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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - SAR Speckle Filtering and Agriculture Field Size: Development of SAR Data Processing Best Practices for the JECAM SAR Inter-Comparison Experiment
摘要： Utilizing Synthetic Aperture Radar (SAR) sensors for crop inventory and condition monitoring offers many advantages, particularly the ability to collect data under cloudy conditions. The JECAM SAR Inter-Comparison Experiment is a multi-year, multi-partner project that aims to compare global methods for SAR crop monitoring and inventory, and Leaf Area Index (LAI) and biomass retrieval. Data sets of SAR imagery including RADARSAT-2 and Sentinel-1 are being prepared for this experiment and it is important to develop best practices to ensure consistency across the data sets. This paper outlines the speckle filter testing results based upon changing filter types and window sizes in comparison with changing field size. In general, it was found that the adaptive Touzi filter resulted in the highest overall classification accuracies for all field sizes. It was also found that there may be importance to speckle filter window size in relation to agriculture field size for other filter types.
关键词： JECAM,GEOGLAM,RADARSAT-2,Sentinel-1,speckle filter,agriculture
更新于2025-09-10 09:29:36
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Evaluation of optic nerve head blood flow in response to increase of intraocular pressure
摘要： The time course of the changes in the optic nerve head (ONH) blood flow in response to changes in the ocular perfusion pressure (OPP) induced by an artificial elevation of the intraocular pressure (IOP) has not been determined. We measured the blood flow, represented by the mean blur rate (MBR), on the ONH determined by laser speckle flowgraphy. The MBR was determined before, during, and after the IOP was elevated by 20 or 30 mmHg by pressure applied on the eye by an ophthalmodynamometer in a total of 27 healthy eyes. For an IOP elevation of 20 mmHg, the percentage reduction in the MBR-vessel was ?24.7%, and in the MBR-tissue was ?16.0% (P < 0.001). For an IOP elevation of 30 mmHg, the percentage reduction of the MBR-vessel was ?35.3% and the MBR-tissue was ?24.7% (P < 0.001). During the 30 mmHg IOP elevation for 10 minutes, both the MBR-vessel and MBR-tissue began returning to the baseline level from 1 minute after the beginning of the IOP elevation (P < 0.01, P < 0.05, respectively) and continued returning during the 10 minutes IOP elevation (P < 0.001, P < 0.01, respectively). We conclude that the ONH can autoregulate its blood flow in response to experimental changes in OPP induced by IOP elevations.
关键词： optic nerve head,autoregulation,laser speckle flowgraphy,blood flow,intraocular pressure
更新于2025-09-10 09:29:36
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High-resolution speckle imaging
摘要： One of the most exciting and challenging pursuits of 21st-century astrophysics is to identify an exoplanet—that is, a planet orbiting an alien sun—on which life may exist. Such a planet is likely to reside in the habitable zone of its sun, meaning that it can harbor liquid water on its surface. Many astrobiologists posit that a life-harboring planet must also be small, rocky, and similar in density to our own. One critical input to any future discovery will be a precise determination of the planet radius, a value that will probably be obtained with the help of high-resolution speckle imaging.
关键词： speckle imaging,exoplanet,adaptive optics,atmospheric turbulence,high-resolution imaging
更新于2025-09-10 09:29:36
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Speckle-free quantitative phase and amplitude imaging using common-path lateral shearing interference microscope with pseudo-thermal light source illumination
摘要： In quantitative phase imaging, generally a highly coherent light source such as laser is used to achieve the interference easily. But due to laser’s high spatio-temporal coherence, speckles and spurious fringes are formed, which degrades the image quality and finally affects the phase measurement results. Here, we report speckle-free quantitative phase and amplitude imaging using common-path lateral shearing interference microscope with pseudo-thermal light source illumination without any spurious fringes. A pseudo-thermal light source was synthesized and partially spatially coherent light was used for illuminating the sample uniformly. The scattered light from the object was collected by microscope objective lens and a 4mm thick optically flat parallel plate was used to generate the interference pattern. Phase maps of human red blood cells (RBCs) are reconstructed and the results are compared for fully and partially coherent light illumination. We found that the results are significantly improved with pseudo-thermal light source as compare to the coherent light source. Since the proposed quantitative phase microscopy setup is based on common-path configuration, it is highly stable and can be utilized to study the dynamic fluctuations of the membrane of cells. The phase stability of the system is calculated to be 0.0066rad without any vibration isolation.
关键词： scattering,coherence,pseudo-thermal,microscopy,phase imaging,speckle,Interferometry
更新于2025-09-10 09:29:36
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Parathyroid gland management using optical technologies during thyroidectomy or parathyroidectomy: A systematic review
摘要： New optical technologies enhancing localization or assessing viability of parathyroid glands (PG) during endocrine surgery have been reported in clinical studies. These technologies could become complementary to the surgeon’s eyes and may improve surgical outcomes in thyroidectomy and parathyroidectomy. Here, we conducted a systematic review focusing on PG identification and functional assessment using optical methods to enhance surgery. A systematic literature review was performed using MEDLINE and Embase database. Two authors selected studies and extracted data; qualitative analysis was performed to summarize the characteristics of reported optical tools for thyroidectomy or parathyroidectomy. Identification and vascularisation of PG during surgery were evaluated. Clinical and biochemical outcomes were appraised when reported. Studies relating to parathyroidectomy or thyroidectomy combined with autofluorescence, fluorescent methylene blue, 5-aminolevulinic acid, indocyanine green (ICG), optical coherence tomography, laser speckle contrast imaging, dynamic optical contrast imaging and Raman spectroscopy were identified with MEDLINE and Embase. We included a total of 47 relevant articles with a total of 1615 patients enrolled. Each optical technique is described and appreciated related to its surgical purpose. Autofluorescence and ICG imaging of PG are the most widely reported optical technologies for identification and assessment of vascularisation of PG. Results are mainly based on observational studies and argue for the feasibility of both techniques in endocrine surgery but prospective randomized studies have not been performed. In vivo applications are still limited for the other methods and further investigations correlating these techniques with post-operative parathormone measurements are still needed before considering these technologies in clinical practice.
关键词： Surgery,Fluorescence,Dynamic optical contrast imaging,Laser speckle contrast imaging,Optical coherence tomography,Raman spectroscopy,Parathyroid gland
更新于2025-09-10 09:29:36
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A Speckle-Enhanced Prism Spectrometer with High Dynamic-Range
摘要： We present a novel spectrometer device, offering a wide wavelength range and high resolution. The device builds upon a conventional prism spectrometer; however, an additional scattering medium is introduced to generate a wavelength-dependent speckle pattern on the detector array. Simultaneous use of the prism and the scattering medium allows for both improved resolution and wavelength range. The generated speckle pattern secures a significant improvement in resolution (up to 100 fold) and dynamic range, over a conventional prism spectrometer. With the proposed spectrometer, implemented using a CCD camera, we demonstrate up to 17 pm resolution at 855 nm central wavelength, and 756.5 nm wavelength range revealing a dynamic range of ~44,500. The dynamic range could be further improved upon using a detector array having larger area and a scattering medium offering a narrower spectral correlation function. With further development, the proposed device could be useful in a variety of spectroscopy applications such as deep imaging of retinal layers in Optical Coherence Tomography.
关键词： Spectroscopy,Speckle,Prism
更新于2025-09-09 09:28:46
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Potential of the Reverse Synthesis Method for the High-Quality SAR Image Synthesis
摘要： A potential of a new Reverse synthesis method proposed at IGARSS 2017 for the high-quality Synthetic Aperture Radar (SAR) image synthesis is presented. Images produced by the method are compared with the best existing approaches for the speckle noise reduction. Further capabilities for the image quality improvement like side lobe, range and azimuth reduction, contrast improvement, autofocusing and target detectability improvement are considered. The novel approach allows both: to produce high quality and high-resolution images from existing SAR raw data and to create new high-quality systems with reduced demands to the on-board equipment.
关键词： SAR,speckle noise,image synthesis,high resolution,synthetic aperture radar,synthetic aperture imaging,image quality
更新于2025-09-09 09:28:46
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Multifrequency Polarimetric SAR Image Despeckling by Iterative Nonlocal Means Based on a Space-Frequency Information Joint Covariance Matrix
摘要： This paper presents an iterative nonlocal means (NLM) filtering method under the Bayesian framework to deal with the issue of multifrequency fully polarimetric synthetic aperture radar (PolSAR) image despeckling. Differing from most of the PolSAR filters designed for single-frequency data, the proposed NLM method is developed based on a space-frequency information joint covariance matrix, which can not only utilize multifrequency polarimetric information but also exploit the correlation between any two pixels in an image patch. Furthermore, with the aim of accelerating the filtering procedure and better retaining image details, an effective preselection step is employed. The filtering results obtained with both a simulated dataset and real multifrequency PolSAR datasets acquired by the AIRSAR system confirm the good performance of the proposed method in both reducing speckle and retaining details, when compared with some of the state-of-the-art despeckling algorithms.
关键词： Nonlocal means (NLM),polarimetric synthetic aperture radar (PolSAR),speckle filtering,Wishart distribution
更新于2025-09-09 09:28:46
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Changes in the Blood Flow of the Optic Nerve Head Induced by Different Concentrations of Epinephrine in Intravitreal Infusion During Vitreous Surgery
摘要： PURPOSE. We investigated whether intravitreal infusion solution containing epinephrine affects optic nerve head (ONH) blood ?ow during vitreous surgeries. METHODS. The subjects were 22 patients with epimacular membrane or idiopathic macular hole. During vitreous surgery, ONH blood ?ow was examined before and 10 minutes after intravitreal infusion of solution containing epinephrine, via a laser speckle ?owgraphy (LSFG) technique modi?ed for acquiring measurements in a supine position. Epinephrine concentration was set at 1.0 mg/500 mL (1:500,000) or 0.5 mg/500 mL (1:1,000,000), with each concentration assigned to 11 consecutive patients. Relative pupil diameter, IOP, blood pressure, and pulse rate also were measured. RESULTS. A signi?cant reduction in blood ?ow throughout the ONH was induced by intravitreal infusion of epinephrine at 1:500,000, but not at 1:1,000,000. Blood ?ow in ONH tissue was diminished at both concentrations, while that in vessels of the ONH was not altered signi?cantly by either concentration. Both epinephrine concentrations induced signi?cant pupillary dilatation, but no signi?cant changes in IOP, blood pressure, or pulse rate. CONCLUSIONS. This study suggests that epinephrine, used in combination with intravitreal infusion solution, may decrease ONH blood ?ow during vitreous surgeries, as indicated by measurements obtained via a modi?ed LSFG technique. Attention must be paid to the effects of intravitreal infusion of epinephrine on ocular circulation, particularly ONH blood ?ow.
关键词： laser speckle ?owgraphy,optic nerve head,epinephrine,supine position,blood ?ow,vitreous surgery
更新于2025-09-09 09:28:46
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[ACM Press the 2nd International Conference - Sydney, NSW, Australia (2018.10.06-2018.10.08)] Proceedings of the 2nd International Conference on Graphics and Signal Processing - ICGSP'18 - A Comparative Analysis of Clustering Algorithms for Ultrasound Image Despeckling Applications
摘要： This paper proposes a novel framework for speckle noise suppression and edge preservation using clustering algorithms in ultrasound images. The algorithms considered are K-means clustering, fuzzy C-means clustering, possibilistic C-means, fuzzy possibilistic C-means, and possibilistic fuzzy C-means clustering. This work presents an exhaustive comparative analysis of the above clustering algorithms to consider their suitability for despeckling and identifies the best clustering algorithm. Two types of dataset are considered: medical ultrasound images of the thyroid, and synthetically modelled ultrasound images. The framework consists of several distinct phases - first the edges of the image are identified using the Canny edge operator, and then a clustering algorithm applied on high frequency coefficients extracted using wavelet transform. Finally, the preserved edges are added back to speckle suppressed image. Thus, the proposed clustering method effectively accomplishes both speckle suppression and edge preservation. This paper also presents a quantitative evaluation of results to demonstrate the effectiveness of the clustering approach.
关键词： speckle noise,Image quality metrics,Wavelet transform,Ultrasound image analysis,Canny edge detector,Clustering algorithms
更新于2025-09-04 15:30:14