusion kurtosis, and the diffusion dispersion rate (Λ), which explores the power-law frequency dependence of mean diffusivity. The dMRI metric maps were analyzed with mean region-of-interest (ROI) and whole brain voxel-wise analysis. Bland-Altman plots and coefficients of variation (CV) were used to assess the reproducibility of OGSE and μA metrics. Furthermore, we estimated sample sizes required to detect a variety of effect sizes. Results Bland-Altman plots showed negligible biases between test and retest sessions. ROI-based CVs revealed high reproducibility for most metrics (CVs < 15%). Voxel-wise CV maps revealed high reproducibility for μA (CVs ~ 10%), but low reproducibility for OGSE metrics (CVs ~ 50%). Conclusion Most of the μA dMRI metrics are reproducible in both ROI-based and voxel-wise analysis, while the OGSE dMRI metrics are only reproducible in ROI-based analysis. Given feasible sample sizes (10–15), μA metrics and OGSE metrics may provide sensitivity to subtle microstructural changes (4–8%) and moderate changes (> 6%), respectively.

Download Full-text

Test-retest reproducibility of in vivo oscillating gradient and microscopic anisotropy diffusion MRI in mice at 9.4 Tesla

10.1101/2021.08.04.455122 ◽

2021 ◽

Author(s):

Naila Rahman ◽

Kathy Xu ◽

Mohammad Omer ◽

Matthew Budde ◽

Arthur Brown ◽

...

Keyword(s):

Diffusion Mri ◽

Spin Echo ◽

Spatial Scales ◽

Mean Diffusivity ◽

Region Of Interest ◽

Sample Sizes ◽

High Reproducibility ◽

Microstructural Changes ◽

Increased Sensitivity

Background and Purpose: Microstructure imaging with advanced diffusion MRI (dMRI) techniques have shown increased sensitivity and specificity to microstructural changes in various disease and injury models. Oscillating gradient spin echo (OGSE) dMRI, implemented by varying the oscillating gradient frequency, and microscopic anisotropy (µA) dMRI, implemented via tensor valued diffusion encoding, may provide additional insight by increasing sensitivity to smaller spatial scales and disentangling fiber orientation dispersion from true microstructural changes, respectively. The aims of this study were to characterize the test-retest reproducibility of in vivo OGSE and µA dMRI metrics in the mouse brain at 9.4 Tesla and provide estimates of required sample sizes for future investigations. Methods: Eight adult C57Bl/6 mice were scanned twice (5 days apart). Each imaging session consisted of multifrequency OGSE and µA dMRI protocols. Metrics investigated included µA, isotropic and anisotropic kurtosis, and the diffusion dispersion rate (Λ), which explores the power-law frequency dependence of mean diffusivity. The dMRI metric maps were analyzed with mean region-of-interest (ROI) and whole brain voxel-wise analysis. Bland-Altman plots and coefficients of variation (CV) were used to assess the reproducibility of OGSE and µA metrics. Furthermore, we estimated sample sizes required to detect a variety of effect sizes. Results: Bland-Altman plots showed negligible biases between test and retest sessions. ROI-based CVs revealed high reproducibility for both µA (CVs < 8 %) and Λ (CVs < 15 %). Voxel-wise CV maps revealed high reproducibility for µA (CVs ~ 10 %), but low reproducibility for OGSE metrics (CVs ~ 50 %). Conclusion: Most of the µA dMRI metrics are reproducible in both ROI-based and voxel-wise analysis, while the OGSE dMRI metrics are only reproducible in ROI-based analysis. µA and Λ may provide sensitivity to subtle microstructural changes (4 - 8 %) with feasible sample sizes (10 – 15).

Download Full-text

Phenomena Associated with Oxygen in Titanium

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100061562 ◽

1967 ◽

Vol 25 ◽

pp. 310-311

Author(s):

E. U. Lee ◽

P. A. Garner ◽

J. S. Owens

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Electron Microscope ◽

Microstructural Changes ◽

Electrolytic Polishing ◽

Interstitial Impurities ◽

Thin Foils ◽

Transmission Electron ◽

Iodide Titanium ◽

Alpha Titanium

Evidence for ordering (1-6) of interstitial impurities (O and C) has been obtained in b.c.c. metals, such as niobium and tantalum. In this paper we report the atomic and microstructural changes in an oxygenated c.p.h. metal (alpha titanium) as observed by transmission electron microscopy and diffraction.Oxygen was introduced into zone-refined iodide titanium sheets of 0.005 in. thickness in an atmosphere of oxygen and argon at 650°C, homogenized at 800°C and furnace-cooled in argon. Subsequently, thin foils were prepared by electrolytic polishing and examined in a JEM-7 electron microscope, operated at 100 KV.

Download Full-text

Tensile Creep of Y-Si3N4: II. Cavitation

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100089172 ◽

1991 ◽

Vol 49 ◽

pp. 972-973 ◽

Cited By ~ 1

Author(s):

B. J. Hockey ◽

S. M. Wiederhorn

Keyword(s):

Silicon Nitride ◽

Creep Rupture ◽

Tensile Creep ◽

Sintering Aids ◽

Microstructural Changes

ATEM has been used to characterize three different silicon nitride materials after tensile creep in air at 1200 to 1400° C. In Part I, the microstructures and microstructural changes that occur during testing were described, and consistent with that description the designations and sintering aids for these materials were: W/YAS, a SiC whisker reinforced Si3N4 processed with yttria (6w/o) and alumina (1.5w/o); YAS, Si3N4 processed with yttria (6 w/o) and alumina (1.5w/o); and YS, Si3N4 processed with yttria (4.0 w/o). This paper, Part II, addresses the interfacial cavitation processes that occur in these materials and which are ultimately responsible for creep rupture.

Download Full-text