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Neurodegeneration in ocular and central nervous systems: optical coherence tomography study in normal-tension glaucoma and Alzheimer disease*
摘要： To evaluate, in vivo, the optical coherence tomography (OCT) of the retinal nerve fiber layer (RNFL) and ganglion cell complex (GCC) in patients with normal-tension glaucoma (NTG) and those with Alzheimer disease (AD) in comparison with healthy subjects. This cross-sectional study included 18 patients with NTG, 20 with AD, and 20 control subjects. An ophthalmologic examination and OCT scans of both eyes were performed in all patients. There was a significant reduction in peripapillary RNFL thickness and macular GCC thickness and a significant increase in the global loss volume (GLV) rate in both the NTG and AD patients when compared to the control subjects (P = 0.004, P = 0.006, P < 0.001, respectively). The statistical evaluation showed no difference in any RNFL or GCC parameters between the AD and NTG groups (P > 0.05). There was a negative correlation between disease duration and average RNFL and GCC thicknesses (r = ?0.350, P = 0.027 and r = ?0.471, P = 0.002, respectively) and a positive correlation between duration and GLV (r = 0.427, P = 0.006) in the AD group. The average RNFL thickness, GCC thickness, and GLV rates may help in the diagnosis of AD as an additional examination and may provide some important clues about the duration of the disease.
关键词： ganglion cell complex,Alzheimer disease,retinal nerve fiber layer,Optical coherence tomography,normal-tension glaucoma
更新于2025-09-04 15:30:14
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An inverse problem for one-dimensional diffusion equation in optical tomography
摘要： In this paper, we study the one-dimensional inverse problem for the di?usion equation based optical tomography. The objective of the present work is a mathematical and numerical analysis concerning one-dimensional inverse problem. In the ?rst stage, the forward di?usion equation with boundary conditions is solved using an intermediate elliptic equation. We give the existence and the uniqueness results of the solution. An approximation of the photon density in frequency-domain is proposed using a Splines Galerkin method. In the second stage, we give theoretical results such as the stability and lipschitz-continuity of the forward solution and the Fr′echet di?erentiability of the Dirichlet-to-Neumann nonlinear map with respect to the optical parameters. The Fr′echet derivative is used to linearize the considered inverse problem. The Newton method based on the regularization technique will allow us to compute the approximate solutions of the inverse problem. Several test examples are used to verify high accuracy, e?ectiveness and good resolution properties for smooth and discontinuous optical property solutions.
关键词： Nonlinear inverse problem,Spline basis functions,Fourier transform,Di?usion transport problem,Newton method,Tikhonov regularization,Optical tomography
更新于2025-09-04 15:30:14
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Central serous chorioretinopathy in elderly subjects: angiographic and tomographic characteristics
摘要： Purpose To investigate the angiographic, tomographic, and clinical characteristics of idiopathic central serous chorioretinopathy (CSC) in elderly patients. Methods The patients were divided into two groups according to a cutoff age of 60 years at baseline. Patients underwent spectral domain optical coherence tomography, fluorescein angiography, and indocyanine green angiography. Angiographic and tomographic features were compared between the two groups (young vs. elderly group). Results Of 176 patients, 26 patients (15.1%) were 60 years or older. Complete resolution of subretinal fluid after treatment was noted in 72.0% of the elderly group and 90.8% of the young group (P = 0.021). The elderly group showed worse baseline and final vision, more bilateral involvement, and lower male preponderance than the young group (P < 0.05, respectively). The elderly group was also associated with a higher frequency of retinal pigment epithelium depigmentation, foveal thinning, and double-layer sign compared with the young group (P < 0.05, respectively). Conclusion CSC in elderly patients was associated with a lower resolution of serous detachment, increased impairment of retinal pigment epithelial layers, foveal thinning, and worse visual outcome, suggesting a chronic insult to the choroidal vessels involving more severe damage to the outer retinal layers.
关键词： Pachychoroid,Polypoidal choroidal vasculopathy,Fluorescein angiography,Photo dynamic therapy,Imaging,Optical coherence tomography,Indocyanine green angiography,Central serous chorioretinopathy
更新于2025-09-04 15:30:14
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A two-year study of diffused retinal pigment epitheliopathy treated with half-dose photodynamic therapy guided by simultaneous angiography and optical coherence tomography
摘要： Objectives Diffused retinal pigment epitheliopathy (DRPE) is not necessarily the same as chronic central serous chorioretinopathy (CSC), but a severe subgroup under the umbrella of chronic CSC. This study was to evaluate the efficacy and safety of half-dose PDT treating DRPE. Methods A retrospective case series design was used. Forty-eight consecutive patients (48 eyes) with DRPE treated with half-dose PDT underwent follow-up at baseline, 3 months, 6 months, 12 months and 24 months. Simultaneous FA, ICGA and OCT were used for the treatment and follow-up. The primary outcomes were the subretinal fluid and best-corrected visual acuity in optical coherence tomography. Results Complete fluid absorption was achieved in 95.8% of eyes at 3 months and 100.0% of eyes at 24 months. The baseline logarithm of the minimum angle of resolution (logMAR) BCVA, which was 0.51 ± 0.36, significantly improved to 0.43 ± 0.38 (p < 0.001) at 6 months. The boost continued to 0.29 ± 0.37 (p < 0.001) at 12 months and 0.19 ± 0.39 (p < 0.001) at 24 months. The integrities of the ellipsoid zone (EZ) and interdigitation zone (IZ) improved throughout. Regression analyses showed the BCVA in logMAR was inversely correlated with the EZ (p < 0.01) and IZ (p < 0.01). The recurrence rate was 6.3%. No severe complications were witnessed. Conclusions In 48 eyes with DRPE, simultaneous angiography and OCT facilitated a more comprehensive guidance for half-dose PDT treatment and follow-up. The BCVA improvement occurred at 6 months, which may be attributed to the restoration of the outer retinal structure.
关键词： chronic central serous chorioretinopathy,half-dose photodynamic therapy,Diffused retinal pigment epitheliopathy,angiography,CSC,optical coherence tomography,OCT,DRPE,PDT
更新于2025-09-04 15:30:14
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Estimation of refractive index for biological tissue using micro-optical coherence tomography
摘要： The refractive index of biological tissue is required for investigating the tissue’s optical properties. Efforts have been made to characterize refractive indices of biological tissues at a single wavelength, but it is more convenient to know the Cauchy’s coefficients, which provide refractive index over a wide range of wavelengths. We demonstrate a method to noninvasively provide the Cauchy’s dispersion coefficients of biological tissues using micro-optical coherence tomography. Using short-frequency Fourier transforms, the relative optical thickness of the sample in the wavelength range of the broadband source was obtained from interferograms. The coefficients of Cauchy’s equation were estimated based on the wavelength-dependent sample thickness. We validated the proposed method using distilled water and fresh rat cornea ex vivo, and the experimental results were consistent with the reference data.
关键词： Cauchy’s formula,Refractive index,Optical coherence tomography,Cauchy’s dispersion coefficients
更新于2025-09-04 15:30:14
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Confidence interval constraint based regularization framework for PET quantization
摘要： In this paper, a new generic regularized reconstruction framework based on confidence interval constraints for tomographic reconstruction is presented. As opposed to usual state-of-the-art regularization methods that try to minimize a cost function expressed as the sum of a data-fitting term and a regularization term weighted by a scalar parameter, the proposed algorithm is a two-step process. The first step concentrates on finding a set of images that relies on direct estimation of confidence intervals for each reconstructed value. Then, the second step uses confidence intervals as a constraint to choose the most appropriate candidate according to a regularization criterion. Two different constraints are proposed in this paper. The first one has the main advantage of strictly ensuring that the regularized solution will respect the interval-valued data-fitting constraint, thus preventing over-smoothing of the solution while offering interesting properties in terms of spatial and statistical bias/variance trade-off. Another regularization proposition based on the design of a smoother constraint also with appealing properties is proposed as an alternative. The competitiveness of the proposed framework is illustrated in comparison to other regularization schemes using analytical and GATE-based simulation and real PET acquisition.
关键词： confidence intervals,constrained regularization,Image reconstruction,total variation,positron emission tomography
更新于2025-09-04 15:30:14
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Impact of image averaging on wide-field choroidal thickness measurements using enhanced-depth imaging optical coherence tomography
摘要： Background: The aim of this study was to examine the influence of B-scan averaging on choroidal thickness using wide-field enhanced-depth imaging optical coherence tomography. Methods: Six high-resolution trans-foveal horizontal enhanced-depth imaging line scans (spanning a 60° field) were acquired consecutively from the right eye of 10 healthy adults (mean age 30 ± 5 years), with each line scan an average of 10, 20, 30, 40, 50 or 100 B-scans, using the automated real-time image averaging and follow-up features of a Spectralis device. The impact of B-scan averaging on regional measures of wide-field choroidal thickness (across macular and peripheral regions) and their accuracy was investigated, assuming that averaging 100 B-scans would provide the most accurate estimate of choroidal thickness. Results: Regional estimates of wide-field choroidal thickness did not vary across the different B-scan averaging conditions (all p > 0.05). The mean choroidal thickness averaged across the full wide-field area exhibited the closest agreement to measures obtained with 100 averaged B-scans, when frame averaging exceeded 30 B-scans (95 per cent limits of agreement +10 to ?7, +7 to ?7 and +6 to ?3 μm for 30, 40 and 50 averaged B-scans, respectively), compared to 10 and 20 averaged B-scans (95 per cent limits of agreement +13 to ?8 and +13 to ?6 μm, respectively; p < 0.01 and p < 0.02 compared to the accuracy of 50 averaged B-scans). Conclusion: Averaging 30 B-scans for an individual enhanced-depth imaging optical coherence tomography line scan provided accurate measures of choroidal thickness across a wide-field (60°) area in young healthy eyes. This information can assist in designing the volumetric scan protocols required for detailed examination of the macular and peripheral choroid.
关键词： wide-field imaging,choroidal thickness,optical coherence tomography,enhanced-depth imaging,B-scan averaging
更新于2025-09-04 15:30:14
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Melanin Pigmentation in Rat Eyes: In Vivo Imaging by Polarization-Sensitive Optical Coherence Tomography and Comparison to Histology
摘要： The purpose of this study was to demonstrate polarization-sensitive optical coherence tomography (PS-OCT) for imaging pigmented structures in the posterior eye segments of albino and pigmented rats and to correlate depolarization contrast of the retinal pigment epithelium (RPE) and choroid in in vivo PS-OCT to melanin pigmentation detected in postmortem histologic serial sections. In vivo three-dimensional PS-OCT imaging was performed in adult albino and pigmented rat eyes at 70-kHz A-line rate. Degree of polarization uniformity (DOPU) fundus maps and radial DOPU pro?les were generated. Postmortem histomorphologic analysis was performed in order to investigate melanin pigmentation of the RPE and choroid. Fundus pigmentation maps were extracted from histologic serial sections. Pigmentation pro?les were correlated to DOPU pro?les of the same eyes. Strong depolarization was found in the RPE/choroid complex of pigmented rats, whereas the same structures exhibited uniform polarization in albino rats. The difference between the depolarization characteristics between albino and pigmented animals was statistically signi?cant. In the fundus pigmentation maps, optical pigment density was zero in albino rat eyes. In pigmented rat eyes, a strong negative correlation between optical pigment density and DOPU was observed. This in vivo and ex vivo investigation of posterior rat eyes indicates that melanin is the cause of depolarization in retinal PS-OCT images. It further demonstrates that melanin pigmentation in the RPE and choroid can be quanti?ed via depolarization imaging and therefore suggests that PS-OCT is a useful tool for the noninvasive quantitative assessment of pigmentary changes in vision-threatening diseases such as age-related macular degeneration.
关键词： choroid,melanin,optical coherence tomography,depolarization,retinal pigment epithelium,polarization sensitive devices
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Krakow, Poland (2018.10.16-2018.10.18)] 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Measurement of External-Solids Circulation Flux in a Circulating Fluidized Bed by Electrical Capacitance Tomography and Microwave Doppler Radar
摘要： In a gas-solids circulating fluidized bed (CFB), the external-solids circulating flux (Gs) has important effect on the mass and heat transfer inside the CFB system. To improve the process operation efficiency and reduce the emission of pollution, it is important to accurately measure Gs. In this paper, the authors proposed a new approach to measuring Gs using electrical capacitance tomography (ECT) and microwave Doppler radar (MDR) velocity meter based on a lab-scale CFB system with multi-cyclone separators. The ECT sensor is used to get the solids volume fraction in the cross section of the standpipe and MDR is used to measure the averaged solids velocity along the standpipes. Based on those two values, Gs can be addressed. Meanwhile, computation particle fluid dynamic (CPFD) is used to investigated the gas-solids flow hydrodynamic characteristics and verified the measurement results.
关键词： CPFD simulation,Microwave Doppler radar,External-Solids Circulating flux,Electrical capacitance tomography
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Krakow, Poland (2018.10.16-2018.10.18)] 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Development of an iTomography infrastructure for non-destructive documentation of cultural heritage objects
摘要： In this paper, an new setup for the non-destructive scanning for cultural heritage applications is proposed. First, a multi-degree of freedom mechanical implementation is designed, for multiple angle and distance scanning of artworks via different modalities. Moreover, a specialized acquisition and control software is developed consequently created for the uni?ed platform. Additionally, various, onboard, post-processing image registration algorithms are realized for the combination of images originating on various sensors. The ?nal setup is tested on a mock-up icon, verifying the merits of the developed prototype for cultural heritage science work and research.
关键词： mapping tomography,ultrasound,spectroscopy,image processing,heritage science,non destructive testing
更新于2025-09-04 15:30:14