Investigation of microstructure changes in Al2O3-YSZ coatings and YSZ coatings and their effect on thermal cycle life

Yttria-stabilized zirconia (YSZ) coatings and Al2O3-YSZ coatings were prepared by atmospheric plasma spraying (APS). Their microstructural changes during thermal cycling were investigated via scanning electron microscopy (SEM) equipped with electron backscatter diffraction (EBSD) and X-ray diffraction (XRD). It was found that the microstructure and microstructure changes of the two coatings were different, including crystallinity, grain orientation, phase, and phase transition. These differences are closely related to the thermal cycle life of the coatings. There is a relationship between crystallinity and crack size. Changes in grain orientation are related to microscopic strain and cracks. Phase transition is the direct cause of coating failure. In this study, the relationship between the changes in the coating microstructure and the thermal cycle life is discussed in detail. The failure mechanism of the coating was comprehensively analyzed from a microscopic perspective.

Widespread White Matter Microstructure Alterations Based on Diffusion Tensor Imaging and Diffusion Kurtosis Imaging in Patients With Pontine Infarction

Neurological deficits after stroke are closely related to white matter microstructure damage. However, secondary changes in white matter microstructure after pontine infarction (PI) in the whole brain remain unclear. This study aimed to investigate the correlation of diffusion kurtosis imaging (DKI)-derived diffusion and kurtosis parameters of abnormal white matter tracts with behavioral function in patients with chronic PI. Overall, 60 patients with unilateral chronic PI (33 patients with left PI and 27 patients with right PI) and 30 normal subjects were recruited and underwent DKI scans. Diffusion parameters derived from diffusion tensor imaging (DTI) and DKI and kurtosis parameters derived from DKI were obtained. Between-group differences in multiple parameters were analyzed to assess the changes in abnormal white matter microstructure. Moreover, we also calculated the sensitivities of different diffusion and kurtosis parameters of DTI and DKI for identifying abnormal white matter tracts. Correlations between the DKI-derived parameters in secondary microstructure changes and behavioral scores in the PI were analyzed. Compared with the NC group, both left PI and right PI groups showed more extensive perilesional and remote white matter microstructure changes. The DKI-derived diffusion parameters showed higher sensitivities than did the DTI-derived parameters. Further, DKI-derived diffusion and kurtosis parameters in abnormal white matter regions were correlated with impaired motor and cognitive function in patients with PI. In conclusion, PI could lead to extensive white matter tracts impairment in perilesional and remote regions. Further, the diffusion and kurtosis parameters could be complementary for identifying comprehensive tissue microstructural damage after PI.

Evaluation of retinal sensitivity and microstructure in areas of capillary nonperfusion of eyes with branch retinal vein occlusion

Background To evaluate macular microstructure alterations in the parafoveal nonperfusion areas of eyes with branch retinal vein occlusions (BRVO), and to investigate their impact on retinal sensitivity. Methods This was a cross-sectional study including thirteen BRVO patients with parafoveal capillary nonperfusion areas (NPA). Multiple modalities including microperimetry, optical coherence tomography angiography, and optical coherence tomography were performed to measure retinal sensitivity and thickness, and to identify the microstructure changes and perfusion status. Results The retinal sensitivity and thickness in the NPA were significantly lower than those in the perfusion areas (PA) (P = 0.001, P = 0.003). Microstructure changes, including disorganization of the retinal inner layers (DRIL), disruption of the outer retinal layers, and cysts were more frequently observed in NPA (P = 0.002, P = 0.018, P = 0.068). Within NPA, the retinal sensitivity of areas with DRIL, and outer retinal layers disruption was significantly lower than that of the areas without DRIL (P = 0.016), and with intact outer retinal layers (P < 0.001), respectively. 1dB increase in retinal sensitivity was correlated with 2.2 μm (95 % confidence interval, 1.71–2.7) increase of the thickness (P < 0.001). The retinal sensitivity was significantly lower at points with both DRIL and outer retinal layers disruption than at the points with DRIL or outer retina layers disruption alone (P = 0.001, P = 0.001). Conclusions Alterations in the macular microstructure are associated with ischemia, especially DRIL. DRIL and outer retinal layers disruption are imaging features that have important implications for local retinal sensitivity in the ischemic areas, and where the microstructure of both inner and outer retinal layers is disrupted the function is further destructed.

Early Microstructure Changes of White Matter Fiber Bundles in Patients with Amnestic Mild Cognitive Impairment Predicts Progression of Mild Cognitive Impairment to Alzheimer’s Disease

Background: Amnestic mild cognitive impairment (aMCI) is the transitional stage between normal aging and Alzheimer’s disease (AD). Some aMCI patients will progress into AD eventually, whereas others will not. If the trajectory of aMCI can be predicted, it would enable early diagnosis and early therapy of AD. Objective: To explore the development trajectory of aMCI patients, we used diffusion tensor imaging to analyze the white matter microstructure changes of patients with different trajectories of aMCI. Methods: We included three groups of subjects:1) aMCI patients who convert to AD (MCI-P); 2) aMCI patients who remain in MCI status (MCI-S); 3) normal controls (NC). We analyzed the fractional anisotropy and mean diffusion rate of brain regions, and we adopted logistic binomial regression model to predicate the development trajectory of aMCI. Results: The fraction anisotropy value is significantly reduced, the mean diffusivity value is significantly increased in the two aMCI patient groups, and the MCI-P patients presented greater changes. Significant changes are mainly located in the cingulum, fornix, hippocampus, and uncinate fasciculus. These changed brain regions significantly correlated with the patient’s Mini-Mental State Examination scores. Conclusion: The study predicted the disease trajectory of different types of aMCI patients based on the characteristic values of the above-mentioned brain regions. The prediction accuracy rate can reach 90.2%, and the microstructure characteristics of the right cingulate band and the right hippocampus may have potential clinical application value to predict the disease trajectory.

Value of Magnetic Resonance Diffusion Tensor Imaging Combined with Quantitative Electroencephalogram in Diagnosis of Neurocognitive Impairment in Patients with White Matter Demyelination

This paper aimed to explore the clinical value of combined adoption of magnetic resonance diffusion tensor imaging (DTI) and quantitative electroencephalogram (QEEG) in assessing microstructure changes and mild neurocognitive dysfunction in patients with white matter demyelination. 128 cases of white matter demyelination admitted to the hospital from October 2018 to October 2019 were rolled into the research group, and 100 healthy patients physically examined during the same period were rolled into the control (ctrl) group. QEEG and magnetic resonance DTI examinations were performed for all patients. The wave power of δ, θ, α, and β and the ratio of α/θ and (δ + θ)/(α + β) were recorded. The FA values of white matter fibers in different brain areas were measured, and the Montreal Cognitive Assessment (MoCA) and Addenbrooke Cognitive Evaluation rating (ACE-R) were adopted to assess the neurocognitive function of patients. It was found that the dominant frequency of each brain area in the research group was 8-9 Hz slow α wave. In contrast with the ctrl, the α wave and α/θ values in the research group were lower, while θ wave and δ + θ/α + β values were higher ( P < 0.05 ); the scores of ACE-R and MoCA were lower ( P < 0.01 ); the fractional anisotropy (FA) values of the right frontal lobe white matter (0.335 ± 0.068), the left temporal lobe white matter (0.391 ± 0.032), and the corpus callosum knee white matter (0.658 ± 0.053) were lower ( P < 0.05 ). The FA values of these three areas were positively correlated with attention and calculation, memory, and memory of MoCA scale, respectively ( P < 0.05 ). The FA value of the right frontal white matter was positively correlated with the attention and calculation score of the ACE-R scale ( P < 0.05 ). In conclusion, magnetic resonance DTI combined with QEEG could reflect the microstructural changes of white matter, which may be associated with mild neurocognitive impairment. The primary objective of the study was to explore the clinical value of combined adoption of magnetic resonance DTI and QEEG in assessing microstructure changes and mild neurocognitive dysfunction in patients with white matter demyelination, expected to provide a theoretical basis for the treatment of white matter demyelination.