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Sequential phases of RGC axonal and somatic injury in EAE mice examined using DTI and OCT
摘要： Background: Clinical imaging modalities including optical coherence tomography (OCT) and di?usion tensor imaging (DTI) are vital in Multiple Sclerosis (MS), but their relationships during the di?erent phases of Retinal ganglion cell (RGC) degeneration are not clear. We hypothesize that initial injury in optic nerve causes axonal degeneration leading to RGC loss in retina, which can be characterized by a combination of DTI and OCT. Our objective was to examine the correlation between noninvasive and histological data to chronicle the degeneration pro?le of RGCs in the retina and optic nerve in a mouse model of MS. Materials and methods: Experimental Autoimmune Encephalomyelitis (EAE) was induced in 11 C57Bl/6 mice, with 8 mice reserved as controls. OCT and DTI was conducted 2–8 weeks after induction of EAE. The thickness of the retinal ganglion cell complex (GCC) was measured using OCT and compared to DTI indices measured in optic nerves. End-stage histology was used to quantify axon/myelin loss in the optic nerve and retinal thinning/RGC loss in the retina. Results: Signi?cant changes in DTI-derived Axial Di?usivity (AD, ?17.2%) and Trace Di?usivity (TR, ?18.3%) began after 2 weeks of EAE. Later signi?cant reductions in Fractional Anisotropy (FA) and AD, with increases in Radial Di?usion (RD) were apparent after 4 and 8 weeks. OCT-derived measures of GCC thickness were reduced after 4 weeks, and reached signi?cant reduction after 8 weeks. Among EAE mice, DTI (FA, AD and RD measures) and OCT measures were all signi?cantly correlated after 4 and 8 weeks. Among histology measures, RGC density (?23%), RGC size (?27%), and the number of SMI31+ axons (?54%) were reduced signi?cantly. DTI measures of FA and AD along with GCC thinning were the best independent predictors of axon loss. Conclusions: DTI and OCT measures are tightly correlated during the chronic phase of axonal degeneration (4–8 weeks) in EAE mice. After 8 weeks of EAE, both OCT and DTI measures are strong predictors of axon loss in the Optic Nerve.
关键词： longitudinal study,Optical coherence tomography (OCT),Retinal ganglion cell (RGC),Experimental Autoimmune Encephalomyelitis (EAE),Di?usion tensor imaging (DTI)
更新于2025-09-10 09:29:36
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Evaluation of Structure-Function Relationships in Longitudinal Changes of Glaucoma using the Spectralis OCT Follow-Up Mode
摘要： The detection of glaucoma progression is an essential part of glaucoma management. Subjectivity of standard automated perimetry (SAP) prevents the accurate evaluation of progression, thus the detection of structural changes by optical coherence tomography (OCT) is attracting attention. Despite its objectivity, there is controversy about the appropriateness of the use of OCT, because many previous studies have indicated OCT results may not reflect the deterioration of visual field. A reason for this dissociation may be the test-retest variability of OCT, a major cause of which is misplacement of the measurement location. Recent advantages of spectral-domain OCT (SD-OCT), especially Spectralis OCT with an eye-tracking system (follow-up mode) enable measurement at approximately the same location as previous examinations. In addition to utilizing Spectralis follow-up mode, we introduced structure-function relationship map and nonlinear relationship between SAP and OCT results in considering structure-function relationship in longitudinal changes. The introduction of these two ideas in our study population improved the correlation between the SAP and OCT (R = 0.589 at most). The results of this study support the practical use of OCT in glaucoma progression but also stress the importance of focus on the corresponding focal changes and the consideration of disease severity.
关键词： longitudinal study,standard automated perimetry,optical coherence tomography,structure-function relationship,glaucoma progression
更新于2025-09-10 09:29:36
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Influence of temperature on the oscillations of longitudinal magnetoresistance in semiconductors with a nonparabolic dispersion law
摘要： The density of energy states were obtained in a quantizing magnetic ?eld at different temperature and for nonquadratic dispersion law. The dependence of the density of energy states on temperature in quantizing magnetic ?elds is studied with the nonquadratic dispersion law. The continuous spectrum of the energy density of states at low temperature is transformed into discrete Landau levels. The theory of the temperature dependence of the oscillation Shubnikov–de Haas in semiconductors with a nonparabolic dispersion law is constructed, taking into account the thermal broadening of the Landau levels. The cyclotron effective mass of the electrons is determined from the Shubnikov–de Haas data. The theoretical results are compared with experimental data in Bi1.99Tl0.01Se3.
关键词： Nonparabolic dispersion law,Longitudinal magnetoresistance,Landau levels,Cyclotron effective mass,The density of states,Oscillation Shubnikov–de Haas
更新于2025-09-10 09:29:36
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Selective thermal radiation at longitudinal optical phonon energy under geometric condition of metal-semiconductor mesa stripe structures
摘要： Selective thermal emission at approximately 284 cm?1 with a line width of 13 cm–1 at 628 K is obtained by heating the Au-GaAs mesa-type line and space structures. This emission demonstrates a characteristic polar radiation distribution of electric dipoles and a wavelength independent of the structure size or the direction of emission; thus, it is ascribed to thermally generated electric dipoles resonating with the longitudinal optical phonon energy. This dipole is formed by the interface polarization charges of metal-GaAs-metal stripes. These distinct features are different from the radiation properties of interface phonon polaritons or electronic systems such as intersubband transitions of quantum wells. It is estimated that the mesa height and GaAs space width ranging from hundreds of nanometers to several micrometers provide high generation ef?ciency of electric dipoles and resultant radiation at high temperatures.
关键词： metal-semiconductor mesa stripe structures,longitudinal optical phonon,electric dipoles,thermal emission
更新于2025-09-10 09:29:36
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Lattice considerations for the use of an X-band transverse deflecting structure (TDS) at SINBAD, DESY
摘要： An X-band TDS is a well-known device for the characterization of the longitudinal properties of an electron bunch in a linear accelerator. It is planned that a novel X-band TDS with variable polarization will be installed within the next few years at SINBAD, an upcoming accelerator R&D facility at DESY. There are several measurements that can be performed with the TDS, each with specific optics requirements to reach the highest possible resolution and keep induced energy spread to a tolerable level. Quadrupoles will be installed between the TDS and the screen to help satisfy these conditions. In this paper, the requirements for the bunch length measurements, a novel 3D charge density reconstruction technique and slice energy measurements are discussed and some simulation results for the slice energy measurement using example lattices are presented.
关键词： DESY,slice energy measurements,X-band TDS,3D charge density reconstruction,electron bunch,longitudinal properties,SINBAD
更新于2025-09-09 09:28:46
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Longitudinal Associations Between Microstructural Changes and Microperimetry in the Early Stages of Age-Related Macular Degeneration
摘要： PURPOSE. To determine whether longitudinal changes in mesopic visual function on microperimetry occurred independent of its associations with microstructural parameters on spectral-domain optical coherence tomography (SD-OCT) in the early stages of AMD. METHODS. Forty-one AMD eyes underwent microperimetry testing and SD-OCT scans over a 12-month period at 6-month intervals. Microstructural parameters analyzed include the retinal pigment epithelium-drusen complex (RPEDC) layer thickness, number of hyperre?ective foci (HF) and their inner retinal migration (represented by a weighted axial distribution score; AxD), and the number of atrophic areas. RESULTS. Microperimetric sensitivity was 0.29 dB (95% con?dence interval [CI] ? (cid:2)0.38 to (cid:2)0.20 dB, P < 0.001) and 0.13 dB (95% CI ? (cid:2)0.22 to (cid:2)0.03 dB, P ? 0.008) lower in each sector for every 10-lm higher RPEDC layer thickness and 1-HF present, but was not associated with the AxD score or the number of atrophic areas present (P (cid:3) 0.464). However, each 10- lm greater RPEDC layer thickness and 1-HF present was not independently associated with a further decline in sensitivity ((cid:2)0.08 dB/year, 95% CI ? (cid:2)0.24 to 0.07 dB/year, P ? 0.288 and 0.09 dB/year, 95% CI ? (cid:2)0.06 to 0.24 dB/year, P ? 0.242, respectively) over time when accounting for the association between RPEDC layer thickness and number of HF with microperimetric sensitivity. CONCLUSIONS. Longitudinal changes in mesopic visual function measured on microperimetry paralleled changes in the microstructural changes over a 12-month time frame, without any changes occurring independent of the associations between structure and function alone.
关键词： age-related macular degeneration,optical coherence tomography,microperimetry,longitudinal
更新于2025-09-04 15:30:14