Scatter Signal Research Articles

Speckle Filtering and its Influence on the Decomposition and Classification of Hybrid Polarimetric Data of RISAT-1

Decomposition and classification are crucial steps in the PolSAR (polarimetric synthetic aperture radar) data processing. Speckle noise influences synthetic aperture radar data because of the coherent integration of back scattered signals from various targets. This study examined the influence of speckle noise filtering on the classification and decomposition of hybrid polarimetric data of Radar Imaging Satellite-1 (RISAT-1). A despeckling algorithm should suppress speckle noise and simultaneously maintain the polarimetric data and spatial features. Performances of the boxcar, Lee-sigma, intensity-driven adaptive-neighborhood (IDAN), and refined Lee filters were evaluated using a spaceborne dataset. RISAT‐1 C‐band hybrid polarimetric data of the Mumbai region, India, was utilized. This study addressed the influence of speckle filtering on decomposition. Various speckle suppression techniques were applied on the RISAT-1 dataset, and the m−χ decomposition was subsequently conducted on the dataset. The obtained results indicated that the IDAN filter exhibited a superior improvement in double-bounce scattering in the urban area and in diffuse scattering in the forest area compared with the other filters considered in this study. Furthermore, the effectiveness of various speckle filters was evaluated. The Wishart supervised classification was applied on the filtered and unfiltered data to evaluate the effectiveness of the speckle suppression algorithm. The refined Lee, boxcar, Lee-sigma, and IDAN filters were evaluated for improving their classification accuracy. The classification accuracy of the settlement and mangrove classes was considerably improved. A marginal improvement was observed for the forest and bare soil classes. The improvement in the classification accuracy of the water class was insignificant.

All-optical imaging and tracking technology for rectilinear motion targets through scattering media

Light scattering is a main factor that restricts optical transmission and deteriorates optical imaging performance. All-optical imaging for moving targets through complex scattering media is one of the most challenging techniques. In this paper, a method for real-time tracking of moving targets through scattering medium is presented by utilizing optical memory-effect and autocorrelation of speckle difference. In the experiment on imaging through a scattering medium, an object is hidden at a distance u behind a highly scattering medium. The object is illuminated by a spatially incoherent pseudothermal light source. The light is diffused through the scattering medium. Camera placed at a distance u0 on the other side of the medium records the pattern of the scattered light. According to the theory of optical memory-effect, the process of scattering imaging is a convolution process of point spread function (PSF) and object. In the procedure of object moving, the scattered signals from two frames are captured. The background noise could be removed by subtracting the two captured image. Then, the autocorrelation operation calculates the speckle difference, and hidden targets can be effectively reconstructed with the phase retrieval algorithm. The experiment demonstrates the imaging of targets with different speeds. The results have shown that the faster the speed, the worse the imaging quality is. High-speed moving objects can be imaged by using a high frame rate camera to reduce the exposure time or by disambiguating the speckle pattern. In subsequent experiments, the distance of the target movement is calculated with the magnification of the system. The collected two frames of speckle must be within the same memory effect angle. Only in this way can the calculation accuracy of the motion distance be guaranteed. With the moving of the target, the cross-correlation information of the target appears at different positions of the speckle difference autocorrelation map. Finally, according to the cross-correlation of the target at different locations, the real-time tracking of the moving target can be realized. Due to the Gaussian distribution of the laser beam, the cross-correlation intensity of the speckle difference autocorrelation map decreases with the object moving further. Therefore the target moving range is limited by the laser beam diameter, intensity distribution and camera field angle. It is verified experimentally that the imaging and tracking of moving targets which are hidden behind the ground glass can be achieved successfully by using this method. This kind of imaging and real-time tracking technology for targets moving through the scattering medium has important potential applications in biomedicine and other fields.

Enhancement of optical resolution in three-dimensional refractive-index tomograms of biological samples by employing micromirror-embedded coverslips.

Optical diffraction tomography (ODT) enables the reconstruction of the three-dimensional (3D) refractive-index (RI) distribution of a biological cell, which provides invaluable information for cellular and subcellular structures in a non-invasive manner. However, ODT suffers from an inferior axial resolution, due to the limited accessible angles imposed by the numerical aperture of the objective lens. In this study, we propose and experimentally demonstrate an approach to enhance the 3D reconstruction performance in ODT. By employing trapezoidal micromirrors, side scattered signals from the sample are measured for various side plane-wave-illumination angles. By combining the side scattered fields with the forward scattered fields, the axial resolution and 3D image quality of ODT are improved, without changing optical instruments. The feasibility and applicability of the proposed method are demonstrated by reconstructing the 3D RI distribution of a red blood cell and HeLa cells in hydrogel. We also present systematic analyses of the improved 3D imaging performance using numerical simulations and experimental measurements for the 3D transfer function, a point object, and a microsphere. The analyses demonstrate an improved axial resolution of 0.31 μm, 4.8 times smaller than that of the conventional method. The proposed method enables the non-invasive and accurate 3D imaging of 3D cultured cells, which is crucial for cell biology studies.

Application of Deconvolution Algorithm of Point Spread Function in Improving Image Quality: An Observer Preference Study on Chest Radiography.

ObjectiveTo evaluate the preference of observers for image quality of chest radiography using the deconvolution algorithm of point spread function (PSF) (TRUVIEW ART algorithm, DRTECH Corp.) compared with that of original chest radiography for visualization of anatomic regions of the chest.Materials and MethodsProspectively enrolled 50 pairs of posteroanterior chest radiographs collected with standard protocol and with additional TRUVIEW ART algorithm were compared by four chest radiologists. This algorithm corrects scattered signals generated by a scintillator. Readers independently evaluated the visibility of 10 anatomical regions and overall image quality with a 5-point scale of preference. The significance of the differences in reader's preference was tested with a Wilcoxon's signed rank test.ResultsAll four readers preferred the images applied with the algorithm to those without algorithm for all 10 anatomical regions (mean, 3.6; range, 3.2–4.0; p < 0.001) and for the overall image quality (mean, 3.8; range, 3.3–4.0; p < 0.001). The most preferred anatomical regions were the azygoesophageal recess, thoracic spine, and unobscured lung.ConclusionThe visibility of chest anatomical structures applied with the deconvolution algorithm of PSF was superior to the original chest radiography.

Erratum: Application of Deconvolution Algorithm of Point Spread Function in Improving Image Quality: An Observer Preference Study on Chest Radiography.

[This corrects the article on p. 147 in vol. 19, PMID: 29354011.].

Robust moving-blocker scatter correction for cone-beam computed tomography using multiple-view information.

Scatter contamination is one of the main sources of decreasing the image quality in cone-beam computed tomography (CBCT). The moving blocker method is economic and effective for scatter correction (SC), which can simultaneously estimate scatter and reconstruct the complete volume within the field of view (FOV) from a single CBCT scan. However, at the regions with large intensity transition in the projection images along the axial blocker moving direction, the estimation of scatter signal from blocked regions in a single projection view can produce large error and cause significant artifacts in reconstructed images and null the usability of these regions. Furthermore, blocker edge detection error can significantly deteriorate both primary signal and scatter signal estimation and lead to unacceptable reconstruction results. In this study, we propose to use the adjacent multi-view projection images to jointly estimate scatter signal more accurately. In return, the more accurately estimated scatter signal can be utilized to detect blocker edges more accurately for greatly improved robustness of moving-blocker based SC. The experimental results using a Catphan phantom and an anthropomorphic pelvis phantom CBCT data show that the new method can effectively suppress the estimation errors of scatter signal in the fast signal transition regions and is able to correct the blocker detection errors. This development will expand the utility of moving-blocker based SC for the target with sharp intensity changes in the projection images and provide the needed robustness for its clinical translation.

Deconvolution model to resolve cytometric microbial community patterns in flowing waters.

Flow cytometry is suitable to discriminate and quantify aquatic microbial cells within a spectrum of fluorescence and light scatter signals. Using fixed gating and operational settings, we developed a finite distribution mixture model, followed by the Voronoi tessellation, to resolve bivariate cytometric profiles into cohesive subgroups of events. This procedure was applied to outline recurrent patterns and quantitative changes of the aquatic microbial community along a river hydrologic continuum. We found five major subgroups within each of the commonly retrieved populations of cells with Low and High content of Nucleic Acids (namely, LNA, and HNA cells). Moreover, the advanced analysis allowed assessing changes of community patterns perturbed by a wastewater feed. Our approach for cytometric data deconvolution confirmed that flow cytometry could represent a prime candidate technology for assessing microbial community patterns in flowing waters. © 2017 International Society for Advancement of Cytometry.

Researching migration methods, entropy and energy diagram to process ground penetrating radar data

Electromagnetic wave velocity is the most important parameter in processing ground penetrating radar data. Migration algorithm which heavily depends on wave velocity is used to concentrate scattered signals back to their correct locations. Depending wave velocity in urban area is not easy task by using traditional methods (i.e., common midpoint). We suggest using entropy and energy diagram as standard for achieving suitable velocity estimation. The results of one numerical model and areal data indicate that migrated section using accurate velocity has minimum entropy or maximum energy. From the interpretation, size and depth of anomalies are reliably identified.

Uncovering the molecular organization of unusual highly scattered 5S rDNA: The case of Chariesterus armatus (Heteroptera)

One cluster of 5S rDNA per haploid genome is the most common pattern among Heteroptera. However, in Chariesterus armatus, highly scattered signals were noticed. We isolated and characterized the entire 5S rDNA unit of C. armatus aiming to a deeper knowledge of molecular organization of the 5S rDNA among Heteroptera and to understand possible causes and consequences of 5S rDNA chromosomal spreading. For a comparative analysis, we performed the same approach in Holymenia histrio with 5S rDNA restricted to one bivalent. Multiple 5S rDNA variants were observed in both species, though they were more variable in C. armatus, with some of variants corresponding to pseudogenes. These pseudogenes suggest birth-and-death mechanism, though homogenization was also observed (concerted evolution), indicating evolution through mixed model. Association between transposable elements and 5S rDNA was not observed, suggesting spreading of 5S rDNA through other mechanisms, like ectopic recombination. Scattered organization is a rare example for 5S rDNA, and such organization in C. armatus genome could have led to the high diversification of sequences favoring their pseudogenization.

LIDAR TS for ITER core plasma. Part II: simultaneous two wavelength LIDAR TS

We have shown recently, and in more detail at this conference (Salzmann et al) that the LIDAR approach to ITER core TS measurements requires only two mirrors in the inaccessible port plug area of the machine. This leads to simplified and robust alignment, lower risk of mirror damage by plasma contamination and much simpler calibration, compared with the awkward and vulnerable optical geometry of the conventional imaging TS approach, currently under development by ITER. In the present work we have extended the simulation code used previously to include the case of launching two laser pulses, of different wavelengths, simultaneously in LIDAR geometry. The aim of this approach is to broaden the choice of lasers available for the diagnostic. In the simulation code it is assumed that two short duration (300 ps) laser pulses of different wavelengths, from an Nd:YAG laser are launched through the plasma simultaneously. The temperature and density profiles are deduced in the usual way but from the resulting combined scattered signals in the different spectral channels of the single spectrometer. The spectral response and quantum efficiencies of the detectors used in the simulation are taken from catalogue data for commercially available Hamamatsu MCP-PMTs. The response times, gateability and tolerance to stray light levels of this type of photomultiplier have already been demonstrated in the JET LIDAR system and give sufficient spatial resolution to meet the ITER specification. Here we present the new simulation results from the code. They demonstrate that when the detectors are combined with this two laser, LIDAR approach, the full range of the specified ITER core plasma Te and ne can be measured with sufficient accuracy. So, with commercially available detectors and a simple modification of a Nd:YAG laser similar to that currently being used in the design of the conventional ITER core TS design mentioned above, the ITER requirements can be met.

Space weather impact on radio device operation

This paper reviews the space weather impact on operation of radio devices. The review is based on recently published papers, books, and strategic scientific plans of space weather investigations. The main attention is paid to ionospheric effects on propagation of radiowaves, basically short ones. Some examples of such effects are based on 2012–2016 ISTP SB RAS EKB radar data: attenuation of ground backscatter signals during solar flares, effects of traveling ionospheric disturbances of different scales in ground backscatter signals, effects of magnetospheric waves in ionospheric scatter signals.

Scatter Signal Elimination by Localized Primary Modulation in Industrial Computed Radiography

In industrial computed radiography, same as the other projection imaging systems, quantitative integrated information of total beam path including the object is carried by primary part of the beam. It is well known that the accuracy of the image useful data carried by the primary part degrades by scattered part of the beam. In order to have the beam path quantitative information accurately, it is essential to obtain the primary part of the total signal purely. In current study, a practical approach using localized primary modulation has been proposed to extract the primary signal. A semi-transparent beam attenuation grid was used as the beam intensity modulator. Efficiency and accuracy of the approach was practically validated through thickness measurement of metallic planar steps as an illustrative example. Simplified practical implementation and availability of the required accessories are some of advantages of the proposed approach. The results are indicative of the fact that this approach can also be applied as a new technique in thickness measurement, yielding a noticeable accuracy improvement in the most radiography methods. A procedure is included to explain the approach implementation for thickness measurement in computed radiography systems. The procedure overcomes some practical limitations and difficulties of the approach adaptation for computed radiography.

Abstract ID: 85 Investigating the physics of a CBCT projection shading correction based on a prior CT

The adoption of cone beam computed tomography (CBCT) image guidance in proton therapy has spurred research on CBCT image correction for dose calculation. Initially, methods based on deformable image registration gained attention [1] , however projection correction approaches based on prior CT information [2] have been shown to perform well for several body sites [3] . The shading correction algorithm used in [2] , [3] relies on image processing of the subtraction of digitally reconstructed radiographs (DRR) of a DIR-registered prior CT, and CBCT projections. In this study we have performed Monte Carlo (MC) simulation of CBCT imaging to disentangle the different sources of projection degradation, and to evaluate the physicality of the shading correction. The GATE MC toolkit’s fixed-forced-detection actor was employed, along with source and detector models optimized for an Elekta XVI CBCT system, to simulate CBCT imaging of an electron density phantom. The shading correction algorithm was applied to the measured projections and the so-called scatter component (SCA) was compared to the MC simulated scatter. Measured and simulated CBCT projections (scatter + primary) agreed well, with the largest discrepancy found for a bone insert (3% of log transformed projections). Important disagreement was observed with the MC scatter signal when the contribution from beam hardening was kept in the SCA. Undoing the beam hardening correction from the SCA using functions derived from MC primary projections and DRRs greatly improved agreement of scatter signals from MC and SCA (3% on average), with the largest discrepancy found for the bone insert (12%). Residual discrepancies were shown to stem from the intrinsic limitations of the SCA. Proton therapy dose calculations on corrected CBCT will be presented in addition to the results above.

Влияние факторов космической погоды на работу радиосредств

This paper reviews the space weather impact on operation of radio devices. The review is based on recently published papers, books, and strategic scientific plans of space weather investigations. The main attention is paid to ionospheric effects on propagation of radiowaves, basically short ones. Some examples of such effects are given based on 2012–2016 ISTP SB RAS EKB radar data: attenuation of ground backscatter signals during solar flares, effects of travelling ionospheric disturbances of different scales in ground backscatter signals, effects of magnetospheric waves in ionospheric scatter signals.

Sheathless Microflow Cytometry Using Viscoelastic Fluids

Microflow cytometry is a powerful technique for characterization of particles suspended in a solution. In this work, we present a microflow cytometer based on viscoelastic focusing. 3D single-line focusing of microparticles was achieved in a straight capillary using viscoelastic focusing which alleviated the need for sheath flow or any other actuation mechanism. Optical detection was performed by fiber coupled light source and photodetectors. Using this system, we present the detection of microparticles suspended in three different viscoelastic solutions. The rheological properties of the solutions were measured and used to assess the focusing performance both analytically and numerically. The results were verified experimentally, and it has been shown that polyethlyene oxide (PEO) and hyaluronic acid (HA) based sheathless microflow cytometer demonstrates similar performance to state-of-the art flow cytometers. The sheathless microflow cytometer was shown to present 780 particles/s throughput and 5.8% CV for the forward scatter signal for HA-based focusing. The presented system is composed of a single capillary to accommodate the fluid and optical fibers to couple the light to the fluid of interest. Thanks to its simplicity, the system has the potential to widen the applicability of microflow cytometers.

μPAD Fluorescence Scattering Immunoagglutination Assay for Cancer Biomarkers from Blood and Serum.

A microfluidic paper analytical device (μPAD) was created for the sensitive quantification of cancer antigens, carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA 19-9), from human whole blood and serum, toward diagnosis and prognosis of colorectal cancer. Anti-CEA and anti-CA 19-9 antibodies were covalently linked to submicron, fluorescent polystyrene particles, loaded, and then dried in the center of the μPAD channel. CEA- or CA 19-9-spiked blood or serum samples were loaded to the inlet of μPAD, and subsequent immunoagglutination changed the fluorescent scatter signals upon ultraviolet (UV) excitation. The total assay time was about 1 min. Detection limits were 1 pg/mL for CEA and 0.1 U/mL for CA 19-9 from both 10% diluted blood and undiluted serum. The use of UV excitation and subsequent fluorescence scattering enabled much higher double-normalized intensities (up to 1.28-3.51, compared with 1.067 with the elastic Mie scatter detection), successful detection in the presence of blood or serum, and distinct multiplex assays with minimum cross-reaction of antibodies. The results with undiluted serum showed the larger dynamic range and smaller standard errors, which can be attributed to the presence of serum proteins, functioning as a stabilizer or a passivating protein for the particles within paper fibers.

Flow cytometric analysis of CD64 expression pattern and density in the diagnosis of acute promyelocytic leukemia: a multi-center study in Shanghai, China.

No unified immunophenotypic profiles and corresponding analytic strategies have been established for the rapid diagnosis of acute promyelocytic leukemia (APL) using flow cytometry (FCM). Here we describe a characteristic immunophenotypic panel that can rapidly and accurately distinguish APL from other types of adult acute myeloid leukemia (AML) using only FCM. By comparing APL cells and non-APL AML cells that share APL common immunophenotypes (CD34−CD117+HLA−DR−) we found that CD64 was a significant factor that differentiated APL from other AMLs. Further retrospective analyses of 205 APL and 629 non-APL AML patients from different hematology centers showed that either the CD64dim and homoCD13+homo CD33+homoMPO+ (myeloperoxidase) CD11c− panel or the CD64dim and homoCD13+homo CD33+homoMPO+ CD11c+CD10−CD117+ SSChigh (high side scatter signal) panel could distinguish APL from non-APL AML patients with nearly 100% sensitivity, specificity and accuracy. Moreover, relative quantification of CD64 expression enhanced the applicability of our APL diagnostic immunophenotypic panels (ADI-panels) in different hematology centers. Application of the ADI-panels will decrease diagnosis time and improve personalized treatment for APL, a life-threatening disease with very rapid progression.

Ultrasonic backscatter from elongated grains using line focused ultrasound

Ultrasonic backscattering from polycrystalline materials with elongated grains is investigated. A normal incident line-focus transducer is employed such that refracted longitudinal and transverse waves are focused within the polycrystal and scatter at grain boundaries back to the transducer. A ray-based scattering model is developed to explain the dependence of the statistics of scattering measurements on grain elongation. The spatial variance of measured scattered signals from Al alloy (7475-T7) is compared to the model. This work promotes the ultrasonic backscatter technique for monitoring grain elongation of metals using one transducer with access to a single sample face.

Platelet Detection in Unaltered Whole Blood

Abstract Platelets are non-nucleated cellular fragments circulating in the peripheral blood, derived from megakaryocytes. They are critical in the maintenance of hemostasis. Alterations in their function are associated with a range of clinical conditions. Using flow cytometry, light scatter signals from platelets typically overlap signals from red blood cells (RBC). Since RBC outnumber platelets by more than an order of magnitude in whole blood, platelets are typically studied by depleting samples of RBCs by centrifugation methods or selective RBC cell lysis. These sample preparation procedures require manipulations that may affect platelet health and function, and result in loss of cells. Additionally, lysed samples require labeling of the platelets with a fluorescent marker to adequately resolve the platelets from debris/noise. We present a novel technique for resolving leukocytes and platelets from RBC in whole blood using orthogonal light scatter from 2 lasers. This method exploits the differences in light-scattering properties between RBCs and platelets and white blood cells (WBC). Hemoglobin readily absorbs 405 nm laser light, reducing the scatter signal from RBC relative to WBCs and platelets, resulting in a reproducible scatter pattern when analyzing human whole blood with both blue (488 nm) and violet (405 nm) side scatter. Using this approach, a distinct platelet population can be discerned in unaltered whole blood, requiring only dilution of whole blood in buffer. Combining this approach with acoustic cytometry allows great flexibility in determining optimal dilution and sample collection rates for minimal coincidence and rapid analysis. For research use only. Not for use in diagnostic procedures.

Convolution-based scatter correction usingkernels combining measurements andMonte Carlo simulations.

One of the well-recognized challenge of Cone-Beam Computed Tomography (CBCT) is scatter contamination within the projection images. Scatter degrades the image quality by decreasing the contrast, introducing cupping and shading artifacts and thus leading to inaccuracies in the reconstructed values. The higher scatter to primary ratio experienced in industrial applications leads to even more important artifacts. Various strategies have been investigated to manage the scatter signal in CBCT projection data. One of these strategies is to calculate the scatter intensity by deconvolution of primary intensity using Scatter Kernel Superposition (SKS). In this paper, we present an approach combining experimental measurements and Monte Carlo simulations to estimate the scatter kernels for industrial applications based on the continuously thickness-adapted kernels strategy with a four-Gaussian modeling of kernels. We compare this approach with an experimental technique based on a two-Gaussian modeling of the kernels. The results obtained prove the superiority of a four-Gaussian model to effectively take into account both the contribution of object and detector scattering as compared to a two-Gaussian approach. We also present the parameterisation of the scatter kernels with respect to object to detector distance. This approach facilitates the use of a single geometry for calculation of scatter kernels over the whole magnification range of the acquisition setup.