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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 Image Restoration via a NL Approach Based on the KS Test
摘要： Synthetic Aperture Radar (SAR) image despeckling is still an open issue. Several approaches have been proposed in the last decades. The recently proposed NonLocal approaches are often considered as the state of art of SAR despeckling. The difference between the NL algorithms presented in literature is mainly related to the adopted distance metric between patches and on the rule used for averaging the selected pixels. Within this manuscript a new metric for selecting similar patches is presented. The metric is based on the statistical distribution of the complex noisy image. The Kolmogorov-Smirnov (KS) test is adopted to compare the statistical distribution and to select similar patches. The approach has been tested and validate on real data, showing interesting performances.
关键词： NonLocal Filters,Synthetic Aperture Radar,Speckle
更新于2025-09-04 15:30:14
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[IEEE 2018 Second International Conference on Electronics, Communication and Aerospace Technology (ICECA) - Coimbatore (2018.3.29-2018.3.31)] 2018 Second International Conference on Electronics, Communication and Aerospace Technology (ICECA) - Analysis and Evaluation of Speckle Filters by Using Polarimetric Synthetic Aperture Radar Data Through Local Statistics
摘要： Speckle noise, a granular noise, occurs in synthetic aperture radar (SAR) data due to the interference of reflected signals with several scatterers in a resolution cell. One of the simplest techniques to suppress speckle noise from polarimetric SAR data is to use local statistics. The Lee filter employs sample mean and variance of pixels of data degraded by speckle noise, which can be multiplicative, additive, or a mixture of both, in a searching window. The refined Lee method utilizes directional windows with local minimum mean square error (LMMSE), which ensures superior maintenance of spatial resolution and features. The Lee–Sigma filter is constructed on the basis of the two-sigma probability, which effectively suppresses the speckle noise. However, insufficiencies were observed in the generation of a biased evaluation, blurring of edges, and suppression of point targets. To eliminate these insufficiencies, the improved Lee–Sigma filter was developed, which employs the minimum mean square error estimate as a priori mean. Thus, an excellent maintenance of point targets and subtle details is displayed. In this study, the Lee, refined Lee, Lee–Sigma, and improved Lee–Sigma filters were evaluated using full polarimetric data. The evaluated results indicated that the improved Lee–Sigma filter performed better than other local statistics filters.
关键词： Speckle noise,Synthetic aperture radar,Minimum mean square error,Polarimetric synthetic aperture radar
更新于2025-09-04 15:30:14
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Pulse Waveform Changes in Macular Choroidal Hemodynamics With Regression of Acute Central Serous Chorioretinopathy
摘要： PURPOSE. To quantitatively evaluate the pulse waveform changes in macular choroidal blood ?ow by using laser speckle ?owgraphy (LSFG) with regression of acute central serous chorioretinopathy (CSC). METHODS. This retrospective observational case series included 20 eyes of 20 patients with acute CSC. Laser speckle ?owgraphy was performed at baseline and after 6 months. On the LSFG monochrome map, automatically divided 5 3 5 grid segments within the macula were classi?ed into predominantly delayed ?lling (PDF) or minimally or no delayed ?lling (MDF) areas according to the degree of choroidal ?lling delay on early-phase indocyanine green angiography. The average mean blur rate (MBR) and the pulse waveform parameters, including the skew and blowout time (BOT), were compared between the total PDF and MDF areas during follow-up. RESULTS. The average MBR signi?cantly decreased in both PDF (P ? 0.005) and MDF (P < 0.001) areas during follow-up; in both areas, the skew decreased (P < 0.001 and P ? 0.006, respectively) and BOT increased (P < 0.001 for each), showing signi?cant reduction in vascular resistance at 6 months. The degree of the changes in the skew and BOT was signi?cantly larger (P ? 0.02 and P < 0.001, respectively) in the PDF area than in the MDF area. CONCLUSIONS. Changes in the skew and BOT, indices for vascular resistance, con?rmed the involvement of circulatory disturbance at the acute stage of CSC. The present ?ndings suggested that the pathogenesis of CSC stems from imbalanced distribution of choroidal blood ?ow due to augmented vascular resistance.
关键词： central serous chorioretinopathy,pulse waveform,skew,blowout time,mean blur rate,laser speckle ?owgraphy,choroidal blood ?ow velocity
更新于2025-09-04 15:30:14
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Ultra–Short-Term Reproducibility of Speckle-Noise Freed Fluid and Tissue Compartmentalization of the Choroid Analyzed by Standard OCT
摘要： Purpose: We measured reproducibility of speckle-noise freed fluid and tissue compartmentalization of the choroid (choroidal angiography and tissue characterization). Methods: This study included 26 eyes of 13 healthy females: 13 were used for repeated measurements and 13 were used for side comparison. A semiautomated algorithm removed speckle-noise with structure preservation. Results: Intraclass correlation (ICC), with respect to reproducibility of the method, showed an ICC for choroidal fluid inner space analysis (FISA) of 95.15% (90.01–98.24). The ICC of tissue inner space analysis (TISA) was 99.75% (99.47–99.91). The total choroid ratio (TCR), calculated from volumes of tissue to vessels, showed an ICC of 88.84% (78.28–95.82). Comparison of eyes (left to right) showed a difference for FISA of 0.033 (95% confidence interval [CI] (cid:2)0.0018–0.0680, P ? 0.063), TISA (cid:2)0.118 (CI (cid:2)0.2373–0.0023, P ? 0.055), and TCR (cid:2)0.590 (CI (cid:2)0.9047 to (cid:2)0.2754, P ? 0.004). The ICC for FISA and TISA showed a trend in the difference comparing left and right eyes; however, TCR showed a significant difference between the eyes in the measured area (P , 0.001). Mean overall FISA was 0.58 mm3 (range, 0.25–0.98 mm3, SD ? 0.14). Mean TISA was 3.45 mm3 (range, 2.38–5.0 mm3, SD 0.072). Mean TCR was 6.13 (overall range, 3.93–10.2, SD ? 1.34). Conclusions: Differences in choroidal layers between subjects were found mainly due to alterations in choroidal tissue. Reproducibility of speckle-noise freed choroidal angiography appeared excellent.
关键词： choroid,imaging,speckle noise,angiography,optical coherence tomography,tissue
更新于2025-09-04 15:30:14
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Novel Boundary Edge Detection for Accurate 3D Surface Profilometry Using Digital Image Correlation
摘要： Digital image correlation (DIC) has emerged as a popular full-field surface profiling technique for analyzing both in-plane and out-of-plane dynamic structures. However, conventional DIC-based surface 3D profilometry often yields erroneous contours along surface edges. Boundary edge detection remains one of the key issues in DIC because a discontinuous surface edge cannot be detected due to optical diffraction and height ambiguity. To resolve the ambiguity of edge measurement in optical surface profilometry, this study develops a novel edge detection approach that incorporates a new algorithm using both the boundary subset and corner subset for accurate edge reconstruction. A pre-calibrated gauge block and a circle target were reconstructed to prove the feasibility of the proposed approach. Experiments on industrial objects with various surface reflective characteristics were also conducted. The results showed that the developed method achieved a 15-fold improvement in detection accuracy, with measurement error controlled within 1%.
关键词： automated optical inspection (AOI),edge detection,digital image correlation (DIC),random speckle images,surface profilometry
更新于2025-09-04 15:30:14
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Motility-based label-free detection of parasites in bodily fluids using holographic speckle analysis and deep learning
摘要： Parasitic infections constitute a major global public health issue. Existing screening methods that are based on manual microscopic examination often struggle to provide sufficient volumetric throughput and sensitivity to facilitate early diagnosis. Here, we demonstrate a motility-based label-free computational imaging platform to rapidly detect motile parasites in optically dense bodily fluids by utilizing the locomotion of the parasites as a specific biomarker and endogenous contrast mechanism. Based on this principle, a cost-effective and mobile instrument, which rapidly screens ~3.2 mL of fluid sample in three dimensions, was built to automatically detect and count motile microorganisms using their holographic time-lapse speckle patterns. We demonstrate the capabilities of our platform by detecting trypanosomes, which are motile protozoan parasites, with various species that cause deadly diseases affecting millions of people worldwide. Using a holographic speckle analysis algorithm combined with deep learning-based classification, we demonstrate sensitive and label-free detection of trypanosomes within spiked whole blood and artificial cerebrospinal fluid (CSF) samples, achieving a limit of detection of ten trypanosomes per mL of whole blood (~five-fold better than the current state-of-the-art parasitological method) and three trypanosomes per mL of CSF. We further demonstrate that this platform can be applied to detect other motile parasites by imaging Trichomonas vaginalis, the causative agent of trichomoniasis, which affects 275 million people worldwide. With its cost-effective, portable design and rapid screening time, this unique platform has the potential to be applied for sensitive and timely diagnosis of neglected tropical diseases caused by motile parasites and other parasitic infections in resource-limited regions.
关键词： parasitic infections,holographic speckle analysis,trypanosomes,resource-limited settings,deep learning,Trichomonas vaginalis,label-free imaging,motility-based detection
更新于2025-09-04 15:30:14