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Sample records for adaptive speckle imaging

  1. An adaptive Kalman filter for speckle reductions in ultrasound images

    Speckle is the term used to describe the granular appearance found in ultrasound images. The presence of speckle reduces the diagnostic potential of the echographic technique because it tends to mask small inhomogeneities of the investigated tissue. We developed a new method of speckle reductions that utilizes an adaptive one-dimensional Kalman filter based on the assumption that the observed image can be considered as a superimposition of speckle on a ''true images''. The filter adaptivity, necessary to avoid loss of resolution, has been obtained by statistical considerations on the local signal variations. The results of the applications of this particular Kalman filter, both on A-Mode and B-MODE images, show a significant speckle reduction

  2. Adaptive filtering for reduction of speckle in ultrasonic pulse-echo images.

    Bamber, J C; Daft, C

    1986-01-01

    Current medical ultrasonic scanning instrumentation permits the display of fine image detail (speckle) which does not transfer useful information but degrades the apparent low contrast resolution in the image. An adaptive two-dimensional filter has been developed which uses local features of image texture to recognize and maximally low-pass filter those parts of the image which correspond to fully developed speckle, while substantially preserving information associated with resolved-object structure. A first implementation of the filter is described which uses the ratio of the local variance and the local mean as the speckle recognition feature. Preliminary results of applying this form of display processing to medical ultrasound images are very encouraging; it appears that the visual perception of features such as small discrete structures, subtle fluctuations in mean echo level and changes in image texture may be enhanced relative to that for unprocessed images. PMID:3510500

  3. Structural adaptive and optimal speckle filtering in multilook full polarimetric SAR images

    Sun Nan; Zhang Bingchen; Wang Yanfei

    2007-01-01

    A novel approach is proposed for speckle reduction in multilook full polarimetric SAR images.In contrast to others, this approach adopts an enhanced structure detection method to estimate the parameters of the polarimetric covariance matrix for the multilook polarimetric whitening filtering (MPWF) algorithm and thus a structural adaptive and optimal speckle filter is developed.To evaluate the present approach, NASA SIR-C/X-SAR, L band, four-look processed polarimetric SAR data of the Tian-Mountain Forest is used for simulation.Experimental results demonstrate the effectiveness of this novel filtering algorithm in case of both speckle reduction and preservation of texture information.Comparisons with other methods are also made.

  4. An adaptive total variation image reconstruction method for speckles through disordered media

    Gong, Changmei; Shao, Xiaopeng; Wu, Tengfei

    2013-09-01

    Multiple scattering of light in highly disordered medium can break the diffraction limit of conventional optical system combined with image reconstruction method. Once the transmission matrix of the imaging system is obtained, the target image can be reconstructed from its speckle pattern by image reconstruction algorithm. Nevertheless, the restored image attained by common image reconstruction algorithms such as Tikhonov regularization has a relatively low signal-tonoise ratio (SNR) due to the experimental noise and reconstruction noise, greatly reducing the quality of the result image. In this paper, the speckle pattern of the test image is simulated by the combination of light propagation theories and statistical optics theories. Subsequently, an adaptive total variation (ATV) algorithm—the TV minimization by augmented Lagrangian and alternating direction algorithms (TVAL3), which is based on augmented Lagrangian and alternating direction algorithm, is utilized to reconstruct the target image. Numerical simulation experimental results show that, the TVAL3 algorithm can effectively suppress the noise of the restored image and preserve more image details, thus greatly boosts the SNR of the restored image. It also indicates that, compared with the image directly formed by `clean' system, the reconstructed results can overcoming the diffraction limit of the `clean' system, therefore being conductive to the observation of cells and protein molecules in biological tissues and other structures in micro/nano scale.

  5. ICA Based Speckle Filtering for Target Extraction in SAR Images Using Adaptive Space Separation

    LI Yu-tong; ZHOU Yue; YANG Lei

    2008-01-01

    A novel approach based on independent component analysis (ICA) for speckle filtering and target extraction of synthetic aperture radar (SAR) images is proposed using adaptive space separation with weighted information entropy (WIE) incorporated. First the basis and the independent components are respectively obtained by ICA technique, and WIE of the image is computed; then based on the threshold computed from function T-WIE (threshold versus weighted-information-entropy), independent components are adaptively separated and the bases are classified accordingly. Thus, the image space is separated into two subspaces: "clean" and "noise". Then, a proposed nonlinear operator ABO is applied on each component of the 'clean' subspace for further optimization. Finally, recovery image is obtained reconstructing this subspace and target is easily extracted with binarisation. Note that here T-WIE is an interpolated function based on several representative target SAR images using proposed space separation algorithm.

  6. Photothermal laser speckle imaging

    Regan, Caitlin; Ramirez-San-Juan, Julio C.; Choi, Bernard

    2014-01-01

    The analysis of speckle contrast in a time-integrated speckle pattern enables visualization of superficial blood flow in exposed vasculature, a method we call laser speckle imaging (LSI). With current methods, LSI does not enable visualization of subsurface or small vasculature, because of optical scattering by stationary structures. In this work we propose a new technique called photothermal LSI to improve the visualization of blood vessels. A 595 nm laser pulse was used to excite blood in b...

  7. Video surveillance with speckle imaging

    Carrano, Carmen J.; Brase, James M.

    2007-07-17

    A surveillance system looks through the atmosphere along a horizontal or slant path. Turbulence along the path causes blurring. The blurring is corrected by speckle processing short exposure images recorded with a camera. The exposures are short enough to effectively freeze the atmospheric turbulence. Speckle processing is used to recover a better quality image of the scene.

  8. Speckle noise reduction techniques for high-dynamic range imaging

    Bordé, Pascal J

    2007-01-01

    High-dynamic range imaging from space in the visible, aiming in particular at the detection of terrestrial exoplanets, necessitates not only the use of a coronagraph, but also of adaptive optics to correct optical defects in real time. Indeed, these defects scatter light and give birth to speckles in the image plane. Speckles can be cancelled by driving a deformable mirror to measure and compensate wavefront aberrations. In a first approach, targeted speckle nulling, speckles are cancelled iteratively by starting with the brightest ones. This first method has demonstrated a contrast better than 1e9 in laboratory. In a second approach, zonal speckle nulling, the total energy of speckles is minimized in a given zone of the image plane. This second method has the advantage to tackle simultaneously all speckles from the targeted zone, but it still needs better experimental demonstration.

  9. Speckle imaging algorithms for planetary imaging

    Johansson, E. [Lawrence Livermore National Lab., CA (United States)

    1994-11-15

    I will discuss the speckle imaging algorithms used to process images of the impact sites of the collision of comet Shoemaker-Levy 9 with Jupiter. The algorithms use a phase retrieval process based on the average bispectrum of the speckle image data. High resolution images are produced by estimating the Fourier magnitude and Fourier phase of the image separately, then combining them and inverse transforming to achieve the final result. I will show raw speckle image data and high-resolution image reconstructions from our recent experiment at Lick Observatory.

  10. Speckle Noise Reduction in Medical Ultrasound Images

    Faouzi Benzarti

    2012-03-01

    Full Text Available Ultrasound imaging is an incontestable vital tool for diagnosis, it provides in non-invasive manner the internal structure of the body to detect eventually diseases or abnormalities tissues. Unfortunately, the presence of speckle noise in these images affects edges and fine details which limit the contrast resolution and make diagnostic more difficult. In this paper, we propose a denoising approach which combines logarithmic transformation and a non linear diffusion tensor. Since speckle noise is multiplicative and nonwhite process, the logarithmic transformation is a reasonable choice to convert signal-dependent or pure multiplicative noise to an additive one. The key idea from using diffusion tensor is to adapt the flow diffusion towards the local orientation by applying anisotropic diffusion along the coherent structure direction of interesting features in the image. To illustrate the effective performance of our algorithm, we present some experimental results on synthetically and real echographic images.

  11. Nonlocal Total-Variation-Based Speckle Filtering for Ultrasound Images.

    Wen, Tiexiang; Gu, Jia; Li, Ling; Qin, Wenjian; Wang, Lei; Xie, Yaoqin

    2016-07-01

    Ultrasound is one of the most important medical imaging modalities for its real-time and portable imaging advantages. However, the contrast resolution and important details are degraded by the speckle in ultrasound images. Many speckle filtering methods have been developed, but they are suffered from several limitations, difficult to reach a balance between speckle reduction and edge preservation. In this paper, an adaptation of the nonlocal total variation (NLTV) filter is proposed for speckle reduction in ultrasound images. The speckle is modeled via a signal-dependent noise distribution for the log-compressed ultrasound images. Instead of the Euclidian distance, the statistical Pearson distance is introduced in this study for the similarity calculation between image patches via the Bayesian framework. And the Split-Bregman fast algorithm is used to solve the adapted NLTV despeckling functional. Experimental results on synthetic and clinical ultrasound images and comparisons with some classical and recent algorithms are used to demonstrate its improvements in both speckle noise reduction and tissue boundary preservation for ultrasound images. PMID:26316172

  12. Speckles in laser Doppler perfusion imaging

    Rajan, V; Varghese, B.; Leeuwen, van; W. Steenbergen

    2006-01-01

    We report on the quantitative influence of speckles in laser Doppler perfusion imaging. The influence of speckles on the signal amplitude and on the Doppler spectrum is demonstrated experimentally for particle suspensions with different scattering levels and various beam widths. It is shown that the type of tissue affects the instrumental response through the effect of lateral light diffusion on the number of speckles involved in the detection process. These effects are largest for narrow beams.

  13. Speckle Suppression Method for SAR Image

    Jiming Guo

    2013-04-01

    Full Text Available In this study, a new speckle reduction method was proposed in terms of by Bidimensional Empirical Mode Decomposition (BEMD. In this method, the SAR image containing speckle noise was decomposed into a number of elementary components by using BEMD and then the extremal points are done the boundary equivalent extension after screening and the residual continue to be done the boundary equivalent extension until screening is completed, finally, the image was reconstructed, which reduced the speckle noise. Experimental results show that this method has good effect on suppressing speckle noise, compared to the average filter, median filter and gaussian filter and has advantages of sufficiently retaining edge and detail information while suppressing speckle noise.

  14. Fractality of pulsatile flow in speckle images

    Nemati, M.; Kenjeres, S.; Urbach, H. P.; Bhattacharya, N.

    2016-05-01

    The scattering of coherent light from a system with underlying flow can be used to yield essential information about dynamics of the process. In the case of pulsatile flow, there is a rapid change in the properties of the speckle images. This can be studied using the standard laser speckle contrast and also the fractality of images. In this paper, we report the results of experiments performed to study pulsatile flow with speckle images, under different experimental configurations to verify the robustness of the techniques for applications. In order to study flow under various levels of complexity, the measurements were done for three in-vitro phantoms and two in-vivo situations. The pumping mechanisms were varied ranging from mechanical pumps to the human heart for the in vivo case. The speckle images were analyzed using the techniques of fractal dimension and speckle contrast analysis. The results of these techniques for the various experimental scenarios were compared. The fractal dimension is a more sensitive measure to capture the complexity of the signal though it was observed that it is also extremely sensitive to the properties of the scattering medium and cannot recover the signal for thicker diffusers in comparison to speckle contrast.

  15. Image recovery from polarimetric, nonimaged laser speckle

    Dixon, Donald B.; Cain, Stephen C.

    2010-11-01

    The addition of polarization diversity for a non-imaging laser speckle system provides improvement for the phase retrieval problem. The polarization diversity of the remote scene provides additional information for successfully recovering a two-dimensional image from noisy autocorrelations obtained from laser speckle patterns or pupil plane images. The proposed system may be used to characterize space-borne objects and debris with an earthbased sensor array. We propose an Expectation-Maximization (EM) algorithm with a simple, statistical-based stopping criteria. Results from both simulation and laboratory experiment are presented.

  16. Enhanced Video Surveillance (EVS) with speckle imaging

    Carrano, C J

    2004-01-13

    Enhanced Video Surveillance (EVS) with Speckle Imaging is a high-resolution imaging system that substantially improves resolution and contrast in images acquired over long distances. This technology will increase image resolution up to an order of magnitude or greater for video surveillance systems. The system's hardware components are all commercially available and consist of a telescope or large-aperture lens assembly, a high-performance digital camera, and a personal computer. The system's software, developed at LLNL, extends standard speckle-image-processing methods (used in the astronomical community) to solve the atmospheric blurring problem associated with imaging over medium to long distances (hundreds of meters to tens of kilometers) through horizontal or slant-path turbulence. This novel imaging technology will not only enhance national security but also will benefit law enforcement, security contractors, and any private or public entity that uses video surveillance to protect their assets.

  17. Adaptive ultrasonic speckle reduction based on the slope-facet model.

    Huang, Huan-Chao; Chen, Jau-Yuen; Wang, Sheng-De; Chen, Chung-Ming

    2003-08-01

    The flat-facet model has been implicitly assumed for the structure of the image surface by most conventional speckle-reduction algorithms. However, this model is rarely found in a real ultrasound (US) image. To preserve the higher order structures and to capture the spatially variant property of the speckle, a new adaptive speckle-reduction algorithm, called the symmetrical speckle-reduction filter (SSRF), was developed based on the slope-facet model. The basic idea of the SSRF was to estimate the uncorrupted signal on the largest symmetrical slope facet centered at each target pixel. The symmetry constraint ensured the correctness of the mean value. An empirical speckle model was incorporated to account for the nature of the speckle in US image. A two-stage despeckling strategy was employed to enhance the statistical reliability of each estimate by forming a union of a set of symmetrical despeckling windows. The proposed SSRF algorithm was compared with two filtered-based and one wavelet-based approaches and the experimental results showed that the proposed SSRF outperformed these three previous approaches in both the synthetic images and the clinical US images tested in this study. PMID:12946519

  18. Speckle Imaging: a boon for astronomical observations

    Saha, S. K.

    2000-01-01

    The speckle imaging is a photographic technique that resolves objects viewed through severely distorted media. The results are insensitive to the errors caused by apparent size of the isoplanatic patch and the telescope aberrations. In this article, a short descriptions of the atmospheric turbulence and its effect on the flat wavefront from a stellar source is presented; the shortcomings of the conventional long-exposure images in the presence of Earth's atmosphere are discussed. The advantag...

  19. Laser Speckle Imaging of Cerebral Blood Flow

    Luo, Qingming; Jiang, Chao; Li, Pengcheng; Cheng, Haiying; Wang, Zhen; Wang, Zheng; Tuchin, Valery V.

    Monitoring the spatio-temporal characteristics of cerebral blood flow (CBF) is crucial for studying the normal and pathophysiologic conditions of brain metabolism. By illuminating the cortex with laser light and imaging the resulting speckle pattern, relative CBF images with tens of microns spatial and millisecond temporal resolution can be obtained. In this chapter, a laser speckle imaging (LSI) method for monitoring dynamic, high-resolution CBF is introduced. To improve the spatial resolution of current LSI, a modified LSI method is proposed. To accelerate the speed of data processing, three LSI data processing frameworks based on graphics processing unit (GPU), digital signal processor (DSP), and field-programmable gate array (FPGA) are also presented. Applications for detecting the changes in local CBF induced by sensory stimulation and thermal stimulation, the influence of a chemical agent on CBF, and the influence of acute hyperglycemia following cortical spreading depression on CBF are given.

  20. Effect of speckle on APSCI method and Mueller Imaging

    Upadhyay, Debajyoti; Lacot, Eric; De Martino, Antonello; Orlik, Xavier

    2014-01-01

    The principle of the polarimetric imaging method called APSCI (Adapted Polarization State Contrast Imaging) is to maximize the polarimetric contrast between an object and its background using specific polarization states of illumination and detection. We perform here a comparative study of the APSCI method with existing Classical Mueller Imaging(CMI) associated with polar decomposition in the presence of fully and partially polarized circular Gaussian speckle. The results show a noticeable increase of the Bhattacharyya distance used as our contrast parameter for the APSCI method, especially when the object and background exhibit several polarimetric properties simultaneously.

  1. Noise analysis in laser speckle contrast imaging

    Yuan, Shuai; Chen, Yu; Dunn, Andrew K.; Boas, David A.

    2010-02-01

    Laser speckle contrast imaging (LSCI) is becoming an established method for full-field imaging of blood flow dynamics in animal models. A reliable quantitative model with comprehensive noise analysis is necessary to fully utilize this technique in biomedical applications and clinical trials. In this study, we investigated several major noise sources in LSCI: periodic physiology noise, shot noise and statistical noise. (1) We observed periodic physiology noise in our experiments and found that its sources consist principally of motions induced by heart beats and/or ventilation. (2) We found that shot noise caused an offset of speckle contrast (SC) values, and this offset is directly related to the incident light intensity. (3) A mathematical model of statistical noise was also developed. The model indicated that statistical noise in speckle contrast imaging is related to the SC values and the total number of pixels used in the SC calculation. Our experimental results are consistent with theoretical predications, as well as with other published works.

  2. High-contrast Imaging from Space: Speckle Nulling in a Low Aberration Regime

    Bordé, P J; Borde, Pascal J.; Traub, Wesley A.

    2006-01-01

    High-contrast imaging from space must overcome two major noise sources to successfully detect a terrestrial planet angularly close to its parent star: photon noise from diffracted star light, and speckle noise from star light scattered by instrumentally-generated wavefront perturbation. Coronagraphs tackle only the photon noise contribution by reducing diffracted star light at the location of a planet. Speckle noise should be addressed with adaptative-optics systems. Following the tracks of Malbet, Yu and Shao (1995), we develop in this paper two analytical methods for wavefront sensing and control that aims at creating dark holes, i.e. areas of the image plane cleared out of speckles, assuming an ideal coronagraph and small aberrations. The first method, speckle field nulling, is a fast FFT-based algorithm that requires the deformable-mirror influence functions to have identical shapes. The second method, speckle energy minimization, is more general and provides the optimal deformable mirror shape via matrix...

  3. Artificial incoherent speckles enable precision astrometry and photometry in high-contrast imaging

    Jovanovic, Nemanja; Martinache, Frantz; Pathak, Prashant; Hagelberg, Janis; Kudo, Tomoyuki

    2015-01-01

    State-of-the-art coronagraphs employed on extreme adaptive optics enabled instruments, are constantly improving the contrast detection limit for companions at ever closer separations to the host star. In order to constrain their properties and ultimately compositions, it is important to precisely determine orbital parameters and contrasts with respect to the stars they orbit. This can be difficult in the post coronagraphic image plane, as by definition the central star has been occulted by the coronagraph. We demonstrate the flexibility of utilizing the deformable mirror in the adaptive optics system in SCExAO to generate a field of speckles for the purposes of calibration. Speckles can be placed up to $22.5~\\lambda/D$ from the star, with any position angle, brightness and abundance required. Most importantly, we show that a fast modulation of the added speckle phase, between $0$ and $\\pi$, during a long science integration renders these speckles effectively incoherent with the underlying halo. We quantitativ...

  4. Robust non-homomorphic approach for speckle reduction in medical ultrasound images.

    Gupta, S; Chauhan, R C; Saxena, S C

    2005-03-01

    Most existing wavelet-based image denoising techniques are developed for additive white Gaussian noise. In applications to speckle reduction in medical ultrasound (US) images, the traditional approach is first to perform the logarithmic transform (homomorphic processing) to convert the multiplicative speckle noise model to an additive one, and then the wavelet filtering is performed on the log-transformed image, followed by an exponential operation. However, this non-linear operation leads to biased estimation of the signal and increases the computational complexity of the filtering method. To overcome these drawbacks, an efficient, non-homomorphic technique for speckle reduction in medical US images is proposed. The method relies on the true characterisation of the marginal statistics of the signal and speckle wavelet coefficients. The speckle component was modelled using the generalised Nakagami distribution, which is versatile enough to model the speckle statistics under various scattering conditions of interest in medical US images. By combining this speckle model with the generalised Gaussian signal first, the Bayesian shrinkage functions were derived using the maximum a posteriori (MAP) criterion. The resulting Bayesian processor used the local image statistics to achieve soft-adaptation from homogeneous to highly heterogeneous areas. Finally, the results showed that the proposed method, named GNDShrink, yielded a signal-to-noise ratio (SNR) gain of 0.42dB over the best state-of-the-art despeckling method reported in the literature, 1.73dB over the Lee filter and 1.31dB over the Kaun filter at an input SNR of 12.0dB, when tested on a US image. Further, the visual comparison of despeckled US images indicated that the new method suppressed the speckle noise well, while preserving the texture and organ surfaces. PMID:15865126

  5. Flux or speed? Examining speckle contrast imaging of vascular flows.

    Kazmi, S M Shams; Faraji, Ehssan; Davis, Mitchell A; Huang, Yu-Yen; Zhang, Xiaojing J; Dunn, Andrew K

    2015-07-01

    Speckle contrast imaging enables rapid mapping of relative blood flow distributions using camera detection of back-scattered laser light. However, speckle derived flow measures deviate from direct measurements of erythrocyte speeds by 47 ± 15% (n = 13 mice) in vessels of various calibers. Alternatively, deviations with estimates of volumetric flux are on average 91 ± 43%. We highlight and attempt to alleviate this discrepancy by accounting for the effects of multiple dynamic scattering with speckle imaging of microfluidic channels of varying sizes and then with red blood cell (RBC) tracking correlated speckle imaging of vascular flows in the cerebral cortex. By revisiting the governing dynamic light scattering models, we test the ability to predict the degree of multiple dynamic scattering across vessels in order to correct for the observed discrepancies between relative RBC speeds and multi-exposure speckle imaging estimates of inverse correlation times. The analysis reveals that traditional speckle contrast imagery of vascular flows is neither a measure of volumetric flux nor particle speed, but rather the product of speed and vessel diameter. The corrected speckle estimates of the relative RBC speeds have an average 10 ± 3% deviation in vivo with those obtained from RBC tracking. PMID:26203384

  6. A Level Set Filter for Speckle Reduction in SAR Images

    Huang Bo

    2010-01-01

    Full Text Available Despite much effort and significant progress in recent years, speckle removal for Synthetic Aperture Radar (SAR image still is a challenging problem in image processing. Unlike the traditional noise filters, which are mainly based on local neighborhood statistical average or frequencies transform, in this paper, we propose a speckle reduction method based on the theory of level set, one form of curvature flow propagation. Firstly, based on partial differential equation, the Lee filter can be cast as a formulation of anisotropic diffusion function; furthermore, we continued to deduce it into a level set formulation. Level set flow into the method allows the front interface to propagate naturally with topological changes, where the speed is proportional to the curvature of the intensity contours in an image. Hence, small speckle will disappear quickly, while large scale interfaces will be slow to evolve. Secondly, for preserving finer detailed structures in images when smoothing the speckle, the evolution is switched between minimum or maximum curvature speed depending on the scale of speckle. The proposed method has been illustrated by experiments on simulation image and ERS-2 SAR images under different circumstances. Its advantages over the traditional speckle reduction filter approaches have also been demonstrated.

  7. Evaluation of various speckle reduction filters on medical ultrasound images.

    Wu, Shibin; Zhu, Qingsong; Xie, Yaoqin

    2013-01-01

    At present, ultrasound is one of the essential tools for noninvasive medical diagnosis. However, speckle noise is inherent in medical ultrasound images and it is the cause for decreased resolution and contrast-to-noise ratio. Low image quality is an obstacle for effective feature extraction, recognition, analysis, and edge detection; it also affects image interpretation by doctor and the accuracy of computer-assisted diagnostic techniques. Thus, speckle reduction is significant and critical step in pre-processing of ultrasound images. Many speckle reduction techniques have been studied by researchers, but to date there is no comprehensive method that takes all the constraints into consideration. In this paper we discuss seven filters, namely Lee, Frost, Median, Speckle Reduction Anisotropic Diffusion (SRAD), Perona-Malik's Anisotropic Diffusion (PMAD) filter, Speckle Reduction Bilateral Filter (SRBF) and Speckle Reduction filter based on soft thresholding in the Wavelet transform. A comparative study of these filters has been made in terms of preserving the features and edges as well as effectiveness of de-noising.We computed five established evaluation metrics in order to determine which despeckling algorithm is most effective and optimal for real-time implementation. In addition, the experimental results have been demonstrated by filtered images and statistical data table. PMID:24109896

  8. Optical Processing of Speckle Images with Bacteriorhodopsin for Pattern Recognition

    Downie, John D.; Tucker, Deanne (Technical Monitor)

    1994-01-01

    Logarithmic processing of images with multiplicative noise characteristics can be utilized to transform the image into one with an additive noise distribution. This simplifies subsequent image processing steps for applications such as image restoration or correlation for pattern recognition. One particularly common form of multiplicative noise is speckle, for which the logarithmic operation not only produces additive noise, but also makes it of constant variance (signal-independent). We examine the optical transmission properties of some bacteriorhodopsin films here and find them well suited to implement such a pointwise logarithmic transformation optically in a parallel fashion. We present experimental results of the optical conversion of speckle images into transformed images with additive, signal-independent noise statistics using the real-time photochromic properties of bacteriorhodopsin. We provide an example of improved correlation performance in terms of correlation peak signal-to-noise for such a transformed speckle image.

  9. BL_Wiener Denoising Method for Removal of Speckle Noise in Ultrasound Image

    Suhaila Sari

    2015-02-01

    Full Text Available Medical imaging techniques are extremely important tools in medical diagnosis. One of these important imaging techniques is ultrasound imaging. However, during ultrasound image acquisition process, the quality of image can be degraded due to corruption by speckle noise. The enhancement of ultrasound images quality from the 2D ultrasound imaging machines is expected to provide medical practitioners more reliable medical images in their patients’ diagnosis. However, developing a denoising technique which could remove noise effectively without eliminating the image’s edges and details is still an ongoing issue. The objective of this paper is to develop a new method that is capable to remove speckle noise from the ultrasound image effectively. Therefore, in this paper we proposed the utilization of Bilateral Filter and Adaptive Wiener Filter (BL_Wiener denoising method for images corrupted by speckle noise. Bilateral Filter is a non-linear filter effective in removing noise, while Adaptive Wiener Filter balances the tradeoff between inverse filtering and noise smoothing by removing additive noise while inverting blurring. From our simulation results, it is found that the BL_Wiener method has improved between 0.89 [dB] to 3.35 [dB] in terms of PSNR for test images in different noise levels in comparison to conventional methods.

  10. Modeled and measured image-plane polychromatic speckle contrast

    Van Zandt, Noah R.; McCrae, Jack E.; Fiorino, Steven T.

    2016-02-01

    The statistical properties of speckle relevant to short- to medium-range (tactical) active tracking involving polychromatic illumination are investigated. A numerical model is developed to allow rapid simulation of speckled images including the speckle contrast reduction effects of illuminator bandwidth, surface slope, and roughness, and the polarization properties of both the source and the reflection. Regarding surface slope (relative orientation of the surface normal and illumination/observation directions), Huntley's theory for speckle contrast, which employs geometrical approximations to decrease computation time, is modified to increase accuracy by incorporation of a geometrical correction factor and better treatment of roughness and polarization. The resulting model shows excellent agreement with more exact theory over a wide range. An experiment is conducted to validate both the numerical model developed here and existing theory. A diode laser source with coherence length of 259±7 μm is reflected off of a silver-coated diffuse surface. Speckle data are gathered for 16 surface slope angles corresponding to speckle contrast between about 0.55 and 1. Taking the measured data as truth, both equations show error mean and standard deviation of less than 3%. Thus, the theory is validated over the range of this experiment.

  11. Laser Speckle Imaging: A Novel Method for Detecting Dental Erosion

    Koshoji, Nelson H.; Bussadori, Sandra K.; Bortoletto, Carolina C.; Prates, Renato A.; Oliveira, Marcelo T.; Deana, Alessandro M.

    2015-01-01

    Erosion is a highly prevalent condition known as a non-carious lesion that causes progressive tooth wear due to chemical processes that do not involve the action of bacteria. Speckle images proved sensitive to even minimal mineral loss from the enamel. The aim of the present study was to investigate the use of laser speckle imaging analysis in the spatial domain to quantify shifts in the microstructure of the tooth surface in an erosion model. 32 fragments of the vestibular surface of bovine ...

  12. Speckle imaging with the MAMA detector: Preliminary results

    Horch, E.; Heanue, J. F.; Morgan, J. S.; Timothy, J. G.

    1994-01-01

    We report on the first successful speckle imaging studies using the Stanford University speckle interferometry system, an instrument that uses a multianode microchannel array (MAMA) detector as the imaging device. The method of producing high-resolution images is based on the analysis of so-called 'near-axis' bispectral subplanes and follows the work of Lohmann et al. (1983). In order to improve the signal-to-noise ratio in the bispectrum, the frame-oversampling technique of Nakajima et al. (1989) is also employed. We present speckle imaging results of binary stars and other objects from V magnitude 5.5 to 11, and the quality of these images is studied. While the Stanford system is capable of good speckle imaging results, it is limited by the overall quantum efficiency of the current MAMA detector (which is due to the response of the photocathode at visible wavelengths and other detector properties) and by channel saturation of the microchannel plate. Both affect the signal-to-noise ratio of the power spectrum and bispectrum.

  13. Speckle noise reduction of medical ultrasound images in complex wavelet domain using mixture priors.

    Rabbani, Hossein; Vafadust, Mansur; Abolmaesumi, Purang; Gazor, Saeed

    2008-09-01

    Speckle noise is an inherent nature of ultrasound images, which may have negative effect on image interpretation and diagnostic tasks. In this paper, we propose several multiscale nonlinear thresholding methods for ultrasound speckle suppression. The wavelet coefficients of the logarithm of image are modeled as the sum of a noise-free component plus an independent noise. Assuming that the noise-free component has some local mixture distribution (MD), and the noise is either Gaussian or Rayleigh, we derive the minimum mean squared error (MMSE) and the averaged maximum a posteriori (AMAP) estimators for noise reduction. We use Gaussian and Laplacian MD for each noise-free wavelet coefficient to characterize their heavy-tailed property. Since we estimate the parameters of the MD using the expectation maximization (EM) algorithm and local neighbors, the proposed MD incorporates some information about the intrascale dependency of the wavelet coefficients. To evaluate our spatially adaptive despeckling methods, we use both real medical ultrasound and synthetically introduced speckle images for speckle suppression. The simulation results show that our method outperforms several recently and the state-of-the-art techniques qualitatively and quantitatively. PMID:18713684

  14. Nephron blood flow dynamics measured by laser speckle contrast imaging

    von Holstein-Rathlou, Niels-Henrik; Sosnovtseva, Olga V; Pavlov, Alexey N;

    2011-01-01

    simultaneously. The interacting nephron fields are likely to be more extensive. We have turned to laser speckle contrast imaging to measure the blood flow dynamics of 50-100 nephrons simultaneously on the renal surface of anesthetized rats. We report the application of this method and describe analytic...

  15. Learning of speckle statistics for in vivo and noninvasive characterization of cutaneous wound regions using laser speckle contrast imaging.

    Basak, Kausik; Dey, Goutam; Mahadevappa, Manjunatha; Mandal, Mahitosh; Sheet, Debdoot; Dutta, Pranab Kumar

    2016-09-01

    Laser speckle contrast imaging (LSCI) provides a noninvasive and cost effective solution for in vivo monitoring of blood flow. So far, most of the researches consider changes in speckle pattern (i.e. correlation time of speckle intensity fluctuation), account for relative change in blood flow during abnormal conditions. This paper introduces an application of LSCI for monitoring wound progression and characterization of cutaneous wound regions on mice model. Speckle images are captured on a tumor wound region at mice leg in periodic interval. Initially, raw speckle images are converted to their corresponding contrast images. Functional characterization begins with first segmenting the affected area using k-means clustering, taking wavelet energies in a local region as feature set. In the next stage, different regions in wound bed are clustered based on progressive and non-progressive nature of tissue properties. Changes in contrast due to heterogeneity in tissue structure and functionality are modeled using LSCI speckle statistics. Final characterization is achieved through supervised learning of these speckle statistics using support vector machine. On cross evaluation with mice model experiment, the proposed approach classifies the progressive and non-progressive wound regions with an average sensitivity of 96.18%, 97.62% and average specificity of 97.24%, 96.42% respectively. The clinical information yield with this approach is validated with the conventional immunohistochemistry result of wound to justify the ability of LSCI for in vivo, noninvasive and periodic assessment of wounds. PMID:27131831

  16. Laser speckle imaging: a novel method for detecting dental erosion.

    Nelson H Koshoji

    Full Text Available Erosion is a highly prevalent condition known as a non-carious lesion that causes progressive tooth wear due to chemical processes that do not involve the action of bacteria. Speckle images proved sensitive to even minimal mineral loss from the enamel. The aim of the present study was to investigate the use of laser speckle imaging analysis in the spatial domain to quantify shifts in the microstructure of the tooth surface in an erosion model. 32 fragments of the vestibular surface of bovine incisors were divided in for groups (10 min, 20 min. 30 min and 40 min of acid etching immersed in a cola-based beverage (pH approximately 2.5 twice a day during 7 days to create an artificial erosion. By analyzing the laser speckle contrast map (LASCA in the eroded region compared to the sound it was observed that the LASCA map shifts, proportionally to the acid each duration, by: 18%; 23%; 39% and 44% for the 10 min; 20 min; 30 min and 40 min groups, respectively. To the best of our knowledge, this is the first study to demonstrate the correlation between speckle patterns and erosion progression.

  17. Sensitivity, noise and quantitative model of Laser Speckle Contrast Imaging

    Yuan, Shuai

    In the dissertation, I present several studies on Laser Speckle Contrast Imaging (LSCI). The two major goals of those studies are: (1) to improve the signal-noise-ratio (SNR) of LSCI so it can be used to detect small blood flow change due to brain activities; (2) to find a reliable quantitative model so LSCI results can be compared among experiments and subjects and even with results from other blood flow monitoring techniques. We sought to improve SNR in the following ways: (1) We investigated the relationship between exposure time and the sensitivities of LSCI. We found that relative sensitivity reaches its maximum at an exposure time of around 5 ms. (2) We studied the relationship between laser speckle and camera aperture stop, which is actually the relationship between laser speckle and speckle/pixel size ratio. In general, speckle and pixel size should be approximately 1.5 - 2 to reach the maximum of detection factor beta as well as speckle contrast (SC) value and absolute sensitivity. This is also an important study for quantitative model development. (3) We worked on noise analysis and modeling. Noise affects both SNR and quantitative model. Usually random noise is more critical for SNR analysis. The main random noises in LSCI are statistical noise and physiological noise. Some physiological noises are caused by the small motions induced by heart beat or breathing. These are periodic and can be eliminated using methods discussed in this dissertation. Statistical noise is more fundamental and cannot be eliminated entirely. However it can be greatly reduced by increasing the effective pixel number N for speckle contrast processing. To develop the quantitative model, we did the following: (1) We considered more experimental factors in the quantitative model and removed several ideal case assumptions. In particular, in our model we considered the general detection factor beta, static scatterers and systematic noise. A simple calibration procedure is suggested

  18. Subspace-based technique for speckle noise reduction in ultrasound images

    Yahya, Norashikin; Nidal S. Kamel; Malik, Aamir S

    2014-01-01

    Background and purpose Ultrasound imaging is a very essential technique in medical diagnosis due to its being safe, economical and non-invasive nature. Despite its popularity, the US images, however, are corrupted with speckle noise, which reduces US images qualities, hampering image interpretation and processing stage. Hence, there are many efforts made by researches to formulate various despeckling methods for speckle reduction in US images. Methods In this paper, a subspace-based speckle r...

  19. Super-resolution photoacoustic fluctuation imaging with multiple speckle illumination

    Chaigne, Thomas; Allain, Marc; Katz, Ori; Gigan, Sylvain; Sentenac, Anne; Bossy, Emmanuel

    2015-01-01

    In deep tissue photoacoustic imaging, the spatial resolution is inherently limited by acoustic diffraction. Moreover, as the ultrasound attenuation increases with frequency, resolution is often traded-off for penetration depth. Here we report on super-resolution photoacoustic imaging by use of multiple speckle illumination. Specifically, we show that the analysis of second-order fluctuations of the photoacoustic images combined with image deconvolution enables resolving optically absorbing structures beyond the acoustic diffraction limit. A resolution increase of almost a factor 2 is demonstrated experimentally. Our method introduces a new framework that could potentially lead to deep tissue photoacoustic imaging with sub-acoustic resolution.

  20. A method to transfer speckle patterns for digital image correlation

    Chen, Zhenning; Quan, Chenggen; Zhu, Feipeng; He, Xiaoyuan

    2015-09-01

    A simple and repeatable speckle creation method based on water transfer printing (WTP) is proposed to reduce artificial measurement error for digital image correlation (DIC). This technique requires water, brush, and a piece of transfer paper that is made of prefabricated decal paper, a protected sheet, and printed speckle patterns. The speckle patterns are generated and optimized via computer simulations, and then printed on the decal paper. During the experiments, operators can moisten the basement with water and the brush, so that digital patterns can be simply transferred to the carriers’ surfaces. Tensile experiments with an extended three-dimensional (3D) DIC system are performed to test and verify the validity of WTP patterns. It is shown that by comparing with a strain gage, the strain error is less than 50με in a uniform tensile test. From five carbon steel tensile experiments, Lüders bands in both WTP patterns and spray paint patterns are demonstrated to propagate symmetrically. In the necking part where the strain is up to 66%, WTP patterns are proved to adhere to the specimens well. Hence, WTP patterns are capable of maintaining coherence and adherence to the specimen surface. The transfer paper, working as the role of strain gage in the electrometric method, will contribute to speckle creation.

  1. A method to transfer speckle patterns for digital image correlation

    A simple and repeatable speckle creation method based on water transfer printing (WTP) is proposed to reduce artificial measurement error for digital image correlation (DIC). This technique requires water, brush, and a piece of transfer paper that is made of prefabricated decal paper, a protected sheet, and printed speckle patterns. The speckle patterns are generated and optimized via computer simulations, and then printed on the decal paper. During the experiments, operators can moisten the basement with water and the brush, so that digital patterns can be simply transferred to the carriers’ surfaces. Tensile experiments with an extended three-dimensional (3D) DIC system are performed to test and verify the validity of WTP patterns. It is shown that by comparing with a strain gage, the strain error is less than 50με in a uniform tensile test. From five carbon steel tensile experiments, Lüders bands in both WTP patterns and spray paint patterns are demonstrated to propagate symmetrically. In the necking part where the strain is up to 66%, WTP patterns are proved to adhere to the specimens well. Hence, WTP patterns are capable of maintaining coherence and adherence to the specimen surface. The transfer paper, working as the role of strain gage in the electrometric method, will contribute to speckle creation. (paper)

  2. Dynamic speckle image segmentation using self-organizing maps

    Pra, Ana L. Dai; Meschino, Gustavo J.; Guzmán, Marcelo N.; Scandurra, Adriana G.; González, Mariela A.; Weber, Christian; Trivi, Marcelo; Rabal, Héctor; Passoni, Lucía I.

    2016-08-01

    The aim of this work is to build a computational model able to automatically identify, after training, dynamic speckle pattern regions with similar properties. The process is carried out using a set of descriptors applied to the intensity variations with time in every pixel of a speckle image sequence. An image obtained by projecting a self-organized map is converted into regions of similar activity that can be easily distinguished. We propose a general procedure that could be applied to numerous situations. As examples we show different situations: (a) an activity test in a simplified situation; (b) a non-biological example and (c) biological active specimens. The results obtained are encouraging; they significantly improve upon those obtained using a single descriptor and will eventually permit automatic quantitative assessment.

  3. Rayleigh-maximum-likelihood filtering for speckle reduction of ultrasound images.

    Aysal, Tuncer C; Barner, Kenneth E

    2007-05-01

    Speckle is a multiplicative noise that degrades ultrasound images. Recent advancements in ultrasound instrumentation and portable ultrasound devices necessitate the need for more robust despeckling techniques, for both routine clinical practice and teleconsultation. Methods previously proposed for speckle reduction suffer from two major limitations: 1) noise attenuation is not sufficient, especially in the smooth and background areas; 2) existing methods do not sufficiently preserve or enhance edges--they only inhibit smoothing near edges. In this paper, we propose a novel technique that is capable of reducing the speckle more effectively than previous methods and jointly enhancing the edge information, rather than just inhibiting smoothing. The proposed method utilizes the Rayleigh distribution to model the speckle and adopts the robust maximum-likelihood estimation approach. The resulting estimator is statistically analyzed through first and second moment derivations. A tuning parameter that naturally evolves in the estimation equation is analyzed, and an adaptive method utilizing the instantaneous coefficient of variation is proposed to adjust this parameter. To further tailor performance, a weighted version of the proposed estimator is introduced to exploit varying statistics of input samples. Finally, the proposed method is evaluated and compared to well-accepted methods through simulations utilizing synthetic and real ultrasound data. PMID:17518065

  4. Twinkle Twinkle Little Star - Speckle Imaging for Exoplanet Characterization

    Howell, Steve B.; Scott, Nic; Horch, Elliott

    2016-06-01

    The NASA K2 mission is finding many high-value exoplanets and world-wide follow-up is ensuing. The NASA TESS mission will soon be launched, requiring additional ground-based observations as well. As a part of the NASA-NSFNN-EXPLORE program to enable exoplanet research, our group is building two new speckle interferometry cameras for the Kitt Peak WIYN 3.5-m telescope and the Gemini-N 8-m telescope. Modeled after the successful DSSI visitor instrument that has been used at these telescopes for many years, speckle observations provide the highest resolution images available today from any ground- or space-based single telescope. They are the premier method through which small, rocky exoplanets can be validated. Available for public use in early 2017, WIYNSPKL and GEMSPKL will obtain simultaneous images in two filters with fast EMCCD readout, "speckle" and “wide-field” imaging modes, and user support for proposal writing, observing, and data reduction. We describe the new cameras, their design, and their benefits for exoplanet follow-up, characterization, and validation. Funding for this project comes from the NASA Exoplanet Exploration Program and NASA HQ.

  5. Functional laser speckle imaging of cerebral blood flow under hypothermia

    Li, Minheng; Miao, Peng; Zhu, Yisheng; Tong, Shanbao

    2011-08-01

    Hypothermia can unintentionally occur in daily life, e.g., in cardiovascular surgery or applied as therapeutics in the neurosciences critical care unit. So far, the temperature-induced spatiotemporal responses of the neural function have not been fully understood. In this study, we investigated the functional change in cerebral blood flow (CBF), accompanied with neuronal activation, by laser speckle imaging (LSI) during hypothermia. Laser speckle images from Sprague-Dawley rats (n = 8, male) were acquired under normothermia (37°C) and moderate hypothermia (32°C). For each animal, 10 trials of electrical hindpaw stimulation were delivered under both temperatures. Using registered laser speckle contrast analysis and temporal clustering analysis (TCA), we found a delayed response peak and a prolonged response window under hypothermia. Hypothermia also decreased the activation area and the amplitude of the peak CBF. The combination of LSI and TCA is a high-resolution functional imaging method to investigate the spatiotemporal neurovascular coupling in both normal and pathological brain functions.

  6. Speckle lifetime in XAO coronagraphic images: temporal evolution of SPHERE coronagraphic images

    Milli, J; Mouill, D; Mawet, D; Girard, J G; Vigan, A; Boccaletti, A; Kasper, M; Wahhaj, Z; Lagrange, A -M; Beuzit, J -L; Fusco, T; Sauvage, J -F; Galicher, R

    2016-01-01

    The major source of noise in high-contrast imaging is the presence of slowly evolving speckles that do not average with time. The temporal stability of the point-spread-function (PSF) is therefore critical to reach a high contrast with extreme adaptive optics (xAO) instruments. Understanding on which timescales the PSF evolves and what are the critical parameters driving the speckle variability allow to design an optimal observing strategy and data reduction technique to calibrate instrumental aberrations and reveal faint astrophysical sources. We have obtained a series of 52 min, AO-corrected, coronagraphically occulted, high-cadence (1.6Hz), H-band images of the star HR 3484 with the SPHERE (Spectro-Polarimeter High-contrast Exoplanet REsearch instrument on the VLT. This is a unique data set from an xAO instrument to study its stability on timescales as short as one second and as long as several tens of minutes. We find different temporal regimes of decorrelation. We show that residuals from the atmospheric...

  7. A PDE based Method for Speckle Reduction of Log-compressed Ultrasound Image

    Jie Huang

    2011-04-01

    Full Text Available Speckle noise is widely existence in coherent imaging systems, such as synthetic aperture radar, sonar, ultrasound and laser imaging, and is commonly described as signal correlated. In this paper, we focus on speckle reduction problem in real ultrasound image. Unlike traditional anisotropic diffusion methods usually taking image gradient as a diffusion index, in this paper, we present a new texture based anisotropic diffusion method for speckle reduction in real ultrasound image. The results comparing our new method with other well known methods on both synthetic images and real ultrasound images are reported to show the superiority of our method in keeping important features of real ultrasound images.

  8. Nonlinear multiscale wavelet diffusion for speckle suppression and edge enhancement in ultrasound images.

    Yue, Yong; Croitoru, Mihai M; Bidani, Akhil; Zwischenberger, Joseph B; Clark, John W

    2006-03-01

    This paper introduces a novel nonlinear multiscale wavelet diffusion method for ultrasound speckle suppression and edge enhancement. This method is designed to utilize the favorable denoising properties of two frequently used techniques: the sparsity and multiresolution properties of the wavelet, and the iterative edge enhancement feature of nonlinear diffusion. With fully exploited knowledge of speckle image models, the edges of images are detected using normalized wavelet modulus. Relying on this feature, both the envelope-detected speckle image and the log-compressed ultrasonic image can be directly processed by the algorithm without need for additional preprocessing. Speckle is suppressed by employing the iterative multiscale diffusion on the wavelet coefficients. With a tuning diffusion threshold strategy, the proposed method can improve the image quality for both visualization and auto-segmentation applications. We validate our method using synthetic speckle images and real ultrasonic images. Performance improvement over other despeckling filters is quantified in terms of noise suppression and edge preservation indices. PMID:16524086

  9. Multiscale entropy study of medical laser speckle contrast images.

    Humeau-Heurtier, Anne; Mahé, Guillaume; Durand, Sylvain; Abraham, Pierre

    2013-03-01

    Laser speckle contrast imaging (LSCI) is a noninvasive full-field optical imaging technique that gives a 2-D microcirculatory blood flow map of tissue. Due to novelty of commercial laser speckle contrast imagers, image processing of LSCI data is new. By opposition, the numerous signal processing works of laser Doppler flowmetry (LDF) data-that give a 1-D view of microvascular blood flow-have led to interesting physiological information. Recently, analysis of multiscale entropy (MSE) of LDF signals has been proposed. A nonmonotonic evolution of MSE with two distinctive scales-probably dominated by the cardiac activity-has been reported. We herein analyze MSE of LSCI data. We compare LSCI results with the ones of LDF signals obtained during the same experiment. We show that when time evolution of LSCI single pixels is studied, MSE presents a monotonic decreasing pattern, similar to the one of Gaussian white noises. By opposition, when the mean of LSCI pixel values is computed in a region of interest (ROI) and followed with time, MSE pattern becomes close to the one of LDF data, for ROI large enough. LSCI is gaining increased interest for blood flow monitoring. The physiological implications of our results require future study. PMID:22868525

  10. Speckle reduction algorithm for laser underwater image based on curvelet transform

    Wei Ni; Baolong Guo; Liu Yang; Peiyan Fei

    2006-01-01

    @@ Based on the analysis on the statistical model of speckle noise in laser underwater image, a novel speckle reduction algorithm using curvelet transform is proposed. Logarithmic transform is performed to transform the original multiplicative speckle noise into additive noise. An improved hard thresholding algorithm is applied in curvelet transform domain. The classical Monte-Carlo method is adopted to estimate the statistics of contourlet coefficients for speckle noise, thus determining the optimal threshold set. To further improve the visual quality of despeckling laser image, the cycle spinning technique is also utilized. Experimental results show that the proposed algorithm can achieve better performance than classical wavelet method and maintain more detail information.

  11. Constructive role of sensors nonlinearities in the acquisition of partially polarized speckle images

    We study the impact of the level of the speckle noise on data acquisition in a partially polarized coherent imaging system with the presence of a nonlinearity in the imaging sensor characteristic. In perfectly linear acquisition conditions, due to the essentially multiplicative action of the speckle, the image contrast is unchanged as the speckle noise level increases, and so it has no impact on the quality of the acquired images. On the contrary, in nonlinear conditions the acquisition is affected by the speckle noise level. However, this effect of the speckle is not always detrimental. We show that, in definite nonlinear conditions, there is usually an optimal level of the speckle noise that leads to a maximum quality of the acquired images. We theoretically analyze such nonlinear regimes with partially polarized speckled images. We specifically exhibit the existence of an optimal speckle noise level in the interesting case of images realized only by a depolarization contrast. Illustrations are given with a simple 1-bit hard limiter and binary images. Then, we propose and discuss as perspectives an experimental optical setup to confront theory and experiment.

  12. Integration of speckle de-noising and image segmentation using synthetic aperture radar image for flood extent extraction

    J Senthilnath; Shenoy, Vikram H; Rajendra, Ritwik; Omkar, SN; Mani, V.; Diwakar, PG

    2013-01-01

    Flood is one of the detrimental hydro-meteorological threats to mankind. This compels very efficient flood assessment models. In this paper, we propose remote sensing based flood assessment using Synthetic Aperture Radar (SAR) image because of its imperviousness to unfavourable weather conditions. However, they suffer from the speckle noise. Hence, the processing of SAR image is applied in two stages: speckle removal filters and image segmentation methods for flood mapping. The speckle noise ...

  13. SPECKLE NOISE FILTERING FOR ULTRASOUND IMAGES OF COMMON CAROTID ARTERY: A REVIEW

    D. Sasikala; Madheswaran, M.

    2014-01-01

    Speckle is modeled as a signal dependent noise, which tends to reduce the image resolution and contrast, thereby reducing the diagnostic values of the ultrasound imaging modality. Reduction of speckle noise is one of the most important processes to increase the quality of biomedical images. Filters are used to improve the quality of ultrasound images by removing the noise. This paper compares the performance of the thresholding technique Bayes Shrink in despeckling the medical ultrasound imag...

  14. Experimental imaging coding system using three-dimensional subjective speckle structures

    We propose, and experimentally demonstrate, an optical encoding system employing a three-dimensional subjective speckle distribution as a secure information carrier. An image mask (containing the information to be sent) is illuminated by randomly distributed light. The outgoing wavefront reaches a lens, and thus three-dimensional subjective speckle distributions are generated in the normal direction of the scattering plane. These speckle structures are sampled by registering consecutive planes along the optical axis with a complementary metal-oxide semiconductor camera. Along with the optical parameters (keys), these intensity patterns are sent through independent channels to a receiver. By replicating the original system with the keys and implementing a single-beam multiple-intensity reconstruction, we show that the message recipient needs a minimum set of speckle images to successfully recover the original information. Moreover, intercepting a partial set of speckle images with the keys may not result in a successful interception. (paper)

  15. Experimental imaging coding system using three-dimensional subjective speckle structures

    Mosso, F.; Peters, E.; Bolognini, N.; Tebaldi, M.; Torroba, R.; Pérez, D. G.

    2013-12-01

    We propose, and experimentally demonstrate, an optical encoding system employing a three-dimensional subjective speckle distribution as a secure information carrier. An image mask (containing the information to be sent) is illuminated by randomly distributed light. The outgoing wavefront reaches a lens, and thus three-dimensional subjective speckle distributions are generated in the normal direction of the scattering plane. These speckle structures are sampled by registering consecutive planes along the optical axis with a complementary metal-oxide semiconductor camera. Along with the optical parameters (keys), these intensity patterns are sent through independent channels to a receiver. By replicating the original system with the keys and implementing a single-beam multiple-intensity reconstruction, we show that the message recipient needs a minimum set of speckle images to successfully recover the original information. Moreover, intercepting a partial set of speckle images with the keys may not result in a successful interception.

  16. Low-cost laser speckle contrast imaging of blood flow using a webcam

    Richards, Lisa M.; Kazmi, S. M. Shams; Davis, Janel L.; Olin, Katherine E.; Dunn, Andrew K.

    2013-01-01

    Laser speckle contrast imaging has become a widely used tool for dynamic imaging of blood flow, both in animal models and in the clinic. Typically, laser speckle contrast imaging is performed using scientific-grade instrumentation. However, due to recent advances in camera technology, these expensive components may not be necessary to produce accurate images. In this paper, we demonstrate that a consumer-grade webcam can be used to visualize changes in flow, both in a microfluidic flow phanto...

  17. DE-SPECKLING OF SAR IMAGES BASED ON OPTIMAL BASIS WAVELET VIA PATCH ORDERING

    Anakha Satheesh P*, Dr. D. Loganathan

    2016-01-01

    Synthetic Aperture Radar (SAR) technology has mainly used for capturing high quality images from higher altitudes. SAR imagery has become an important application over optical satellite imagery because of its ability to operate in any whether condition. The SAR image acquired via coherent imaging are associated with a noise called speckle noise, which is multiplicative in nature. The presence of speckle noise degrades the quality of SAR image then leads to loss of crucial information. So it h...

  18. Integration of image exposure time into a modified laser speckle imaging method

    Speckle-based methods have been developed to characterize tissue blood flow and perfusion. One such method, called modified laser speckle imaging (mLSI), enables computation of blood flow maps with relatively high spatial resolution. Although it is known that the sensitivity and noise in LSI measurements depend on image exposure time, a fundamental disadvantage of mLSI is that it does not take into account this parameter. In this work, we integrate the exposure time into the mLSI method and provide experimental support of our approach with measurements from an in vitro flow phantom.

  19. Fast multiscale directional filter bank-based speckle mitigation in gallstone ultrasound images.

    Leavline, Epiphany Jebamalar; Sutha, Shunmugam; Singh, Danasingh Asir Antony Gnana

    2014-02-01

    Speckle noise is a multiplicative type of noise commonly seen in medical and remote sensing images. It gives a granular appearance that degrades the quality of the recorded images. These speckle noise components need to be mitigated before the image is used for further processing and analysis. This paper presents a novel approach for removing granular speckle noise in gray scale images. We used an efficient multiscale image representation scheme named fast multiscale directional filter bank (FMDFB) along with simple threshold methods such as Vishushrink for image processing. It is a perfect reconstruction framework that can be used for a wide range of image processing applications because of its directionality and reduced computational complexity. The FMDFB-based speckle mitigation is appealing over other traditional multiscale approaches such as wavelets and Contourlets. Our experimental results show that the despeckling performance of the proposed method outperforms the wavelet and Contourlet-based despeckling methods. PMID:24562027

  20. System of acquisition and processing of images of dynamic speckle

    In this paper we show the design and implementation of a system to capture and analysis of dynamic speckle. The device consists of a USB camera, an isolated system lights for imaging, a laser pointer 633 nm 10 mw as coherent light source, a diffuser and a laptop for processing video. The equipment enables the acquisition and storage of video, also calculated of different descriptors of statistical analysis (vector global accumulation of activity, activity matrix accumulation, cross-correlation vector, autocorrelation coefficient, matrix Fujji etc.). The equipment is designed so that it can be taken directly to the site where the sample for biological study and is currently being used in research projects within the group

  1. System of acquisition and processing of images of dynamic speckle

    Vega, F.; >C Torres,

    2015-01-01

    In this paper we show the design and implementation of a system to capture and analysis of dynamic speckle. The device consists of a USB camera, an isolated system lights for imaging, a laser pointer 633 nm 10 mw as coherent light source, a diffuser and a laptop for processing video. The equipment enables the acquisition and storage of video, also calculated of different descriptors of statistical analysis (vector global accumulation of activity, activity matrix accumulation, cross-correlation vector, autocorrelation coefficient, matrix Fujji etc.). The equipment is designed so that it can be taken directly to the site where the sample for biological study and is currently being used in research projects within the group.

  2. Early diagnosis of teeth erosion using polarized laser speckle imaging

    Nader, Christelle Abou; Pellen, Fabrice; Loutfi, Hadi; Mansour, Rassoul; Jeune, Bernard Le; Brun, Guy Le; Abboud, Marie

    2016-07-01

    Dental erosion starts with a chemical attack on dental tissue causing tooth demineralization, altering the tooth structure and making it more sensitive to mechanical erosion. Medical diagnosis of dental erosion is commonly achieved through a visual inspection by the dentist during dental checkups and is therefore highly dependent on the operator's experience. The detection of this disease at preliminary stages is important since, once the damage is done, cares become more complicated. We investigate the difference in light-scattering properties between healthy and eroded teeth. A change in light-scattering properties is observed and a transition from volume to surface backscattering is detected by means of polarized laser speckle imaging as teeth undergo acid etching, suggesting an increase in enamel surface roughness.

  3. Early diagnosis of teeth erosion using polarized laser speckle imaging.

    Abou Nader, Christelle; Pellen, Fabrice; Loutfi, Hadi; Mansour, Rassoul; Le Jeune, Bernard; Le Brun, Guy; Abboud, Marie

    2016-07-01

    Dental erosion starts with a chemical attack on dental tissue causing tooth demineralization, altering the tooth structure and making it more sensitive to mechanical erosion. Medical diagnosis of dental erosion is commonly achieved through a visual inspection by the dentist during dental checkups and is therefore highly dependent on the operator's experience. The detection of this disease at preliminary stages is important since, once the damage is done, cares become more complicated. We investigate the difference in light-scattering properties between healthy and eroded teeth. A change in light-scattering properties is observed and a transition from volume to surface backscattering is detected by means of polarized laser speckle imaging as teeth undergo acid etching, suggesting an increase in enamel surface roughness. PMID:26720050

  4. Speckle reduction in optical coherence tomography imaging by affine-motion image registration

    Alonso-Caneiro, David; Read, Scott A.; Collins, Michael J.

    2011-11-01

    Signal-degrading speckle is one factor that can reduce the quality of optical coherence tomography images. We demonstrate the use of a hierarchical model-based motion estimation processing scheme based on an affine-motion model to reduce speckle in optical coherence tomography imaging, by image registration and the averaging of multiple B-scans. The proposed technique is evaluated against other methods available in the literature. The results from a set of retinal images show the benefit of the proposed technique, which provides an improvement in signal-to-noise ratio of the square root of the number of averaged images, leading to clearer visual information in the averaged image. The benefits of the proposed technique are also explored in the case of ocular anterior segment imaging.

  5. Lung vasculature imaging using speckle variance optical coherence tomography

    Cua, Michelle; Lee, Anthony M. D.; Lane, Pierre M.; McWilliams, Annette; Shaipanich, Tawimas; MacAulay, Calum E.; Yang, Victor X. D.; Lam, Stephen

    2012-02-01

    Architectural changes in and remodeling of the bronchial and pulmonary vasculature are important pathways in diseases such as asthma, chronic obstructive pulmonary disease (COPD), and lung cancer. However, there is a lack of methods that can find and examine small bronchial vasculature in vivo. Structural lung airway imaging using optical coherence tomography (OCT) has previously been shown to be of great utility in examining bronchial lesions during lung cancer screening under the guidance of autofluorescence bronchoscopy. Using a fiber optic endoscopic OCT probe, we acquire OCT images from in vivo human subjects. The side-looking, circumferentially-scanning probe is inserted down the instrument channel of a standard bronchoscope and manually guided to the imaging location. Multiple images are collected with the probe spinning proximally at 100Hz. Due to friction, the distal end of the probe does not spin perfectly synchronous with the proximal end, resulting in non-uniform rotational distortion (NURD) of the images. First, we apply a correction algorithm to remove NURD. We then use a speckle variance algorithm to identify vasculature. The initial data show a vascaulture density in small human airways similar to what would be expected.

  6. Simulations of multi-contrast x-ray imaging using near-field speckles

    Zdora, Marie-Christine [Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching (Germany); Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom and Department of Physics & Astronomy, University College London, London, WC1E 6BT (United Kingdom); Thibault, Pierre [Department of Physics & Astronomy, University College London, London, WC1E 6BT (United Kingdom); Herzen, Julia; Pfeiffer, Franz [Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching (Germany); Zanette, Irene [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE (United Kingdom); Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching (Germany)

    2016-01-28

    X-ray dark-field and phase-contrast imaging using near-field speckles is a novel technique that overcomes limitations inherent in conventional absorption x-ray imaging, i.e. poor contrast for features with similar density. Speckle-based imaging yields a wealth of information with a simple setup tolerant to polychromatic and divergent beams, and simple data acquisition and analysis procedures. Here, we present a simulation software used to model the image formation with the speckle-based technique, and we compare simulated results on a phantom sample with experimental synchrotron data. Thorough simulation of a speckle-based imaging experiment will help for better understanding and optimising the technique itself.

  7. Simulations of multi-contrast x-ray imaging using near-field speckles

    X-ray dark-field and phase-contrast imaging using near-field speckles is a novel technique that overcomes limitations inherent in conventional absorption x-ray imaging, i.e. poor contrast for features with similar density. Speckle-based imaging yields a wealth of information with a simple setup tolerant to polychromatic and divergent beams, and simple data acquisition and analysis procedures. Here, we present a simulation software used to model the image formation with the speckle-based technique, and we compare simulated results on a phantom sample with experimental synchrotron data. Thorough simulation of a speckle-based imaging experiment will help for better understanding and optimising the technique itself

  8. Fabrication and optimization of micro-scale speckle patterns for digital image correlation

    Experimental investigations are performed on the fabrication and optimization of micro-scale speckle patterns formed by spinning an epoxy resin and powder for digital image correlation measurements. New factors influencing the fabrication process, including the ambient temperature, centrifugal velocity, and solidifying time, are carefully analyzed and are evaluated in terms of the average gray gradient and particle agglomeration, and the optimal micro-scale speckle pattern is obtained with the proposed parameters in the fabrication process. Additionally, the micro-scale speckle pattern is experimentally verified by performing prescribed rigid-body translation tests, and the relative errors are approximately 1.5%. Finally, the micro-scale speckle patterns are transferred to tensile specimens of aluminum and a polymer material with a V notch. The measurement results are consistent with the theoretical predictions, and this agreement demonstrates the feasibility and accuracy of the micro-scale speckle patterns. (paper)

  9. Fabrication and optimization of micro-scale speckle patterns for digital image correlation

    Zhu, Jianguo; Yan, Gaoshen; He, Guanglong; Chen, Lei

    2016-01-01

    Experimental investigations are performed on the fabrication and optimization of micro-scale speckle patterns formed by spinning an epoxy resin and powder for digital image correlation measurements. New factors influencing the fabrication process, including the ambient temperature, centrifugal velocity, and solidifying time, are carefully analyzed and are evaluated in terms of the average gray gradient and particle agglomeration, and the optimal micro-scale speckle pattern is obtained with the proposed parameters in the fabrication process. Additionally, the micro-scale speckle pattern is experimentally verified by performing prescribed rigid-body translation tests, and the relative errors are approximately 1.5%. Finally, the micro-scale speckle patterns are transferred to tensile specimens of aluminum and a polymer material with a V notch. The measurement results are consistent with the theoretical predictions, and this agreement demonstrates the feasibility and accuracy of the micro-scale speckle patterns.

  10. On the origin of speckle in x-ray phase contrast images of lung tissue

    Phase contrast x-ray imaging of small animal lungs reveals a speckled intensity pattern not seen in other tissues, making the lungs highly visible in comparison to other organs. Although bearing a superficial resemblance to alveoli, the cause of this speckle has not been established. With a view to determining the mechanism for the formation of speckle, this paper details the results of propagation-based phase contrast experiments performed on mice lungs, together with packed glass microspheres used to emulate lung tissue. These experimental studies are compared to numerical simulations, based on wave propagation techniques. We find that speckle arises from focusing effects, with multiple alveoli acting as aberrated compound refractive lenses. Both experiments and modelling suggest that this speckle-formation phenomenon may lead to better screening methods for human lungs than conventional radiography

  11. On the origin of speckle in x-ray phase contrast images of lung tissue

    Kitchen, M J [Centre for X-ray Physics and Imaging, School of Physics and Materials Engineering, Monash University, VIC 3800 (Australia); Paganin, D [Centre for X-ray Physics and Imaging, School of Physics and Materials Engineering, Monash University, VIC 3800 (Australia); Lewis, R A [Centre for X-ray Physics and Imaging, School of Physics and Materials Engineering, Monash University, VIC 3800 (Australia); Yagi, N [SPring-8/JASRI, Mikazuki, Hyogo 679-5198 (Japan); Uesugi, K [SPring-8/JASRI, Mikazuki, Hyogo 679-5198 (Japan); Mudie, S T [Centre for X-ray Physics and Imaging, School of Physics and Materials Engineering, Monash University, VIC 3800 (Australia)

    2004-09-21

    Phase contrast x-ray imaging of small animal lungs reveals a speckled intensity pattern not seen in other tissues, making the lungs highly visible in comparison to other organs. Although bearing a superficial resemblance to alveoli, the cause of this speckle has not been established. With a view to determining the mechanism for the formation of speckle, this paper details the results of propagation-based phase contrast experiments performed on mice lungs, together with packed glass microspheres used to emulate lung tissue. These experimental studies are compared to numerical simulations, based on wave propagation techniques. We find that speckle arises from focusing effects, with multiple alveoli acting as aberrated compound refractive lenses. Both experiments and modelling suggest that this speckle-formation phenomenon may lead to better screening methods for human lungs than conventional radiography.

  12. Spatial sub-Rayleigh imaging analysis via speckle laser illumination

    Wang, Yunlong; Liu, Ruifeng; Chen, Dongxu; Gao, Hong; Zhang, Pei; Li, Fuli

    2016-01-01

    It is commonly accepted that optical sub-Rayleigh imaging has potential application in many fields. In this Letter, by confining the divergence of the optical field, as well as the size of the illumination source, we show that the first-order averaged intensity measurement via speckle laser illumina- tion can make an actual breakthrough on the Rayleigh limit. For a high-order algorithm, it has been reported that the autocorrelation function can be utilized to achieve the sub-Rayleigh feature. However, we find that this sub- Rayleigh feature for the high-order algorithm is limited only to binary objects, and the image will be distorted when a gray object is placed. This property encourages us to find the physics behind the high-order correlation imaging algo- rithm. We address these explanations in this Letter and find that for different types of high-order algorithm, there is always a seat in the right place from the cross-correlation function.

  13. Estimation of vessel diameter and blood flow dynamics from laser speckle images

    Postnov, Dmitry D.; Tuchin, Valery V.; Sosnovtseva, Olga

    2016-01-01

    Laser speckle imaging is a rapidly developing method to study changes of blood velocity in the vascular networks. However, to assess blood flow and vascular responses it is crucial to measure vessel diameter in addition to blood velocity dynamics. We suggest an algorithm that allows for dynamical...... masking of a vessel position and measurements of it's diameter from laser speckle images. This approach demonstrates high reliability and stability....

  14. Estimation of vessel diameter and blood flow dynamics from laser speckle images

    Postnov, Dmitry D.; Tuchin, Valery V.; Sosnovtseva, Olga

    2016-01-01

    Laser speckle imaging is a rapidly developing method to study changes of blood velocity in the vascular networks. However, to assess blood flow and vascular responses it is crucial to measure vessel diameter in addition to blood velocity dynamics. We suggest an algorithm that allows for dynamical masking of a vessel position and measurements of it’s diameter from laser speckle images. This approach demonstrates high reliability and stability.

  15. Fast blood flow visualization of high-resolution laser speckle imaging data using graphics processing unit.

    Liu, Shusen; Li, Pengcheng; Luo, Qingming

    2008-09-15

    Laser speckle contrast analysis (LASCA) is a non-invasive, full-field optical technique that produces two-dimensional map of blood flow in biological tissue by analyzing speckle images captured by CCD camera. Due to the heavy computation required for speckle contrast analysis, video frame rate visualization of blood flow which is essentially important for medical usage is hardly achieved for the high-resolution image data by using the CPU (Central Processing Unit) of an ordinary PC (Personal Computer). In this paper, we introduced GPU (Graphics Processing Unit) into our data processing framework of laser speckle contrast imaging to achieve fast and high-resolution blood flow visualization on PCs by exploiting the high floating-point processing power of commodity graphics hardware. By using GPU, a 12-60 fold performance enhancement is obtained in comparison to the optimized CPU implementations. PMID:18794967

  16. Ultrasound harmonic imaging with reducing speckle noise by spatial-frequency compounding approach

    Guo, Wei; Wang, Yuanyuan; Yu, Jinhua

    2015-12-01

    Speckle noise is a phenomenon inherent in any coherent imaging process and decreases the signal-to-noise ratio (SNR), which brings down the imaging quality. Speckle noise reduction is particularly important in the tissue harmonic imaging (THI) since it has the lower energy and the poorer SNR than the fundamental imaging (FI). Recently plane wave imaging (PWI) has been widely explored. Since the entire imaging region can be covered in one emission, the frame rate increases greatly. In PWI, speckle can be reduced by incoherently averaging images with different speckle patterns. Such images can be acquired by varying the angle from which a target is imaged (spatial compounding, SC) or by changing the spectrum of the pulse (frequency compounding, FC). In this paper we demonstrate here that each approach is only a partial solution and that combining them provides a better result than applying either approach separately. We propose a spatial-frequency compounding (SFC) method for THI. The new method brings a good speckle suppression result. To illustrate the performance of our method, experiments have been conducted on the simulated data. A nonlinear simulation platform based on the full-wave model is used in the harmonic imaging simulation. Results show that our method brings the SNR an improvement of up to 50% in comparison with the single frame HI while maintaining a far better performance in both terms of resolution and contrast than the FI. Similar results can be obtained from our further experiments.

  17. Modeling laser speckle imaging of perfusion in the skin (Conference Presentation)

    Regan, Caitlin; Hayakawa, Carole K.; Choi, Bernard

    2016-02-01

    Laser speckle imaging (LSI) enables visualization of relative blood flow and perfusion in the skin. It is frequently applied to monitor treatment of vascular malformations such as port wine stain birthmarks, and measure changes in perfusion due to peripheral vascular disease. We developed a computational Monte Carlo simulation of laser speckle contrast imaging to quantify how tissue optical properties, blood vessel depths and speeds, and tissue perfusion affect speckle contrast values originating from coherent excitation. The simulated tissue geometry consisted of multiple layers to simulate the skin, or incorporated an inclusion such as a vessel or tumor at different depths. Our simulation used a 30x30mm uniform flat light source to optically excite the region of interest in our sample to better mimic wide-field imaging. We used our model to simulate how dynamically scattered photons from a buried blood vessel affect speckle contrast at different lateral distances (0-1mm) away from the vessel, and how these speckle contrast changes vary with depth (0-1mm) and flow speed (0-10mm/s). We applied the model to simulate perfusion in the skin, and observed how different optical properties, such as epidermal melanin concentration (1%-50%) affected speckle contrast. We simulated perfusion during a systolic forearm occlusion and found that contrast decreased by 35% (exposure time = 10ms). Monte Carlo simulations of laser speckle contrast give us a tool to quantify what regions of the skin are probed with laser speckle imaging, and measure how the tissue optical properties and blood flow affect the resulting images.

  18. Improved quality of optical coherence tomography imaging of basal cell carcinomas using speckle reduction

    Mogensen, Mette; Jørgensen, Thomas Martini; Thrane, Lars;

    2010-01-01

    suggests a method for improving OCT image quality for skin cancer imaging. EXPERIMENTAL DESIGN: OCT is an optical imaging method analogous to ultrasound. Two basal cell carcinomas (BCC) were imaged using an OCT speckle reduction technique (SR-OCT) based on repeated scanning by altering the distance between...

  19. A theoretical analysis of the super-resolution capacity of imagers using speckle illuminations

    Idier, Jérôme; Liu, Penghuan; Allain, Marc; Bourguignon, Sébastien; Sentenac, Anne

    2015-01-01

    Speckle based imaging consists in forming a super-resolved reconstruction of an unknown object from low-resolution images obtained under random inhomogeneous illuminations (speckles). However, the origin of this super-resolution is unclear. In this work, we demonstrate that, under physically realistic conditions, the correlation of the data have a super-resolution power corresponding to the squaring of the imager point spread function. This theoretical result is important for many practical imaging systems such as acoustic and electromagnetic tomographies, fluorescence and photoacoustic microscopies or synthetic aperture radar imaging.

  20. In vivo small animal lung speckle imaging with a benchtop in-line XPC system

    Garson, A. B.; Gunsten, S.; Vasireddi, S.; Brody, S.; Anastasio, M. A.

    2016-04-01

    X-ray phase-contrast (XPC) images of mouse lungs were acquired in vivo with a benchtop XPC system employing a conventional microfocus source. A strong speckled intensity pattern was present in lung regions of the XPC radiographs, previously only observed in synchroton experiments and in situ benchtop studies. We showed how the texture characteristics of the speckle is influenced by the amount of air present in the lungs at different points in the breathing cycle.

  1. Laser speckle contrast imaging of cerebral blood flow in humans during neurosurgery: a pilot clinical study

    Parthasarathy, Ashwin B.; Weber, Erica L.; Richards, Lisa M.; Fox, Douglas J.; Dunn, Andrew K.

    2010-11-01

    Monitoring cerebral blood flow (CBF) during neurosurgery can provide important physiological information for a variety of surgical procedures. CBF measurements are important for assessing whether blood flow has returned to presurgical baseline levels and for assessing postsurgical tissue viability. Existing techniques for intraoperative monitoring of CBF based on magnetic resonance imaging are expensive and often impractical, while techniques such as indocyanine green angiography cannot produce quantitative measures of blood flow. Laser speckle contrast imaging (LSCI) is an optical technique that has been widely used to quantitatively image relative CBF in animal models in vivo. In a pilot clinical study, we adapted an existing neurosurgical operating microscope to obtain LSCI images in humans in real time during neurosurgery under baseline conditions and after bipolar cautery. Simultaneously recorded ECG waveforms from the patient were used to develop a filter that helped reduce measurement variabilities due to motion artifacts. Results from this study demonstrate the feasibility of using LSCI to obtain blood flow images during neurosurgeries and its capability to produce full field CBF image maps with excellent spatial resolution in real-time with minimal disruption to the surgical procedure.

  2. Three Dimensional Speckle Imaging Employing a Frequency-Locked Tunable Diode Laser

    Cannon, Bret D.; Bernacki, Bruce E.; Schiffern, John T.; Mendoza, Albert

    2015-09-01

    We describe a high accuracy frequency stepping method for a tunable diode laser to improve a three dimensional (3D) imaging approach based upon interferometric speckle imaging. The approach, modeled after Takeda, exploits tuning an illumination laser in frequency as speckle interferograms of the object (specklegrams) are acquired at each frequency in a Michelson interferometer. The resulting 3D hypercube of specklegrams encode spatial information in the x-y plane of each image with laser tuning arrayed along its z-axis. We present laboratory data of before and after results showing enhanced 3D imaging resulting from precise laser frequency control.

  3. Optimum exposure time for speckle imaging through the atmosphere using the bispectrum technique

    McCrae, Kimberley A.; Roggemann, Michael C.; Welsh, Byron M.

    1996-10-01

    Bispectrum speckle imaging uses the average of many short exposure frames to eliminate atmospheric effects on images. Unfortunately, objects are often dim, requiring longer exposure times to collect enough photons to reconstruct an image. We investigate this trade-off using a computer simulation to create image frames under various seeing conditions, then determine the exposure time that yields the highest signal-to-noise ratio for the unbiased speckle interferometry estimator and the lowest mean square error for the reconstructed phase. We have found that for low light levels and for high read noise cases the optimum exposure time is greater than one Greenwood coherence time.

  4. High-order correlation of non-Rayleigh speckle fields and its application in super-resolution imaging

    Zhang, Suzhen; Wang, Wei; Yu, Rong; Yang, Xiaoxue

    2016-05-01

    Classical correlation of Rayleigh speckle fields E(x) can only mimic second-order correlation in quantum imaging. Here, we propose a method to explore the high-order correlation of non-Rayleigh speckle fields E N (x) which shows a totally different property from the Rayleigh speckle fields. As a specific example, we illustrate and analyze in detail the third-order speckle scanning imaging which overcomes the diffraction barrier by a factor of \\sqrt{3} . The influences of diffractions in the illumination path and the detection path are also discussed. This investigation may pave the way for applications in super-resolution imaging.

  5. Speckle filtering of medical ultrasonic images using wavelet and guided filter.

    Zhang, Ju; Lin, Guangkuo; Wu, Lili; Cheng, Yun

    2016-02-01

    Speckle noise is an inherent yet ineffectual residual artifact in medical ultrasound images, which significantly degrades quality and restricts accuracy in automatic diagnostic techniques. Speckle reduction is therefore an important step prior to the analysis and processing of the ultrasound images. A new de-noising method based on an improved wavelet filter and guided filter is proposed in this paper. According to the characteristics of medical ultrasound images in the wavelet domain, an improved threshold function based on the universal wavelet threshold function is developed. The wavelet coefficients of speckle noise and noise-free signal are modeled as Rayleigh distribution and generalized Gaussian distribution respectively. The Bayesian maximum a posteriori estimation is applied to obtain a new wavelet shrinkage algorithm. The coefficients of the low frequency sub-band in the wavelet domain are filtered by guided filter. The filtered image is then obtained by using the inverse wavelet transformation. Experiments with the comparison of the other seven de-speckling filters are conducted. The results show that the proposed method not only has a strong de-speckling ability, but also keeps the image details, such as the edge of a lesion. PMID:26489484

  6. Assessment of incident intensity on laser speckle contrast imaging using a nematic liquid crystal spatial light modulator (Conference Presentation)

    Kirby, Mitchell A.; Khaksari, Kosar; Kirkpatrick, Sean J.

    2016-03-01

    In this work the effects of incident intensity and effective camera dynamic range on image acquisition of both frozen and time-averaged dynamic speckle patterns, and their effects on laser speckle contrast imaging are addressed. A nematic liquid crystal, phase-only, spatial light modulator (SLM) was employed to generate laser speckle in a controlled and repeatable fashion. By addressing the calculated spatial contrast of frozen and time-averaged dynamic speckle patterns imaged across a wide range of intensities, we present a description of optimum intensity characteristics that should be observed when using LSCI. The results indicate the importance of assessing the intensity of the signal quantized by the camera in LSCI. By analyzing intensity PDF's during image acquisition of speckle patterns used in LSCI, an optimum incident intensity can be detected when a single, polarized speckle frame displays the first order statistics characteristic of fully developed speckle. Our results indicate that there is a range of laser power densities where the ensuing imaged speckle exhibit optimum sensitivity to flow as well as relatively constant calculated contrast values. It is clear that at high intensities, high frequency information is lost due to camera saturation, resulting in a decrease in contrast. When imaging speckle at low intensity, there is a risk for loss of data during the digital quantization process. The results are presented in a generalized fashion, so they should be applicable to any LSCI system, regardless of incident laser power or camera depth.

  7. Bayesian-Based Speckle Suppression for SAR Image Using Contourlet Transform

    De-Xiang Zhang; Qing-Wei Gao; Xiao-Pei Wu

    2008-01-01

    A novel and efficient speckle noise reduction algorithm based on Bayesian contourlet shrinkage using contourlet transform is proposed. First, we show the sub-band decompositions of SAR images using contourlet transforms, which provides sparse representation at both spatial and directional resolutions. Then, a Bayesian contourlet shrinkage factor is applied to the decomposed data to estimate the best value for noise-free contourlet coefficients. Experimental results show that compared with conventional wavelet despeckling algorithm, the proposed algorithm can achieve an excellent balance between suppresses speckle effectively and preserves image details, and the significant information of original image like textures and contour details is well maintained.

  8. Multiresolution edge detection using enhanced fuzzy c-means clustering for ultrasound image speckle reduction

    Tsantis, Stavros [Department of Medical Physics, School of Medicine, University of Patras, Rion, GR 26504 (Greece); Spiliopoulos, Stavros; Karnabatidis, Dimitrios [Department of Radiology, School of Medicine, University of Patras, Rion, GR 26504 (Greece); Skouroliakou, Aikaterini [Department of Energy Technology Engineering, Technological Education Institute of Athens, Athens 12210 (Greece); Hazle, John D. [Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States); Kagadis, George C., E-mail: gkagad@gmail.com, E-mail: George.Kagadis@med.upatras.gr, E-mail: GKagadis@mdanderson.org [Department of Medical Physics, School of Medicine, University of Patras, Rion, GR 26504, Greece and Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States)

    2014-07-15

    Purpose: Speckle suppression in ultrasound (US) images of various anatomic structures via a novel speckle noise reduction algorithm. Methods: The proposed algorithm employs an enhanced fuzzy c-means (EFCM) clustering and multiresolution wavelet analysis to distinguish edges from speckle noise in US images. The edge detection procedure involves a coarse-to-fine strategy with spatial and interscale constraints so as to classify wavelet local maxima distribution at different frequency bands. As an outcome, an edge map across scales is derived whereas the wavelet coefficients that correspond to speckle are suppressed in the inverse wavelet transform acquiring the denoised US image. Results: A total of 34 thyroid, liver, and breast US examinations were performed on a Logiq 9 US system. Each of these images was subjected to the proposed EFCM algorithm and, for comparison, to commercial speckle reduction imaging (SRI) software and another well-known denoising approach, Pizurica's method. The quantification of the speckle suppression performance in the selected set of US images was carried out via Speckle Suppression Index (SSI) with results of 0.61, 0.71, and 0.73 for EFCM, SRI, and Pizurica's methods, respectively. Peak signal-to-noise ratios of 35.12, 33.95, and 29.78 and edge preservation indices of 0.94, 0.93, and 0.86 were found for the EFCM, SIR, and Pizurica's method, respectively, demonstrating that the proposed method achieves superior speckle reduction performance and edge preservation properties. Based on two independent radiologists’ qualitative evaluation the proposed method significantly improved image characteristics over standard baseline B mode images, and those processed with the Pizurica's method. Furthermore, it yielded results similar to those for SRI for breast and thyroid images significantly better results than SRI for liver imaging, thus improving diagnostic accuracy in both superficial and in-depth structures. Conclusions: A

  9. Speckle reduction in optical coherence tomography by two-step image registration

    Zhang, Hang; Li, Zhongliang; Wang, Xiangzhao; Zhang, Xiangyang

    2015-03-01

    The image quality of optical coherence tomography can be severely influenced by speckle noise (i.e., signal-degrading speckle). Averaging multiple B-scans can effectively suppress speckle noise. Because of sample motion, images subject to averaging must be aligned exactly. We propose a two-step image registration scheme that combines global and local registrations for speckle reduction by the averaging of multiple B-scans. The method begins with a global registration to compensate for overall motion, which is estimated based on the rigid transformation model involving translation and rotation. Then each A-scan is aligned by cross-correlation using a graph-based algorithm, followed by a pixel subdivision method to improve smoothness in local registration. The method does not rely on any information about the retinal layer boundaries. We have applied this method to the registration of macular optical coherence tomography images. The results show the reduction of speckle noise and the enhanced visualization of layer structures. A signal-to-noise ratio improvement of nearly the square root of the number of averaged B-scans and a contrast-to-noise ratio improvement of around 11 are achieved through our method.

  10. Evaluating multi-exposure speckle imaging estimates of absolute autocorrelation times.

    Kazmi, S M Shams; Wu, Rebecca K; Dunn, Andrew K

    2015-08-01

    Multi-exposure speckle imaging (MESI) is a camera-based flow-imaging technique for quantitative blood-flow monitoring by mapping the speckle-contrast dependence on camera exposure duration. The ability of laser speckle contrast imaging to measure the temporal dynamics of backscattered and interfering coherent fields, in terms of the accuracy of autocorrelation measurements, is a major unresolved issue in quantitative speckle flowmetry. MESI fits for a number of parameters including an estimate of the electric field autocorrelation decay time from the imaged speckles. We compare the MESI-determined correlation times in vitro and in vivo with accepted true values from direct temporal measurements acquired with a photon-counting photon-multiplier tube and an autocorrelator board. The correlation times estimated by MESI in vivo remain on average within 14±11% of those obtained from direct temporal autocorrelation measurements, demonstrating that MESI yields highly comparable statistics of the time-varying fields that can be useful for applications seeking not only quantitative blood flow dynamics but also absolute perfusion. PMID:26258378

  11. A Study of Speckle Noise Reduction Filters

    Jyoti Jaybhay

    2015-06-01

    Full Text Available Ultrasound images and SAR i.e. synthetic aperture radar images are usually corrupted because of speckle noise also called as granular noise. It is quite a tedious task to remove such noise and analyze those corrupted images. Till now many researchers worked to remove speckle noise using frequency domain methods, temporal methods, and adaptive methods. Different filters have been developed as Mean and Median filters, Statistic Lee filter, Statistic Kuan filter, Frost filter, Srad filter. This paper reviews filters used to remove speckle noise.

  12. Speckle suppression in digital holographic imaging with random phases and different wavelengths

    Leng, Junmin; Sang, Xinzhu; Yan, Binbin

    2014-03-01

    An effective speckle suppression method in digital holography is experimentally demonstrated with a wavelength-tunable coherent light source and a moving diffuser. Multiple off-axis digital holograms with different wavelengths and random phases are obtained. The Fresnel transformation algorithm is used to calculate the diffraction integral in the reconstruction. The speckle noise in the reconstructed images is suppressed by superposing and averaging the intensity of multiple reconstruction images. Experiment results and the parameter evaluation show that the presented method is effective and feasible.

  13. Probabilistic graphical modeling of speckle statistics in laser speckle contrast imaging for noninvasive and label-free retinal angiography.

    Basak, Kausik; Dey, Goutam; Sheet, Debdoot; Mahadevappa, Manjunatha; Mandal, Mahitosh; Dutta, Pranab K

    2015-08-01

    This paper introduces a noninvasive and label-free approach for retinal angiography using Laser speckle contrast imaging (LSCI). Retinal vessel structure is segmented using a Hidden Markov Random Field (HMRF) based model. Prior to that, k-means clustering is used to obtain initial parameter set and labels for HMRF. Final parameter set for HMRF is estimated using expectation-maximization (EM) algorithm and final labeling is achieved using maximum aposteriori (MAP) algorithm. Clique energy for HMRF is computed from eigenvalue analysis of structure tensor for each pixel. This helps to get connectivity in the direction of strongest tangents in its neighborhood, facilitating the tracking of fine vessels in retinal vascular network. Quantitative evaluation shows an average vessel segmentation accuracy of 96.41% in normal condition with substantial improvement in tracking capability of fine vessels. Changes in blood flow can be tracked and observed at segmented output; particularly applicable for the study of different pathological conditions. PMID:26737719

  14. The influence of hologram aperture on speckle noise in the reconstructed image of digital holography and its reduction

    Cai, Xiao-ou; Wang, Hui

    2008-01-01

    Based on the whole process of the recording and reconstruction of digital holography, we study the formation cause of speckle noise in its reconstructed image and acquire the conclusion that the small size of hologram aperture diffraction aggravates the speckle noise of reconstructed image and the speckle noise has been one of primary noise sources in the reconstruction process. In order to reduce the speckle noise resulting from little hologram aperture diffraction, we set an appropriate aperture function matching the recording parameter and aperture size of hologram and deconvolve the reconstructed image with it. The validity has been proved in theory and experiment. Therefore, it offers a brand-new thought and practical way to reduce the speckle noise in the reconstructed image of digital holography.

  15. Probability-based non-local means filter for speckle noise suppression in optical coherence tomography images.

    Yu, Hancheng; Gao, Jianlin; Li, Aiting

    2016-03-01

    In this Letter, a probability-based non-local means filter is proposed for speckle reduction in optical coherence tomography (OCT). Originally developed for additive white Gaussian noise, the non-local means filter is not suitable for multiplicative speckle noise suppression. This Letter presents a two-stage non-local means algorithm using the uncorrupted probability of each pixel to effectively reduce speckle noise in OCT. Experiments on real OCT images demonstrate that the proposed filter is competitive with other state-of-the-art speckle removal techniques and able to accurately preserve edges and structural details with small computational cost. PMID:26974099

  16. New speckle analysis algorithm for flow visualization in optical coherence tomography images

    De Pretto, Lucas R.; Nogueira, Gesse E. C.; Freitas, Anderson Z.

    2015-06-01

    Optical Coherence Tomography (OCT) is a noninvasive technique capable of generating in vivo high-resolution images. However, OCT images are degraded by a granular and random noise called speckle. Nevertheless, such a noise may be used to gather information regarding the sample, as is exploited by techniques like Speckle Variance - OCT (SV-OCT). SV-OCT is widely used in the literature, but the variance calculation is computationally expensive. Therefore, we propose a new algorithm to employ speckle in identifying flow based on the evaluation of intensity fluctuation between two consecutively acquired OCT images. Our results were compared to those obtained by traditional method of Speckle Variance to demonstrate the feasibility of the technique. Both algorithms were applied to series of OCT images from a microchannel flow phantom, as well as from a biological tissue with blood flow. The results obtained by our method are in good agreement with those from SV-OCT. We've also analyzed the performance of both algorithms, registering the processing time and memory use. Our method performed 31% faster with the same use of memory. Therefore, we demonstrated a new method to map flow on OCT images.

  17. Speckle reduction approach for breast ultrasound image and its application to breast cancer diagnosis

    Objectives: To retrospectively evaluate the effects of a speckle reduction algorithm on radiologists' diagnosis of malignant and benign breast lesions on ultrasound (US) images. Methods: Using a database of 603 breast (US) images of 211 cases (109 benign lesions and 102 malignant ones), the original and speckle-reduced images were assessed by five radiologists and final assessment categories were assigned to indicate the probability of malignancy according to BI-RADS-US. The diagnostic sensitivity and specificity were investigated by the areas (Az) under the receiver operating characteristic (ROC) curves. Results: The sensitivity and specificity of breast lesions on Ultrasound images improved from 88.7% to 94.3%, from 68.6% to 75.2%, respectively, and the area (Az) under ROC curve of diagnosis also increased from 0.843 to 0.939, Z = 4.969, there were significant differences in the Az between the original breast lesions and speckle-reduced ones on Ultrasound images (P < 0.001). The diagnostic accuracy of breast lesions had been highly improved from 78.67% to 92.73% after employing this algorithm. Conclusions: The results demonstrate the promising performance of the proposed speckle reduction algorithm in distinguishing malignant from benign breast lesions which will be useful for breast cancer diagnosis.

  18. Visualization of perfusion changes with laser speckle contrast imaging using the method of motion history image.

    Ansari, Mohammad Zaheer; Humeau-Heurtier, Anne; Offenhauser, Nikolas; Dreier, Jens P; Nirala, Anil Kumar

    2016-09-01

    Laser speckle contrast imaging (LSCI) is a real-time imaging modality reflecting microvascular perfusion. We report on the application of the motion history image (MHI) method on LSCI data obtained from the two hemispheres of a mouse. Through the generation of a single image, MHI stresses the microvascular perfusion changes. Our experimental results performed during a pinprick-triggered spreading depolarization demonstrate the effectiveness of MHI: MHI allows the visualization of perfusion changes without loss of resolution and definition. Moreover, MHI provides close results to the ones given by the generalized differences (GD) algorithm. However, MHI has the advantage of giving information on the temporal evolution of the perfusion variations, which GD does not. PMID:27321386

  19. Laser speckle contrast imaging for monitoring changes in microvascular blood flow

    Ambrus, Rikard; Strandby, Rune B.; Svendsen, Lars Bo;

    2016-01-01

    BACKGROUND/AIMS: Microvascular blood flow is essential for healing and predicts surgical outcome. The aim of the current study was to investigate the relation between fluxes measured with the laser speckle contrast imaging (LSCI) technique and changes in absolute blood flow. In addition, we studied...

  20. Intraoperative laser speckle contrast imaging for monitoring cerebral blood flow: results from a 10-patient pilot study

    Richards, Lisa M.; Weber, Erica L.; Parthasarathy, Ashwin B.; Kappeler, Kaelyn L.; Fox, Douglas J.; Dunn, Andrew K.

    2012-02-01

    Monitoring cerebral blood flow (CBF) during neurosurgery can provide important physiological information for a variety of surgical procedures. Although multiple intraoperative vascular monitoring technologies are currently available, a quantitative method that allows for continuous monitoring is still needed. Laser speckle contrast imaging (LSCI) is an optical imaging method with high spatial and temporal resolution that has been widely used to image CBF in animal models in vivo. In this pilot clinical study, we adapted a Zeiss OPMI Pentero neurosurgical microscope to obtain LSCI images by attaching a camera and a laser diode. This LSCI adapted instrument has been used to acquire full field flow images from 10 patients during tumor resection procedures. The patient's ECG was recorded during acquisition and image registration was performed in post-processing to account for pulsatile motion artifacts. Digital photographs confirmed alignment of vasculature and flow images in four cases, and a relative change in blood flow was observed in two patients after bipolar cautery. The LSCI adapted instrument has the capability to produce real-time, full field CBF image maps with excellent spatial resolution and minimal intervention to the surgical procedure. Results from this study demonstrate the feasibility of using LSCI to monitor blood flow during neurosurgery.

  1. In vivo laser speckle imaging reveals microvascular remodeling and hemodynamic changes during wound healing angiogenesis

    Rege, Abhishek; Thakor, Nitish V; Rhie, Kevin; Pathak, Arvind P.

    2011-01-01

    Laser speckle contrast imaging (LSCI) is a high-resolution and high contrast optical imaging technique often used to characterize hemodynamic changes in short-term physiological experiments. In this study, we demonstrate the utility of LSCI for characterizing microvascular remodeling and hemodynamic changes during wound healing angiogenesis in vivo. A 2 mm diameter hole was made in the mouse ear and the periphery of the wound imaged in vivo using LSCI over 12 days. We were able to visualize a...

  2. Myocardial Strain and Strain Rate Imaging: Comparison between Doppler Derived Strain Imaging and Speckle Tracking Echocardiography

    Anita Sadeghpour

    2013-05-01

    Full Text Available Regional myocardial function has been traditionally assessed by visual estimation (1. Echocardiographic strain imaging which is known as deformation imaging, has been emerged as a quantitative technique to accurately estimate regional myocardial function and contractility. Currently, strain imaging has been regarded as a research tool in the most echocardiography laboratories. However, in recent years, strain imaging has gain momentum in daily clinical practice (2. The following two techniques have dominated the research arena of echocardiography: (1 Doppler based tissue velocity measurements, frequently referred to tissue Doppler or myocardial Doppler, and (2 speckle tracking on the basis of displacement measurements (3. Over the past two decades, Tissue Doppler Imaging (TDI and Doppler –derived strain (S and strain rate (SR imaging were introduced to quantify regional myocardial function. However, Doppler–derived strain variables faced criticisms, with regard to the angle dependency, noise interference, and substantial intraobserver and interobserver variability. The angle dependency is the major weakness of Doppler based methodology; however, it has the advantage of online measurements of velocities and time intervals with excellent temporal resolution, which is essential for the assessment of ischemia (4. Speckle-tracking echocardiography (STE or Non Doppler 2D strain echocardiography is a relatively new, largely angle-independent technique that analyzes motion by tracking natural acoustic reflections and interference patterns within an ultrasonic window. The image-processing algorithm tracks elements with approximately 20 to 40 pixels containing stable patterns and are described as ‘‘speckles’’ or ‘‘fingerprints’’. The speckles seen in grayscale B-mode (2D images are tracked consecutively frame to frame (5, 6. Assessment of 2D strain by STE is a semiautomatic method that requires definition of the myocardium

  3. Modelling laser speckle photographs of decayed teeth by applying a digital image information technique

    Ansari, M. Z.; da Silva, L. C.; da Silva, J. V. P.; Deana, A. M.

    2016-09-01

    We report on the application of a digital image model to assess early carious lesions on teeth. When decay is in its early stages, the lesions were illuminated with a laser and the laser speckle images were obtained. Due to the differences in the optical properties between healthy and carious tissue, both regions produced different scatter patterns. The digital image information technique allowed us to produce colour-coded 3D surface plots of the intensity information in the speckle images, where the height (on the z-axis) and the colour in the rendering correlate with the intensity of a pixel in the image. The quantitative changes in colour component density enhance the contrast between the decayed and sound tissue, and visualization of the carious lesions become significantly evident. Therefore, the proposed technique may be adopted in the early diagnosis of carious lesions.

  4. Comparison of laser Doppler and laser speckle contrast imaging using a concurrent processing system

    Sun, Shen; Hayes-Gill, Barrie R.; He, Diwei; Zhu, Yiqun; Huynh, Nam T.; Morgan, Stephen P.

    2016-08-01

    Full field laser Doppler imaging (LDI) and single exposure laser speckle contrast imaging (LSCI) are directly compared using a novel instrument which can concurrently image blood flow using both LDI and LSCI signal processing. Incorporating a commercial CMOS camera chip and a field programmable gate array (FPGA) the flow images of LDI and the contrast maps of LSCI are simultaneously processed by utilizing the same detected optical signals. The comparison was carried out by imaging a rotating diffuser. LDI has a linear response to the velocity. In contrast, LSCI is exposure time dependent and does not provide a linear response in the presence of static speckle. It is also demonstrated that the relationship between LDI and LSCI can be related through a power law which depends on the exposure time of LSCI.

  5. Assessing spatial resolution versus sensitivity from laser speckle contrast imaging: application to frequency analysis.

    Bricq, Stéphanie; Mahé, Guillaume; Rousseau, David; Humeau-Heurtier, Anne; Chapeau-Blondeau, François; Varela, Julio Rojas; Abraham, Pierre

    2012-10-01

    For blood perfusion monitoring, laser speckle contrast (LSC) imaging is a recent non-contact technique that has the characteristic of delivering noise-like speckled images. To exploit LSC images for quantitative physiological measurements, we developed an approach that implements controlled spatial averaging to reduce the detrimental impact of the noise and improve measurement sensitivity. By this approach, spatial resolution and measurement sensitivity can be traded-off in a flexible way depending on the quantitative prospect of the study. As an application, detectability of the cardiac activity from LSC images of forearm using power spectrum analysis is studied through the construction of spatial activity maps offering a window on the blood flow perfusion and its regional distribution. Comparisons with results obtained with signals of laser Doppler flowmetry probes are performed. PMID:22644256

  6. Speckle reduction for medical ultrasound images with an expectation-maximization framework

    HOU Tao; WANG Yuanyuan; GUO Yi

    2011-01-01

    In view of inherent speckle noise in medical images, a speckle reduction method was proposed based on an expectation-maximization (EM) framework. First, the real component of the in-phase/quadrature (I/Q) ultrasound image is extracted. Then, it is used to blindly estimate the point spread function (PSF) of the imaging system. Finally, based on the EM framework, an iterative algorithm alternating between the Wiener Filter and the anisotropic diffusion (AD) is exploited to produce despeckled images. The comparison experiment is carried out on both simulated and in vivo ultrasound images. It is shown that, with respect to the I/Q image, the proposed method averagely improves the speckle-signal-to-noise ratio (S-SNR) and the edge preservation index (β) of images by the factor of 1.94 and 7.52. Meanwhile, it averagely reduces the normalized mean-squared error (NMSE) by the factor of 3.95. The simulation and in vivo results indicates that the proposed method has a better overall performance than exited ones.

  7. Reconstruction of static line images with reduced speckle using interlaced holograms for holographic laser cutting

    Lee, Hwihyeong; Park, Sangwoo; Jeon, Byoung Goo; Kong, Hong Jin

    2016-07-01

    A hologram can be used for high-power laser processing applications such as cutting, drilling, patterning, or welding. However, not much progress has been made in cutting application compared to the others, because it requires optical reconstruction of static and uniform line images using holograms which have a high damage threshold. These static and uniform line images are difficult to be reconstructed with a single hologram, since they usually suffer from speckle between neighboring spots. We propose a method to reconstruct reduced-speckle static line images using two interlaced holograms which reconstruct odd and even pixel line images, corresponding to two orthogonal polarizations. Then, the two orthogonally polarized line images are superposed for interlacing in the image plane. The proposed method was studied by numerical simulations and demonstrated experimentally. The experimental results show that speckle contrast decreased by about one-third, compared to that of a non-interlaced hologram. This method can be applied also for complex-shaped images which include curved lines as well as straight lines, and we have a plan for laser cutting with this method in the near future.

  8. Microvascular blood flow monitoring with laser speckle contrast imaging using the generalized differences algorithm

    Humeau-Heurtier, Anne; Mahé, Guillaume; Abraham, Pierre

    2015-01-01

    Laser speckle contrast imaging (LSCI) is a full-field optical technique to monitor microvascular blood flow with high spatial and temporal resolutions. It is used in many medical fields such as dermatology, vascular medicine, or neurosciences. However, LSCI leads to a large amount of data: image sampling frequency is often of several Hz and recordings usually last several minutes. Therefore, clinicians often perform regions of interest in which a spatial averaging of blood flow is performed a...

  9. SPECKLE NOISE FILTERING FOR ULTRASOUND IMAGES OF COMMON CAROTID ARTERY: A REVIEW

    D. Sasikala

    2014-05-01

    Full Text Available Speckle is modeled as a signal dependent noise, which tends to reduce the image resolution and contrast, thereby reducing the diagnostic values of the ultrasound imaging modality. Reduction of speckle noise is one of the most important processes to increase the quality of biomedical images. Filters are used to improve the quality of ultrasound images by removing the noise. This paper compares the performance of the thresholding technique Bayes Shrink in despeckling the medical ultrasound images with other classical speckle reduction filters like Lee, Frost, Median, Kaun, Wavelet Bayes, Anisotropic diffusion and Wavelet. The performance of these filters is analyzed by the statistical measures such as Peak Signal-to Noise Ratio, Mean Square Error and Equivalent Number of Looks. To produce a better quality resolution picture, the filter should have high Peak Signal to Noise Ratio, low Mean Square Error, high Equivalent Number of Looks. The results obtained are presented in the form of filtered images, statistical tables and graphs. Finally, the best filter has been recommended based on the statistical and experimental results. From the results obtained Lee and Frost filter outperforms the other mentioned filters in terms of high PSNR and low MSE for high variance of noise where as anisotropic diffusion filter outperforms with high PSNR and low MSE with maximum ENL for low variance values of noise.

  10. Analysis of speckle patterns in phase-contrast images of lung tissue

    Kitchen, M. J.; Paganin, D.; Lewis, R. A.; Yagi, N.; Uesugi, K.

    2005-08-01

    Propagation-based phase-contrast images of mice lungs have been obtained at the SPring-8 synchrotron research facility. Such images exhibit a speckled intensity pattern that bears a superficial resemblance to alveolar structures. This speckle results from focussing effects as projected air-filled alveoli form aberrated compound refractive lenses. An appropriate phase-retrieval algorithm has been utilized to reconstruct the approximate projected lung tissue thickness from single-phase-contrast mice chest radiographs. The results show projected density variations across the lung, highlighting regions of low density corresponding to air-filled regions. Potentially, this offers a better method than conventional radiography for detecting lung diseases such as fibrosis, emphysema and cancer, though this has yet to be demonstrated. As such, the approach can assist in continuing studies of lung function utilizing propagation-based phase-contrast imaging.

  11. Analysis of speckle patterns in phase-contrast images of lung tissue

    Kitchen, M.J. [School of Physics and Materials Engineering, Monash University, Victoria 3800 (Australia)]. E-mail: Marcus.Kitchen@spme.monash.edu.au; Paganin, D. [School of Physics and Materials Engineering, Monash University, Victoria 3800 (Australia); Lewis, R.A. [School of Physics and Materials Engineering, Monash University, Victoria 3800 (Australia); Yagi, N. [Japan Synchrotron Radiation Research Institute (JASRI), SPring-8, Hyogo 679-5198 (Japan); Uesugi, K. [Japan Synchrotron Radiation Research Institute (JASRI), SPring-8, Hyogo 679-5198 (Japan)

    2005-08-11

    Propagation-based phase-contrast images of mice lungs have been obtained at the SPring-8 synchrotron research facility. Such images exhibit a speckled intensity pattern that bears a superficial resemblance to alveolar structures. This speckle results from focussing effects as projected air-filled alveoli form aberrated compound refractive lenses. An appropriate phase-retrieval algorithm has been utilized to reconstruct the approximate projected lung tissue thickness from single-phase-contrast mice chest radiographs. The results show projected density variations across the lung, highlighting regions of low density corresponding to air-filled regions. Potentially, this offers a better method than conventional radiography for detecting lung diseases such as fibrosis, emphysema and cancer, though this has yet to be demonstrated. As such, the approach can assist in continuing studies of lung function utilizing propagation-based phase-contrast imaging.

  12. Integration of speckle de-noising and image segmentation using Synthetic Aperture Radar image for flood extent extraction

    J Senthilnath; H Vikram Shenoy; Ritwik Rajendra; S N Omkar; V Mani; P G Diwakar

    2013-06-01

    Flood is one of the detrimental hydro-meteorological threats to mankind. This compels very efficient flood assessment models. In this paper, we propose remote sensing based flood assessment using Synthetic Aperture Radar (SAR) image because of its imperviousness to unfavourable weather conditions. However, they suffer from the speckle noise. Hence, the processing of SAR image is applied in two stages: speckle removal filters and image segmentation methods for flood mapping. The speckle noise has been reduced with the help of Lee, Frost and Gamma MAP filters. A performance comparison of these speckle removal filters is presented. From the results obtained, we deduce that the Gamma MAP is reliable. The selected Gamma MAP filtered image is segmented using Gray Level Co-occurrence Matrix (GLCM) and Mean Shift Segmentation (MSS). The GLCM is a texture analysis method that separates the image pixels into water and non-water groups based on their spectral feature whereas MSS is a gradient ascent method, here segmentation is carried out using spectral and spatial information. As test case, Kosi river flood is considered in our study. From the segmentation result of both these methods are comprehensively analysed and concluded that the MSS is efficient for flood mapping.

  13. Elasticity imaging of speckle-free tissue regions with moving acoustic radiation force and phase-sensitive optical coherence tomography

    Hsieh, Bao-Yu; Song, Shaozhen; Nguyen, Thu-Mai; Yoon, Soon Joon; Shen, Tueng; Wang, Ruikang; O'Donnell, Matthew

    2016-03-01

    Phase-sensitive optical coherence tomography (PhS-OCT) can be utilized for quantitative shear-wave elastography using speckle tracking. However, current approaches cannot directly reconstruct elastic properties in speckle-less or speckle-free regions, for example within the crystalline lens in ophthalmology. Investigating the elasticity of the crystalline lens could improve understanding and help manage presbyopia-related pathologies that change biomechanical properties. We propose to reconstruct the elastic properties in speckle-less regions by sequentially launching shear waves with moving acoustic radiation force (mARF), and then detecting the displacement at a specific speckle-generating position, or limited set of positions, with PhS-OCT. A linear ultrasound array (with a center frequency of 5 MHz) interfaced with a programmable imaging system was designed to launch shear waves by mARF. Acoustic sources were electronically translated to launch shear waves at laterally shifted positions, where displacements were detected by speckle tracking images produced by PhS-OCT operating in M-B mode with a 125-kHz A-line rate. Local displacements were calculated and stitched together sequentially based on the distance between the acoustic source and the detection beam. Shear wave speed, and the associated elasticity map, were then reconstructed based on a time-of-flight algorithm. In this study, moving-source shear wave elasticity imaging (SWEI) can highlight a stiff inclusion within an otherwise homogeneous phantom but with a CNR increased by 3.15 dB compared to a similar image reconstructed with moving-detector SWEI. Partial speckle-free phantoms were also investigated to demonstrate that the moving-source sequence could reconstruct the elastic properties of speckle-free regions. Results show that harder inclusions within the speckle-free region can be detected, suggesting that this imaging method may be able to detect the elastic properties of the crystalline lens.

  14. Adaptive Image Denoising by Mixture Adaptation.

    Luo, Enming; Chan, Stanley H; Nguyen, Truong Q

    2016-10-01

    We propose an adaptive learning procedure to learn patch-based image priors for image denoising. The new algorithm, called the expectation-maximization (EM) adaptation, takes a generic prior learned from a generic external database and adapts it to the noisy image to generate a specific prior. Different from existing methods that combine internal and external statistics in ad hoc ways, the proposed algorithm is rigorously derived from a Bayesian hyper-prior perspective. There are two contributions of this paper. First, we provide full derivation of the EM adaptation algorithm and demonstrate methods to improve the computational complexity. Second, in the absence of the latent clean image, we show how EM adaptation can be modified based on pre-filtering. The experimental results show that the proposed adaptation algorithm yields consistently better denoising results than the one without adaptation and is superior to several state-of-the-art algorithms. PMID:27416593

  15. Ear swelling test by using laser speckle imaging with a long exposure time

    Kalchenko, Vyacheslav; Kuznetsov, Yuri; Preise, Dina; Meglinski, Igor; Harmelin, Alon

    2014-06-01

    Laser speckle imaging with long exposure time has been applied noninvasively to visualize the immediate reaction of cutaneous vessels in mice in response to a known primary irritant and potential allergen-methyl salicylate. The compound has been used topically on the surface of the pinna and the reaction of the vascular network was examined. We demonstrate that irritant-induced acute vascular reaction can be effectively and accurately detected by laser speckle imaging technique. The current approach holds a great promise for application in routine screening of the cutaneous vascular response induced by contact agents, screenings of mouse ear swelling test, and testing the allergenic potential of new synthetic materials and healthcare pharmaceutical products.

  16. Low-spatial-coherence broadband fiber source for speckle free imaging

    Redding, Brandon; Mokan, Vadim; Seifert, Martin; Choma, Michael A; Cao, Hui

    2015-01-01

    We designed and demonstrate a fiber-based amplified spontaneous emission (ASE) source with low spatial coherence, low temporal coherence, and high power per mode. ASE is produced by optically pumping a large gain core multimode fiber while minimizing optical feedback to avoid lasing. The fiber ASE source provides 270 mW of continuous wave emission, centered at {\\lambda}=1055 nm with a full-width half-maximum bandwidth of 74 nm. The emission is distributed among as many as ~70 spatial modes, enabling efficient speckle suppression when combined with spectral compounding. Finally, we demonstrate speckle-free full field imaging using the fiber ASE source. The fiber ASE source provides a unique combination of high power per mode with both low spatial and low temporal coherence, making it an ideal source for full-field imaging and ranging applications.

  17. Probing depth and dynamic response of speckles in near infrared region for spectroscopic blood flow imaging

    Yokoi, Naomichi; Aizu, Yoshihisa

    2016-04-01

    Imaging method based on bio-speckles is a useful means for blood flow visualization of living bodies and, it has been utilized for analyzing the condition or the health state of living bodies. Actually, the sensitivity of blood flow is influenced by tissue optical properties, which depend on the wavelength of illuminating laser light. In the present study, we experimentally investigate characteristics of the blood flow images obtained with two wavelengths of 780 nm and 830 nm in the near-infrared region. Experiments are conducted for sample models using a pork layer, horse blood layer and mirror, and for a human wrist and finger, to investigate optical penetration depth and dynamic response of speckles to the blood flow velocity for two wavelengths.

  18. Strain Imaging: The Emergence of Speckle Tracking Echocardiography into Clinical Pediatric Cardiology.

    Colquitt, John L; Pignatelli, Ricardo H

    2016-01-01

    Speckle tracking echocardiography measures myocardial strain and allows for the quantification of regional and global left and right ventricular function. A growing body of literature is supporting its transition from research into clinical practice. This article aims to provide a practical review of strain imaging as it applies to congenital and pediatric heart disease, with the goals of increasing literacy and advocating for greater clinical integration. PMID:26879728

  19. Speckle noise reduction in ultrasound biomedical B-scan images using discrete topological derivative.

    Damodaran, Nedumaran; Ramamurthy, Sivakumar; Velusamy, Sekar; Manickam, Gayathri Kanakaraj

    2012-02-01

    Over three decades, several despeckling techniques have been developed by researchers to reduce the speckle noise inherently present in ultrasound B-scan images without losing the diagnostic information. The topological derivative (TD) is the recently adopted technique in the area of biomedical image processing. In this work, we computed the topological derivative for an appropriate function associated to the ultrasound B-scan image gradient by assigning a diffusion factor k, which indicates the cost endowed to that particular image. In this article, a novel image denoising approach, called discrete topological derivative (DTD) has been implemented. The algorithm has been developed in MATLAB7.1 and tested over 200 ultrasound B-scan images of several organs such as the liver, kidney, gall bladder and pancreas. Further, the performance of the DTD algorithm has been estimated by calculating important performance metrics. A comparative study was carried out between the DTD and the traditional despeckling techniques. The calculated peak signal-to-noise ratio (PSNR) (the ratio between the maximum possible power of a signal and the power of corrupting noise that affects the fidelity of its representation) value of the DTD despeckled liver image is found to be 28 which is comparable with the outperformed speckle reducing anisotropic diffusion (SRAD) filter. SRAD filter is an edge-sensitive diffusion method for speckled images of ultrasonic and radar imaging applications. Canny edge detection and visual inspection of DTD filtered images by the trained radiologist found that the DTD algorithm preserves the hypoechoic and hyperechoic regions resulting in improved diagnosis as well as tissue characterization. PMID:22230135

  20. Laser speckle imaging of rat retinal blood flow with hybrid temporal and spatial analysis method

    Cheng, Haiying; Yan, Yumei; Duong, Timothy Q.

    2009-02-01

    Noninvasive monitoring of blood flow in retinal circulation will reveal the progression and treatment of ocular disorders, such as diabetic retinopathy, age-related macular degeneration and glaucoma. A non-invasive and direct BF measurement technique with high spatial-temporal resolution is needed for retinal imaging. Laser speckle imaging (LSI) is such a method. Currently, there are two analysis methods for LSI: spatial statistics LSI (SS-LSI) and temporal statistical LSI (TS-LSI). Comparing these two analysis methods, SS-LSI has higher signal to noise ratio (SNR) and TSLSI is less susceptible to artifacts from stationary speckle. We proposed a hybrid temporal and spatial analysis method (HTS-LSI) to measure the retinal blood flow. Gas challenge experiment was performed and images were analyzed by HTS-LSI. Results showed that HTS-LSI can not only remove the stationary speckle but also increase the SNR. Under 100% O2, retinal BF decreased by 20-30%. This was consistent with the results observed with laser Doppler technique. As retinal blood flow is a critical physiological parameter and its perturbation has been implicated in the early stages of many retinal diseases, HTS-LSI will be an efficient method in early detection of retina diseases.

  1. The Speckle Noise Reduction and the Boundary Enhancement on Medical Ultrasound Images using the Cellular Neural Networks

    Park, Hyunkyung; Miyazaki, Ryota; Nishimura, Toshihiro; Tamaki, Yasuhiro

    The purpose is to remove the speckle noise and to emphasize the boundary of a tumor by filtering based on the intensity difference in the medical ultrasound images. The proposed method is evaluated using numerical phantom simulating ultrasound B-mode images, and the effect is confirmed by applying to medical ultrasound images. Therefore, some important features such as tissue boundaries and small tumors may be overlooked. A CNN (cellular neural networks) for the speckle reduction and the edge enhancement are proposed in this paper. A CNN which is a kind of recurrent neural network can deal with images by the weight of neurons called a cell. It could be obtained more detail images recognition compared with the previous studies. A determination template parameters of the CNN for ultrasound image processing is discussed. The experimental results show effectiveness of applying the proposed method to boundary enhancement and the speckle reduction of medical ultrasound image.

  2. Simulations of x-ray speckle-based dark-field and phase-contrast imaging with a polychromatic beam

    Following the first experimental demonstration of x-ray speckle-based multimodal imaging using a polychromatic beam [I. Zanette et al., Phys. Rev. Lett. 112(25), 253903 (2014)], we present a simulation study on the effects of a polychromatic x-ray spectrum on the performance of this technique. We observe that the contrast of the near-field speckles is only mildly influenced by the bandwidth of the energy spectrum. Moreover, using a homogeneous object with simple geometry, we characterize the beam hardening artifacts in the reconstructed transmission and refraction angle images, and we describe how the beam hardening also affects the dark-field signal provided by speckle tracking. This study is particularly important for further implementations and developments of coherent speckle-based techniques at laboratory x-ray sources

  3. Simulations of x-ray speckle-based dark-field and phase-contrast imaging with a polychromatic beam

    Zdora, Marie-Christine, E-mail: marie-christine.zdora@diamond.ac.uk [Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching (Germany); Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom); Department of Physics & Astronomy, University College London, London WC1E 6BT (United Kingdom); Thibault, Pierre [Department of Physics & Astronomy, University College London, London WC1E 6BT (United Kingdom); Pfeiffer, Franz [Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching (Germany); Zanette, Irene [Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching (Germany); Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom)

    2015-09-21

    Following the first experimental demonstration of x-ray speckle-based multimodal imaging using a polychromatic beam [I. Zanette et al., Phys. Rev. Lett. 112(25), 253903 (2014)], we present a simulation study on the effects of a polychromatic x-ray spectrum on the performance of this technique. We observe that the contrast of the near-field speckles is only mildly influenced by the bandwidth of the energy spectrum. Moreover, using a homogeneous object with simple geometry, we characterize the beam hardening artifacts in the reconstructed transmission and refraction angle images, and we describe how the beam hardening also affects the dark-field signal provided by speckle tracking. This study is particularly important for further implementations and developments of coherent speckle-based techniques at laboratory x-ray sources.

  4. Application of speckle and (multi-object) multi-frame blind deconvolution techniques on imaging and imaging spectropolarimetric data

    Puschmann, K G

    2011-01-01

    We test the effects of reconstruction techniques on 2D data to determine the best approach. We obtained a time-series of spectropolarimetric data in the Fe I line at 630.25 nm with the Goettingen Fabry-Perot Interferometer (FPI) that are accompanied by imaging data at 431.3 nm and Ca II H. We apply both speckle and (MO)MFBD techniques. We compare the spatial resolution and investigate the impact of the reconstruction on spectral characteristics. The speckle reconstruction and MFBD perform similar for our imaging data with nearly identical intensity contrasts. MFBD provides a better and more homogeneous resolution at the shortest wavelength. The MOMFBD and speckle deconvolution of the intensity spectra lead to similar results, but our choice of settings for the MOMFBD yields an intensity contrast smaller by about 2% at a comparable spatial resolution. None of the reconstruction techniques introduces artifacts in the intensity spectra. The speckle deconvolution (MOMFBD) has a rms noise in V/I of 0.32% (0.20%). ...

  5. Application of fast CCD drift scanning to speckle imaging of binary stars

    Fors, O; Nuñez, J

    2004-01-01

    A new application of a fast CCD drift scanning technique that allows us to perform speckle imaging of binary stars is presented. For each observation, an arbitrary number of speckle frames is periodically stored on a computer disk, each with an appropriate exposure time given both atmospheric and instrumental considerations. The CCD charge is shifted towards the serial register and read out sufficiently rapidly to avoid an excessive amount of interframe dead time. Four well-known binary systems (ADS 755, ADS 2616, ADS 3711 and ADS 16836) are observed in to show the feasibility of the proposed technique. Bispectral data analysis and power spectrum fitting is carried out for each observation, yielding relative astrometry and photometry. A new approach for self-calibrating this analysis is also presented and validated. The proposed scheme does not require any additional electronic or optical hardware, so it should allow most small professional observatories and advanced amateurs to enjoy the benefits of diffract...

  6. Microvascular blood flow monitoring with laser speckle contrast imaging using the generalized differences algorithm.

    Humeau-Heurtier, Anne; Mahé, Guillaume; Abraham, Pierre

    2015-03-01

    Laser speckle contrast imaging (LSCI) is a full-field optical technique to monitor microvascular blood flow with high spatial and temporal resolutions. It is used in many medical fields such as dermatology, vascular medicine, or neurosciences. However, LSCI leads to a large amount of data: image sampling frequency is often of several Hz and recordings usually last several minutes. Therefore, clinicians often perform regions of interest in which a spatial averaging of blood flow is performed and the result is followed with time. Unfortunately, this leads to a poor spatial resolution for the analyzed data. At the same time, a higher spatial resolution for the perfusion maps is wanted. To get over this dilemma we propose a new post-acquisition visual representation for LSCI perfusion data using the so-called generalized differences (GD) algorithm. From a stack of perfusion images, the procedure leads to a new single image with the same spatial resolution as the original images and this new image reflects perfusion changes. The algorithm is herein applied on simulated stacks of images and on experimental LSCI perfusion data acquired in three different situations with a commercialized laser speckle contrast imager. The results show that the GD algorithm provides a new way of visualizing LSCI perfusion data. PMID:25576743

  7. Speckle reduction of SAR images using ICA basis enhancement and separation

    Yutong Li; Yue zhou

    2007-01-01

    @@ An approach for synthetic aperture radax (SAR) image de-noising based on independent component analysis (ICA) basis images is proposed. Firstly, the basis images and the code matrix of the original image are obtained using ICA algorithm. Then, pointwise H(o)lder exponent of each basis is computed as a cost criterion for basis enhancement, and then the enhanced basis images are classified into two sets according to a separation rule which separates the clean basis from the original basis. After these key procedures for speckle reduction, the clean image is finally obtained by reconstruction on the clean basis and original code matrix. The reconstructed image shows better visual perception and image quality compared with those obtained by other traditional techniques.

  8. Intravascular laser speckle imaging for the mechanical analysis of coronary plaques (Conference Presentation)

    Hosoda, Masaki; Wang, Jing; Tsikudi, Diane; Nadkarni, Seemantini

    2016-02-01

    Acute myocardial infarction is frequently caused by the rupture of coronary plaques with severely compromised viscoelastic properties. We have developed a new optical technology termed intravascular laser speckle imaging (ILSI) that evaluates plaque viscoelastic properties, by measuring the time scale (time constant, τ) of temporally evolving laser speckle fluctuations. To enable coronary evaluation in vivo, an optical ILSI catheter has been developed that accomplishes omni-directional illumination and viewing of the entire coronary circumference without the need for mechanical rotation. Here, we describe the capability of ILSI for evaluating human coronary atherosclerosis in cadaveric hearts. ILSI was conducted in conjunction with optical coherence tomography (OCT) imaging in five human cadaveric hearts. The left coronary artery (LCA), left anterior descending (LAD), left circumflex artery (LCx), and right coronary artery (RCA) segments were resected and secured on custom-developed coronary holders to enable accurate co-registration between ILSI, OCT, and histopathology. Speckle time constants, τ, calculated from each ILSI section were compared with lipid and collagen content measured from quantitative Histopathological analysis of the corresponding Oil Red O and Picrosirius Red stained sections. Because the presence of low viscosity lipid elicits rapid speckle fluctuations, we observed an inverse correlation between τ measured by ILSI and lipid content (R= -0.64, p< 0.05). In contrast, the higher viscoelastic modulus of fibrous regions resulted in a positive correlation between τ and collagen content (R= 0.54, p< 0.05). These results demonstrate the feasibility of conducting ILSI evaluation of arterial mechanical properties using a miniaturized omni-directional catheter.

  9. Speckle-reduction algorithm for ultrasound images in complex wavelet domain using genetic algorithm-based mixture model.

    Uddin, Muhammad Shahin; Tahtali, Murat; Lambert, Andrew J; Pickering, Mark R; Marchese, Margaret; Stuart, Iain

    2016-05-20

    Compared with other medical-imaging modalities, ultrasound (US) imaging is a valuable way to examine the body's internal organs, and two-dimensional (2D) imaging is currently the most common technique used in clinical diagnoses. Conventional 2D US imaging systems are highly flexible cost-effective imaging tools that permit operators to observe and record images of a large variety of thin anatomical sections in real time. Recently, 3D US imaging has also been gaining popularity due to its considerable advantages over 2D US imaging. It reduces dependency on the operator and provides better qualitative and quantitative information for an effective diagnosis. Furthermore, it provides a 3D view, which allows the observation of volume information. The major shortcoming of any type of US imaging is the presence of speckle noise. Hence, speckle reduction is vital in providing a better clinical diagnosis. The key objective of any speckle-reduction algorithm is to attain a speckle-free image while preserving the important anatomical features. In this paper we introduce a nonlinear multi-scale complex wavelet-diffusion based algorithm for speckle reduction and sharp-edge preservation of 2D and 3D US images. In the proposed method we use a Rayleigh and Maxwell-mixture model for 2D and 3D US images, respectively, where a genetic algorithm is used in combination with an expectation maximization method to estimate mixture parameters. Experimental results using both 2D and 3D synthetic, physical phantom, and clinical data demonstrate that our proposed algorithm significantly reduces speckle noise while preserving sharp edges without discernible distortions. The proposed approach performs better than the state-of-the-art approaches in both qualitative and quantitative measures. PMID:27411128

  10. Estimation of spectral transmittance curves from RGB images in color digital holographic microscopy using speckle illuminations

    Funamizu, Hideki; Tokuno, Yuta; Aizu, Yoshihisa

    2016-06-01

    We investigate the estimation of spectral transmittance curves in color digital holographic microscopy using speckle illuminations. In color digital holography, it has the disadvantage in that the color-composite image gives poor color information due to the use of lasers with the two or three wavelengths. To overcome this disadvantage, the Wiener estimation method and an averaging process using multiple holograms are applied to color digital holographic microscopy. Estimated spectral transmittance and color-composite images are shown to indicate the usefulness of the proposed method.

  11. Low-cost laser speckle contrast imaging of blood flow using a webcam.

    Richards, Lisa M; Kazmi, S M Shams; Davis, Janel L; Olin, Katherine E; Dunn, Andrew K

    2013-01-01

    Laser speckle contrast imaging has become a widely used tool for dynamic imaging of blood flow, both in animal models and in the clinic. Typically, laser speckle contrast imaging is performed using scientific-grade instrumentation. However, due to recent advances in camera technology, these expensive components may not be necessary to produce accurate images. In this paper, we demonstrate that a consumer-grade webcam can be used to visualize changes in flow, both in a microfluidic flow phantom and in vivo in a mouse model. A two-camera setup was used to simultaneously image with a high performance monochrome CCD camera and the webcam for direct comparison. The webcam was also tested with inexpensive aspheric lenses and a laser pointer for a complete low-cost, compact setup ($90, 5.6 cm length, 25 g). The CCD and webcam showed excellent agreement with the two-camera setup, and the inexpensive setup was used to image dynamic blood flow changes before and after a targeted cerebral occlusion. PMID:24156082

  12. Use of a speckle reduction technique to improve the reconstruction image quality of CCD-based optical computed tomography scanner

    This study proposed a speckle reduction technique (SRT) that employs a rotating diffuser in the parallel beam optical computed tomography (CT). Results showed that the mean and standard deviation of the gray level are 89.79±4.53 and 89.16±2.88 for reconstruction images without SRT and with SRT, respectively. The proposed SRT effectively removed ring artifacts. In addition, two image processing techniques, namely, the mean and Wiener filters, were also used to improve the reconstructed images. The image processing technique alone effectively reduced ring artifacts, but some fluctuations were still observed in the line profiles of the reconstructed images. Results proved that the proposed SRT is a simple method that is easily implemented to improve image quality for parallel beam optical CT. The combination of SRT and image filters was suggested to achieve the best image reconstruction quality through the full removal of ring artifacts. - Highlights: • Speckle reduction technique is effective to remove ring artifacts. • The fluctuation in reconstruction image can be reduced using speckle reduction technique. • The image processing technique can reduce the ring artifacts effectively, but few fluctuations can still be observed in line profiles. • The combination speckle reduction technique and image filters can achieve the best quality of reconstruction image

  13. Non-invasive real-time imaging through scattering layers and around corners via speckle correlations

    Katz, Ori; Fink, Mathias; Gigan, Sylvain

    2014-01-01

    Imaging with optical resolution through and inside complex samples is a difficult challenge with important applications in many fields. The fundamental problem is that inhomogeneous samples, such as biological tissues, randomly scatter and diffuse light, impeding conventional image formation. Despite many advancements, no current method enables to noninvasively image in real-time using diffused light. Here, we show that owing to the memory-effect for speckle correlations, a single image of the scattered light, captured with a standard high-resolution camera, encodes all the information that is required to image through the medium or around a corner. We experimentally demonstrate single-shot imaging through scattering media and around corners using incoherent light and various samples, from white paint to dynamic biological samples. Our lensless technique is simple, does not require laser sources, wavefront-shaping, nor time-gated detection, and is realized here using a camera-phone. It has the potential to en...

  14. Laser speckle contrast imaging of skin blood perfusion responses induced by laser coagulation

    We report application of laser speckle contrast imaging (LSCI), i.e., a fast imaging technique utilising backscattered light to distinguish such moving objects as red blood cells from such stationary objects as surrounding tissue, to localise skin injury. This imaging technique provides detailed information about the acute perfusion response after a blood vessel is occluded. In this study, a mouse ear model is used and pulsed laser coagulation serves as the method of occlusion. We have found that the downstream blood vessels lacked blood flow due to occlusion at the target site immediately after injury. Relative flow changes in nearby collaterals and anastomotic vessels have been approximated based on differences in intensity in the nearby collaterals and anastomoses. We have also estimated the density of the affected downstream vessels. Laser speckle contrast imaging is shown to be used for highresolution and fast-speed imaging for the skin microvasculature. It also allows direct visualisation of the blood perfusion response to injury, which may provide novel insights to the field of cutaneous wound healing. (laser biophotonics)

  15. Laser speckle contrast imaging of skin blood perfusion responses induced by laser coagulation

    Ogami, M; Kulkarni, R; Wang, H; Reif, R; Wang, R K [University of Washington, Department of Bioengineering, Seattle, Washington 98195 (United States)

    2014-08-31

    We report application of laser speckle contrast imaging (LSCI), i.e., a fast imaging technique utilising backscattered light to distinguish such moving objects as red blood cells from such stationary objects as surrounding tissue, to localise skin injury. This imaging technique provides detailed information about the acute perfusion response after a blood vessel is occluded. In this study, a mouse ear model is used and pulsed laser coagulation serves as the method of occlusion. We have found that the downstream blood vessels lacked blood flow due to occlusion at the target site immediately after injury. Relative flow changes in nearby collaterals and anastomotic vessels have been approximated based on differences in intensity in the nearby collaterals and anastomoses. We have also estimated the density of the affected downstream vessels. Laser speckle contrast imaging is shown to be used for highresolution and fast-speed imaging for the skin microvasculature. It also allows direct visualisation of the blood perfusion response to injury, which may provide novel insights to the field of cutaneous wound healing. (laser biophotonics)

  16. Laser speckle contrast imaging of skin blood perfusion responses induced by laser coagulation

    Ogami, M.; Kulkarni, R.; Wang, H.; Reif, R.; Wang, R. K.

    2014-08-01

    We report application of laser speckle contrast imaging (LSCI), i.e., a fast imaging technique utilising backscattered light to distinguish such moving objects as red blood cells from such stationary objects as surrounding tissue, to localise skin injury. This imaging technique provides detailed information about the acute perfusion response after a blood vessel is occluded. In this study, a mouse ear model is used and pulsed laser coagulation serves as the method of occlusion. We have found that the downstream blood vessels lacked blood flow due to occlusion at the target site immediately after injury. Relative flow changes in nearby collaterals and anastomotic vessels have been approximated based on differences in intensity in the nearby collaterals and anastomoses. We have also estimated the density of the affected downstream vessels. Laser speckle contrast imaging is shown to be used for highresolution and fast-speed imaging for the skin microvasculature. It also allows direct visualisation of the blood perfusion response to injury, which may provide novel insights to the field of cutaneous wound healing.

  17. Suppressing Speckle Noise for Simultaneous Differential Extrasolar Planet Imaging (SDI) at the VLT and MMT

    Biller, B A; Lenzen, R; Brandner, W; McCarthy, D; Nielsen, E; Kellner, S; Hartung, M; Biller, Beth A.; Close, Laird M.; Lenzen, Rainer; Brandner, Wolfgang; Carthy, Donald Mc; Nielsen, Eric; Kellner, Stephan; Hartung, Markus

    2006-01-01

    We discuss the instrumental and data reduction techniques used to suppress speckle noise with the Simultaneous Differential Imager (SDI) implemented at the VLT and the MMT. SDI uses a double Wollaston prism and a quad filter to take 4 identical images simultaneously at 3 wavelengths surrounding the 1.62 um methane bandhead found in the spectrum of cool brown dwarfs and gas giants. By performing a difference of images in these filters, speckle noise from the primary can be significantly attenuated, resulting in photon noise limited data past 0.5''. Non-trivial data reduction tools are necessary to pipeline the simultaneous differential imaging. Here we discuss a custom algorithm implemented in IDL to perform this reduction. The script performs basic data reduction tasks but also precisely aligns images taken in each of the filters using a custom shift and subtract routine. In our survey of nearby young stars at the VLT and MMT (see Biller et al., this conference), we achieved H band contrasts >25000 (5 sigma D...

  18. A Multi-Chanel Speckle Imaging for the DOT

    Sütterlin, P.; Hammerschlag, R.H.; Bettonvil, F.C.M.; Rutten, R.J.; Skomorovsky, V.I.; Domyshev, G.N.

    2001-01-01

    The Dutch Open Telescope (DOT) had its initial observing campaighn in September 1999. Alhough only a simple video system was used, the results demonstrated the excellent high-resolution capabilities of the combination of the open-teloscope concept, the DOT optics, the remaining image degradation due

  19. Spatio-temporal speckle correlations for imaging in turbid media

    Skipetrov, S.E.

    2001-01-01

    We discuss the far-field spatio-temporal cross-correlations of waves multiple-scattered in a turbid medium in which is embedded a hidden heterogeneous region (inclusion) characterized by a distinct scatterer dynamics (as compared to the rest of the medium). We show that the spatio-temporal correlation is affected by the inclusion which suggests a new method of imaging in turbid media. Our results allow qualitative interpretation in terms of diffraction theory: the cross-correlation of scatter...

  20. Optical diagnostics of vascular reactions triggered by weak allergens using laser speckle-contrast imaging technique

    Kuznetsov, Yu L; Kalchenko, V V [Department of Veterinary Resources, Weizmann Institute of Science, Rehovot, 76100 (Israel); Astaf' eva, N G [V.I.Razumovsky Saratov State Medical University, Saratov (Russian Federation); Meglinski, I V [N.G. Chernyshevsky Saratov State University, Saratov (Russian Federation)

    2014-08-31

    The capability of using the laser speckle contrast imaging technique with a long exposure time for visualisation of primary acute skin vascular reactions caused by a topical application of a weak contact allergen is considered. The method is shown to provide efficient and accurate detection of irritant-induced primary acute vascular reactions of skin. The presented technique possesses a high potential in everyday diagnostic practice, preclinical studies, as well as in the prognosis of skin reactions to the interaction with potentially allergenic materials. (laser biophotonics)

  1. High-speed multi-exposure laser speckle contrast imaging with a single-photon counting camera.

    Dragojević, Tanja; Bronzi, Danilo; Varma, Hari M; Valdes, Claudia P; Castellvi, Clara; Villa, Federica; Tosi, Alberto; Justicia, Carles; Zappa, Franco; Durduran, Turgut

    2015-08-01

    Laser speckle contrast imaging (LSCI) has emerged as a valuable tool for cerebral blood flow (CBF) imaging. We present a multi-exposure laser speckle imaging (MESI) method which uses a high-frame rate acquisition with a negligible inter-frame dead time to mimic multiple exposures in a single-shot acquisition series. Our approach takes advantage of the noise-free readout and high-sensitivity of a complementary metal-oxide-semiconductor (CMOS) single-photon avalanche diode (SPAD) array to provide real-time speckle contrast measurement with high temporal resolution and accuracy. To demonstrate its feasibility, we provide comparisons between in vivo measurements with both the standard and the new approach performed on a mouse brain, in identical conditions. PMID:26309751

  2. Development of a laser speckle imaging system for measuring relative blood flow velocity

    Smith, Michael S. D.; Packulak, Ernie F.; Sowa, Michael G.

    2006-09-01

    Determining the viability of damaged or surgically reconstructed tissue is critical in most plastic and reconstructive surgery procedures. Information about tissue blood flow in the region in question can make this determination much easier. Laser speckle imaging (LSI) is one technique that could potentially aid in making this determination. LSI is a non-contact full-field imaging technique with simultaneous high spatial and temporal resolution. Tissue is illuminated with diffuse red laser light and the spatial and/or temporal statistics of the resulting speckle pattern can be used to calculate relative flow velocities. We have developed a LSI system that produces relative velocity blood flow images. Bench tests of the system indicate that it may be used to distinguish between normal, decreased, and increased blood flow states of a human finger. The system has also been used to take some initial laboratory measurements using an animal model - an epigastric free flap on a rat. Preliminary results indicate that the method may be used to distinguish states of venous or arterial occlusion from unoccluded states of the skin flap. While further experimentation is necessary, these initial results indicate that LSI could be a useful aid to the plastic surgeon for assessing tissue viability.

  3. Stick based Non-local Means Filter for Speckle Reduction in Ultrasonic Images

    Liu Ting

    2015-01-01

    Full Text Available Accurate visualization and quantification of human structure is an important prerequisite for a number of clinical procedures. Specially, a current challenging issue in medical ultrasonic images is the problem of speckle reduction while keeping the structure and texture information. A stick based non-local means filter is proposed in this paper. An asymmetric stick filter kernel is firstly defined by decomposing the rectangle search window of non-local means (NLM filter into a set of line segments with variable orientations. Then, the sticks which used to search for similar pixels are selected by a normalized variance function. Finally, the weighted sum of averages of the similar pixels searched along each selected stick is used to produce the filtered image. With the introduction of the asymmetric stick, it is possible to implement the NLM filter in an oriented diffusion way. Experiments of synthetic and real clinical ultrasound images show that the stick based NLM filter performs effectively in suppressing speckle while pre-serving resolvable structures and even enhancing linear features such as the edges.

  4. Low spatial coherence electrically pumped semiconductor laser for speckle-free full-field imaging.

    Redding, Brandon; Cerjan, Alexander; Huang, Xue; Lee, Minjoo Larry; Stone, A Douglas; Choma, Michael A; Cao, Hui

    2015-02-01

    The spatial coherence of laser sources has limited their application to parallel imaging and projection due to coherent artifacts, such as speckle. In contrast, traditional incoherent light sources, such as thermal sources or light emitting diodes (LEDs), provide relatively low power per independent spatial mode. Here, we present a chip-scale, electrically pumped semiconductor laser based on a novel design, demonstrating high power per mode with much lower spatial coherence than conventional laser sources. The laser resonator was fabricated with a chaotic, D-shaped cavity optimized to achieve highly multimode lasing. Lasing occurs simultaneously and independently in ∼1,000 modes, and hence the total emission exhibits very low spatial coherence. Speckle-free full-field imaging is demonstrated using the chaotic cavity laser as the illumination source. The power per mode of the sample illumination is several orders of magnitude higher than that of a LED or thermal light source. Such a compact, low-cost source, which combines the low spatial coherence of a LED with the high spectral radiance of a laser, could enable a wide range of high-speed, full-field imaging and projection applications. PMID:25605946

  5. Quantitative assessment of reactive hyperemia using laser speckle contrast imaging at multiple wavelengths

    Young, Anthony; Vishwanath, Karthik

    2016-03-01

    Reactive hyperemia refers to an increase of blood flow in tissue post release of an occlusion in the local vasculature. Measuring the temporal response of reactive hyperemia, post-occlusion in patients has the potential to shed information about microvascular diseases such as systemic sclerosis and diabetes. Laser speckle contrast imaging (LSCI) is an imaging technique capable of sensing superficial blood flow in tissue which can be used to quantitatively assess reactive hyperemia. Here, we employ LSCI using coherent sources in the blue, green and red wavelengths to evaluate reactive hyperemia in healthy human volunteers. Blood flow in the forearms of subjects were measured using LSCI to assess the time-course of reactive hyperemia that was triggered by a pressure cuff applied to the biceps of the subjects. Raw speckle images were acquired and processed to yield blood-flow parameters from a region of interest before, during and after application of occlusion. Reactive hyperemia was quantified via two measures - (1) by calculating the difference between the peak LSCI flow during the hyperemia and baseline flow, and (2) by measuring the amount of time that elapsed between the release of the occlusion and peak flow. These measurements were acquired in three healthy human participants, under the three laser wavelengths employed. The studies shed light on the utility of in vivo LSCI-based flow sensing for non-invasive assessment of reactive hyperemia responses and how they varied with the choice source wavelength influences the measured parameters.

  6. Contrast enhancement of laser speckle skin image: use of optical clearing agent in conjunction with micro-needling

    Son, Taeyoon; Yoon, Jinhee; Ko, Chang-Yong; Lee, Yong-Heum; Kwon, Kiwoon; Kim, Han Sung; Lee, Kyoung Joung; Jung, Byungjo

    2008-02-01

    Laser speckle imaging modality is one of widely used methods to evaluate blood flow because of its simplicity. However, laser speckle image has a limitation in the evaluation of subcutaneous blood flow due to its low contrast perfusion image. Various methods have been tried to enhance the perfusion image contrast. Such methods presented positive results in some degree. However, it could not be fundamental solutions due to low penetration depth of lasers restricted by optical tissue scattering property. This study suggests a method to enhance the perfusion image contrast of laser speckle imaging modality by increasing the penetration depth of lasers. An optical clearing agent (glycerol) was topically applied on skin treated with micro-needle roller in order to reduce the time period of optical tissue clearing and therefore, enhance the penetration depth of laser. In this study, we investigated the effect of glycerol and micro-needling methods in the contrast enhancement of laser speckle perfusion skin image and presented the results of in-vitro and in-vivo animal experiment.

  7. [Non-linear real-time adaptive filtration of ultrasound TI628A echotomoscope images].

    Barannik, E A; Volokhov, Iu V; Marusenko, A I

    1997-01-01

    The statistical uncertainty caused by speckle noise artifacts is the reason for the great importance of the problem which is the optimum choice between the medical diagnostic systems resolution and the statistical accuracy of histological tissue identification. The way of speckle noise suppression, which is closely associated with the well-known idea of adaptive filtration and based on the physical analysis of the origin of true and false signals, is very promising. The testing results of the nonlinear real-time adaptive filter which has been designed for a TI628A echotomoscope are presented. The filter has been shown to have a rather high contrast and space resolution and reduces the speckle noise and other artifacts of the images. PMID:9445983

  8. Imaging through diffusive layers using speckle pattern fractal analysis and application to embedded object detection in tissues

    Tremberger, George, Jr.; Flamholz, A.; Cheung, E.; Sullivan, R.; Subramaniam, R.; Schneider, P.; Brathwaite, G.; Boteju, J.; Marchese, P.; Lieberman, D.; Cheung, T.; Holden, Todd

    2007-09-01

    The absorption effect of the back surface boundary of a diffuse layer was studied via laser generated reflection speckle pattern. The spatial speckle intensity provided by a laser beam was measured. The speckle data were analyzed in terms of fractal dimension (computed by NIH ImageJ software via the box counting fractal method) and weak localization theory based on Mie scattering. Bar code imaging was modeled as binary absorption contrast and scanning resolution in millimeter range was achieved for diffusive layers up to thirty transport mean free path thick. Samples included alumina, porous glass and chicken tissue. Computer simulation was used to study the effect of speckle spatial distribution and observed fractal dimension differences were ascribed to variance controlled speckle sizes. Fractal dimension suppressions were observed in samples that had thickness dimensions around ten transport mean free path. Computer simulation suggested a maximum fractal dimension of about 2 and that subtracting information could lower fractal dimension. The fractal dimension was shown to be sensitive to sample thickness up to about fifteen transport mean free paths, and embedded objects which modified 20% or more of the effective thickness was shown to be detectable. The box counting fractal method was supplemented with the Higuchi data series fractal method and application to architectural distortion mammograms was demonstrated. The use of fractals in diffusive analysis would provide a simple language for a dialog between optics experts and mammography radiologists, facilitating the applications of laser diagnostics in tissues.

  9. Content adaptive screen image scaling

    Zhai, Yao; Wang, Qifei; Lu, Yan; Li, Shipeng

    2015-01-01

    This paper proposes an efficient content adaptive screen image scaling scheme for the real-time screen applications like remote desktop and screen sharing. In the proposed screen scaling scheme, a screen content classification step is first introduced to classify the screen image into text and pictorial regions. Afterward, we propose an adaptive shift linear interpolation algorithm to predict the new pixel values with the shift offset adapted to the content type of each pixel. The shift offse...

  10. Three-dimensional Dynamic Deformation Measurements using Stereoscopic Imaging and Digital Speckle Photography

    Prentice, Helen

    2005-07-01

    A technique has been developed in order to determine experimentally the three-dimensional displacement field on the rear surface of a dynamically deforming plate. The technique combines speckle analysis with stereoscopy, using a modified translated-lens method: this allows split-frame photography, increased image resolution and a larger effective lens separation in order to increase image disparity and reduce errors in the shape reconstruction. Whilst several analytical models exist to predict deformation in extended or semi-infinite targets, the non-trivial nature of the wave interactions complicates the generation and development of analytical models for targets with significantly finite depth. By interrogating specimens experimentally to acquire three-dimensional strain data points, both analytical and numerical model predictions can be verified more rigorously. The technique is applied to the quasi-static deformation of a rubber sheet and dynamically to sheets of Copper and Mild Steel of various thicknesses.

  11. From synchrotron radiation to lab source: advanced speckle-based X-ray imaging using abrasive paper

    Hongchang Wang; Yogesh Kashyap; Kawal Sawhney

    2016-01-01

    X-ray phase and dark-field imaging techniques provide complementary and inaccessible information compared to conventional X-ray absorption or visible light imaging. However, such methods typically require sophisticated experimental apparatus or X-ray beams with specific properties. Recently, an X-ray speckle-based technique has shown great potential for X-ray phase and dark-field imaging using a simple experimental arrangement. However, it still suffers from either poor resolution or the time...

  12. Improving high resolution retinal image quality using speckle illumination HiLo imaging

    Zhou, Xiaolin; Bedggood, Phillip; Metha, Andrew

    2014-01-01

    Retinal image quality from flood illumination adaptive optics (AO) ophthalmoscopes is adversely affected by out-of-focus light scatter due to the lack of confocality. This effect is more pronounced in small eyes, such as that of rodents, because the requisite high optical power confers a large dioptric thickness to the retina. A recently-developed structured illumination microscopy (SIM) technique called HiLo imaging has been shown to reduce the effect of out-of-focus light scatter in flood i...

  13. Enhancement and bias removal of optical coherence tomography images: An iterative approach with adaptive bilateral filtering.

    Sudeep, P V; Issac Niwas, S; Palanisamy, P; Rajan, Jeny; Xiaojun, Yu; Wang, Xianghong; Luo, Yuemei; Liu, Linbo

    2016-04-01

    Optical coherence tomography (OCT) has continually evolved and expanded as one of the most valuable routine tests in ophthalmology. However, noise (speckle) in the acquired images causes quality degradation of OCT images and makes it difficult to analyze the acquired images. In this paper, an iterative approach based on bilateral filtering is proposed for speckle reduction in multiframe OCT data. Gamma noise model is assumed for the observed OCT image. First, the adaptive version of the conventional bilateral filter is applied to enhance the multiframe OCT data and then the bias due to noise is reduced from each of the filtered frames. These unbiased filtered frames are then refined using an iterative approach. Finally, these refined frames are averaged to produce the denoised OCT image. Experimental results on phantom images and real OCT retinal images demonstrate the effectiveness of the proposed filter. PMID:26907572

  14. Laser speckle analysis synchronised with cardiac cycle

    Zakharov, Pavel; Scheffold, Frank; Weber, Bruno

    2015-07-01

    We present an improved Laser speckle imaging approach to investigate the cerebral blood flow response following function stimulation of a single vibrissa. By synchronising speckle analysis with the cardiac cycle we are able to obtain robust averaging of the correlation signals while at the same time removing the contributions due to the pulsation of blood flow and associated tissue adaptation. With our inter-pulse correlation analysis we can follow second-scale dynamics of the cortical vascular system in response to functional brain activation. We find evidence for two temporally separated processes in the blood flow pattern following stimulation we tentatively attribute to vasodilation and vasoconstriction phases, respectively.

  15. Preliminary images from an adaptive imaging system

    J.A. Griffiths; M.G. Metaxas; S. Pani; H. Schulerud; C. Esbrand; G.J. Royle; B. Price; T. Rokvic; R. Longo; A. Asimidis; E. Bletsas; D. Cavouras; A. Fant; P. Gasiorek; H. Georgiou; G. Hall; J. Jones; J. Leaver; G. Li; D. Machin; N. Manthos; J. Matheson; M. Noy; J.M. Østby; F. Psomadellis; P.F. van der Stelt; S. Theodoridis; F. Triantis; R. Turchetta; C. Venanzi; R.D. Speller

    2008-01-01

    I-ImaS (Intelligent Imaging Sensors) is a European project aiming to produce real-time adaptive X-ray imaging systems using Monolithic Active Pixel Sensors (MAPS) to create images with maximum diagnostic information within given dose constraints. Initial systems concentrate on mammography and cephal

  16. Detection of early carious lesions using contrast enhancement with coherent light scattering (speckle imaging)

    Deana, A. M.; Jesus, S. H. C.; Koshoji, N. H.; Bussadori, S. K.; Oliveira, M. T.

    2013-07-01

    Currently, dental caries still represent one of the chronic diseases with the highest prevalence and present in most countries. The interaction between light and teeth (absorption, scattering and fluorescence) is intrinsically connected to the constitution of the dental tissue. Decay induced mineral loss introduces a shift in the optical properties of the affected tissue; therefore, study of these properties may produce novel techniques aimed at the early diagnosis of carious lesions. Based on the optical properties of the enamel, we demonstrate the application of first-order spatial statistics in laser speckle imaging, allowing the detection of carious lesions in their early stages. A highlight of this noninvasive, non-destructive, real time and cost effective approach is that it allows a dentist to detect a lesion even in the absence of biofilm or moisture.

  17. Intraoperative laser speckle contrast imaging improves the stability of rodent middle cerebral artery occlusion model

    Yuan, Lu; Li, Yao; Li, Hangdao; Lu, Hongyang; Tong, Shanbao

    2015-09-01

    Rodent middle cerebral artery occlusion (MCAO) model is commonly used in stroke research. Creating a stable infarct volume has always been challenging for technicians due to the variances of animal anatomy and surgical operations. The depth of filament suture advancement strongly influences the infarct volume as well. We investigated the cerebral blood flow (CBF) changes in the affected cortex using laser speckle contrast imaging when advancing suture during MCAO surgery. The relative CBF drop area (CBF50, i.e., the percentage area with CBF less than 50% of the baseline) showed an increase from 20.9% to 69.1% when the insertion depth increased from 1.6 to 1.8 cm. Using the real-time CBF50 marker to guide suture insertion during the surgery, our animal experiments showed that intraoperative CBF-guided surgery could significantly improve the stability of MCAO with a more consistent infarct volume and less mortality.

  18. Detection of early carious lesions using contrast enhancement with coherent light scattering (speckle imaging)

    Currently, dental caries still represent one of the chronic diseases with the highest prevalence and present in most countries. The interaction between light and teeth (absorption, scattering and fluorescence) is intrinsically connected to the constitution of the dental tissue. Decay induced mineral loss introduces a shift in the optical properties of the affected tissue; therefore, study of these properties may produce novel techniques aimed at the early diagnosis of carious lesions. Based on the optical properties of the enamel, we demonstrate the application of first-order spatial statistics in laser speckle imaging, allowing the detection of carious lesions in their early stages. A highlight of this noninvasive, non-destructive, real time and cost effective approach is that it allows a dentist to detect a lesion even in the absence of biofilm or moisture. (paper)

  19. Electronic speckle pattern interferometry for fracture expansion in nuclear graphite based on PDE image processing methods

    Tang, Chen; Zhang, Junjiang; Sun, Chen; Su, Yonggang; Su, Kai Leung

    2015-05-01

    Nuclear graphite has been widely used as moderating and reflecting materials. However, due to severe neutron irradiation under high temperature, nuclear graphite is prone to deteriorate, resulting in massive microscopic flaws and even cracks under large stress in the later period of its service life. It is indispensable, therefore, to understand the fracture behavior of nuclear graphite to provide reference to structural integrity and safety analysis of nuclear graphite members in reactors. In this paper, we investigated the fracture expansion in nuclear graphite based on PDE image processing methods. We used the second-order oriented partial differential equations filtering model (SOOPDE) to denoise speckle noise, then used the oriented gradient vector fields for to obtain skeletons. The full-field displacement of fractured nuclear graphite and the location of the crack tip were lastly measured under various loading conditions.

  20. High-frame-rate color-encoded speckle imaging for visually intuitive rendering of complex flow dynamics

    Yiu, BYS; Yu, ACH

    2013-01-01

    BACKGROUND, MOTIVATION AND OBJECTIVE: Realization of flow imaging at high frame rates can undoubtedly benefit the visualization of complex flow patterns with significant spatiotemporal variations. It would be even better if fluid motion can be coherently rendered through parallel display of both flow trajectory and flow speed. Driven by these motivations, we have developed a new high-frame-rate ultrasound flow visualization technique called color-encoded speckle imaging (CESI). It provides a ...

  1. Clutter filtering issues in speckle tracking for two-dimensional blood velocity estimation: a potential solution based on compounded imaging

    Søvik Alnes, Solveig; Swillens, Abigaïl; Segers, Patrick; Torp, Hans; Lovstakken, Lasse

    2012-01-01

    Clutter filtering issues remains a major limitation in multi-dimensional blood velocity estimation. In this work we investigate how compounded plane wave imaging can be used to minimize clutter filtering issues when using speckle tracking for two-dimensional velocity estimation. By using a dual scan angle approach one can ensure a sufficient beam-to-flow angle for most imaging scenarios. Segmentation algorithms based on the estimated power and mean axial velocity were used to determine whethe...

  2. InnoPOL: an EMCCD imaging polarimeter and 85-element curvature AO system on the 3.6-m AEOS telescope for cost effective polarimetric speckle suppression

    Harrington, David; Chun, Mark; Ftaclas, Christ; Gisler, Daniel; Kuhn, Jeff

    2016-01-01

    The Hokupa'a-85 curvature adaptive optics system components have been adapted to create a new AO-corrected coud\\'{e} instrument at the 3.67m Advanced Electro-Optical System (AEOS) telescope. This new AO-corrected optical path is designed to deliver an f/40 diffraction-limited focus at wavelengths longer than 800nm. A new EMCCD-based dual-beam imaging polarimeter called InnoPOL has been designed and is presently being installed behind this corrected f/40 beam. The InnoPOL system is a flexible platform for optimizing polarimetric performance using commercial solutions and for testing modulation strategies. The system is designed as a technology test and demonstration platform as the coud\\'{e} path is built using off-the-shelf components wherever possible. Models of the polarimetric performance after AO correction show that polarization modulation at rates as slow as 200Hz can cause speckle correlations in brightness and focal plane location sufficient enough to change the speckle suppression behavior of the mod...

  3. Dynamical properties of speckled speckles

    Hanson, Steen Grüner; Iversen, Theis Faber Quist; Hansen, Rene Skov

    2010-01-01

    the static diffuser and the plane of observation consist of an optical system that can be characterized by a complex-valued ABCD-matrix (e.g. simple and complex imaging systems, free space propagation in both the near-and far-field, and Fourier transform systems). The use of the complex ABCD...... diffuser is assumed to be Gaussian but the derived expressions are not restricted to a plane incident beam. The results are applicable for speckle-based systems for determining mechanical displacements, especially for long-range systems, and for analyzing systems for measuring biological activity beyond a...

  4. Nanoparticles speckled by ready-to-conjugate lanthanide complexes for multimodal imaging

    Biju, Vasudevanpillai; Hamada, Morihiko; Ono, Kenji; Sugino, Sakiko; Ohnishi, Takashi; Shibu, Edakkattuparambil Sidharth; Yamamura, Shohei; Sawada, Makoto; Nakanishi, Shunsuke; Shigeri, Yasushi; Wakida, Shin-Ichi

    2015-09-01

    Multimodal and multifunctional contrast agents receive enormous attention in the biomedical imaging field. Such contrast agents are routinely prepared by the incorporation of organic molecules and inorganic nanoparticles (NPs) into host materials such as gold NPs, silica NPs, polymer NPs, and liposomes. Despite their non-cytotoxic nature, the large size of these NPs limits the in vivo distribution and clearance and inflames complex pharmacokinetics, which hinder the regulatory approval for clinical applications. Herein, we report a unique method that combines magnetic resonance imaging (MRI) and fluorescence imaging modalities together in nanoscale entities by the simple, direct and stable conjugation of novel biotinylated coordination complexes of gadolinium(iii) to CdSe/ZnS quantum dots (QD) and terbium(iii) to super paramagnetic iron oxide NPs (SPION) but without any host material. Subsequently, we evaluate the potentials of such lanthanide-speckled fluorescent-magnetic NPs for bioimaging at single-molecule, cell and in vivo levels. The simple preparation and small size make such fluorescent-magnetic NPs promising contrast agents for biomedical imaging.

  5. Effect of cranial window type on monitoring neurovasculature using laser speckle contrast imaging

    Yu, Hang; Senarathna, Janaka; Tyler, Betty M.; Hossain, Syed; Thakor, Nitish V.; Pathak, Arvind P.

    2016-03-01

    The cranial window preparation provides optical access to the rodent brain for high-resolution in vivo optical imaging. Two types of cranial windows are commonly employed, namely the open-skull window and thinned-skull window. Chronic in vivo laser speckle contrast imaging (LSCI) through the cranial window permits characterization of neurovascular morphology and blood flow changes over days or weeks. However, the effects of window type and their long-term stability for in vivo LSCI have not been studied. Here we systematically characterize the effect of each cranial window type on in vivo neurovascular monitoring with LSCI over two weeks. Imaging outcomes for each window were assessed in terms of contrast-to-noise ratio (CNR), microvessel density (MVD) and total vessel length (TVL). We found that the thinned-skull window required a shorter recovery period (~ 4 days), provided a larger field of view and was a good choice for short-term (i.e. type for LSCI-based neurovascular imaging.

  6. Laser speckle contrast imaging identifies ischemic areas on gastric tube reconstructions following esophagectomy.

    Milstein, Dan M J; Ince, Can; Gisbertz, Suzanne S; Boateng, Kofi B; Geerts, Bart F; Hollmann, Markus W; van Berge Henegouwen, Mark I; Veelo, Denise P

    2016-06-01

    Gastric tube reconstruction (GTR) is a high-risk surgical procedure with substantial perioperative morbidity. Compromised arterial blood supply and venous congestion are believed to be the main etiologic factors associated with early and late anastomotic complications. Identifying low blood perfusion areas may provide information on the risks of future anastomotic leakage and could be essential for improving surgical techniques. The aim of this study was to generate a method for gastric microvascular perfusion analysis using laser speckle contrast imaging (LSCI) and to test the hypothesis that LSCI is able to identify ischemic regions on GTRs.Patients requiring elective laparoscopy-assisted GTR participated in this single-center observational investigation. A method for intraoperative evaluation of blood perfusion and postoperative analysis was generated and validated for reproducibility. Laser speckle measurements were performed at 3 different time pointes, baseline (devascularized) stomach (T0), after GTR (T1), and GTR at 20° reverse Trendelenburg (T2).Blood perfusion analysis inter-rater reliability was high, with intraclass correlation coefficients for each time point approximating 1 (P generalized significant decrease in mean blood perfusion was observed across all GTR regions of interest during 20° reverse Trendelenburg (P < 0.05).It was feasible to implement LSCI intraoperatively to produce blood perfusion assessments on intact and reconstructed whole stomachs. The analytical design presented in this study resulted in good reproducibility of gastric perfusion measurements between different investigators. LSCI provides spatial and temporal information on the location of adequate tissue perfusion and may thus be an important aid in optimizing surgical and anesthesiological procedures for strategically selecting anastomotic site in patients undergoing esophagectomy with GTR. PMID:27336874

  7. Comet Shoemaker-Levy 9/Jupiter collision observed with a high resolution speckle imaging system

    Gravel, D. [Lawrence Livermore National Lab., CA (United States)

    1994-11-15

    During the week of July 16, 1994, comet Shoemaker-Levy 9, broken into 20 plus pieces by tidal forces on its last orbit, smashed into the planet Jupiter, releasing the explosive energy of 500 thousand megatons. A team of observers from LLNL used the LLNL Speckle Imaging Camera mounted on the University of California`s Lick Observatory 3 Meter Telescope to capture continuous sequences of planet images during the comet encounter. Post processing with the bispectral phase reconstruction algorithm improves the resolution by removing much of the blurring due to atmospheric turbulence. High resolution images of the planet surface showing the aftermath of the impact are probably the best that were obtained from any ground-based telescope. We have been looking at the regions of the fragment impacts to try to discern any dynamic behavior of the spots left on Jupiter`s cloud tops. Such information can lead to conclusions about the nature of the comet and of Jupiter`s atmosphere. So far, the Hubble Space Telescope has observed expanding waves from the G impact whose mechanism is enigmatic since they appear to be too slow to be sound waves and too fast to be gravity waves, given the present knowledge of Jupiter`s atmosphere. Some of our data on the G and L impact region complements the Hubble observations but, so far, is inconclusive about spot dynamics.

  8. Features on photorefractive registered speckles

    Ángel-Toro, Luciano; Bolognini, Néstor; Tebaldi, Myrian

    1999-01-01

    The recording and read-out of a volume speckle pattern is investigated for transmission geometry. The modulation of the 3D speckle grains appears when the image of a coherently illuminated random diffusor is formed onto the crystal by an optical system whose pupil consists of two identical holes. The intensity distribution of the speckle pattern imaged onto the BSO crystal leads to a space-charge field by drift of photocarriers, resulting in a refractive index modulation. The main features of...

  9. Imaging functional blood vessels by the laser speckle imaging (LSI) technique using Q-statistics of the generalized differences algorithm.

    Ansari, Mohammad Zaheer; Cabrera, Humberto; Ramírez-Miquet, Evelio E

    2016-09-01

    In this work, we report about q statistics concept to improve the performance of generalized differences algorithm based on intensity histogram for imaging functional blood vessel structures in a rodent window chamber of a mice. The method uses the dynamic speckle signals obtained by transilluminating the rodent window chamber to create activity maps of vasculatures. The proposed method of generalized differences with q statistics (GDq) is very sensitive to the values of defined parameters such as: camera exposure time, the q value and the camera frame number. Appropriate choice of q values enhances the visibility (contrast) of functional blood vessels but at the same time without sacrificing the spatial resolution, which is of utmost importance for in-vivo vascular imaging. PMID:27154269

  10. Widefield lensless endoscopy via speckle-correlations

    Porat, Amir; Rigneault, Hervé; Oron, Dan; Gigan, Sylvain; Katz, Ori

    2016-01-01

    Flexible fiber-optic endoscopes provide a minimally-invasive solution for imaging at depths beyond the reach of conventional microscopes. Current endoscopes require focusing and/or scanning mechanisms at the distal end, which limit miniaturization and frame-rate, and induce aberrations. Alternative lensless solutions are based on adaptive wavefront-correction, but are extremely sensitive to fiber bending. Here, we demonstrate a novel endoscopic approach, which enables single-shot imaging at a variable working distance through a conventional fiber bundle, without the use of any distal optics. Our approach computationally retrieves the object image from a single speckle pattern transmitted through the bundle, exploiting phase information preserved through inherent angular speckle correlations. Unlike conventional fiber-bundle endoscopes, the resulting image is unpixelated, the resolution is diffraction-limited, objects can be imaged at variable working distance, and the technique is completely insensitive to fi...

  11. Real-time motion stabilization with B-mode ultrasound using image speckle information and visual servoing

    Krupa, A; Fichtinger, G.; Hager, G.D.

    2009-01-01

    Special Issue on Medical Robotics, Ayache, N. and Desai, J. (Eds.) International audience We develop visual servo control to stabilize the image of moving soft tissue in B-mode ultrasound (US) imaging. We define the target region in a B-mode US image, and automatically control a robot to manipulate an US probe by minimizing the difference between the target and the most recently acquired US image. We exploit tissue speckle information to compute the relative pose between the probe and t...

  12. Low-spatial coherence electrically-pumped semiconductor laser for speckle-free full-field imaging

    Redding, B; Huang, X; Lee, M L; Stone, A D; Choma, M A; Cao, H

    2014-01-01

    The spatial coherence of laser sources has limited their application to parallel imaging and projection due to coherent artifacts, such as speckle. In contrast, traditional incoherent light sources, such as thermal sources or light emitting diodes (LEDs), provide relatively low power per independent spatial mode. Here, we present a chip-scale, electrically-pumped semiconductor laser based on a novel design, demonstrating high power per mode with much lower spatial coherence than conventional laser sources. The laser resonator was fabricated with a chaotic, D-shaped cavity optimized to achieve highly multimode lasing. Lasing occurs simultaneously and independently in ~1000 modes, and hence the total emission exhibits very low spatial coherence. Speckle-free full-field imaging is demonstrated using the chaotic cavity laser as the illumination source. The power per mode of the sample illumination is several orders of magnitude higher than that of a LED or thermal light source. Such a compact, low-cost source, wh...

  13. Linear response range characterization and in vivo application of laser speckle imaging of blood flow dynamics

    Choi, Bernard; Ramírez-San-Juan, Julio C.; Lotfi, Justin; Nelson, J. S.

    2006-07-01

    Noninvasive blood flow imaging can provide critical information on the state of biological tissue and the efficacy of approaches to treat disease. With laser speckle imaging (LSI), relative changes in blood flow are typically reported, with the assumption that the measured values are on a linear scale. A linear relationship between the measured and actual flow rate values has been suggested. The actual flow rate range, over which this linear relationship is valid, is unknown. Herein we report the linear response range and velocity dynamic range (VDR) of our LSI instrument at two relevant camera integration times. For integration times of 1 and 10 ms, the best case VDR was 80 and 60 dB, respectively, and the worst case VDR was 20 and 50 dB. The best case VDR values were similar to those reported in the literature for optical Doppler tomography. We also demonstrate the potential of LSI for monitoring blood flow dynamics in the rodent dorsal skinfold chamber model. These findings imply that LSI can provide accurate wide-field maps of microvascular blood flow rate dynamics and highlight heterogeneities in flow response to the application of exogenous agents.

  14. Digital adaptive optics line-scanning confocal imaging system

    Liu, Changgeng; Kim, Myung K.

    2015-11-01

    A digital adaptive optics line-scanning confocal imaging (DAOLCI) system is proposed by applying digital holographic adaptive optics to a digital form of line-scanning confocal imaging system. In DAOLCI, each line scan is recorded by a digital hologram, which allows access to the complex optical field from one slice of the sample through digital holography. This complex optical field contains both the information of one slice of the sample and the optical aberration of the system, thus allowing us to compensate for the effect of the optical aberration, which can be sensed by a complex guide star hologram. After numerical aberration compensation, the corrected optical fields of a sequence of line scans are stitched into the final corrected confocal image. In DAOLCI, a numerical slit is applied to realize the confocality at the sensor end. The width of this slit can be adjusted to control the image contrast and speckle noise for scattering samples. DAOLCI dispenses with the hardware pieces, such as Shack-Hartmann wavefront sensor and deformable mirror, and the closed-loop feedbacks adopted in the conventional adaptive optics confocal imaging system, thus reducing the optomechanical complexity and cost. Numerical simulations and proof-of-principle experiments are presented that demonstrate the feasibility of this idea.

  15. Determination of astrometry and photometry of faint companions in the presence of residual speckle noise

    Burke, Daniel; Devaney, Nicholas; Gladysz, Szymon

    In this paper we examine approaches to faint companion detection and estimation in multi-spectral images. We will employ the Hotelling observer which is the optimal linear algorithm for signal detection. We have shown how to use this observer to estimate faint object position and brightness in the presence of residual speckle which usually limit astrometric and photometric techniques. These speckles can be reduced by differential imaging techniques such as Angular Differential Imaging and Spectral Differential Imaging. Here we present results based on simulations of adaptive optics corrected images from an ELT which contain quasi-static speckle noise. The simulation includes Angular Differential Imaging to reduce the residual speckle and subsequent multi-wavelenght processing. We examine the feasibility of this approach on simulated ELT observations of faint companions.

  16. Comparison of cerebral microcirculation of alloxan diabetes and healthy mice using laser speckle contrast imaging

    Timoshina, Polina A.; Shi, Rui; Zhang, Yang; Zhu, Dan; Semyachkina-Glushkovskaya, Oxana V.; Tuchin, Valery V.; Luo, Qingming

    2015-03-01

    The study of blood microcirculation is one of the most important problems of the medicine. This paper presents results of experimental study of cerebral blood flow microcirculation in mice with alloxan-induced diabetes using Temporal Laser Speckle Imaging (TLSI). Additionally, a direct effect of glucose water solution (concentration 20% and 45%) on blood flow microcirculation was studied. In the research, 20 white laboratory mice weighing 20-30 g were used. The TLSI method allows one to investigate time dependent scattering from the objects with complex dynamics, since it possesses greater temporal resolution. Results show that in brain of animal diabetic group diameter of sagittal vein is increased and the speed of blood flow reduced relative to the control group. Topical application of 20%- or 45%-glucose solutions also causes increase of diameter of blood vessels and slows down blood circulation. The results obtained show that diabetes development causes changes in the cerebral microcirculatory system and TLSI techniques can be effectively used to quantify these alterations.

  17. From synchrotron radiation to lab source: advanced speckle-based X-ray imaging using abrasive paper

    Wang, Hongchang; Kashyap, Yogesh; Sawhney, Kawal

    2016-02-01

    X-ray phase and dark-field imaging techniques provide complementary and inaccessible information compared to conventional X-ray absorption or visible light imaging. However, such methods typically require sophisticated experimental apparatus or X-ray beams with specific properties. Recently, an X-ray speckle-based technique has shown great potential for X-ray phase and dark-field imaging using a simple experimental arrangement. However, it still suffers from either poor resolution or the time consuming process of collecting a large number of images. To overcome these limitations, in this report we demonstrate that absorption, dark-field, phase contrast, and two orthogonal differential phase contrast images can simultaneously be generated by scanning a piece of abrasive paper in only one direction. We propose a novel theoretical approach to quantitatively extract the above five images by utilising the remarkable properties of speckles. Importantly, the technique has been extended from a synchrotron light source to utilise a lab-based microfocus X-ray source and flat panel detector. Removing the need to raster the optics in two directions significantly reduces the acquisition time and absorbed dose, which can be of vital importance for many biological samples. This new imaging method could potentially provide a breakthrough for numerous practical imaging applications in biomedical research and materials science.

  18. Laser speckle

    Tiziani, Hans J.

    1993-01-01

    Im Gegensatz zu der holografischen Interferometrie ermöglicht die Speckle-Interferometrie eine reine elektrooptische Datenaufzeichnung mit fernsehtechnischen Mitteln. Die zumeist fotografische Aufzeichnung und umständliche, aber auch zeitintensive Entwicklung der Speckle-lnterferogramme kann entfallen. Dies wird möglich, weil in der Speckle-lnterferometrie die Specklegröße der Ortsauflösung des Speichers angepaßt werden kann. Damit bietet sich die Speckle-Interferometrie für die industrielle ...

  19. Query Adaptive Image Retrieval System

    Amruta Dubewar

    2014-03-01

    Full Text Available Images play a crucial role in various fields such as art gallery, medical, journalism and entertainment. Increasing use of image acquisition and data storage technologies have enabled the creation of large database. So, it is necessary to develop appropriate information management system to efficiently manage these collections and needed a system to retrieve required images from these collections. This paper proposed query adaptive image retrieval system (QAIRS to retrieve images similar to the query image specified by user from database. The goal of this system is to support image retrieval based on content properties such as colour and texture, usually encoded into feature vectors. In this system, colour feature extracted by various techniques such as colour moment, colour histogram and autocorrelogram and texture feature extracted by using gabor wavelet. Hashing technique is used to embed high dimensional image features into hamming space, where search can be performed by hamming distance of compact hash codes. Depending upon minimum hamming distance it returns the similar image to query image.

  20. Characterization of SEM speckle pattern marking and imaging distortion by digital image correlation

    Surface patterning by e-beam lithography and scanning electron microscope (SEM) imaging distortions are studied via digital image correlation. The global distortions from the reference pattern, which has been numerically generated, are first quantified from a digital image correlation procedure between the (virtual) reference pattern and the actual SEM image both in secondary and backscattered electron imaging modes. These distortions result from both patterning and imaging techniques. These two contributions can be separated (without resorting to an external caliper) based on the images of the same patterned surface acquired at different orientations. Patterning distortions are much smaller than those due to imaging on wide field images. (paper)

  1. Speckle reduction in optical coherence tomography images of human skin by a spatial diversity method - art. no. 66270P

    Jørgensen, Thomas Martini; Thrane, Lars; Mogensen, M.; Pedersen, Finn; Andersen, Peter E.

    2007-01-01

    system. Here, we consider a method that in principle can be fitted to most OCT systems without major modifications. Specifically, we address a spatial diversity technique for suppressing speckle noise in OCT images of human skin. The method is a variant of changing the position of the sample relative to...... the measuring probe. Instead of physically moving the sample, which is often not feasible for in vivo imaging, the position of the focal plane of the probe beam is shifted. If the numerical aperture is sufficiently high this spatial diversity scheme incorporates a variant of angular compounding. We...

  2. Echokardiographische Prädiktoren eines Vorhofflimmerrezidives und atriales Remodeling nach Pulmonalvenenisolation mit einem methodischen Vergleich von Strainmessungen mit Tissue Doppler Imaging und Speckle Tracking Imaging

    Kim, Tu-Won

    2011-01-01

    First, we aimed to compare strain measurement with tissue Doppler imaging (TDI) and speckle tracking imaging (STI). Secondly we wanted to evaluate the changes of diastolic and systolic function after pulmonary vein isolation (PVI) in atrial fibrillation (AF) and to identify the echocardiographic predictors of recurrence. Methods and Results: We included 71 patients undergoing PVI (mean age 58.5 ± 9.8 Years, 28 Women). In 9 Patients a second intervention was done because of recurrence ...

  3. Characterization of SEM speckle pattern marking and imaging distortion by Digital Image Correlation

    Guery, Adrien; Latourte, Felix; Hild, François; Roux, Stéphane

    2014-01-01

    Surface patterning by e-beam lithography and SEM imaging distortions are studied via digital image correlation. The global distortions from the reference pattern, which has been numerically generated, are first quantified from a digital image correlation procedure between the (virtual) reference pattern and the actual SEM image both in secondary and backscattered electron imaging modes. These distortions result from both patterning and imaging techniques. These two contributions can be separa...

  4. Two-dimentional speckle tracking strain imaging in the assessment of myocardial diastolic function in patients with stable angina pectoris

    Somaye Farokhnejad

    2015-06-01

    Full Text Available Introduction: Ischemic heart disease is caused mainly by obstruction of coronary arteries. The ischemic assessment through echocardiography is dependent on wall motion abnormality detection during systole. In patients with ischemic heart disease the diastolic function is impaired before systolic function and measurement of regional diastolic dysfunction if possible will be most sensitive for assessment of obstructed coronary artery region. This study was designed to determine whether regional left ventricular delayed relaxation diagnosis could be detected with strain imaging derived from two-dimensional speckle-tracking echocardiography in patients with coronary artery disease.Methods: All the articles reviewed were obtained using MEDLINE & ScienceDirect (up to October 2014. All data extracted by speckle tracking echocardiography. The index which is used is strain imaging diastolic index which is calculated as: (A-B A×100  . A is the amount of strain at the time Aortic value closure and B is the amount of strain in first one-third point of diastolic duration.Result: Four articles were reviewed. Three articles assessed patients with echocardiography at rest and one with stress echocardiography. All articles showed the coronary artery tracking with significant stenosis is possible by regional deformation analysis through two-dimensional strain.Discussion: The usage of strain images obtained through two-dimensional speckle tracking has been validated for the quantitation assessment of regional dysfunction in ischemic heart disease. Regional LV delayed relaxation diagnosis with strain imaging is a reliable method after treadmill stress test.Conclusion:  Strain imaging is reasonable for evaluation of ischemia as a low cost noninvasive test with high accuracy.

  5. Compressive adaptive computational ghost imaging

    Aßmann, Marc; 10.1038/srep01545

    2013-01-01

    Compressive sensing is considered a huge breakthrough in signal acquisition. It allows recording an image consisting of $N^2$ pixels using much fewer than $N^2$ measurements if it can be transformed to a basis where most pixels take on negligibly small values. Standard compressive sensing techniques suffer from the computational overhead needed to reconstruct an image with typical computation times between hours and days and are thus not optimal for applications in physics and spectroscopy. We demonstrate an adaptive compressive sampling technique that performs measurements directly in a sparse basis. It needs much fewer than $N^2$ measurements without any computational overhead, so the result is available instantly.

  6. Preliminary images from an adaptive imaging system.

    Griffiths, J A; Metaxas, M G; Pani, S; Schulerud, H; Esbrand, C; Royle, G J; Price, B; Rokvic, T; Longo, R; Asimidis, A; Bletsas, E; Cavouras, D; Fant, A; Gasiorek, P; Georgiou, H; Hall, G; Jones, J; Leaver, J; Li, G; Machin, D; Manthos, N; Matheson, J; Noy, M; Ostby, J M; Psomadellis, F; van der Stelt, P F; Theodoridis, S; Triantis, F; Turchetta, R; Venanzi, C; Speller, R D

    2008-06-01

    I-ImaS (Intelligent Imaging Sensors) is a European project aiming to produce real-time adaptive X-ray imaging systems using Monolithic Active Pixel Sensors (MAPS) to create images with maximum diagnostic information within given dose constraints. Initial systems concentrate on mammography and cephalography. In our system, the exposure in each image region is optimised and the beam intensity is a function of tissue thickness and attenuation, and also of local physical and statistical parameters in the image. Using a linear array of detectors, the system will perform on-line analysis of the image during the scan, followed by optimisation of the X-ray intensity to obtain the maximum diagnostic information from the region of interest while minimising exposure of diagnostically less important regions. This paper presents preliminary images obtained with a small area CMOS detector developed for this application. Wedge systems were used to modulate the beam intensity during breast and dental imaging using suitable X-ray spectra. The sensitive imaging area of the sensor is 512 x 32 pixels 32 x 32 microm(2) in size. The sensors' X-ray sensitivity was increased by coupling to a structured CsI(Tl) scintillator. In order to develop the I-ImaS prototype, the on-line data analysis and data acquisition control are based on custom-developed electronics using multiple FPGAs. Images of both breast tissues and jaw samples were acquired and different exposure optimisation algorithms applied. Results are very promising since the average dose has been reduced to around 60% of the dose delivered by conventional imaging systems without decrease in the visibility of details. PMID:18291697

  7. Episcopic coaxial illumination device for the simultaneous recording of the speckle signature in the spectrum and in the image of scattering reflective surfaces

    Fernández, José L.; López-Vázquez, José Carlos; Trillo, Cristina; Doval, Ángel F.

    2012-10-01

    Inspection of optically rough surfaces in search of defects or other surface features with deterministic reflectance distributions is a subject well suited to optical techniques. We present a device with episcopic coaxial illumination, specifically developed for such kind of inspection tasks, which simultaneously renders both a coherent image and the spatial spectrum of a portion of the surface, precisely defined by the illuminating laser spot. It is based on the wellknown single-lens coherent image processing system, with beamsplitters added to insert the illuminating laser beam and to allow simultaneous access to the Fourier transform and the image planes. The device allows inspecting the speckle signature of surface features in both planes, thus allowing different defect recognition approaches. By selecting the size of the illuminated area of the object or the lens aperture, different speckle sizes can be obtained. If the speckle size is made large enough, identification of individual features can be made on the basis of their particular speckle signatures. Some envisaged applications are the characterization of defects or structures in rough surfaces, the evaluation of speckle statistics in precisely defined zones of surfaces or the identification of authentication marks.

  8. Nuclear Speckles

    Spector, David L.; Lamond, Angus I.

    2011-01-01

    Nuclear speckles, also known as interchromatin granule clusters, are nuclear domains enriched in pre-mRNA splicing factors, located in the interchromatin regions of the nucleoplasm of mammalian cells. When observed by immunofluorescence microscopy, they usually appear as 20–50 irregularly shaped structures that vary in size. Speckles are dynamic structures, and their constituents can exchange continuously with the nucleoplasm and other nuclear locations, including active transcription sites. ...

  9. Local intensity adaptive image coding

    Huck, Friedrich O.

    1989-01-01

    The objective of preprocessing for machine vision is to extract intrinsic target properties. The most important properties ordinarily are structure and reflectance. Illumination in space, however, is a significant problem as the extreme range of light intensity, stretching from deep shadow to highly reflective surfaces in direct sunlight, impairs the effectiveness of standard approaches to machine vision. To overcome this critical constraint, an image coding scheme is being investigated which combines local intensity adaptivity, image enhancement, and data compression. It is very effective under the highly variant illumination that can exist within a single frame or field of view, and it is very robust to noise at low illuminations. Some of the theory and salient features of the coding scheme are reviewed. Its performance is characterized in a simulated space application, the research and development activities are described.

  10. Despeckling of medical ultrasound images using data and rate adaptive lossy compression.

    Gupta, Nikhil; Swamy, M N S; Plotkin, Eugene

    2005-06-01

    A novel technique for despeckling the medical ultrasound images using lossy compression is presented. The logarithm of the input image is first transformed to the multiscale wavelet domain. It is then shown that the subband coefficients of the log-transformed ultrasound image can be successfully modeled using the generalized Laplacian distribution. Based on this modeling, a simple adaptation of the zero-zone and reconstruction levels of the uniform threshold quantizer is proposed in order to achieve simultaneous despeckling and quantization. This adaptation is based on: (1) an estimate of the corrupting speckle noise level in the image; (2) the estimated statistics of the noise-free subband coefficients; and (3) the required compression rate. The Laplacian distribution is considered as a special case of the generalized Laplacian distribution and its efficacy is demonstrated for the problem under consideration. Context-based classification is also applied to the noisy coefficients to enhance the performance of the subband coder. Simulation results using a contrast detail phantom image and several real ultrasound images are presented. To validate the performance of the proposed scheme, comparison with two two-stage schemes, wherein the speckled image is first filtered and then compressed using the state-of-the-art JPEG2000 encoder, is presented. Experimental results show that the proposed scheme works better, both in terms of the signal to noise ratio and the visual quality. PMID:15957598

  11. The Subaru Coronagraphic Extreme Adaptive Optics Imager: First Results and On-Sky Performance

    Currie, Thayne; Martinache, Frantz; Clergeon, Christophe; McElwain, Michael; Thalmann, Christian; Jovanovic, Nemanja; Singh, Garima; Kudo, Tomoyuki

    2013-01-01

    We present new on-sky results for the Subaru Coronagraphic Extreme Adaptive Optics imager (SCExAO) verifying and quantifying the contrast gain enabled by key components: the closed-loop coronagraphic low-order wavefront sensor (CLOWFS) and focal plane wavefront control ("speckle nulling"). SCExAO will soon be coupled with a high-order, Pyramid wavefront sensor which will yield > 90% Strehl ratio and enable 10^6--10^7 contrast at small angular separations allowing us to image gas giant planets at solar system scales. Upcoming instruments like VAMPIRES, FIRST, and CHARIS will expand SCExAO's science capabilities.

  12. Three-dimensional shear wave imaging based on full-field laser speckle contrast imaging with one-dimensional mechanical scanning.

    Chao, Pei-Yu; Li, Pai-Chi

    2016-08-22

    The high imaging resolution and motion sensitivity of optical-based shear wave detection has made it an attractive technique in biomechanics studies with potential for improving the capabilities of shear wave elasticity imaging. In this study we implemented laser speckle contrast imaging for two-dimensional (X-Z) tracking of transient shear wave propagation in agarose phantoms. The mechanical disturbances induced by the propagation of the shear wave caused temporal and spatial fluctuations in the local speckle pattern, which manifested as local blurring. By mechanically moving the sample in the third dimension (Y), and performing two-dimensional shear wave imaging at every scan position, the three-dimensional shear wave velocity distribution of the phantom could be reconstructed. Based on comparisons with the reference shear wave velocity measurements obtained using a commercial ultrasound shear wave imaging system, the developed system can estimate the shear wave velocity with an error of less than 6% for homogeneous phantoms with shear moduli ranging from 1.52 kPa to 7.99 kPa. The imaging sensitivity of our system makes it capable of measuring small variations in shear modulus; the estimated standard deviation of the shear modulus was found to be less than 0.07 kPa. A submillimeter spatial resolution for three-dimensional shear wave imaging has been achieved, as demonstrated by the ability to detect a 1-mm-thick stiff plate embedded inside heterogeneous agarose phantoms. PMID:27557169

  13. Blurred Image Classification based on Adaptive Dictionary

    Xiaofei Zhou; Guangling Sun; Jie Yin

    2012-01-01

    Two frameworks for blurred image classification bas ed on adaptive dictionary are proposed. Given a blurred image, instead of image deblurring, the sem antic category of the image is determined by blur insensitive sparse coefficients calculated dependin g on an adaptive dictionary. The dictionary is adap tive to an assumed space invariant Point Spread Function (PSF) estimated from the input blurred image. In o ne of th...

  14. Application of speckle image correlation for real-time assessment of metabolic activity in herpes virus-infected cells

    Earlier we reported developing a speckle interferometry technique and a device designed to assess the metabolic activity of a cell monolayer cultivated on a glass substrate. This paper aimed at upgrading the technique and studying its potential for real-time assessment of herpes virus development process. Speckle dynamics was recorded in the image plane of intact and virus-infected cell monolayer. HLE-3, L-41 and Vero cells were chosen as research targets. Herpes simplex virus-1-(HSV-1)- infected cell cultures were studied. For 24 h we recorded the digital value of optical signal I in one pixel and parameter η characterizing change in the distribution of the optical signal on 10 × 10-pixel areas. The coefficient of multiple determination calculated by η time dependences for three intact cell cultures equals 0.94. It was demonstrated that the activity parameters are significantly different for intact and virus-infected cells. The difference of η value for intact and HSV-1-infected cells is detectable 10 minutes from the experiment start.

  15. Adaptive Computed Tomography Imaging Spectrometer Project

    National Aeronautics and Space Administration — The present proposal describes the development of an adaptive Computed Tomography Imaging Spectrometer (CTIS), or "Snapshot" spectrometer which can...

  16. A novel effective method for the assessment of microvascular function in male patients with coronary artery disease: a pilot study using laser speckle contrast imaging

    J.P. Borges

    2016-01-01

    Full Text Available Evaluation of microvascular endothelial function is essential for investigating the pathophysiology and treatment of cardiovascular and metabolic diseases. Although laser speckle contrast imaging technology is well accepted as a noninvasive methodology for assessing microvascular endothelial function, it has never been used to compare male patients with coronary artery disease with male age-matched healthy controls. Thus, the aim of this study was to determine whether laser speckle contrast imaging could be used to detect differences in the systemic microvascular functions of patients with established cardiovascular disease (n=61 and healthy age-matched subjects (n=24. Cutaneous blood flow was assessed in the skin of the forearm using laser speckle contrast imaging coupled with the transdermal iontophoretic delivery of acetylcholine and post-occlusive reactive hyperemia. The maximum increase in skin blood flow induced by acetylcholine was significantly reduced in the cardiovascular disease patients compared with the control subjects (74 vs 116%; P<0.01. With regard to post-occlusive reactive hyperemia-induced vasodilation, the patients also presented reduced responses compared to the controls (0.42±0.15 vs 0.50±0.13 APU/mmHg; P=0.04. In conclusion, laser speckle contrast imaging can identify endothelial and microvascular dysfunctions in male individuals with cardiovascular disease. Thus, this technology appears to be an efficient non-invasive technique for evaluating systemic microvascular and endothelial functions, which could be valuable as a peripheral marker of atherothrombotic diseases in men.

  17. A novel effective method for the assessment of microvascular function in male patients with coronary artery disease: a pilot study using laser speckle contrast imaging.

    Borges, J P; Lopes, G O; Verri, V; Coelho, M P; Nascimento, P M C; Kopiler, D A; Tibirica, E

    2016-01-01

    Evaluation of microvascular endothelial function is essential for investigating the pathophysiology and treatment of cardiovascular and metabolic diseases. Although laser speckle contrast imaging technology is well accepted as a noninvasive methodology for assessing microvascular endothelial function, it has never been used to compare male patients with coronary artery disease with male age-matched healthy controls. Thus, the aim of this study was to determine whether laser speckle contrast imaging could be used to detect differences in the systemic microvascular functions of patients with established cardiovascular disease (n=61) and healthy age-matched subjects (n=24). Cutaneous blood flow was assessed in the skin of the forearm using laser speckle contrast imaging coupled with the transdermal iontophoretic delivery of acetylcholine and post-occlusive reactive hyperemia. The maximum increase in skin blood flow induced by acetylcholine was significantly reduced in the cardiovascular disease patients compared with the control subjects (74 vs 116%; PAPU/mmHg; P=0.04). In conclusion, laser speckle contrast imaging can identify endothelial and microvascular dysfunctions in male individuals with cardiovascular disease. Thus, this technology appears to be an efficient non-invasive technique for evaluating systemic microvascular and endothelial functions, which could be valuable as a peripheral marker of atherothrombotic diseases in men. PMID:27599202

  18. Near Field Speckles

    Brogioli, Doriano

    2008-01-01

    Elastic light scattering has been extensively used to study samples showing a non uniform refraction index on lengthscales from a fraction of a micrometer to a fraction of a millimeter. Typically, a wide laser beam is sent through the sample, and the light scattered at any angle is measured by a detector in the far field. In this Ph. D. thesis, I describe three new techniques, which allow to measure the scattering intensities, working in the near field: hOmoyne Near Field Speckles (ONFS), hEterodyne Near Field Speckles (ENFS) and Schlieren-like Near Field Speckles (SNFS). Basically, the experimental setup consists in a wide laser beam passing through the sample; a lens forms an image of a plane at a given distance from the cell on a CCD sensor. The image, in the near field, shows speckles, since it is formed by the stochastical interference of the light coming from a random sample. I show that, under suitable conditions, the correlation function of such a field closely mirrors the correlation function of the ...

  19. An in vivo analysis of facial muscle change treated with botulinum toxin type A using digital image speckle correlation

    Xu, Yan; Palmaccio, Samantha Palmaccio; Bui, Duc; Dagum, Alexander; Rafailovich, Miriam

    Been famous for clinical use from early 1980s, the neuromuscular blocking agent Botulinum toxin type A (BTX-A), has been used to reduce wrinkles for a long time. Only little research has been done to quantify the change of muscle contraction before and after injection and most research paper depend on subjective evaluation from both patients and surgeons. In our research, Digital Image Speckle Correlation (DISC) was employed to study the mechanical properties of skin, contraction mode of muscles (injected) and reaction of neighbor muscle group (un-injected).At the same time, displacement patterns (vector maps)generated by DISC can predict injection locus for surgeons who normally handle it depending only on visual observation.

  20. Alteration of Blood Flow in a Venular Network by Infusion of Dextran 500: Evaluation with a Laser Speckle Contrast Imaging System

    Namgung, Bumseok; Ng, Yan Cheng; Nam, Jeonghun; Leo, Hwa Liang; Kim, Sangho

    2015-01-01

    This study examined the effect of dextran-induced RBC aggregation on the venular flow in microvasculature. We utilized the laser speckle contrast imaging (LSCI) as a wide-field imaging technique to visualize the flow distribution in venules influenced by abnormally elevated levels of RBC aggregation at a network-scale level, which was unprecedented in previous studies. RBC aggregation in rats was induced by infusing Dextran 500. To elucidate the impact of RBC aggregation on microvascular perf...

  1. Flexibly combined optical microangiography and dual-wavelength laser speckle system for comprehensive imaging of hemodynamic and metabolic responses

    Shi, Lei; Qin, Jia; An, Lin; Wang, Ruikang K.

    2014-03-01

    We have proposed and developed a multi-modal non-invasive biomedical optical imager. It was combined from the subsystems of optical microangiography and dual-wavelength laser speckle contrast imaging. The system was designed to maintain the performances of both subsystems. It was capable of simultaneously imaging the hemodynamic and metabolic responses in tissue environment in vivo. To achieve such requirements, we utilized unique optical setup, such as paired dichroic mirrors to compensate dispersion, additional relay lens to increase working distance and translational sample probe to freely select imaging area and focal plane. The multi-functionality of the system was demonstrated in an investigation of hemodynamic and metabolic responses on an acute wound healing model in mouse pinna in vivo. The microvasculature, blood flow and hemoglobin concentration from millimeter down to capillary level were comprehensively visualized. The captured instantaneous responses to wound onset differed greatly between localized areas; after that blood flow had a rebalance tendency, and hemoglobin concentration dynamically recovered to baseline situation.

  2. EVALUATION OF FILTERS FOR ENVISAT ASAR SPECKLE SUPPRESSION IN PASTURE AREA

    X. Wang

    2012-07-01

    Full Text Available In order to quantify real time pasture biomass from SAR image, regression model between ground measurements of biomass and ENVISAT ASAR backscattering coefficient should be built up. An important prerequisite of valid and accurate regression model is accurate grass backscattering coefficient which, however, cannot be obtained when there is speckle. Speckle noise is the best known problem of SAR images because of the coherent nature of radar illumination imaging system. This study aims to choose better adaptive filter from NEST software to reduce speckle noise in homogeneous pasture area, with little regard to linear feature (e.g. edge between pasture and forest or point feature (e.g. pond, tree preservation. This paper presents the speckle suppression result of ENVISAT ASAR VV/VH images in pasture of Western Australia (WA using four built-in adaptive filters of the NEST software: Frost, Gamma Map, Lee, and Refined Lee filter. Two indices are usually used for evaluation of speckle suppression ability: ENL (Equivalent Number of Looks and SSI (Speckle Suppression Index. These two, however, are not reliable because sometimes they overestimate mean value. Therefore, apart from ENL and SSI, the authors also used a new index SMPI (Speckle Suppression and Mean Preservation Index. It was found that, Lee filter with window size 7×7 and Frost filter (damping factor = 2 with window size 5×5 gave the best performance for VV and VH polarization, respectively. The filtering, together with radiometric calibration and terrain correction, paves the way to extraction of accurate backscattering coefficient of grass in homogeneous pasture area in WA.

  3. Reduction of speckle contrast in HDTV laser projection display.

    Apeland, Knut Øyvind

    2008-01-01

    Abstract In this thesis the focus has been on laser speckle. It is done in collaboration with poLight. They are developing a projector, where laser light is the source of illumination. In such projectors, laser speckle degrades the image quality. The aim of this project is to construct a speckle reduction device to be used in the laser projector. The theory covers a description of laser speckle, how to reduce the speckle contrast, and five methods to so. We explain why speckle arises and whi...

  4. Digital Image Speckle Correlation for the Quantification of the Cosmetic Treatment with Botulinum Toxin Type A (BTX-A)

    Bhatnagar, Divya; Conkling, Nicole; Rafailovich, Miriam; Dagum, Alexander

    2012-02-01

    The skin on the face is directly attached to the underlying muscles. Here, we successfully introduce a non-invasive, non-contact technique, Digital Image Speckle Correlation (DISC), to measure the precise magnitude and duration of facial muscle paralysis inflicted by BTX-A. Subjective evaluation by clinicians and patients fail to objectively quantify the direct effect and duration of BTX-A on the facial musculature. By using DISC, we can (a) Directly measure deformation field of the facial skin and determine the locus of facial muscular tension(b)Quantify and monitor muscular paralysis and subsequent re-innervation following injection; (c) Continuously correlate the appearance of wrinkles and muscular tension. Two sequential photographs of slight facial motion (frowning, raising eyebrows) are taken. DISC processes the images to produce a vector map of muscular displacement from which spatially resolved information is obtained regarding facial tension. DISC can track the ability of different muscle groups to contract and can be used to predict the site of injection, quantify muscle paralysis and the rate of recovery following BOTOX injection.

  5. Monitoring Hypoxia Induced Changes in Cochlear Blood Flow and Hemoglobin Concentration Using a Combined Dual-Wavelength Laser Speckle Contrast Imaging and Doppler Optical Microangiography System

    Reif, Roberto; Qin, Jia; Shi, Lei; Dziennis, Suzan; Zhi, Zhongwei; Nuttall, Alfred L.; Wang, Ruikang K.

    2012-01-01

    A synchronized dual-wavelength laser speckle contrast imaging (DWLSCI) system and a Doppler optical microangiography (DOMAG) system was developed to determine several ischemic parameters in the cochlea due to a systemic hypoxic challenge. DWLSCI can obtain two-dimensional data, and was used to determine the relative changes in cochlear blood flow, and change in the concentrations of oxyhemoglobin (HbO), deoxyhemoglobin (Hb) and total hemoglobin (HbT) in mice. DOMAG can obtain three-dimensiona...

  6. SU-D-210-05: The Accuracy of Raw and B-Mode Image Data for Ultrasound Speckle Tracking in Radiation Therapy

    O’Shea, T; Bamber, J; Harris, E [The Institute of Cancer Research & Royal Marsden, Sutton and London (United Kingdom)

    2015-06-15

    Purpose: For ultrasound speckle tracking there is some evidence that the envelope-detected signal (the main step in B-mode image formation) may be more accurate than raw ultrasound data for tracking larger inter-frame tissue motion. This study investigates the accuracy of raw radio-frequency (RF) versus non-logarithmic compressed envelope-detected (B-mode) data for ultrasound speckle tracking in the context of image-guided radiation therapy. Methods: Transperineal ultrasound RF data was acquired (with a 7.5 MHz linear transducer operating at a 12 Hz frame rate) from a speckle phantom moving with realistic intra-fraction prostate motion derived from a commercial tracking system. A normalised cross-correlation template matching algorithm was used to track speckle motion at the focus using (i) the RF signal and (ii) the B-mode signal. A range of imaging rates (0.5 to 12 Hz) were simulated by decimating the imaging sequences, therefore simulating larger to smaller inter-frame displacements. Motion estimation accuracy was quantified by comparison with known phantom motion. Results: The differences between RF and B-mode motion estimation accuracy (2D mean and 95% errors relative to ground truth displacements) were less than 0.01 mm for stable and persistent motion types and 0.2 mm for transient motion for imaging rates of 0.5 to 12 Hz. The mean correlation for all motion types and imaging rates was 0.851 and 0.845 for RF and B-mode data, respectively. Data type is expected to have most impact on axial (Superior-Inferior) motion estimation. Axial differences were <0.004 mm for stable and persistent motion and <0.3 mm for transient motion (axial mean errors were lowest for B-mode in all cases). Conclusions: Using the RF or B-mode signal for speckle motion estimation is comparable for translational prostate motion. B-mode image formation may involve other signal-processing steps which also influence motion estimation accuracy. A similar study for respiratory-induced motion

  7. SU-D-210-05: The Accuracy of Raw and B-Mode Image Data for Ultrasound Speckle Tracking in Radiation Therapy

    Purpose: For ultrasound speckle tracking there is some evidence that the envelope-detected signal (the main step in B-mode image formation) may be more accurate than raw ultrasound data for tracking larger inter-frame tissue motion. This study investigates the accuracy of raw radio-frequency (RF) versus non-logarithmic compressed envelope-detected (B-mode) data for ultrasound speckle tracking in the context of image-guided radiation therapy. Methods: Transperineal ultrasound RF data was acquired (with a 7.5 MHz linear transducer operating at a 12 Hz frame rate) from a speckle phantom moving with realistic intra-fraction prostate motion derived from a commercial tracking system. A normalised cross-correlation template matching algorithm was used to track speckle motion at the focus using (i) the RF signal and (ii) the B-mode signal. A range of imaging rates (0.5 to 12 Hz) were simulated by decimating the imaging sequences, therefore simulating larger to smaller inter-frame displacements. Motion estimation accuracy was quantified by comparison with known phantom motion. Results: The differences between RF and B-mode motion estimation accuracy (2D mean and 95% errors relative to ground truth displacements) were less than 0.01 mm for stable and persistent motion types and 0.2 mm for transient motion for imaging rates of 0.5 to 12 Hz. The mean correlation for all motion types and imaging rates was 0.851 and 0.845 for RF and B-mode data, respectively. Data type is expected to have most impact on axial (Superior-Inferior) motion estimation. Axial differences were <0.004 mm for stable and persistent motion and <0.3 mm for transient motion (axial mean errors were lowest for B-mode in all cases). Conclusions: Using the RF or B-mode signal for speckle motion estimation is comparable for translational prostate motion. B-mode image formation may involve other signal-processing steps which also influence motion estimation accuracy. A similar study for respiratory-induced motion

  8. Arterial elasticity imaging: comparison of finite-element analysis models with high-resolution ultrasound speckle tracking

    Park Dae

    2010-06-01

    Full Text Available Abstract Background The nonlinear mechanical properties of internal organs and tissues may be measured with unparalleled precision using ultrasound imaging with phase-sensitive speckle tracking. The many potential applications of this important noninvasive diagnostic approach include measurement of arterial stiffness, which is associated with numerous major disease processes. The accuracy of previous ultrasound measurements of arterial stiffness and vascular elasticity has been limited by the relatively low strain of nonlinear structures under normal physiologic pressure and the measurement assumption that the effect of the surrounding tissue modulus might be ignored in both physiologic and pressure equalized conditions. Methods This study performed high-resolution ultrasound imaging of the brachial artery in a healthy adult subject under normal physiologic pressure and the use of external pressure (pressure equalization to increase strain. These ultrasound results were compared to measurements of arterial strain as determined by finite-element analysis models with and without a surrounding tissue, which was represented by homogenous material with fixed elastic modulus. Results Use of the pressure equalization technique during imaging resulted in average strain values of 26% and 18% at the top and sides, respectively, compared to 5% and 2%, at the top and sides, respectively, under physiologic pressure. In the artery model that included surrounding tissue, strain was 19% and 16% under pressure equalization versus 9% and 13% at the top and sides, respectively, under physiologic pressure. The model without surrounding tissue had slightly higher levels of strain under physiologic pressure compared to the other model, but the resulting strain values under pressure equalization were > 60% and did not correspond to experimental values. Conclusions Since pressure equalization may increase the dynamic range of strain imaging, the effect of the

  9. Adaptive image processing a computational intelligence perspective

    Guan, Ling; Wong, Hau San

    2002-01-01

    Adaptive image processing is one of the most important techniques in visual information processing, especially in early vision such as image restoration, filtering, enhancement, and segmentation. While existing books present some important aspects of the issue, there is not a single book that treats this problem from a viewpoint that is directly linked to human perception - until now. This reference treats adaptive image processing from a computational intelligence viewpoint, systematically and successfully, from theory to applications, using the synergies of neural networks, fuzzy logic, and

  10. Speckle noise reduction in breast ultrasound images: SMU (srad median unsharp) approch

    Image denoising has become a very essential for better information extraction from the image and mainly from so noised ones, such as ultrasound images. In certain cases, for instance in ultrasound images, the noise can restrain information which is valuable for the general practitioner. Consequently medical images are very inconsistent, and it is crucial to operate case to case. This paper presents a novel algorithm SMU (Srad Median Unsharp) for noise suppression in ultrasound breast images in order to realize a computer aided diagnosis (CAD) for breast cancer.

  11. Non-invasive single-shot 3D imaging through a scattering layer using speckle interferometry

    Somkuwar, Atul S; R., Vinu; Park, Yongkeun; Singh, Rakesh Kumar

    2015-01-01

    Optical imaging through complex scattering media is one of the major technical challenges with important applications in many research fields, ranging from biomedical imaging, astronomical telescopy, and spatially multiplex optical communications. Although various approaches for imaging though turbid layer have been recently proposed, they had been limited to two-dimensional imaging. Here we propose and experimentally demonstrate an approach for three-dimensional single-shot imaging of objects hidden behind an opaque scattering layer. We demonstrate that under suitable conditions, it is possible to perform the 3D imaging to reconstruct the complex amplitude of objects situated at different depths.

  12. Image segmentation of diseased lentil leaves for disease speckle%扁豆病害叶片的病斑剥离分割

    李学俊; 赵礼良

    2014-01-01

    Traditional segmentation methods can obtain better result for these images which have distinct difference between the goal and background area. However these methods are difficult to obtain ideal disease speckle for diseased lentil leave images which have minor difference among normal leaves and disease speckles. So in this paper, it proposes a method that is suitable for diseased lentil leave images. This method has two stages including initial segmentation and secondary segmentation. Color gradient graph of these images is computed, then the Otsu algorithm is applied to eliminate lower gra-dient. Watershed algorithm is used to pre-segment the images, then a rough target zone based on zone area features is gained. FCM algorithm is applied to rough target zone. By analyzing difference between green alley of disease speckle and normal leaves, disease speckle is acquired. Experimental results show good effect of segmenting disease speckle with this method.%传统的分割方法针对目标和背景灰度值差距大的图像能得到较好的分割效果,但在对正常叶片和病斑灰度值相似度高的扁豆病害叶片图像分割时,难以得到理想的目标病斑。针对该问题,提出了一种适合正常叶片和病斑相似度高的图像剥离分割方法。该方法包括初始分割和二次分割两个步骤。初始分割是基于样本图片的彩色梯度图,采用最大类间标准方差与分水岭相结合的算法获得病斑粗略区域。二次分割是对粗略目标区域进行模糊C聚类分割得到目标病斑。实验结果表明,该剥离分割算法能提高病斑分割精确度,较好地分割出病斑目标。

  13. Modified multiscale sample entropy computation of laser speckle contrast images and comparison with the original multiscale entropy algorithm.

    Humeau-Heurtier, Anne; Mahé, Guillaume; Abraham, Pierre

    2015-12-01

    Laser speckle contrast imaging (LSCI) enables a noninvasive monitoring of microvascular perfusion. Some studies have proposed to extract information from LSCI data through their multiscale entropy (MSE). However, for reaching a large range of scales, the original MSE algorithm may require long recordings for reliability. Recently, a novel approach to compute MSE with shorter data sets has been proposed: the short-time MSE (sMSE). Our goal is to apply, for the first time, the sMSE algorithm in LSCI data and to compare results with those given by the original MSE. Moreover, we apply the original MSE algorithm on data of different lengths and compare results with those given by longer recordings. For this purpose, synthetic signals and 192 LSCI regions of interest (ROIs) of different sizes are processed. Our results show that the sMSE algorithm is valid to compute the MSE of LSCI data. Moreover, with time series shorter than those initially proposed, the sMSE and original MSE algorithms give results with no statistical difference from those of the original MSE algorithm with longer data sets. The minimal acceptable length depends on the ROI size. Comparisons of MSE from healthy and pathological subjects can be performed with shorter data sets than those proposed until now. PMID:26220209

  14. Blurred Image Classification Based on Adaptive Dictionary

    Guangling Sun

    2013-02-01

    Full Text Available Two frameworks for blurred image classification bas ed on adaptive dictionary are proposed. Given a blurred image, instead of image deblurring, the sem antic category of the image is determined by blur insensitive sparse coefficients calculated dependin g on an adaptive dictionary. The dictionary is adap tive to an assumed space invariant Point Spread Function (PSF estimated from the input blurred image. In o ne of the proposed two frameworks, the PSF is inferred separately and in the other, the PSF is updated combined with sparse coefficients calculation in an alternative and iterative manner. The experimental results have evaluated three types of blur namely d efocus blur, simple motion blur and camera shake bl ur. The experiment results confirm the effectiveness of the proposed frameworks.

  15. Stochastic parallel gradient descent based adaptive optics used for high contrast imaging coronagraph

    Dong, Bing; Zhang, Xi

    2011-01-01

    An adaptive optics (AO) system based on stochastic parallel gradient descent (SPGD) algorithm is proposed to reduce the speckle noises in the optical system of stellar coronagraph in order to further improve the contrast. The principle of SPGD algorithm is described briefly and a metric suitable for point source imaging optimization is given. The feasibility and good performance of SPGD algorithm is demonstrated by experimental system featured with a 140-actuators deformable mirror (DM) and a Hartmann- Shark wavefront sensor. Then the SPGD based AO is applied to a liquid crystal array (LCA) based coronagraph. The LCA can modulate the incoming light to generate a pupil apodization mask in any pattern. A circular stepped pattern is used in our preliminary experiment and the image contrast shows improvement from 10^-3 to 10^-4.5 at angular distance of 2{\\lambda}/D after corrected by SPGD based AO.

  16. Image segmentation based on adaptive mixture model

    As an important research field, image segmentation has attracted considerable attention. The classical geodesic active contour (GAC) model tends to produce fake edges in smooth regions, while the Chan–Vese (CV) model cannot effectively detect images with holes and obtain the precise boundary. To address the above issues, this paper proposes an adaptive mixture model synthesizing the GAC model and the CV model by a weight function. According to image characteristics, the proposed model can adaptively adjust the weight function. In this way, the model exploits the advantages of the GAC model in regions with rich textures or edges, while exploiting the advantages of the CV model in smooth local regions. Moreover, the proposed model is extended to vector-valued images. Through experiments, it is verified that the proposed model obtains better results than the traditional models. (paper)

  17. A Learning Approach for Adaptive Image Segmentation

    Martin, Vincent; Thonnat, Monique

    2007-01-01

    In this chapter, we have proposed a learning approach for three major issues of image segmentation: context adaptation, algorithm selection and parameter tuning according to the image content and the application need. This supervised learning approach relies on hand-labelled samples. The learning process is guided by the goal of the segmentation and therefore makes the approach reliable for a broad range of applications. The user effort is restrained compared to other supervised methods since...

  18. Laser speckle contrast imaging of blood flow from anesthetized mice: correcting drifts in measurements due to breathing movements

    Nogueira, Gesse E. C.; Ribeiro, Márcio A. C.; Campos, Juliane C.; Ferreira, Julio C. B.

    2015-06-01

    Background: Laser speckle contrast imaging allows non-invasive assessment of cutaneous blood flow. Although the technique is attractive to measure a quantity related to the skin blood flow (SBF) in anesthetized animal models, movements from breathing can mask the SBF signal. As a consequence, the measurement is overestimated because a variable amount of a DC component due to the breathing movements is added to the SBF signal. Objective: To evaluate a method for estimating the background level of the SBF signal, rejecting artefacts from breathing. Methods: A baseline correction method used for accurate DNA sequencing was evaluated, based on estimating the background level of a signal in small temporal sliding-windows. The method was applied to evaluate a mouse model of hindlimb ischemia. SBF signals from hindlimbs of anesthetized C57BL/6 mice (n=13) were registered. The mean SBF (Fi and Fc from ischemic and control hindlimbs) were computed from the registers and from the corresponding estimated background levels (Fib and Fcb from ischemic and control hindlimbs). Results: The mean values of the percentages (a measure of ischemia) MI = (Fi/Fc).100 and MIb = (Fib/Fcb).100 were computed to be 30+/-4% and 23+/-3% respectively (mean +/- SE). Evidences of statistical differences between both, ischemic and control hindlimbs, were obtained (p<0.05, paired student-t). The mean error [(MI-MIb)/MIb].100 obtained was 45+/-14% (mean+/-SE). Conclusion: The recovery of a corrupted SBF signal by breathing artefacts is feasible, allowing more accurate measurements.

  19. The use of digital image speckle correlation to measure the mechanical properties of skin and facial muscular activity

    Staloff, Isabelle Afriat

    Skin mechanical properties have been extensively studied and have led to an understanding of the structure and role of the collagen and elastin fibers network in the dermis and their changes due to aging. All these techniques have either isolated the skin from its natural environment (in vitro), or, when studied in vivo, attempted to minimize the effect of the underlying tissues and muscles. The human facial region is unique compared to the other parts of the body in that the underlying musculature runs through the subcutaneous tissue and is directly connected to the dermis with collagen based fibrous tissues. These fibrous tissues comprise the superficial musculoaponeurotic system, commonly referred to as the SMAS layer. Retaining ligaments anchor the skin to the periosteum, and hold the dermis to the SMAS. In addition, traditional techniques generally collect an average response of the skin. Data gathered in this manner is incomplete as the skin is anisotropic and under constant tension. We therefore introduce the Digital Image Speckle Correlation (DISC) method that maps in two dimensions the skin deformation under the complex set of forces involved during muscular activity. DISC, a non-contact in vivo technique, generates spatial resolved information. By observing the detailed motion of the facial skin we can infer the manner in which the complex ensemble of forces induced by movement of the muscles distribute and dissipate on the skin. By analyzing the effect of aging on the distribution of these complex forces we can measure its impact on skin elasticity and quantify the efficacy of skin care products. In addition, we speculate on the mechanism of wrinkle formation. Furthermore, we investigate the use of DISC to map the mechanism of film formation on skin of various polymers. Finally, we show that DISC can detect the involuntary facial muscular activity induced by various fragrances.

  20. Speckle disturbance limit in laser-based cinema projection systems

    Verschaffelt, Guy; Roelandt, Stijn; Meuret, Youri; van den Broeck, Wendy; Kilpi, Katriina; Lievens, Bram; Jacobs, An; Janssens, Peter; Thienpont, Hugo

    2015-09-01

    In a multi-disciplinary effort, we investigate the level of speckle that can be tolerated in a laser cinema projector based on a quality of experience experiment with movie clips shown to a test audience in a real-life movie theatre setting. We identify a speckle disturbance threshold by statistically analyzing the observers’ responses for different values of the amount of speckle, which was monitored using a well-defined speckle measurement method. The analysis shows that the speckle perception of a human observer is not only dependent on the objectively measured amount of speckle, but it is also strongly influenced by the image content. The speckle disturbance limit for movies turns out to be substantially larger than that for still images, and hence is easier to attain.

  1. High sensitive fundus autofluorescence imaging combined with speckle-free optical coherence tomography

    Stremplewski, Patrycjusz; Komar, Katarzyna; Szkulmowski, Maciej; Motoczyńska, Marta; Wojtkowski, Maciej

    2013-03-01

    Scattering and fluorescence images provide complementary information about the health condition of the human eye, so getting them in a single measurement, using a single device may significantly improve a quality of diagnosis as it has been already demonstrated in Spectralis (Heidelberg Eng.) OCT instrument. There is still challenge to improve quality of fundus autofluorescence (FAF) images. The biggest obstacle in obtaining in vivo images of sufficient quality is very low fluorescence signal. For eye safety reasons, and because of patient comfort, using highpower fluorescence excitation is not an adequate solution to the low signal problem. In this contribution we show a new detection method in the retinal autofluorescence imaging, which may improve the sensitivity. We used a fast modulated (up to 500 MHz) diode laser of wavelength 473 nm and detected fluorescence in the spectral range 500-680 nm by photomultiplier and lock-in amplifier. Average power of the collimated blue beam on the cornea used for FAF measurements was set to 50 μW, 10 μW, and even 4.5 μW.

  2. Fuzzy epsilon filters for removal of thermal and speckle noise from gray-scale images

    Bessai, H. J.

    1994-11-01

    This paper develops constructions of filters for semi-automatic enhancement of still images. It emphasizes the joint application of linear and nonlinear filtering techniques. The decision which filter type is to be activated predominantly depends on perceptual criteria. These means of judging are readily described in terms of linguistic variables, i.e., the user is relieved from the tedious task of evaluating noise statistics. The decision process itself is supported by standard fuzzy reasoning techniques and corrected updates of the crisp outputs are available on a user-defined frame-by-frame or window-by-window basis. Thus, both handling of the filter tools and the individual filtering depth (gain, bandwidth, etc.) are controlled by a common rule base. Experiments with noisy grayscale images demonstrate that compared to non-joint methods, the proposed solution results in acceptable scene interpretation and clear identification of originally concealed objects.

  3. A Generalized Speckle Tracking Algorithm for Ultrasonic Strain Imaging Using Dynamic Programming

    Jiang, Jingfeng; Hall, Timothy J.

    2009-01-01

    This study developed an improved motion estimation algorithm for ultrasonic strain imaging that employs a dynamic programming technique. In this paper, we model the motion estimation task as an optimization problem. Since tissue motion under external mechanical stimuli often should be reasonably continuous, a set of cost functions combining correlation and various levels of motion continuity constraint were used to regularize the motion estimation. To solve the optimization problem with a rea...

  4. Evaluation of Right Ventricular Global Longitudinal Function in Patients with Tetralogy of Fallot by Two-dimensional Ultrasound Speckle Tracking Imaging

    李玉曼; 谢明星; 王新房; 吕清; 卢晓芳; 杨亚利; 马红; 方凌云; 张静; 李卫芹

    2010-01-01

    Quantification of right ventricular(RV)volume and function remains a challenge because of RV complex geometry by conventional echocardiography.The purpose of this study was to assess RV global longitudinal function in patients with tetralogy of Fallot(TOF)by 2-dimensional ultrasound speckle tracking imaging(STI).Thirty-eight patients with TOF were enrolled in this study and divided into child group(n=25)and adult group(n=13)according to age.Thirty-eight age-and sex-matched normal subjects were selected as c...

  5. Adaptive contrast imaging: transmit frequency optimization

    Ménigot, Sébastien; Novell, Anthony; Voicu, Iulian; Bouakaz, Ayache; Girault, Jean-Marc

    2010-01-01

    Introduction: Since the introduction of ultrasound (US) contrast imaging, the imaging systems use a fixed emitting frequency. However it is known that the insonified medium is time-varying and therefore an adapted time-varying excitation is expected. We suggest an adaptive imaging technique which selects the optimal transmit frequency that maximizes the acoustic contrast. Two algorithms have been proposed to find an US excitation for which the frequency was optimal with microbubbles. Methods and Materials: Simulations were carried out for encapsulated microbubbles of 2 microns by considering the modified Rayleigh-Plesset equation for 2 MHz transmit frequency and for various pressure levels (20 kPa up to 420kPa). In vitro experiments were carried out using a transducer operating at 2 MHz and using a programmable waveform generator. Contrast agent was then injected into a small container filled with water. Results and discussions: We show through simulations and in vitro experiments that our adaptive imaging technique gives: 1) in case of simulations, a gain of acoustic contrast which can reach 9 dB compared to the traditional technique without optimization and 2) for in vitro experiments, a gain which can reach 18 dB. There is a non negligible discrepancy between simulations and experiments. These differences are certainly due to the fact that our simulations do not take into account the diffraction and nonlinear propagation effects. Further optimizations are underway.

  6. Propierties of speckle patterns generated through multiaperture pupils

    ??ngel-Toro, Luciano; Tebaldi, Myrian; Trivi, Marcelo; Bolognini, N??stor

    2001-01-01

    The characteristics of the image speckles obtained through multiple aperture pupils are theoretically analyzed in terms of the parameters defining the pupils. The possibility of interpreting and synthesizing the image speckle distribution in terms of rather elementary structures is considered, based on the Fourier optics analysis. Then, first and second order statistical properties of the speckle patterns are studied by evaluating both the mutual intensity and the auto-correlation intensity o...

  7. REGISTRATION OF BRAIN IMAGES USING MODIFIED ADAPTIVE POLAR TRANSFORM

    D.Sasikala,

    2010-09-01

    Full Text Available Image registration has great significance in medicine, with a lot of techniques anticipated in it. This paper discusses an approach for medical image registration. It registers images of the mono or multi modalities for CT or MRI images using Modified Adaptive Polar Transform. The performance of the Adaptive Polar Transform with theproposed technique is examined. The results prove that the proposed method performs better than Adaptive Polar Transform technique. The proposed method reduces the errors and also the elapsed time for registration. An analysis is presented for the medical image registration of brain images using Adaptive Polar Transform and Modified Adaptive Polar Transform.

  8. Speckle interferometric technique to assess soap films

    ??ngel Toro, Luciano; Bolognini, N??stor Alberto; Tebaldi, Myrian Cristina; Trivi, Marcelo Ricardo

    2003-01-01

    An speckle interferometric technique to monitor the thinning process of vertical soap film before the film rupture is presented -- The interferometric arrangement consists in a double aperture pupil optical system which images an input diffuser -- In a first step, a reference specklegram is stored in the computer buffer memory -- Afterwards, the soap film is located in front of one pupil aperture, an uniform displacement of the diffuser is produced and a new speckle pattern is stored -- The s...

  9. Highly porous nanoberyllium for X-ray beam speckle suppression

    Goikhman, Alexander, E-mail: agoikhman@ymail.com; Lyatun, Ivan; Ershov, Petr [Immanuel Kant Baltic Federal University, Nevskogo str. 14, Kaliningrad 236041 (Russian Federation); Snigireva, Irina [European Synchrotron Radiation Facility, BP 220, 38043 Grenoble (France); Wojda, Pawel [Immanuel Kant Baltic Federal University, Nevskogo str. 14, Kaliningrad 236041 (Russian Federation); Gdańsk University of Technology, 11/12 G. Narutowicza, Gdańsk 80-233 (Poland); Gorlevsky, Vladimir; Semenov, Alexander; Sheverdyaev, Maksim; Koletskiy, Viktor [A. A. Bochvar High-Technology Scientific Research Institute for Inorganic Materials, Rogova str. 5a, Moscow 123098 (Russian Federation); Snigirev, Anatoly [Immanuel Kant Baltic Federal University, Nevskogo str. 14, Kaliningrad 236041 (Russian Federation); European Synchrotron Radiation Facility, BP 220, 38043 Grenoble (France)

    2015-04-09

    A speckle suppression device containing highly porous nanoberyllium is proposed for manipulating the spatial coherence length and removing undesirable speckle structure during imaging experiments. This paper reports a special device called a ‘speckle suppressor’, which contains a highly porous nanoberyllium plate squeezed between two beryllium windows. The insertion of the speckle suppressor in an X-ray beam allows manipulation of the spatial coherence length, thus changing the effective source size and removing the undesirable speckle structure in X-ray imaging experiments almost without beam attenuation. The absorption of the nanoberyllium plate is below 1% for 1 mm thickness at 12 keV. The speckle suppressor was tested on the ID06 ESRF beamline with X-rays in the energy range from 9 to 15 keV. It was applied for the transformation of the phase–amplitude contrast to the pure amplitude contrast in full-field microscopy.

  10. Highly porous nanoberyllium for X-ray beam speckle suppression

    A speckle suppression device containing highly porous nanoberyllium is proposed for manipulating the spatial coherence length and removing undesirable speckle structure during imaging experiments. This paper reports a special device called a ‘speckle suppressor’, which contains a highly porous nanoberyllium plate squeezed between two beryllium windows. The insertion of the speckle suppressor in an X-ray beam allows manipulation of the spatial coherence length, thus changing the effective source size and removing the undesirable speckle structure in X-ray imaging experiments almost without beam attenuation. The absorption of the nanoberyllium plate is below 1% for 1 mm thickness at 12 keV. The speckle suppressor was tested on the ID06 ESRF beamline with X-rays in the energy range from 9 to 15 keV. It was applied for the transformation of the phase–amplitude contrast to the pure amplitude contrast in full-field microscopy

  11. Full-field optical deformation measurement in biomechanics: digital speckle pattern interferometry and 3D digital image correlation applied to bird beaks.

    Soons, Joris; Lava, Pascal; Debruyne, Dimitri; Dirckx, Joris

    2012-10-01

    In this paper two easy-to-use optical setups for the validation of biomechanical finite element (FE) models are presented. First, we show an easy-to-build Michelson digital speckle pattern interferometer (DSPI) setup, yielding the out-of-plane displacement. We also introduce three-dimensional digital image correlation (3D-DIC), a stereo photogrammetric technique. Both techniques are non-contact and full field, but they differ in nature and have different magnitudes of sensitivity. In this paper we successfully apply both techniques to validate a multi-layered FE model of a small bird beak, a strong but very light biological composite. DSPI can measure very small deformations, with potentially high signal-to-noise ratios. Its high sensitivity, however, results in high stability requirements and makes it hard to use it outside an optical laboratory and on living samples. In addition, large loads have to be divided into small incremental load steps to avoid phase unwrapping errors and speckle de-correlation. 3D-DIC needs much larger displacements, but automatically yields the strains. It is more flexible, does not have stability requirements, and can easily be used as an optical strain gage. PMID:23026697

  12. Modulated speckle simulations based on the random-walk model

    Lencina, Alberto; Vaveliuk, Pablo; Tebaldi, Myriam C.; Bolognini, Néstor Alberto

    2003-01-01

    The random walk model is employed to simulate modulated speckle patterns. We demonstrate that the geo metrical image approximation fails to describe the modulated speckle pattern. A new approach to analyzing this phenomenon is proposed. The validity of the approximations employed is verified by comparison of the simulation with the experimental results. Speckle metrological applications and phase measurement tech niques could be improved by taking advantage of this model.

  13. Multidimensional Speckle Noise Model

    Fàbregas Xavier; López-Martínez Carlos; Pottier Eric

    2005-01-01

    One of the main problems of SAR imagery is the presence of speckle noise, originated by the inherent coherent nature of this type of systems. For one-dimensional SAR systems it has been demonstrated that speckle can be considered as a multiplicative noise term. Nevertheless, this simple model cannot be exported when multidimensional SAR imagery is addressed. This paper is devoted to present the latest advances into the definition of a multidimensional speckle noise model which does not depen...

  14. Image-guided and adaptive radiotherapy

    Image-guided radiotherapy (IGRT) aims to take into account anatomical variations occurring during irradiation by visualization of anatomical structures. It may consist of a rigid registration of the tumour by moving the patient, in case of prostatic irradiation for example. IGRT associated with intensity-modulated radiotherapy (IMRT) is strongly recommended when high-dose is delivered in the prostate, where it seems to reduce rectal and bladder toxicity. In case of significant anatomical deformations, as in head and neck tumours (tumour shrinking and decrease in volume of the salivary glands), re-planning appears to be necessary, corresponding to the adaptive radiotherapy. This should ideally be 'monitored' and possibly triggered based on a calculation of cumulative dose, session after session, compared to the initial planning dose, corresponding to the concept of dose-guided adaptive radiotherapy. The creation of 'planning libraries' based on predictable organ positions (as in cervical cancer) is another way of adaptive radiotherapy. All of these strategies still appear very complex and expensive and therefore require stringent validation before being routinely applied. (authors)

  15. Extreme Adaptive Optics Planet Imager: XAOPI

    Macintosh, B A; Graham, J; Poyneer, L; Sommargren, G; Wilhelmsen, J; Gavel, D; Jones, S; Kalas, P; Lloyd, J; Makidon, R; Olivier, S; Palmer, D; Patience, J; Perrin, M; Severson, S; Sheinis, A; Sivaramakrishnan, A; Troy, M; Wallace, K

    2003-09-17

    Ground based adaptive optics is a potentially powerful technique for direct imaging detection of extrasolar planets. Turbulence in the Earth's atmosphere imposes some fundamental limits, but the large size of ground-based telescopes compared to spacecraft can work to mitigate this. We are carrying out a design study for a dedicated ultra-high-contrast system, the eXtreme Adaptive Optics Planet Imager (XAOPI), which could be deployed on an 8-10m telescope in 2007. With a 4096-actuator MEMS deformable mirror it should achieve Strehl >0.9 in the near-IR. Using an innovative spatially filtered wavefront sensor, the system will be optimized to control scattered light over a large radius and suppress artifacts caused by static errors. We predict that it will achieve contrast levels of 10{sup 7}-10{sup 8} at angular separations of 0.2-0.8 inches around a large sample of stars (R<7-10), sufficient to detect Jupiter-like planets through their near-IR emission over a wide range of ages and masses. We are constructing a high-contrast AO testbed to verify key concepts of our system, and present preliminary results here, showing an RMS wavefront error of <1.3 nm with a flat mirror.

  16. Analysis of tilt by modulated speckles generated with a double aperture pupil mask

    Molina Prado, Martha Lucía; Bolognini, Néstor; Tebaldi, Myrian

    2015-03-01

    We present a method based on modulated speckles to detect tilt movement of a diffusing surface. In our proposal a speckle image of the speckle produced by a reflective diffusing surface is formed by a lens having a double aperture. The double aperture yields to an interference process so that the resulting speckle distribution is fringe modulated. The tilting of the diffusing surface is mapped as a shifting of the speckle. Then, the double aperture pupil lens system maps the speckle shifting into a fringes shifting. We study the system performance in terms of the diffuser tilt. Experimental results that confirm our proposal are presented.

  17. Adaptive spatial compounding for improving ultrasound images of the epidural space on human subjects

    Tran, Denis; Hor, King-Wei; Kamani, Allaudin; Lessoway, Vickie; Rohling, Robert N.

    2008-03-01

    Administering epidural anesthesia can be a difficult procedure, especially for inexperienced physicians. The use of ultrasound imaging can help by showing the location of the key surrounding structures: the ligamentum flavum and the lamina of the vertebrae. The anatomical depiction of the interface between ligamentum flavum and epidural space is currently limited by speckle and anisotropic reflection. Previous work on phantoms showed that adaptive spatial compounding with non-rigid registration can improve the depiction of these features. This paper describes the development of an updated compounding algorithm and results from a clinical study. Average-based compounding may obscure anisotropic reflectors that only appear at certain beam angles, so a new median-based compounding technique is developed. In order to reduce the computational cost of the registration process, a linear prediction algorithm is used to reduce the search space for registration. The algorithms are tested on 20 human subjects. Comparisons are made among the reference image plus combinations of different compounding methods, warping and linear prediction. The gradient of the bone surfaces, the Laplacian of the ligamentum flavum, and the SNR and CNR are used to quantitatively assess the visibility of the features in the processed images. The results show a significant improvement in quality when median-based compounding with warping is used to align the set of beam-steered images and combine them. The improvement of the features makes detection of the epidural space easier.

  18. An efficient adaptive arithmetic coding image compression technology

    This paper proposes an efficient lossless image compression scheme for still images based on an adaptive arithmetic coding compression algorithm. The algorithm increases the image coding compression rate and ensures the quality of the decoded image combined with the adaptive probability model and predictive coding. The use of adaptive models for each encoded image block dynamically estimates the probability of the relevant image block. The decoded image block can accurately recover the encoded image according to the code book information. We adopt an adaptive arithmetic coding algorithm for image compression that greatly improves the image compression rate. The results show that it is an effective compression technology. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  19. An effective method for reducing speckle noise in digital holography

    Xin Kang

    2008-01-01

    An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.

  20. Achieving High Contrasts Through Speckle Rejection With Slicer Based Integral Field Spectrographs

    Salter, Graeme; Thatte, Niranjan; Tecza, Matthias; Clarke, Fraser

    2011-09-01

    Speckle noise, not photon noise, remains to be the limiting factor in the direct detection of high contrast companions. With studies for the future exo-planet characterisation and imaging instruments on the ELTs under way, the correct choice of technology must be made that will enable the fitting and removal of the speckle noise that remains after AO. We conclusively demonstrate, through the use of an experimental setup producing a simulated speckle, that slicer based integral field spectrographs (IFS) and post-processing using spectral deconvolution can achieve speckle rejection factors of 1000 in broad band reconstructed images (and 100 per spectral channel). This represents an order of magnitude improvement over current state-of-the-art. Contrary to popular belief, we do not find any evidence that this choice of IFS technology limits the achievable contrast of extra solar planet direct detection instruments. Coupled with extreme adaptive optics systems and high performance coronagraphs, a slicer based integral field spectrograph can achieve contrasts exceeding 10^9, making it an attractive option for the next generation of instruments being designed for the direct detection of extra solar planets (e.g. EPICS for the E-ELT).

  1. Short-term neural adaptation to simultaneous bifocal images.

    Aiswaryah Radhakrishnan

    Full Text Available Simultaneous vision is an increasingly used solution for the correction of presbyopia (the age-related loss of ability to focus near images. Simultaneous Vision corrections, normally delivered in the form of contact or intraocular lenses, project on the patient's retina a focused image for near vision superimposed with a degraded image for far vision, or a focused image for far vision superimposed with the defocused image of the near scene. It is expected that patients with these corrections are able to adapt to the complex Simultaneous Vision retinal images, although the mechanisms or the extent to which this happens is not known. We studied the neural adaptation to simultaneous vision by studying changes in the Natural Perceived Focus and in the Perceptual Score of image quality in subjects after exposure to Simultaneous Vision. We show that Natural Perceived Focus shifts after a brief period of adaptation to a Simultaneous Vision blur, similar to adaptation to Pure Defocus. This shift strongly correlates with the magnitude and proportion of defocus in the adapting image. The magnitude of defocus affects perceived quality of Simultaneous Vision images, with 0.5 D defocus scored lowest and beyond 1.5 D scored "sharp". Adaptation to Simultaneous Vision shifts the Perceptual Score of these images towards higher rankings. Larger improvements occurred when testing simultaneous images with the same magnitude of defocus as the adapting images, indicating that wearing a particular bifocal correction improves the perception of images provided by that correction.

  2. Adaptive Real Time Imaging Synthesis Telescopes

    Wright, Melvyn

    2012-01-01

    The digital revolution is transforming astronomy from a data-starved to a data-submerged science. Instruments such as the Atacama Large Millimeter Array (ALMA), the Large Synoptic Survey Telescope (LSST), and the Square Kilometer Array (SKA) will measure their accumulated data in petabytes. The capacity to produce enormous volumes of data must be matched with the computing power to process that data and produce meaningful results. In addition to handling huge data rates, we need adaptive calibration and beamforming to handle atmospheric fluctuations and radio frequency interference, and to provide a user environment which makes the full power of large telescope arrays accessible to both expert and non-expert users. Delayed calibration and analysis limit the science which can be done. To make the best use of both telescope and human resources we must reduce the burden of data reduction. Our instrumentation comprises of a flexible correlator, beam former and imager with digital signal processing closely coupled...

  3. Speckle-based spectrometer

    Chakrabarti, Maumita; Jakobsen, Michael Linde; Hanson, Steen Grüner

    2015-01-01

    A novel spectrometer concept is analyzed and experimentally verified. The method relies on probing the speckle displacement due to a change in the incident wavelength. A rough surface is illuminated at an oblique angle, and the peak position of the covariance between the speckle patterns observed...

  4. Comparison of amplitude-decorrelation, speckle-variance and phase-variance OCT angiography methods for imaging the human retina and choroid.

    Gorczynska, Iwona; Migacz, Justin V; Zawadzki, Robert J; Capps, Arlie G; Werner, John S

    2016-03-01

    We compared the performance of three OCT angiography (OCTA) methods: speckle variance, amplitude decorrelation and phase variance for imaging of the human retina and choroid. Two averaging methods, split spectrum and volume averaging, were compared to assess the quality of the OCTA vascular images. All data were acquired using a swept-source OCT system at 1040 nm central wavelength, operating at 100,000 A-scans/s. We performed a quantitative comparison using a contrast-to-noise (CNR) metric to assess the capability of the three methods to visualize the choriocapillaris layer. For evaluation of the static tissue noise suppression in OCTA images we proposed to calculate CNR between the photoreceptor/RPE complex and the choriocapillaris layer. Finally, we demonstrated that implementation of intensity-based OCT imaging and OCT angiography methods allows for visualization of retinal and choroidal vascular layers known from anatomic studies in retinal preparations. OCT projection imaging of data flattened to selected retinal layers was implemented to visualize retinal and choroidal vasculature. User guided vessel tracing was applied to segment the retinal vasculature. The results were visualized in a form of a skeletonized 3D model. PMID:27231598

  5. Deformation measurements of materials at low temperatures using laser speckle photography method

    The authors observed deformations of several materials during cooling down process from room temperature to liquid nitrogen temperature using the laser speckle photography method. The in-plane displacements were measured by the image plane speckle photography and the out-of-plane displacement gradients by the defocused speckle photography. The results of measurements of in-plane displacement are compared with those of FEM analysis. The applicability of laser speckle photography method to cryogenic engineering are also discussed

  6. Adaptive image ray-tracing for astrophysical simulations

    Parkin, E. R.

    2010-01-01

    A technique is presented for producing synthetic images from numerical simulations whereby the image resolution is adapted around prominent features. In so doing, adaptive image ray-tracing (AIR) improves the efficiency of a calculation by focusing computational effort where it is needed most. The results of test calculations show that a factor of >~ 4 speed-up, and a commensurate reduction in the number of pixels required in the final image, can be achieved compared to an equivalent calculat...

  7. 非下采样Contourlet域的ICA法SAR图像相干斑抑制%Speckle reduction of SAR image based on independent component analysis in nonsubsampled Contourlet domain

    贺峥嵘; 刘智; 王番; 陈永昌

    2011-01-01

    相干斑是SAR图像固有信息,也是SAR图像处理研究的重要方面之一.将非下采样Contourlet变换和统计信号处理中的独立分量分析相结合进行斑点抑制.对SAR图像进行非下采样金字塔和非下采样方向性滤波器组分解,在分解得到的非下采样Contourlet变换域利用扩展Infomax算法分离SAR图像斑点噪声.实验结果表明,该方法不仅较好抑制噪声,而且能够很好保持SAR图像细节信息.%Speckle noise was generated by the coherent processing of synthetic aperture radar (SAR) signals. Speckle denoising remained the major issues in SAR image processing. In this paper we combined the nonsubsampled contourlet transform (NSCT) and the independent component analysis used in statistical signal processing to filter SAR images. Firstly, we decomposed SAR image by the nonsubsampled pyramid (NSP) and the nonsubsampled directional filter bank (NSDFB). And then implemented the extended Infomax algorithm in this NSCT domain to separate speckles from SAR images. The experimental results presented the proposed method could get preferable results without losing details of SAR images.

  8. Speckle-based wavemeter

    Hanson, Steen Grüner; Jakobsen, Michael Linde; Chakrabarti, Maumita

    2015-01-01

    A spectrometer based on the application of dynamic speckles will be disclosed. The method relies on scattering of primarily coherent radiation from a slanted rough surface. The scattered radiation is collected on a detector array and the speckle displacement is monitored during a change in the...... incident wavelength. The change of wavelength gives an almost linear phaseshift across the scattering surface resulting in an almost linear shift of the speckle pattern, which is subsequently monitored. It is argued that frequency changes close to 100 MHz can be probed using a common CMOS array...

  9. Photothermal speckle modulation for noncontact materials characterization.

    Stolyarov, Alexander M; Sullenberger, Ryan M; Crompton, David R; Jeys, Thomas H; Saar, Brian G; Herzog, William D

    2015-12-15

    We have developed a noncontact, photothermal materials characterization method based on visible-light speckle imaging. This technique is applied to remotely measure the infrared absorption spectra of materials and to discriminate materials based on their thermal conductivities. A wavelength-tunable (7.5-8.7 μm), intensity-modulated, quantum cascade pump laser and a continuous-wave 532 nm probe laser illuminate a sample surface such that the two laser spots overlap. Surface absorption of the intensity-modulated pump laser induces a time-varying thermoelastic surface deformation, resulting in a time-varying 532 nm scattering speckle field from the surface. The speckle modulation amplitude, derived from a series of visible camera images, is found to correlate with the amplitude of the surface motion. By tuning the pump laser's wavelength over a molecular absorption feature, the amplitude spectrum of the speckle modulation is found to correlate to the IR absorption spectrum. As an example, we demonstrate this technique for spectroscopic identification of thin polymeric films. Furthermore, by adjusting the rate of modulation of the pump beam and measuring the associated modulation transfer to the visible speckle pattern, information about the thermal time constants of surface and sub-surface features can be revealed. Using this approach, we demonstrate the ability to distinguish between different materials (including metals, semiconductors, and insulators) based on differences in their thermal conductivities. PMID:26670512

  10. Real-time adaptive video image enhancement

    Garside, John R.; Harrison, Chris G.

    1999-07-01

    As part of a continuing collaboration between the University of Manchester and British Aerospace, a signal processing array has been constructed to demonstrate that it is feasible to compensate a video signal for the degradation caused by atmospheric haze in real-time. Previously reported work has shown good agreement between a simple physical model of light scattering by atmospheric haze and the observed loss of contrast. This model predicts a characteristic relationship between contrast loss in the image and the range from the camera to the scene. For an airborne camera, the slant-range to a point on the ground may be estimated from the airplane's pose, as reported by the inertial navigation system, and the contrast may be obtained from the camera's output. Fusing data from these two streams provides a means of estimating model parameters such as the visibility and the overall illumination of the scene. This knowledge allows the same model to be applied in reverse, thus restoring the contrast lost to atmospheric haze. An efficient approximation of range is vital for a real-time implementation of the method. Preliminary results show that an adaptive approach to fitting the model's parameters, exploiting the temporal correlation between video frames, leads to a robust implementation with a significantly accelerated throughput.