Speckle size in optical Fourier domain imaging

NASA Astrophysics Data System (ADS)

Lamouche, G.; Vergnole, S.; Bisaillon, C.-E.; Dufour, M.; Maciejko, R.; Monchalin, J.-P.

2007-06-01

As in conventional time-domain optical coherence tomography (OCT), speckle is inherent to any Optical Fourier Domain Imaging (OFDI) of biological tissue. OFDI is also known as swept-source OCT (SS-OCT). The axial speckle size is mainly determined by the OCT resolution length and the transverse speckle size by the focusing optics illuminating the sample. There is also a contribution from the sample related to the number of scatterers contained within the probed volume. In the OFDI data processing, there is some liberty in selecting the range of wavelengths used and this allows variation in the OCT resolution length. Consequently the probed volume can be varied. By performing measurements on an optical phantom with a controlled density of discrete scatterers and by changing the probed volume with different range of wavelengths in the OFDI data processing, there is an obvious change in the axial speckle size, but we show that there is also a less obvious variation in the transverse speckle size. This work contributes to a better understanding of speckle in OCT.

Speckle reduction in digital holography with resampling ring masks

NASA Astrophysics Data System (ADS)

Zhang, Wenhui; Cao, Liangcai; Jin, Guofan

2018-01-01

One-shot digital holographic imaging has the advantages of high stability and low temporal cost. However, the reconstruction is affected by the speckle noise. Resampling ring-mask method in spectrum domain is proposed for speckle reduction. The useful spectrum of one hologram is divided into several sub-spectra by ring masks. In the reconstruction, angular spectrum transform is applied to guarantee the calculation accuracy which has no approximation. N reconstructed amplitude images are calculated from the corresponding sub-spectra. Thanks to speckle's random distribution, superimposing these N uncorrelated amplitude images would lead to a final reconstructed image with lower speckle noise. Normalized relative standard deviation values of the reconstructed image are used to evaluate the reduction of speckle. Effect of the method on the spatial resolution of the reconstructed image is also quantitatively evaluated. Experimental and simulation results prove the feasibility and effectiveness of the proposed method.

13-fold resolution gain through turbid layer via translated unknown speckle illumination

PubMed Central

Guo, Kaikai; Zhang, Zibang; Jiang, Shaowei; Liao, Jun; Zhong, Jingang; Eldar, Yonina C.; Zheng, Guoan

2017-01-01

Fluorescence imaging through a turbid layer holds great promise for various biophotonics applications. Conventional wavefront shaping techniques aim to create and scan a focus spot through the turbid layer. Finding the correct input wavefront without direct access to the target plane remains a critical challenge. In this paper, we explore a new strategy for imaging through turbid layer with a large field of view. In our setup, a fluorescence sample is sandwiched between two turbid layers. Instead of generating one focus spot via wavefront shaping, we use an unshaped beam to illuminate the turbid layer and generate an unknown speckle pattern at the target plane over a wide field of view. By tilting the input wavefront, we raster scan the unknown speckle pattern via the memory effect and capture the corresponding low-resolution fluorescence images through the turbid layer. Different from the wavefront-shaping-based single-spot scanning, the proposed approach employs many spots (i.e., speckles) in parallel for extending the field of view. Based on all captured images, we jointly recover the fluorescence object, the unknown optical transfer function of the turbid layer, the translated step size, and the unknown speckle pattern. Without direct access to the object plane or knowledge of the turbid layer, we demonstrate a 13-fold resolution gain through the turbid layer using the reported strategy. We also demonstrate the use of this technique to improve the resolution of a low numerical aperture objective lens allowing to obtain both large field of view and high resolution at the same time. The reported method provides insight for developing new fluorescence imaging platforms and may find applications in deep-tissue imaging. PMID:29359102

SPECKLE IMAGING EXCLUDES LOW-MASS COMPANIONS ORBITING THE EXOPLANET HOST STAR TRAPPIST-1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Howell, Steve B.; Scott, Nicholas J.; Everett, Mark E.

2016-09-20

We have obtained the highest-resolution images available of TRAPPIST-1 using the Gemini-South telescope and our speckle imaging camera. Observing at 692 and 883 nm, we reached the diffraction limit of the telescope providing a best resolution of 27 mas or, at the distance of TRAPPIST-1, a spatial resolution of 0.32 au. Our imaging of the star extends from 0.32 to 14.5 au. We show that to a high confidence level, we can exclude all possible stellar and brown dwarf companions, indicating that TRAPPIST-1 is a single star.

Laser Speckle Contrast Imaging: theory, instrumentation and applications.

PubMed

Senarathna, Janaka; Rege, Abhishek; Li, Nan; Thakor, Nitish V

2013-01-01

Laser Speckle Contrast Imaging (LSCI) is a wide field of view, non scanning optical technique for observing blood flow. Speckles are produced when coherent light scattered back from biological tissue is diffracted through the limiting aperture of focusing optics. Mobile scatterers cause the speckle pattern to blur; a model can be constructed by inversely relating the degree of blur, termed speckle contrast to the scatterer speed. In tissue, red blood cells are the main source of moving scatterers. Therefore, blood flow acts as a virtual contrast agent, outlining blood vessels. The spatial resolution (~10 μm) and temporal resolution (10 ms to 10 s) of LSCI can be tailored to the application. Restricted by the penetration depth of light, LSCI can only visualize superficial blood flow. Additionally, due to its non scanning nature, LSCI is unable to provide depth resolved images. The simple setup and non-dependence on exogenous contrast agents have made LSCI a popular tool for studying vascular structure and blood flow dynamics. We discuss the theory and practice of LSCI and critically analyze its merit in major areas of application such as retinal imaging, imaging of skin perfusion as well as imaging of neurophysiology.

Laser Speckle Imaging of Cerebral Blood Flow

NASA Astrophysics Data System (ADS)

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.

Speckle noise reduction of 1-look SAR imagery

NASA Technical Reports Server (NTRS)

Nathan, Krishna S.; Curlander, John C.

1987-01-01

Speckle noise is inherent to synthetic aperture radar (SAR) imagery. Since the degradation of the image due to this noise results in uncertainties in the interpretation of the scene and in a loss of apparent resolution, it is desirable to filter the image to reduce this noise. In this paper, an adaptive algorithm based on the calculation of the local statistics around a pixel is applied to 1-look SAR imagery. The filter adapts to the nonstationarity of the image statistics since the size of the blocks is very small compared to that of the image. The performance of the filter is measured in terms of the equivalent number of looks (ENL) of the filtered image and the resulting resolution degradation. The results are compared to those obtained from different techniques applied to similar data. The local adaptive filter (LAF) significantly increases the ENL of the final image. The associated loss of resolution is also lower than that for other commonly used speckle reduction techniques.

Speckle-modulation for speckle reduction in optical coherence tomography

NASA Astrophysics Data System (ADS)

Liba, Orly; Lew, Matthew D.; SoRelle, Elliott D.; Dutta, Rebecca; Sen, Debasish; Moshfeghi, Darius M.; Chu, Steven; de la Zerda, Adam

2018-02-01

Optical coherence tomography (OCT) is a powerful biomedical imaging technology that relies on the coherent detection of backscattered light to image tissue morphology in vivo. As a consequence, OCT is susceptible to coherent noise, known as speckle noise, which imposes significant limitations on its diagnostic capabilities. Here we show Speckle- Modulating OCT (SM-OCT), a method based purely on light manipulation, which can remove speckle noise, including noise originating from sample multiple back-scattering. SM-OCT accomplishes this by creating and averaging an unlimited number of scans with uncorrelated speckle patterns, without compromising spatial resolution. The uncorrelated speckle patterns are created by scrambling the phase of the light with sub-resolution features using a moving ground-glass diffuser in the optical path of the sample arm. This method can be implemented in existing OCTs as a relatively low-cost add-on. SM-OCT speckle statistics follow the expected decrease in speckle contrast as the number of averaged scans increases. Within a scattering phantom, SM-OCT provides a 2.5-fold increase in effective resolution compared to conventional OCT. Using SM-OCT, we reveal small structures in the tissues of living animals, such as the inner stromal structure of a live mouse cornea, the fine structures inside the mouse pinna, and sweat ducts and Meissner's corpuscle in the human fingertip skin - features that are otherwise obscured by speckle noise when using conventional OCT or OCT with current state of the art speckle reduction methods. Our results indicate that SM-OCT has the potential to improve the current diagnostic and intra-operative capabilities of OCT.

OCT Amplitude and Speckle Statistics of Discrete Random Media.

PubMed

Almasian, Mitra; van Leeuwen, Ton G; Faber, Dirk J

2017-11-01

Speckle, amplitude fluctuations in optical coherence tomography (OCT) images, contains information on sub-resolution structural properties of the imaged sample. Speckle statistics could therefore be utilized in the characterization of biological tissues. However, a rigorous theoretical framework relating OCT speckle statistics to structural tissue properties has yet to be developed. As a first step, we present a theoretical description of OCT speckle, relating the OCT amplitude variance to size and organization for samples of discrete random media (DRM). Starting the calculations from the size and organization of the scattering particles, we analytically find expressions for the OCT amplitude mean, amplitude variance, the backscattering coefficient and the scattering coefficient. We assume fully developed speckle and verify the validity of this assumption by experiments on controlled samples of silica microspheres suspended in water. We show that the OCT amplitude variance is sensitive to sub-resolution changes in size and organization of the scattering particles. Experimentally determined and theoretically calculated optical properties are compared and in good agreement.

Speckle imaging for planetary research

NASA Technical Reports Server (NTRS)

Nisenson, P.; Goody, R.; Apt, J.; Papaliolios, C.

1983-01-01

The present study of speckle imaging technique effectiveness encompasses image reconstruction by means of a division algorithm for Fourier amplitudes, and the Knox-Thompson (1974) algorithm for Fourier phases. Results which have been obtained for Io, Titan, Pallas, Jupiter and Uranus indicate that spatial resolutions lower than the seeing limit by a factor of four are obtainable for objects brighter than Uranus. The resolutions obtained are well above the diffraction limit, due to inadequacies of the video camera employed. A photon-counting camera has been developed to overcome these difficulties, making possible the diffraction-limited resolution of objects as faint as Charon.

A stochastically fully connected conditional random field framework for super resolution OCT

NASA Astrophysics Data System (ADS)

Boroomand, A.; Tan, B.; Wong, A.; Bizheva, K.

2017-02-01

A number of factors can degrade the resolution and contrast of OCT images, such as: (1) changes of the OCT pointspread function (PSF) resulting from wavelength dependent scattering and absorption of light along the imaging depth (2) speckle noise, as well as (3) motion artifacts. We propose a new Super Resolution OCT (SR OCT) imaging framework that takes advantage of a Stochastically Fully Connected Conditional Random Field (SF-CRF) model to generate a Super Resolved OCT (SR OCT) image of higher quality from a set of Low-Resolution OCT (LR OCT) images. The proposed SF-CRF SR OCT imaging is able to simultaneously compensate for all of the factors mentioned above, that degrade the OCT image quality, using a unified computational framework. The proposed SF-CRF SR OCT imaging framework was tested on a set of simulated LR human retinal OCT images generated from a high resolution, high contrast retinal image, and on a set of in-vivo, high resolution, high contrast rat retinal OCT images. The reconstructed SR OCT images show considerably higher spatial resolution, less speckle noise and higher contrast compared to other tested methods. Visual assessment of the results demonstrated the usefulness of the proposed approach in better preservation of fine details and structures of the imaged sample, retaining biological tissue boundaries while reducing speckle noise using a unified computational framework. Quantitative evaluation using both Contrast to Noise Ratio (CNR) and Edge Preservation (EP) parameter also showed superior performance of the proposed SF-CRF SR OCT approach compared to other image processing approaches.

High-brightness laser imaging with tunable speckle reduction enabled by electroactive micro-optic diffusers.

PubMed

Farrokhi, Hamid; Rohith, Thazhe Madam; Boonruangkan, Jeeranan; Han, Seunghwoi; Kim, Hyunwoong; Kim, Seung-Woo; Kim, Young-Jin

2017-11-10

High coherence of lasers is desirable in high-speed, high-resolution, and wide-field imaging. However, it also causes unavoidable background speckle noise thus degrades the image quality in traditional microscopy and more significantly in interferometric quantitative phase imaging (QPI). QPI utilizes optical interference for high-precision measurement of the optical properties where the speckle can severely distort the information. To overcome this, we demonstrated a light source system having a wide tunability in the spatial coherence over 43% by controlling the illumination angle, scatterer's size, and the rotational speed of an electroactive-polymer rotational micro-optic diffuser. Spatially random phase modulation was implemented for the lower speckle imaging with over a 50% speckle reduction without a significant degradation in the temporal coherence. Our coherence control technique will provide a unique solution for a low-speckle, full-field, and coherent imaging in optically scattering media in the fields of healthcare sciences, material sciences and high-precision engineering.

Reducing Speckle In One-Look SAR Images

NASA Technical Reports Server (NTRS)

Nathan, K. S.; Curlander, J. C.

1990-01-01

Local-adaptive-filter algorithm incorporated into digital processing of synthetic-aperture-radar (SAR) echo data to reduce speckle in resulting imagery. Involves use of image statistics in vicinity of each picture element, in conjunction with original intensity of element, to estimate brightness more nearly proportional to true radar reflectance of corresponding target. Increases ratio of signal to speckle noise without substantial degradation of resolution common to multilook SAR images. Adapts to local variations of statistics within scene, preserving subtle details. Computationally simple. Lends itself to parallel processing of different segments of image, making possible increased throughput.

Speckle-field digital holographic microscopy.

PubMed

Park, YongKeun; Choi, Wonshik; Yaqoob, Zahid; Dasari, Ramachandra; Badizadegan, Kamran; Feld, Michael S

2009-07-20

The use of coherent light in conventional holographic phase microscopy (HPM) poses three major drawbacks: poor spatial resolution, weak depth sectioning, and fixed pattern noise due to unwanted diffraction. Here, we report a technique which can overcome these drawbacks, but maintains the advantage of phase microscopy - high contrast live cell imaging and 3D imaging. A speckle beam of a complex spatial pattern is used for illumination to reduce fixed pattern noise and to improve optical sectioning capability. By recording of the electric field of speckle, we demonstrate high contrast 3D live cell imaging without the need for axial scanning - neither objective lens nor sample stage. This technique has great potential in studying biological samples with improved sensitivity, resolution and optical sectioning capability.

Velocity measurements of heterogeneous RBC flow in capillary vessels using dynamic laser speckle signal.

PubMed

Li, Chenxi; Wang, Ruikang

2017-04-01

We propose an approach to measure heterogeneous velocities of red blood cells (RBCs) in capillary vessels using full-field time-varying dynamic speckle signals. The approach utilizes a low coherent laser speckle imaging system to record the instantaneous speckle pattern, followed by an eigen-decomposition-based filtering algorithm to extract dynamic speckle signal due to the moving RBCs. The velocity of heterogeneous RBC flows is determined by cross-correlating the temporal dynamic speckle signals obtained at adjacent locations. We verify the approach by imaging mouse pinna in vivo, demonstrating its capability for full-field RBC flow mapping and quantifying flow pattern with high resolution. It is expected to investigate the dynamic action of RBCs flow in capillaries under physiological changes.

Speckle imaging with the MAMA detector: Preliminary results

NASA Technical Reports Server (NTRS)

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.

High Resolution Optical Imaging through the Atmosphere

DTIC Science & Technology

1989-12-28

34Iterative Blind Deconvolution Method and its Applications’, Opt. Lett., 13, p.54 7 . Fienup, J.R. 1978, Opt. Lett., 3, 27. Karovska , M., Nisenson, P., and...Noyes, R. (1987), ’High Angular Resolution Speckle Imaging of Alpha Ori", BAAS, Vol.19, No. 2. Karovska , M., Koechlin, L., Nisenson, P., Papaliolios...Publishers. Karovska , M., Nisenson, P., Papaliolios, C., Stendley, C. (1989), "High Angular Speckle Observations of SN1987A. Days 40-580.", BAAS, Vol

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

PubMed Central

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

2015-01-01

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

Laser speckle imaging based on photothermally driven convection.

PubMed

Regan, Caitlin; Choi, Bernard

2016-02-01

Laser speckle imaging (LSI) is an interferometric technique that provides information about the relative speed of moving scatterers in a sample. Photothermal LSI overcomes limitations in depth resolution faced by conventional LSI by incorporating an excitation pulse to target absorption by hemoglobin within the vascular network. Here we present results from experiments designed to determine the mechanism by which photothermal LSI decreases speckle contrast. We measured the impact of mechanical properties on speckle contrast, as well as the spatiotemporal temperature dynamics and bulk convective motion occurring during photothermal LSI. Our collective data strongly support the hypothesis that photothermal LSI achieves a transient reduction in speckle contrast due to bulk motion associated with thermally driven convection. The ability of photothermal LSI to image structures below a scattering medium may have important preclinical and clinical applications.

Real-time speckle reduction in optical coherence tomography using the dual window method.

PubMed

Zhao, Yang; Chu, Kengyeh K; Eldridge, Will J; Jelly, Evan T; Crose, Michael; Wax, Adam

2018-02-01

Speckle is an intrinsic noise of interferometric signals which reduces contrast and degrades the quality of optical coherence tomography (OCT) images. Here, we present a frequency compounding speckle reduction technique using the dual window (DW) method. Using the DW method, speckle noise is reduced without the need to acquire multiple frames. A ~25% improvement in the contrast-to-noise ratio (CNR) was achieved using the DW speckle reduction method with only minimal loss (~17%) in axial resolution. We also demonstrate that real-time speckle reduction can be achieved at a B-scan rate of ~21 frames per second using a graphic processing unit (GPU). The DW speckle reduction technique can work on any existing OCT instrument without further system modification or extra components. This makes it applicable both in real-time imaging systems and during post-processing.

Stochastic speckle noise compensation in optical coherence tomography using non-stationary spline-based speckle noise modelling.

PubMed

Cameron, Andrew; Lui, Dorothy; Boroomand, Ameneh; Glaister, Jeffrey; Wong, Alexander; Bizheva, Kostadinka

2013-01-01

Optical coherence tomography (OCT) allows for non-invasive 3D visualization of biological tissue at cellular level resolution. Often hindered by speckle noise, the visualization of important biological tissue details in OCT that can aid disease diagnosis can be improved by speckle noise compensation. A challenge with handling speckle noise is its inherent non-stationary nature, where the underlying noise characteristics vary with the spatial location. In this study, an innovative speckle noise compensation method is presented for handling the non-stationary traits of speckle noise in OCT imagery. The proposed approach centers on a non-stationary spline-based speckle noise modeling strategy to characterize the speckle noise. The novel method was applied to ultra high-resolution OCT (UHROCT) images of the human retina and corneo-scleral limbus acquired in-vivo that vary in tissue structure and optical properties. Test results showed improved performance of the proposed novel algorithm compared to a number of previously published speckle noise compensation approaches in terms of higher signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and better overall visual assessment.

Stochastic speckle noise compensation in optical coherence tomography using non-stationary spline-based speckle noise modelling

PubMed Central

Cameron, Andrew; Lui, Dorothy; Boroomand, Ameneh; Glaister, Jeffrey; Wong, Alexander; Bizheva, Kostadinka

2013-01-01

Optical coherence tomography (OCT) allows for non-invasive 3D visualization of biological tissue at cellular level resolution. Often hindered by speckle noise, the visualization of important biological tissue details in OCT that can aid disease diagnosis can be improved by speckle noise compensation. A challenge with handling speckle noise is its inherent non-stationary nature, where the underlying noise characteristics vary with the spatial location. In this study, an innovative speckle noise compensation method is presented for handling the non-stationary traits of speckle noise in OCT imagery. The proposed approach centers on a non-stationary spline-based speckle noise modeling strategy to characterize the speckle noise. The novel method was applied to ultra high-resolution OCT (UHROCT) images of the human retina and corneo-scleral limbus acquired in-vivo that vary in tissue structure and optical properties. Test results showed improved performance of the proposed novel algorithm compared to a number of previously published speckle noise compensation approaches in terms of higher signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and better overall visual assessment. PMID:24049697

Velocity measurements of heterogeneous RBC flow in capillary vessels using dynamic laser speckle signal

PubMed Central

Li, Chenxi; Wang, Ruikang

2017-01-01

Abstract. We propose an approach to measure heterogeneous velocities of red blood cells (RBCs) in capillary vessels using full-field time-varying dynamic speckle signals. The approach utilizes a low coherent laser speckle imaging system to record the instantaneous speckle pattern, followed by an eigen-decomposition-based filtering algorithm to extract dynamic speckle signal due to the moving RBCs. The velocity of heterogeneous RBC flows is determined by cross-correlating the temporal dynamic speckle signals obtained at adjacent locations. We verify the approach by imaging mouse pinna in vivo, demonstrating its capability for full-field RBC flow mapping and quantifying flow pattern with high resolution. It is expected to investigate the dynamic action of RBCs flow in capillaries under physiological changes. PMID:28384709

Speckle noise removal applied to ultrasound image of carotid artery based on total least squares model.

PubMed

Yang, Lei; Lu, Jun; Dai, Ming; Ren, Li-Jie; Liu, Wei-Zong; Li, Zhen-Zhou; Gong, Xue-Hao

2016-10-06

An ultrasonic image speckle noise removal method by using total least squares model is proposed and applied onto images of cardiovascular structures such as the carotid artery. On the basis of the least squares principle, the related principle of minimum square method is applied to cardiac ultrasound image speckle noise removal process to establish the model of total least squares, orthogonal projection transformation processing is utilized for the output of the model, and the denoising processing for the cardiac ultrasound image speckle noise is realized. Experimental results show that the improved algorithm can greatly improve the resolution of the image, and meet the needs of clinical medical diagnosis and treatment of the cardiovascular system for the head and neck. Furthermore, the success in imaging of carotid arteries has strong implications in neurological complications such as stroke.

Tunable X-ray speckle-based phase-contrast and dark-field imaging using the unified modulated pattern analysis approach

NASA Astrophysics Data System (ADS)

Zdora, M.-C.; Thibault, P.; Deyhle, H.; Vila-Comamala, J.; Rau, C.; Zanette, I.

2018-05-01

X-ray phase-contrast and dark-field imaging provides valuable, complementary information about the specimen under study. Among the multimodal X-ray imaging methods, X-ray grating interferometry and speckle-based imaging have drawn particular attention, which, however, in their common implementations incur certain limitations that can restrict their range of applications. Recently, the unified modulated pattern analysis (UMPA) approach was proposed to overcome these limitations and combine grating- and speckle-based imaging in a single approach. Here, we demonstrate the multimodal imaging capabilities of UMPA and highlight its tunable character regarding spatial resolution, signal sensitivity and scan time by using different reconstruction parameters.

Structural Information Detection Based Filter for GF-3 SAR Images

NASA Astrophysics Data System (ADS)

Sun, Z.; Song, Y.

2018-04-01

GF-3 satellite with high resolution, large swath, multi-imaging mode, long service life and other characteristics, can achieve allweather and all day monitoring for global land and ocean. It has become the highest resolution satellite system in the world with the C-band multi-polarized synthetic aperture radar (SAR) satellite. However, due to the coherent imaging system, speckle appears in GF-3 SAR images, and it hinders the understanding and interpretation of images seriously. Therefore, the processing of SAR images has big challenges owing to the appearance of speckle. The high-resolution SAR images produced by the GF-3 satellite are rich in information and have obvious feature structures such as points, edges, lines and so on. The traditional filters such as Lee filter and Gamma MAP filter are not appropriate for the GF-3 SAR images since they ignore the structural information of images. In this paper, the structural information detection based filter is constructed, successively including the point target detection in the smallest window, the adaptive windowing method based on regional characteristics, and the most homogeneous sub-window selection. The despeckling experiments on GF-3 SAR images demonstrate that compared with the traditional filters, the proposed structural information detection based filter can well preserve the points, edges and lines as well as smooth the speckle more sufficiently.

Speckle reduction of OCT images using an adaptive cluster-based filtering

NASA Astrophysics Data System (ADS)

Adabi, Saba; Rashedi, Elaheh; Conforto, Silvia; Mehregan, Darius; Xu, Qiuyun; Nasiriavanaki, Mohammadreza

2017-02-01

Optical coherence tomography (OCT) has become a favorable device in the dermatology discipline due to its moderate resolution and penetration depth. OCT images however contain grainy pattern, called speckle, due to the broadband source that has been used in the configuration of OCT. So far, a variety of filtering techniques is introduced to reduce speckle in OCT images. Most of these methods are generic and can be applied to OCT images of different tissues. In this paper, we present a method for speckle reduction of OCT skin images. Considering the architectural structure of skin layers, it seems that a skin image can benefit from being segmented in to differentiable clusters, and being filtered separately in each cluster by using a clustering method and filtering methods such as Wiener. The proposed algorithm was tested on an optical solid phantom with predetermined optical properties. The algorithm was also tested on healthy skin images. The results show that the cluster-based filtering method can reduce the speckle and increase the signal-to-noise ratio and contrast while preserving the edges in the image.

Laser speckle imaging based on photothermally driven convection

PubMed Central

Regan, Caitlin; Choi, Bernard

2016-01-01

Abstract. Laser speckle imaging (LSI) is an interferometric technique that provides information about the relative speed of moving scatterers in a sample. Photothermal LSI overcomes limitations in depth resolution faced by conventional LSI by incorporating an excitation pulse to target absorption by hemoglobin within the vascular network. Here we present results from experiments designed to determine the mechanism by which photothermal LSI decreases speckle contrast. We measured the impact of mechanical properties on speckle contrast, as well as the spatiotemporal temperature dynamics and bulk convective motion occurring during photothermal LSI. Our collective data strongly support the hypothesis that photothermal LSI achieves a transient reduction in speckle contrast due to bulk motion associated with thermally driven convection. The ability of photothermal LSI to image structures below a scattering medium may have important preclinical and clinical applications. PMID:26927221

Ultrahigh resolution retinal imaging by visible light OCT with longitudinal achromatization

PubMed Central

Chong, Shau Poh; Zhang, Tingwei; Kho, Aaron; Bernucci, Marcel T.; Dubra, Alfredo; Srinivasan, Vivek J.

2018-01-01

Chromatic aberrations are an important design consideration in high resolution, high bandwidth, refractive imaging systems that use visible light. Here, we present a fiber-based spectral/Fourier domain, visible light OCT ophthalmoscope corrected for the average longitudinal chromatic aberration (LCA) of the human eye. Analysis of complex speckles from in vivo retinal images showed that achromatization resulted in a speckle autocorrelation function that was ~20% narrower in the axial direction, but unchanged in the transverse direction. In images from the improved, achromatized system, the separation between Bruch’s membrane (BM), the retinal pigment epithelium (RPE), and the outer segment tips clearly emerged across the entire 6.5 mm field-of-view, enabling segmentation and morphometry of BM and the RPE in a human subject. Finally, cross-sectional images depicted distinct inner retinal layers with high resolution. Thus, with chromatic aberration compensation, visible light OCT can achieve volume resolutions and retinal image quality that matches or exceeds ultrahigh resolution near-infrared OCT systems with no monochromatic aberration compensation. PMID:29675296

Speckle imaging through turbulent atmosphere based on adaptable pupil segmentation

NASA Astrophysics Data System (ADS)

Loktev, Mikhail; Soloviev, Oleg; Savenko, Svyatoslav; Vdovin, Gleb

2011-07-01

We report on the first results to our knowledge obtained with adaptable multiaperture imaging through turbulence on a horizontal atmospheric path. We show that the resolution can be improved by adaptively matching the size of the subaperture to the characteristic size of the turbulence. Further improvement is achieved by the deconvolution of a number of subimages registered simultaneously through multiple subapertures. Different implementations of multiaperture geometry, including pupil multiplication, pupil image sampling, and a plenoptic telescope, are considered. Resolution improvement has been demonstrated on a ˜550m horizontal turbulent path, using a combination of aperture sampling, speckle image processing, and, optionally, frame selection.

High-resolution observations of the globular cluster NGC 7099

NASA Astrophysics Data System (ADS)

Sams, Bruce Jones, III

The globular cluster NGC 7099 is a prototypical collapsed core cluster. Through a series of instrumental, observational, and theoretical observations, I have resolved its core structure using a ground based telescope. The core has a radius of 2.15 arcsec when imaged with a V band spatial resolution of 0.35 arcsec. Initial attempts at speckle imaging produced images of inadequate signal to noise and resolution. To explain these results, a new, fully general signal-to-noise model has been developed. It properly accounts for all sources of noise in a speckle observation, including aliasing of high spatial frequencies by inadequate sampling of the image plane. The model, called Full Speckle Noise (FSN), can be used to predict the outcome of any speckle imaging experiment. A new high resolution imaging technique called ACT (Atmospheric Correlation with a Template) was developed to create sharper astronomical images. ACT compensates for image motion due to atmospheric turbulence. ACT is similar to the Shift and Add algorithm, but uses apriori spatial knowledge about the image to further constrain the shifts. In this instance, the final images of NGC 7099 have resolutions of 0.35 arcsec from data taken in 1 arcsec seeing. The PAPA (Precision Analog Photon Address) camera was used to record data. It is subject to errors when imaging cluster cores in a large field of view. The origin of these errors is explained, and several ways to avoid them proposed. New software was created for the PAPA camera to properly take flat field images taken in a large field of view. Absolute photometry measurements of NGC 7099 made with the PAPA camera are accurate to 0.1 magnitude. Luminosity sampling errors dominate surface brightness profiles of the central few arcsec in a collapsed core cluster. These errors set limits on the ultimate spatial accuracy of surface brightness profiles.

Speckle-modulating optical coherence tomography in living mice and humans.

PubMed

Liba, Orly; Lew, Matthew D; SoRelle, Elliott D; Dutta, Rebecca; Sen, Debasish; Moshfeghi, Darius M; Chu, Steven; de la Zerda, Adam

2017-06-20

Optical coherence tomography (OCT) is a powerful biomedical imaging technology that relies on the coherent detection of backscattered light to image tissue morphology in vivo. As a consequence, OCT is susceptible to coherent noise (speckle noise), which imposes significant limitations on its diagnostic capabilities. Here we show speckle-modulating OCT (SM-OCT), a method based purely on light manipulation that virtually eliminates speckle noise originating from a sample. SM-OCT accomplishes this by creating and averaging an unlimited number of scans with uncorrelated speckle patterns without compromising spatial resolution. Using SM-OCT, we reveal small structures in the tissues of living animals, such as the inner stromal structure of a live mouse cornea, the fine structures inside the mouse pinna, and sweat ducts and Meissner's corpuscle in the human fingertip skin-features that are otherwise obscured by speckle noise when using conventional OCT or OCT with current state of the art speckle reduction methods.

Real-time speckle reduction in optical coherence tomography using the dual window method

PubMed Central

Zhao, Yang; Chu, Kengyeh K.; Eldridge, Will J.; Jelly, Evan T.; Crose, Michael; Wax, Adam

2018-01-01

Speckle is an intrinsic noise of interferometric signals which reduces contrast and degrades the quality of optical coherence tomography (OCT) images. Here, we present a frequency compounding speckle reduction technique using the dual window (DW) method. Using the DW method, speckle noise is reduced without the need to acquire multiple frames. A ~25% improvement in the contrast-to-noise ratio (CNR) was achieved using the DW speckle reduction method with only minimal loss (~17%) in axial resolution. We also demonstrate that real-time speckle reduction can be achieved at a B-scan rate of ~21 frames per second using a graphic processing unit (GPU). The DW speckle reduction technique can work on any existing OCT instrument without further system modification or extra components. This makes it applicable both in real-time imaging systems and during post-processing. PMID:29552398

Speckle-modulating optical coherence tomography in living mice and humans

PubMed Central

Liba, Orly; Lew, Matthew D.; SoRelle, Elliott D.; Dutta, Rebecca; Sen, Debasish; Moshfeghi, Darius M.; Chu, Steven; de la Zerda, Adam

2017-01-01

Optical coherence tomography (OCT) is a powerful biomedical imaging technology that relies on the coherent detection of backscattered light to image tissue morphology in vivo. As a consequence, OCT is susceptible to coherent noise (speckle noise), which imposes significant limitations on its diagnostic capabilities. Here we show speckle-modulating OCT (SM-OCT), a method based purely on light manipulation that virtually eliminates speckle noise originating from a sample. SM-OCT accomplishes this by creating and averaging an unlimited number of scans with uncorrelated speckle patterns without compromising spatial resolution. Using SM-OCT, we reveal small structures in the tissues of living animals, such as the inner stromal structure of a live mouse cornea, the fine structures inside the mouse pinna, and sweat ducts and Meissner’s corpuscle in the human fingertip skin—features that are otherwise obscured by speckle noise when using conventional OCT or OCT with current state of the art speckle reduction methods. PMID:28632205

Speckle-modulating optical coherence tomography in living mice and humans

NASA Astrophysics Data System (ADS)

Liba, Orly; Lew, Matthew D.; Sorelle, Elliott D.; Dutta, Rebecca; Sen, Debasish; Moshfeghi, Darius M.; Chu, Steven; de La Zerda, Adam

2017-06-01

Optical coherence tomography (OCT) is a powerful biomedical imaging technology that relies on the coherent detection of backscattered light to image tissue morphology in vivo. As a consequence, OCT is susceptible to coherent noise (speckle noise), which imposes significant limitations on its diagnostic capabilities. Here we show speckle-modulating OCT (SM-OCT), a method based purely on light manipulation that virtually eliminates speckle noise originating from a sample. SM-OCT accomplishes this by creating and averaging an unlimited number of scans with uncorrelated speckle patterns without compromising spatial resolution. Using SM-OCT, we reveal small structures in the tissues of living animals, such as the inner stromal structure of a live mouse cornea, the fine structures inside the mouse pinna, and sweat ducts and Meissner's corpuscle in the human fingertip skin--features that are otherwise obscured by speckle noise when using conventional OCT or OCT with current state of the art speckle reduction methods.

Dynamic laser speckle angiography achieved by eigen-decomposition filtering.

PubMed

Li, Chenxi; Wang, Ruikang

2017-06-01

A new approach is proposed for statistically analysis of laser speckle signals emerged from a living biological tissue based on eigen-decomposition to separate the dynamic speckle signals due to moving blood cells from the static speckle signals due to static tissue components, upon which to achieve angiography of the interrogated tissue in vivo. The proposed approach is tested by imaging mouse ear pinna in vivo, demonstrating its capability of providing detailed microvascular networks with high contrast, and high temporal and spatial resolutions. It is expected to provide further opportunities for laser speckle imaging in the biomedical and clinical applications where microvascular response to certain stimulus or tissue injury is of interest. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of a CCD based solar speckle imaging system

NASA Astrophysics Data System (ADS)

Nisenson, Peter; Stachnik, Robert V.; Noyes, Robert W.

1986-02-01

A program to develop software and hardware for the purpose of obtaining high angular resolution images of the solar surface is described. The program included the procurement of a Charge Coupled Devices imaging system; an extensive laboratory and remote site testing of the camera system; the development of a software package for speckle image reconstruction which was eventually installed and tested at the Sacramento Peak Observatory; and experiments of the CCD system (coupled to an image intensifier) for low light level, narrow spectral band solar imaging.

Retooling Laser Speckle Contrast Analysis Algorithm to Enhance Non-Invasive High Resolution Laser Speckle Functional Imaging of Cutaneous Microcirculation

NASA Astrophysics Data System (ADS)

Gnyawali, Surya C.; Blum, Kevin; Pal, Durba; Ghatak, Subhadip; Khanna, Savita; Roy, Sashwati; Sen, Chandan K.

2017-01-01

Cutaneous microvasculopathy complicates wound healing. Functional assessment of gated individual dermal microvessels is therefore of outstanding interest. Functional performance of laser speckle contrast imaging (LSCI) systems is compromised by motion artefacts. To address such weakness, post-processing of stacked images is reported. We report the first post-processing of binary raw data from a high-resolution LSCI camera. Sharp images of low-flowing microvessels were enabled by introducing inverse variance in conjunction with speckle contrast in Matlab-based program code. Extended moving window averaging enhanced signal-to-noise ratio. Functional quantitative study of blood flow kinetics was performed on single gated microvessels using a free hand tool. Based on detection of flow in low-flow microvessels, a new sharp contrast image was derived. Thus, this work presents the first distinct image with quantitative microperfusion data from gated human foot microvasculature. This versatile platform is applicable to study a wide range of tissue systems including fine vascular network in murine brain without craniotomy as well as that in the murine dorsal skin. Importantly, the algorithm reported herein is hardware agnostic and is capable of post-processing binary raw data from any camera source to improve the sensitivity of functional flow data above and beyond standard limits of the optical system.

Retooling Laser Speckle Contrast Analysis Algorithm to Enhance Non-Invasive High Resolution Laser Speckle Functional Imaging of Cutaneous Microcirculation

PubMed Central

Gnyawali, Surya C.; Blum, Kevin; Pal, Durba; Ghatak, Subhadip; Khanna, Savita; Roy, Sashwati; Sen, Chandan K.

2017-01-01

Cutaneous microvasculopathy complicates wound healing. Functional assessment of gated individual dermal microvessels is therefore of outstanding interest. Functional performance of laser speckle contrast imaging (LSCI) systems is compromised by motion artefacts. To address such weakness, post-processing of stacked images is reported. We report the first post-processing of binary raw data from a high-resolution LSCI camera. Sharp images of low-flowing microvessels were enabled by introducing inverse variance in conjunction with speckle contrast in Matlab-based program code. Extended moving window averaging enhanced signal-to-noise ratio. Functional quantitative study of blood flow kinetics was performed on single gated microvessels using a free hand tool. Based on detection of flow in low-flow microvessels, a new sharp contrast image was derived. Thus, this work presents the first distinct image with quantitative microperfusion data from gated human foot microvasculature. This versatile platform is applicable to study a wide range of tissue systems including fine vascular network in murine brain without craniotomy as well as that in the murine dorsal skin. Importantly, the algorithm reported herein is hardware agnostic and is capable of post-processing binary raw data from any camera source to improve the sensitivity of functional flow data above and beyond standard limits of the optical system. PMID:28106129

Frequency compounded imaging with a high-frequency dual element transducer.

PubMed

Chang, Jin Ho; Kim, Hyung Ham; Lee, Jungwoo; Shung, K Kirk

2010-04-01

This paper proposes a frequency compounding method to reduce speckle interferences, where a concentric annular type high-frequency dual element transducer is used to broaden the bandwidth of an imaging system. In frequency compounding methods, frequency division is carried out to obtain sub-band images containing uncorrelated speckles, which sacrifices axial resolution. Therefore, frequency compounding often deteriorates the target-detecting capability, quantified by the total signal-to-noise ratio (SNR), when the speckle's SNR (SSNR) is not improved as much as the degraded axial resolution. However, this could be avoided if the effective bandwidth required for frequency compounding is increased. The primary goal of the proposed approach, hence, is to improve SSNR by a factor of two under the condition where axial resolution is degraded by a factor of less than two, which indicates the total SNR improvement to higher than 40% compared to that of an original image. Since the method here employs a dual element transducer operating at 20 and 40MHz, the effective bandwidth necessary for frequency compounding becomes broadened. By dividing each spectrum of RF samples from both elements into two sub-bands, this method eventually enables four sets of the sub-band samples to contain uncorrelated speckles. This causes the axial resolution to be reduced by a factor of as low as 1.85, which means that this method would improve total SNR by at least 47%. An in vitro experiment on an excised pig eye was performed to validate the proposed approach, and the results showed that the SSNR was improved from 2.081+/-0.365 in the original image to 4.206+/-0.635 in the final compounding image. Copyright 2009 Elsevier B.V. All rights reserved.

Quantification and Reconstruction in Photoacoustic Tomography

NASA Astrophysics Data System (ADS)

Guo, Zijian

Optical absorption is closely associated with many physiological important parameters, such as the concentration and oxygen saturation of hemoglobin. Conventionally, accurate quantification in PAT requires knowledge of the optical fluence attenuation, acoustic pressure attenuation, and detection bandwidth. We circumvent this requirement by quantifying the optical absorption coefficients from the acoustic spectra of PA signals acquired at multiple optical wavelengths. We demonstrate the method using the optical-resolution photoacoustic microscopy (OR-PAM) and the acoustical-resolution photoacoustic microscopy (AR-PAM) in the optical ballistic regime and in the optical diffusive regime, respectively. The data acquisition speed in photoacoustic computed tomography (PACT) is limited by the laser repetition rate and the number of parallel ultrasound detecting channels. Reconstructing an image with fewer measurements can effectively accelerate the data acquisition and reduce the system cost. We adapted Compressed Sensing (CS) for the reconstruction in PACT. CS-based PACT was implemented as a non-linear conjugate gradient descent algorithm and tested with both phantom and in vivo experiments. Speckles have been considered ubiquitous in all scattering-based coherent imaging technologies. As a coherent imaging modality based on optical absorption, photoacoustic (PA) tomography (PAT) is generally devoid of speckles. PAT suppresses speckles by building up prominent boundary signals, via a mechanism similar to that of specular reflection. When imaging smooth boundary absorbing targets, the speckle visibility in PAT, which is defined as the ratio of the square root of the average power of speckles to that of boundaries, is inversely proportional to the square root of the absorber density. If the surfaces of the absorbing targets have uncorrelated height fluctuations, however, the boundary features may become fully developed speckles. The findings were validated by simulations and experiments. The first- and second-order statistics of PAT speckles were also studied experimentally. While the amplitude of the speckles follows a Gaussian distribution, the autocorrelation of the speckle patterns tracks that of the system point spread function.

Real-time blood flow visualization using the graphics processing unit

NASA Astrophysics Data System (ADS)

Yang, Owen; Cuccia, David; Choi, Bernard

2011-01-01

Laser speckle imaging (LSI) is a technique in which coherent light incident on a surface produces a reflected speckle pattern that is related to the underlying movement of optical scatterers, such as red blood cells, indicating blood flow. Image-processing algorithms can be applied to produce speckle flow index (SFI) maps of relative blood flow. We present a novel algorithm that employs the NVIDIA Compute Unified Device Architecture (CUDA) platform to perform laser speckle image processing on the graphics processing unit. Software written in C was integrated with CUDA and integrated into a LabVIEW Virtual Instrument (VI) that is interfaced with a monochrome CCD camera able to acquire high-resolution raw speckle images at nearly 10 fps. With the CUDA code integrated into the LabVIEW VI, the processing and display of SFI images were performed also at ~10 fps. We present three video examples depicting real-time flow imaging during a reactive hyperemia maneuver, with fluid flow through an in vitro phantom, and a demonstration of real-time LSI during laser surgery of a port wine stain birthmark.

Real-time blood flow visualization using the graphics processing unit

PubMed Central

Yang, Owen; Cuccia, David; Choi, Bernard

2011-01-01

Laser speckle imaging (LSI) is a technique in which coherent light incident on a surface produces a reflected speckle pattern that is related to the underlying movement of optical scatterers, such as red blood cells, indicating blood flow. Image-processing algorithms can be applied to produce speckle flow index (SFI) maps of relative blood flow. We present a novel algorithm that employs the NVIDIA Compute Unified Device Architecture (CUDA) platform to perform laser speckle image processing on the graphics processing unit. Software written in C was integrated with CUDA and integrated into a LabVIEW Virtual Instrument (VI) that is interfaced with a monochrome CCD camera able to acquire high-resolution raw speckle images at nearly 10 fps. With the CUDA code integrated into the LabVIEW VI, the processing and display of SFI images were performed also at ∼10 fps. We present three video examples depicting real-time flow imaging during a reactive hyperemia maneuver, with fluid flow through an in vitro phantom, and a demonstration of real-time LSI during laser surgery of a port wine stain birthmark. PMID:21280915

Effects of speckle/pixel size ratio on temporal and spatial speckle-contrast analysis of dynamic scattering systems: Implications for measurements of blood-flow dynamics.

PubMed

Ramirez-San-Juan, J C; Mendez-Aguilar, E; Salazar-Hermenegildo, N; Fuentes-Garcia, A; Ramos-Garcia, R; Choi, B

2013-01-01

Laser Speckle Contrast Imaging (LSCI) is an optical technique used to generate blood flow maps with high spatial and temporal resolution. It is well known that in LSCI, the speckle size must exceed the Nyquist criterion to maximize the speckle's pattern contrast. In this work, we study experimentally the effect of speckle-pixel size ratio not only in dynamic speckle contrast, but also on the calculation of the relative flow speed for temporal and spatial analysis. Our data suggest that the temporal LSCI algorithm is more accurate at assessing the relative changes in flow speed than the spatial algorithm.

Speckle imaging through turbulent atmosphere based on adaptable pupil segmentation.

PubMed

Loktev, Mikhail; Soloviev, Oleg; Savenko, Svyatoslav; Vdovin, Gleb

2011-07-15

We report on the first results to our knowledge obtained with adaptable multiaperture imaging through turbulence on a horizontal atmospheric path. We show that the resolution can be improved by adaptively matching the size of the subaperture to the characteristic size of the turbulence. Further improvement is achieved by the deconvolution of a number of subimages registered simultaneously through multiple subapertures. Different implementations of multiaperture geometry, including pupil multiplication, pupil image sampling, and a plenoptic telescope, are considered. Resolution improvement has been demonstrated on a ∼550 m horizontal turbulent path, using a combination of aperture sampling, speckle image processing, and, optionally, frame selection. © 2011 Optical Society of America

DARKNESS: A Microwave Kinetic Inductance Detector Integral Field Spectrograph for High-contrast Astronomy

NASA Astrophysics Data System (ADS)

Meeker, Seth R.; Mazin, Benjamin A.; Walter, Alex B.; Strader, Paschal; Fruitwala, Neelay; Bockstiegel, Clint; Szypryt, Paul; Ulbricht, Gerhard; Coiffard, Grégoire; Bumble, Bruce; Cancelo, Gustavo; Zmuda, Ted; Treptow, Ken; Wilcer, Neal; Collura, Giulia; Dodkins, Rupert; Lipartito, Isabel; Zobrist, Nicholas; Bottom, Michael; Shelton, J. Chris; Mawet, Dimitri; van Eyken, Julian C.; Vasisht, Gautam; Serabyn, Eugene

2018-06-01

We present DARKNESS (the DARK-speckle Near-infrared Energy-resolving Superconducting Spectrophotometer), the first of several planned integral field spectrographs to use optical/near-infrared Microwave Kinetic Inductance Detectors (MKIDs) for high-contrast imaging. The photon counting and simultaneous low-resolution spectroscopy provided by MKIDs will enable real-time speckle control techniques and post-processing speckle suppression at frame rates capable of resolving the atmospheric speckles that currently limit high-contrast imaging from the ground. DARKNESS is now operational behind the PALM-3000 extreme adaptive optics system and the Stellar Double Coronagraph at Palomar Observatory. Here, we describe the motivation, design, and characterization of the instrument, early on-sky results, and future prospects.

The influence of processor focus on speckle correlation statistics for a Shuttle imaging radar scene of Hurricane Josephine

NASA Technical Reports Server (NTRS)

Tilley, David G.

1988-01-01

The surface wave field produced by Hurricane Josephine was imaged by the L-band SAR aboard the Challenger on October 12, 1984. Exponential trends found in the two-dimensional autocorrelations of speckled image data support an equilibrium theory model of sea surface hydrodynamics. The notions of correlated specular reflection, surface coherence, optimal Doppler parameterization and spatial resolution are discussed within the context of a Poisson-Rayleigh statistical model of the SAR imaging process.

Speckle noise reduction in SAR images ship detection

NASA Astrophysics Data System (ADS)

Yuan, Ji; Wu, Bin; Yuan, Yuan; Huang, Qingqing; Chen, Jingbo; Ren, Lin

2012-09-01

At present, there are two types of method to detect ships in SAR images. One is a direct detection type, detecting ships directly. The other is an indirect detection type. That is, it firstly detects ship wakes, and then seeks ships around wakes. The two types all effect by speckle noise. In order to improve the accuracy of ship detection and get accurate ship and ship wakes parameters, such as ship length, ship width, ship area, the angle of ship wakes and ship outline from SAR images, it is extremely necessary to remove speckle noise in SAR images before data used in various SAR images ship detection. The use of speckle noise reduction filter depends on the specification for a particular application. Some common filters are widely used in speckle noise reduction, such as the mean filter, the median filter, the lee filter, the enhanced lee filter, the Kuan filter, the frost filter, the enhanced frost filter and gamma filter, but these filters represent some disadvantages in SAR image ship detection because of the various types of ship. Therefore, a mathematical function known as the wavelet transform and multi-resolution analysis were used to localize an SAR ocean image into different frequency components or useful subbands, and effectively reduce the speckle in the subbands according to the local statistics within the bands. Finally, the analysis of the statistical results are presented, which demonstrates the advantages and disadvantages of using wavelet shrinkage techniques over standard speckle filters.

Speckle attenuation by adaptive singular value shrinking with generalized likelihood matching in optical coherence tomography

NASA Astrophysics Data System (ADS)

Chen, Huaiguang; Fu, Shujun; Wang, Hong; Lv, Hongli; Zhang, Caiming

2018-03-01

As a high-resolution imaging mode of biological tissues and materials, optical coherence tomography (OCT) is widely used in medical diagnosis and analysis. However, OCT images are often degraded by annoying speckle noise inherent in its imaging process. Employing the bilateral sparse representation an adaptive singular value shrinking method is proposed for its highly sparse approximation of image data. Adopting the generalized likelihood ratio as similarity criterion for block matching and an adaptive feature-oriented backward projection strategy, the proposed algorithm can restore better underlying layered structures and details of the OCT image with effective speckle attenuation. The experimental results demonstrate that the proposed algorithm achieves a state-of-the-art despeckling performance in terms of both quantitative measurement and visual interpretation.

Reaching the Diffraction Limit - Differential Speckle and Wide-Field Imaging for the WIYN Telescope

NASA Technical Reports Server (NTRS)

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

2016-01-01

Speckle imaging allows telescopes to achieve diffraction limited imaging performance. The technique requires cameras capable of reading out frames at a very fast rate, effectively 'freezing out' atmospheric seeing. The resulting speckles can be correlated and images reconstructed that are at the diffraction limit of the telescope. These new instruments are based on the successful performance and design of the Differential Speckle Survey Instrument (DSSI).The instruments are being built for the Gemini-N and WIYN telescopes and will be made available to the community via the peer review proposal process. We envision their primary use to be validation and characterization of exoplanet targets from the NASA, K2 and TESS missions and RV discovered exoplanets. Such targets will provide excellent follow-up candidates for both the WIYN and Gemini telescopes. We expect similar data quality in speckle imaging mode with the new instruments. Additionally, both cameras will have a wide-field mode and standard SDSS filters. They will be highly versatile instruments and it is that likely many other science programs will request time on the cameras. The limiting magnitude for speckle observations will remain around 13-14th at WIYN and 16-17th at Gemini, while wide-field, normal CCD imaging operation should be able to go to much fainter, providing usual CCD imaging and photometric capabilities. The instruments will also have high utility as scoring cameras for telescope engineering purposes, or other applications where high time resolution is needed. Instrument support will be provided, including a software pipeline that takes raw speckle data to fully reconstructed images.

A review of state-of-the-art speckle reduction techniques for optical coherence tomography fingertip scans

NASA Astrophysics Data System (ADS)

Darlow, Luke N.; Akhoury, Sharat S.; Connan, James

2015-02-01

Standard surface fingerprint scanners are vulnerable to counterfeiting attacks and also failure due to skin damage and distortion. Thus a high security and damage resistant means of fingerprint acquisition is needed, providing scope for new approaches and technologies. Optical Coherence Tomography (OCT) is a high resolution imaging technology that can be used to image the human fingertip and allow for the extraction of a subsurface fingerprint. Being robust toward spoofing and damage, the subsurface fingerprint is an attractive solution. However, the nature of the OCT scanning process induces speckle: a correlative and multiplicative noise. Six speckle reducing filters for the digital enhancement of OCT fingertip scans have been evaluated. The optimized Bayesian non-local means algorithm improved the structural similarity between processed and reference images by 34%, increased the signal-to-noise ratio, and yielded the most promising visual results. An adaptive wavelet approach, originally designed for ultrasound imaging, and a speckle reducing anisotropic diffusion approach also yielded promising results. A reformulation of these in future work, with an OCT-speckle specific model, may improve their performance.

Speckle interferometry. Data acquisition and control for the SPID instrument.

NASA Astrophysics Data System (ADS)

Altarac, S.; Tallon, M.; Thiebaut, E.; Foy, R.

1998-08-01

SPID (SPeckle Imaging by Deconvolution) is a new speckle camera currently under construction at CRAL-Observatoire de Lyon. Its high spectral resolution and high image restoration capabilities open new astrophysical programs. The instrument SPID is composed of four main optical modules which are fully automated and computer controlled by a software written in Tcl/Tk/Tix and C. This software provides an intelligent assistance to the user by choosing observational parameters as a function of atmospheric parameters, computed in real time, and the desired restored image quality. Data acquisition is made by a photon-counting detector (CP40). A VME-based computer under OS9 controls the detector and stocks the data. The intelligent system runs under Linux on a PC. A slave PC under DOS commands the motors. These 3 computers communicate through an Ethernet network. SPID can be considered as a precursor for VLT's (Very Large Telescope, four 8-meter telescopes currently built in Chile by European Southern Observatory) very high spatial resolution camera.

Improving temporal resolution and speed sensitivity of laser speckle contrast analysis imaging based on noise reduction with an anisotropic diffusion filter

NASA Astrophysics Data System (ADS)

Song, Lipei; Wang, Xueyan; Zhang, Ru; Zhang, Kuanshou; Zhou, Zhen; Elson, Daniel S.

2018-07-01

The fluctuation of contrast caused by statistical noise degenerates the temporal/spatial resolution of laser speckle contrast imaging (LSCI) and limits the maximum speed when imaging. In this study, we investigated the application of the anisotropic diffusion filter (ADF) to temporal LSCI and found that the edge magnitude parameter of the ADF can be determined by the mean of the contrast image. Because the edge magnitude parameter is usually denoted as K, we term this the K-constant ADF (KC-ADF) and show that temporal sensitivity is improved when imaging because of the enhanced signal-to-noise ratio when using the KC-ADF in small-animal experiments. The cardiac cycle of a rat as high as 390 bpm can be imaged with an industrial camera.

Speckle noise reduction for optical coherence tomography based on adaptive 2D dictionary

NASA Astrophysics Data System (ADS)

Lv, Hongli; Fu, Shujun; Zhang, Caiming; Zhai, Lin

2018-05-01

As a high-resolution biomedical imaging modality, optical coherence tomography (OCT) is widely used in medical sciences. However, OCT images often suffer from speckle noise, which can mask some important image information, and thus reduce the accuracy of clinical diagnosis. Taking full advantage of nonlocal self-similarity and adaptive 2D-dictionary-based sparse representation, in this work, a speckle noise reduction algorithm is proposed for despeckling OCT images. To reduce speckle noise while preserving local image features, similar nonlocal patches are first extracted from the noisy image and put into groups using a gamma- distribution-based block matching method. An adaptive 2D dictionary is then learned for each patch group. Unlike traditional vector-based sparse coding, we express each image patch by the linear combination of a few matrices. This image-to-matrix method can exploit the local correlation between pixels. Since each image patch might belong to several groups, the despeckled OCT image is finally obtained by aggregating all filtered image patches. The experimental results demonstrate the superior performance of the proposed method over other state-of-the-art despeckling methods, in terms of objective metrics and visual inspection.

Effect of static scatterers in laser speckle contrast imaging: an experimental study on correlation and contrast.

PubMed

Vaz, Pedro G; Humeau-Heurtier, Anne; Figueiras, Edite; Correia, Carlos; Cardoso, João

2017-12-29

Laser speckle contrast imaging (LSCI) is a non-invasive microvascular blood flow assessment technique with good temporal and spatial resolution. Most LSCI systems, including commercial devices, can perform only qualitative blood flow evaluation, which is a major limitation of this technique. There are several factors that prevent the utilization of LSCI as a quantitative technique. Among these factors, we can highlight the effect of static scatterers. The goal of this work was to study the influence of differences in static and dynamic scatterer concentration on laser speckle correlation and contrast. In order to achieve this, a laser speckle prototype was developed and tested using an optical phantom with various concentrations of static and dynamic scatterers. It was found that the laser speckle correlation could be used to estimate the relative concentration of static/dynamic scatterers within a sample. Moreover, the speckle correlation proved to be independent of the dynamic scatterer velocity, which is a fundamental characteristic to be used in contrast correction.

Effect of static scatterers in laser speckle contrast imaging: an experimental study on correlation and contrast

NASA Astrophysics Data System (ADS)

Vaz, Pedro G.; Humeau-Heurtier, Anne; Figueiras, Edite; Correia, Carlos; Cardoso, João

2018-01-01

Laser speckle contrast imaging (LSCI) is a non-invasive microvascular blood flow assessment technique with good temporal and spatial resolution. Most LSCI systems, including commercial devices, can perform only qualitative blood flow evaluation, which is a major limitation of this technique. There are several factors that prevent the utilization of LSCI as a quantitative technique. Among these factors, we can highlight the effect of static scatterers. The goal of this work was to study the influence of differences in static and dynamic scatterer concentration on laser speckle correlation and contrast. In order to achieve this, a laser speckle prototype was developed and tested using an optical phantom with various concentrations of static and dynamic scatterers. It was found that the laser speckle correlation could be used to estimate the relative concentration of static/dynamic scatterers within a sample. Moreover, the speckle correlation proved to be independent of the dynamic scatterer velocity, which is a fundamental characteristic to be used in contrast correction.

Speckle noise reduction in quantitative optical metrology techniques by application of the discrete wavelet transformation

NASA Astrophysics Data System (ADS)

Furlong, Cosme; Pryputniewicz, Ryszard J.

2002-06-01

Effective suppression of speckle noise content in interferometric data images can help in improving accuracy and resolution of the results obtained with interferometric optical metrology techniques. In this paper, novel speckle noise reduction algorithms based on the discrete wavelet transformation are presented. The algorithms proceed by: (a) estimating the noise level contained in the interferograms of interest, (b) selecting wavelet families, (c) applying the wavelet transformation using the selected families, (d) wavelet thresholding, and (e) applying the inverse wavelet transformation, producing denoised interferograms. The algorithms are applied to the different stages of the processing procedures utilized for generation of quantitative speckle correlation interferometry data of fiber-optic based opto-electronic holography (FOBOEH) techniques, allowing identification of optimal processing conditions. It is shown that wavelet algorithms are effective for speckle noise reduction while preserving image features otherwise faded with other algorithms.

Optimal speckle noise reduction filter for range gated laser illuminated imaging

NASA Astrophysics Data System (ADS)

Dayton, David; Gonglewski, John; Lasche, James; Hassall, Arthur

2016-09-01

Laser illuminated imaging has a number of applications in the areas of night time air-to-ground target surveillance, ID, and pointing and tracking. Using a laser illuminator, the illumination intensity and thus the signal to noise ratio can be controlled. With the advent of high performance range gated cameras in the short-wave infra-red band, higher spatial resolution can be achieved over passive thermal night imaging cameras in the mid-wave infra-red due to the shorter wave-length. If a coherent illuminator is used the resulting imagery often suffers from speckle noise due to the scattering off of a rough target surface, which gives it a grainy "salt and pepper" appearance. The probability density function for the intensity of focal plane speckle is well understood to follow a negative exponential distribution. This can be exploited to develop a Bayesian speckle noise filter. The filter has the advantage over simple frame averaging approaches in that it preserves target features and motion while reducing speckle noise without smearing or blurring the images. The resulting filtered images have the appearance of passive imagery and so are more amenable to sensor fusion with simultaneous mid-wave infra-red thermal images for enhanced target ID. The noise filter improvement is demonstrated using examples from real world laser imaging tests on tactical targets.

Bas-relief map using texture analysis with application to live enhancement of ultrasound images.

PubMed

Du, Huarui; Ma, Rui; Wang, Xiaoying; Zhang, Jue; Fang, Jing

2015-05-01

For ultrasound imaging, speckle is one of the most important factors in the degradation of contrast resolution because it masks meaningful texture and has the potential to interfere with diagnosis. It is expected that researchers would explore appropriate ways to reduce the speckle noise, to find the edges of structures and enhance weak borders between different organs in ultrasound imaging. Inspired by the principle of differential interference contrast microscopy, a "bas-relief map" is proposed that depicts the texture structure of ultrasound images. Based on a bas-relief map, an adaptive bas-relief filter was developed for ultrafast despeckling. Subsequently, an edge map was introduced to enhance the edges of images in real time. The holistic bas-relief map approach has been used experimentally with synthetic phantoms and digital ultrasound B-scan images of liver, kidney and gallbladder. Based on the visual inspection and the performance metrics of the despeckled images, it was found that the bas-relief map approach is capable of effectively reducing the speckle while significantly enhancing contrast and tissue boundaries for ultrasonic images, and its speckle reduction ability is comparable to that of Kuan, Lee and Frost filters. Meanwhile, the proposed technique could preserve more intra-region details compared with the popular speckle reducing anisotropic diffusion technique and more effectively enhance edges. In addition, the adaptive bas-relief filter was much less time consuming than the Kuan, Lee and Frost filter and speckle reducing anisotropic diffusion techniques. The bas-relief map strategy is effective for speckle reduction and live enhancement of ultrasound images, and can provide a valuable tool for clinical diagnosis. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Frame rate required for speckle tracking echocardiography: A quantitative clinical study with open-source, vendor-independent software.

PubMed

Negoita, Madalina; Zolgharni, Massoud; Dadkho, Elham; Pernigo, Matteo; Mielewczik, Michael; Cole, Graham D; Dhutia, Niti M; Francis, Darrel P

2016-09-01

To determine the optimal frame rate at which reliable heart walls velocities can be assessed by speckle tracking. Assessing left ventricular function with speckle tracking is useful in patient diagnosis but requires a temporal resolution that can follow myocardial motion. In this study we investigated the effect of different frame rates on the accuracy of speckle tracking results, highlighting the temporal resolution where reliable results can be obtained. 27 patients were scanned at two different frame rates at their resting heart rate. From all acquired loops, lower temporal resolution image sequences were generated by dropping frames, decreasing the frame rate by up to 10-fold. Tissue velocities were estimated by automated speckle tracking. Above 40 frames/s the peak velocity was reliably measured. When frame rate was lower, the inter-frame interval containing the instant of highest velocity also contained lower velocities, and therefore the average velocity in that interval was an underestimate of the clinically desired instantaneous maximum velocity. The higher the frame rate, the more accurately maximum velocities are identified by speckle tracking, until the frame rate drops below 40 frames/s, beyond which there is little increase in peak velocity. We provide in an online supplement the vendor-independent software we used for automatic speckle-tracked velocity assessment to help others working in this field. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Coherent and incoherent imaging through scattering media (Conference Presentation)

NASA Astrophysics Data System (ADS)

Edrei, Eitan

2017-02-01

The shower-curtain effect is a familiar phenomenon, routinely observed in our everyday life: an object placed behind a scattering layer appears blurred but if the object is attached to the scattering layer it can be clearly resolved. The optical system we developed takes advantage of the shower-curtain effect properties and generalizes them to achieve high-resolution imaging of objects placed at a nearly arbitrary distance behind the scattering medium. The imaging procedure is based on retrieving the object Fourier transform from the turbid medium (used as the shower-curtain) through a correlography technique based on speckle illumination. Illuminating the object with a speckle pattern rather than a coherent beam, we show that the correlography principles can be effectively applied in the near field. While the far-field condition is usually known as z<(2D^2)⁄λ (D, size of the object; λ wavelength); by tuning the spatial coherence of the illumination beam, as one can do with speckle illumination, the "far-field" condition can be written as z<(2DRc)⁄λ where Rc is the correlation radius of the speckle pattern. Using our method we present high-resolution imaging of objects hidden behind millimeter-thick tissue or dense lens cataracts, and demonstrate our imaging technique to be insensitive to rapid medium movements (<5 m/s) beyond any biologically relevant motion. Furthermore, we show this method can be extended to several contrast mechanisms and imaging configurations.

Functional laser speckle imaging of cerebral blood flow under hypothermia

NASA Astrophysics Data System (ADS)

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.

Reaching the Diffraction Limit - Differential Speckle and Wide-Field Imaging for the Gemini-N Telescope

NASA Technical Reports Server (NTRS)

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

2016-01-01

Speckle imaging allows telescopes to achieve di raction limited imaging performance. The technique requires cameras capable of reading out frames at a very fast rate, e ectively `freezing out' atmospheric seeing. The resulting speckles can be correlated and images reconstructed that are at the di raction limit of the telescope. These new instruments are based on the successful performance and design of the Di erential Speckle Survey Instrument (DSSI) [2, 1]. The instruments are being built for the Gemini-N and WIYN telescopes and will be made available to the community via the peer review proposal process. We envision their primary use to be validation and characterization of exoplanet targets from the NASA K2 and TESS missions and RV discovered exoplanets. Such targets will provide excellent follow-up candidates for both the WIYN and Gemini telescopes [3]. Examples of DSSI data are shown in the gures below. We expect similar data quality in speckle imaging mode with the new instruments. Additionally, both cameras will have a wide- eld mode and standard SDSS lters. They will be highly versatile instruments and it is that likely many other science programs will request time on the cameras. The limiting magnitude for speckle observations, will remain around 13-14th at WIYN and 16-17th at Gemini, while wide- eld, normal CCD imaging operation should be able to go to much fainter, providing usual CCD imaging and photometric capabilities. The instruments will also have high utility as scoring cameras for telescope engineering purposes, or other applications where high time resolution is needed. Instrument support will be provided, including a software pipeline that takes raw speckle data to fully reconstructed images.

Lensless digital holography with diffuse illumination through a pseudo-random phase mask.

PubMed

Bernet, Stefan; Harm, Walter; Jesacher, Alexander; Ritsch-Marte, Monika

2011-12-05

Microscopic imaging with a setup consisting of a pseudo-random phase mask, and an open CMOS camera, without an imaging objective, is demonstrated. The pseudo random phase mask acts as a diffuser for an incoming laser beam, scattering a speckle pattern to a CMOS chip, which is recorded once as a reference. A sample which is afterwards inserted somewhere in the optical beam path changes the speckle pattern. A single (non-iterative) image processing step, comparing the modified speckle pattern with the previously recorded one, generates a sharp image of the sample. After a first calibration the method works in real-time and allows quantitative imaging of complex (amplitude and phase) samples in an extended three-dimensional volume. Since no lenses are used, the method is free from lens abberations. Compared to standard inline holography the diffuse sample illumination improves the axial sectioning capability by increasing the effective numerical aperture in the illumination path, and it suppresses the undesired so-called twin images. For demonstration, a high resolution spatial light modulator (SLM) is programmed to act as the pseudo-random phase mask. We show experimental results, imaging microscopic biological samples, e.g. insects, within an extended volume at a distance of 15 cm with a transverse and longitudinal resolution of about 60 μm and 400 μm, respectively.

Laser speckle spatiotemporal variance analysis for noninvasive widefield measurements of blood pulsation and pulse rate on a camera-phone.

PubMed

Remer, Itay; Bilenca, Alberto

2015-11-01

Photoplethysmography is a well-established technique for the noninvasive measurement of blood pulsation. However, photoplethysmographic devices typically need to be in contact with the surface of the tissue and provide data from a single contact point. Extensions of conventional photoplethysmography to measurements over a wide field-of-view exist, but require advanced signal processing due to the low signal-to-noise-ratio of the photoplethysmograms. Here, we present a noncontact method based on temporal sampling of time-integrated speckle using a camera-phone for noninvasive, widefield measurements of physiological parameters across the human fingertip including blood pulsation and resting heart-rate frequency. The results show that precise estimation of these parameters with high spatial resolution is enabled by measuring the local temporal variation of speckle patterns of backscattered light from subcutaneous skin, thereby opening up the possibility for accurate high resolution blood pulsation imaging on a camera-phone. Camera-phone laser speckle imager along with measured relative blood perfusion maps of a fingertip showing skin perfusion response to a pulse pressure applied to the upper arm. The figure is for illustration only; the imager was stabilized on a stand throughout the experiments. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Monitoring blood-flow in the mouse cochlea using an endoscopic laser speckle contrast imaging system

PubMed Central

Yu, Sunkon; Jung, Byungjo; Choi, Jin Sil

2018-01-01

Laser speckle contrast imaging (LSCI) enables continuous high-resolution assessment of microcirculation in real-time. We applied an endoscope to LSCI to measure cochlear blood-flow in an ischemia–reperfusion mouse model. We also explored whether using xenon light in combination with LSCI facilitates visualization of anatomical position. Based on a previous preliminary study, the appropriate wavelength for penetrating the thin bony cochlea was 830 nm. A 2.7-mm-diameter endoscope was used, as appropriate for the size of the mouse cochlea. Our endoscopic LSCI system was used to illuminate the right cochlea after dissection of the mouse. We observed changes in the speckle signals when we applied the endoscopic LSCI system to the ischemia-reperfusion mouse model. The anatomical structure of the mouse cochlea and surrounding structures were clearly visible using the xenon light. The speckle signal of the cochlea was scattered, with an intensity that varied between that of the stapes (with the lowest signal), the negative control, and the stapedial artery (with the highest signal), the positive control. In the cochlear ischemia–reperfusion mouse model, the speckle signal of the cochlea decreased during the ischemic phase, and increased during the reperfusion phase, clearly reflecting cochlear blood-flow. The endoscopic LSCI system generates high-resolution images in real-time, allowing visualization of blood-flow and its changes in the mouse cochlea. Anatomical structures were clearly matched using LSCI along with visible light. PMID:29489849

Monitoring blood-flow in the mouse cochlea using an endoscopic laser speckle contrast imaging system.

PubMed

Kong, Tae Hoon; Yu, Sunkon; Jung, Byungjo; Choi, Jin Sil; Seo, Young Joon

2018-01-01

Laser speckle contrast imaging (LSCI) enables continuous high-resolution assessment of microcirculation in real-time. We applied an endoscope to LSCI to measure cochlear blood-flow in an ischemia-reperfusion mouse model. We also explored whether using xenon light in combination with LSCI facilitates visualization of anatomical position. Based on a previous preliminary study, the appropriate wavelength for penetrating the thin bony cochlea was 830 nm. A 2.7-mm-diameter endoscope was used, as appropriate for the size of the mouse cochlea. Our endoscopic LSCI system was used to illuminate the right cochlea after dissection of the mouse. We observed changes in the speckle signals when we applied the endoscopic LSCI system to the ischemia-reperfusion mouse model. The anatomical structure of the mouse cochlea and surrounding structures were clearly visible using the xenon light. The speckle signal of the cochlea was scattered, with an intensity that varied between that of the stapes (with the lowest signal), the negative control, and the stapedial artery (with the highest signal), the positive control. In the cochlear ischemia-reperfusion mouse model, the speckle signal of the cochlea decreased during the ischemic phase, and increased during the reperfusion phase, clearly reflecting cochlear blood-flow. The endoscopic LSCI system generates high-resolution images in real-time, allowing visualization of blood-flow and its changes in the mouse cochlea. Anatomical structures were clearly matched using LSCI along with visible light.

Ultrasound-aided high-resolution biophotonic imaging

NASA Astrophysics Data System (ADS)

Wang, Lihong V.

2003-10-01

We develop novel biophotonic imaging for early-cancer detection, a grand challenge in cancer research, using nonionizing electromagnetic and ultrasonic waves. Unlike ionizing x-ray radiation, nonionizing electromagnetic waves such as optical waves are safe for biomedical applications and reveal new contrast mechanisms and functional information. For example, our spectroscopic oblique-incidence reflectometry can detect skin cancers based on functional hemoglobin parameters and cell nuclear size with 95% accuracy. Unfortunately, electromagnetic waves in the nonionizing spectral region do not penetrate biological tissue in straight paths as do x-rays. Consequently, high-resolution tomography based on nonionizing electromagnetic waves alone, as demonstrated by our Mueller optical coherence tomography, is limited to superficial tissue imaging. Ultrasonic imaging, on the contrary, furnishes good imaging resolution but has poor contrast in early-stage tumors and has strong speckle artifacts as well. We developed ultrasound-mediated imaging modalities by combining electromagnetic and ultrasonic waves synergistically. The hybrid modalities yield speckle-free electromagnetic-contrast at ultrasonic resolution in relatively large biological tissue. In ultrasound-modulated (acousto)-optical tomography, a focused ultrasonic wave encodes diffuse laser light in scattering biological tissue. In photo-acoustic (thermo-acoustic) tomography, a low-energy laser (RF) pulse induces ultrasonic waves in biological tissue due to thermoelastic expansion.

Evaluation of phase-diversity techniques for solar-image restoration

NASA Technical Reports Server (NTRS)

Paxman, Richard G.; Seldin, John H.; Lofdahl, Mats G.; Scharmer, Goran B.; Keller, Christoph U.

1995-01-01

Phase-diversity techniques provide a novel observational method for overcomming the effects of turbulence and instrument-induced aberrations in ground-based astronomy. Two implementations of phase-diversity techniques that differ with regard to noise model, estimator, optimization algorithm, method of regularization, and treatment of edge effects are described. Reconstructions of solar granulation derived by applying these two implementations to common data sets are shown to yield nearly identical images. For both implementations, reconstructions from phase-diverse speckle data (involving multiple realizations of turbulence) are shown to be superior to those derived from conventional phase-diversity data (involving a single realization). Phase-diverse speckle reconstructions are shown to achieve near diffraction-limited resolution and are validated by internal and external consistency tests, including a comparison with a reconstruction using a well-accepted speckle-imaging method.

Wavefront sensing with a thin diffuser

NASA Astrophysics Data System (ADS)

Berto, Pascal; Rigneault, Hervé; Guillon, Marc

2017-12-01

We propose and implement a broadband, compact, and low-cost wavefront sensing scheme by simply placing a thin diffuser in the close vicinity of a camera. The local wavefront gradient is determined from the local translation of the speckle pattern. The translation vector map is computed thanks to a fast diffeomorphic image registration algorithm and integrated to reconstruct the wavefront profile. The simple translation of speckle grains under local wavefront tip/tilt is ensured by the so-called "memory effect" of the diffuser. Quantitative wavefront measurements are experimentally demonstrated both for the few first Zernike polynomials and for phase-imaging applications requiring high resolution. We finally provided a theoretical description of the resolution limit that is supported experimentally.

Observing Exoplanets with High-dispersion Coronagraphy. II. Demonstration of an Active Single-mode Fiber Injection Unit

NASA Astrophysics Data System (ADS)

Mawet, D.; Ruane, G.; Xuan, W.; Echeverri, D.; Klimovich, N.; Randolph, M.; Fucik, J.; Wallace, J. K.; Wang, J.; Vasisht, G.; Dekany, R.; Mennesson, B.; Choquet, E.; Delorme, J.-R.; Serabyn, E.

2017-04-01

High-dispersion coronagraphy (HDC) optimally combines high-contrast imaging techniques such as adaptive optics/wavefront control plus coronagraphy to high spectral resolution spectroscopy. HDC is a critical pathway toward fully characterizing exoplanet atmospheres across a broad range of masses from giant gaseous planets down to Earth-like planets. In addition to determining the molecular composition of exoplanet atmospheres, HDC also enables Doppler mapping of atmosphere inhomogeneities (temperature, clouds, wind), as well as precise measurements of exoplanet rotational velocities. Here, we demonstrate an innovative concept for injecting the directly imaged planet light into a single-mode fiber, linking a high-contrast adaptively corrected coronagraph to a high-resolution spectrograph (diffraction-limited or not). Our laboratory demonstration includes three key milestones: close-to-theoretical injection efficiency, accurate pointing and tracking, and on-fiber coherent modulation and speckle nulling of spurious starlight signal coupling into the fiber. Using the extreme modal selectivity of single-mode fibers, we also demonstrated speckle suppression gains that outperform conventional image-based speckle nulling by at least two orders of magnitude.

Fundamental uncertainty limit for speckle displacement measurements.

PubMed

Fischer, Andreas

2017-09-01

The basic metrological task in speckle photography is to quantify displacements of speckle patterns, allowing for instance the investigation of the mechanical load and modification of objects with rough surfaces. However, the fundamental limit of the measurement uncertainty due to photon shot noise is unknown. For this reason, the Cramér-Rao bound (CRB) is derived for speckle displacement measurements, representing the squared minimal achievable measurement uncertainty. As result, the CRB for speckle patterns is only two times the CRB for an ideal point light source. Hence, speckle photography is an optimal measurement approach for contactless displacement measurements on rough surfaces. In agreement with a derivation from Heisenberg's uncertainty principle, the CRB depends on the number of detected photons and the diffraction limit of the imaging system described by the speckle size. The theoretical results are verified and validated, demonstrating the capability for displacement measurements with nanometer resolution.

The POKEMON Speckle Survey of Nearby M-Dwarfs

NASA Astrophysics Data System (ADS)

van Belle, Gerard; von Braun, Kaspar; Horch, Elliott; Clark, Catherine; DSSI Speckle Team

2018-01-01

The POKEMON (Pervasive Overview of Kompanions of Every M-dwarf in Our Neighborhood) survey of nearby M-dwarfs intends to inspect, at diffraction-limited resolution, every low-mass star out to 15pc, along with selected additional objects to 25pc. The primary emphasis of the survey is detection of low-mass companions to these M-dwarfs for refinement of the low-mass star multiplicity rate. The resultant catalog of M-dwarf companions will also guide immediate refinement of transit planet detection results from surveys such as TESS. POKEMON is using Lowell Observatory's 4.3-m Discovery Channel Telescope (DCT) with the Differential Speckle Survey Instrument (DSSI) speckle camera, along with the NN-Explore Exoplanet Stellar Speckle Imager (NESSI) speckle imager on 3.5-m WIYN; the survey takes advantage of the extremely rapid observing cadence rates possible with WIYN and (especially) DCT. The current status and preliminary results from the first 20+ nights of observing will be presented. Gotta observe them all!

Speckle reduction in optical coherence tomography using two-step iteration method (Conference Presentation)

NASA Astrophysics Data System (ADS)

Wang, Xianghong; Liu, Xinyu; Wang, Nanshuo; Yu, Xiaojun; Bo, En; Chen, Si; Liu, Linbo

2017-02-01

Optical coherence tomography (OCT) provides high resolution and cross-sectional images of biological tissue and is widely used for diagnosis of ocular diseases. However, OCT images suffer from speckle noise, which typically considered as multiplicative noise in nature, reducing the image resolution and contrast. In this study, we propose a two-step iteration (TSI) method to suppress those noises. We first utilize augmented Lagrange method to recover a low-rank OCT image and remove additive Gaussian noise, and then employ the simple and efficient split Bregman method to solve the Total-Variation Denoising model. We validated such proposed method using images of swine, rabbit and human retina. Results demonstrate that our TSI method outperforms the other popular methods in achieving higher peak signal-to-noise ratio (PSNR) and structure similarity (SSIM) while preserving important structural details, such as tiny capillaries and thin layers in retinal OCT images. In addition, the results of our TSI method show clearer boundaries and maintains high image contrast, which facilitates better image interpretations and analyses.

High resolution astrophysical observations using speckle imaging

NASA Astrophysics Data System (ADS)

Noyes, R. W.; Nisenson, P.; Papaliolios, C.; Stachnik, R. V.

1986-04-01

This report describes progress under a contract to develop a complete astronomical speckle image reconstruction facility and to apply that facility to the solution of astronomical problems. During the course of the contract we have developed the procedures, algorithms, theory and hardware required to perform that function and have made and interpreted astronomical observations of substantial significance. A principal result of the program was development of a photon-counting camera of innovative design, the PAPA detector. Development of this device was, in our view, essential to making the speckle process into a useful astronomical tool, since the principal impediment to that circumstance in the past was the necessity for application of photon noise compensation procedures which were difficult if not impossible to calibrate. The photon camera made this procedure unnecessary and permitted precision image recovery. The result of this effort and the associated algorithm development was an active program of astronomical observation which included investigations into young stellar objects, supergiant structure and measurements of the helium abundance of the early universe. We have also continued research on recovery of high angular resolution images of the solar surface working with scientists at the Sacramento Peak Observatory in this area.

Speckle Imaging at Gemini and the DCT

NASA Astrophysics Data System (ADS)

Horch, E. P.; Löbb, J.; Howell, S. B.; van Altena, W. F.; Henry, T. J.; van Belle, G. T.

2018-01-01

A program of speckle observations at Lowell Observatory's Discovery Channel Telescope (DCT) and the Gemini North and South Telescopes will be described. It has featured the Differential Speckle Survey Instrument (DSSI), built at Southern Connecticut State University in 2008. DSSI is a dual-port system that records speckle images in two colors simultaneously and produces diffraction limited images to V˜ 16.5 mag at Gemini and V˜ 14.5 mag at the DCT. Of the several science projects that are being pursued at these telescopes, three will be highlighted here. The first is high-resolution follow-up observations for Kepler and K2 exoplanet missions, the second is a study of metal-poor spectroscopic binaries in an attempt to resolve these systems and determine their visual orbits en route to making mass determinations, and the third is a systematic survey of nearby late-type dwarfs, where the multiplicity fraction will be directly measured and compared to that of G dwarfs. The current status of these projects is discussed and some representative results are given.

Dedicated hardware processor and corresponding system-on-chip design for real-time laser speckle imaging.

PubMed

Jiang, Chao; Zhang, Hongyan; Wang, Jia; Wang, Yaru; He, Heng; Liu, Rui; Zhou, Fangyuan; Deng, Jialiang; Li, Pengcheng; Luo, Qingming

2011-11-01

Laser speckle imaging (LSI) is a noninvasive and full-field optical imaging technique which produces two-dimensional blood flow maps of tissues from the raw laser speckle images captured by a CCD camera without scanning. We present a hardware-friendly algorithm for the real-time processing of laser speckle imaging. The algorithm is developed and optimized specifically for LSI processing in the field programmable gate array (FPGA). Based on this algorithm, we designed a dedicated hardware processor for real-time LSI in FPGA. The pipeline processing scheme and parallel computing architecture are introduced into the design of this LSI hardware processor. When the LSI hardware processor is implemented in the FPGA running at the maximum frequency of 130 MHz, up to 85 raw images with the resolution of 640×480 pixels can be processed per second. Meanwhile, we also present a system on chip (SOC) solution for LSI processing by integrating the CCD controller, memory controller, LSI hardware processor, and LCD display controller into a single FPGA chip. This SOC solution also can be used to produce an application specific integrated circuit for LSI processing.

Estimation of Articular Cartilage Surface Roughness Using Gray-Level Co-Occurrence Matrix of Laser Speckle Image.

PubMed

Youssef, Doaa; El-Ghandoor, Hatem; Kandel, Hamed; El-Azab, Jala; Hassab-Elnaby, Salah

2017-06-28

The application of He-Ne laser technologies for description of articular cartilage degeneration, one of the most common diseases worldwide, is an innovative usage of these technologies used primarily in material engineering. Plain radiography and magnetic resonance imaging are insufficient to allow the early assessment of the disease. As surface roughness of articular cartilage is an important indicator of articular cartilage degeneration progress, a safe and noncontact technique based on laser speckle image to estimate the surface roughness is provided. This speckle image from the articular cartilage surface, when illuminated by laser beam, gives very important information about the physical properties of the surface. An experimental setup using a low power He-Ne laser and a high-resolution digital camera was implemented to obtain speckle images of ten bovine articular cartilage specimens prepared for different average roughness values. Texture analysis method based on gray-level co-occurrence matrix (GLCM) analyzed on the captured speckle images is used to characterize the surface roughness of the specimens depending on the computation of Haralick's texture features. In conclusion, this promising method can accurately estimate the surface roughness of articular cartilage even for early signs of degeneration. The method is effective for estimation of average surface roughness values ranging from 0.09 µm to 2.51 µm with an accuracy of 0.03 µm.

Estimation of Articular Cartilage Surface Roughness Using Gray-Level Co-Occurrence Matrix of Laser Speckle Image

PubMed Central

El-Ghandoor, Hatem; Kandel, Hamed; El-Azab, Jala; Hassab-Elnaby, Salah

2017-01-01

The application of He-Ne laser technologies for description of articular cartilage degeneration, one of the most common diseases worldwide, is an innovative usage of these technologies used primarily in material engineering. Plain radiography and magnetic resonance imaging are insufficient to allow the early assessment of the disease. As surface roughness of articular cartilage is an important indicator of articular cartilage degeneration progress, a safe and noncontact technique based on laser speckle image to estimate the surface roughness is provided. This speckle image from the articular cartilage surface, when illuminated by laser beam, gives very important information about the physical properties of the surface. An experimental setup using a low power He-Ne laser and a high-resolution digital camera was implemented to obtain speckle images of ten bovine articular cartilage specimens prepared for different average roughness values. Texture analysis method based on gray-level co-occurrence matrix (GLCM) analyzed on the captured speckle images is used to characterize the surface roughness of the specimens depending on the computation of Haralick’s texture features. In conclusion, this promising method can accurately estimate the surface roughness of articular cartilage even for early signs of degeneration. The method is effective for estimation of average surface roughness values ranging from 0.09 µm to 2.51 µm with an accuracy of 0.03 µm. PMID:28773080

Frequency Compounded Imaging with a High-Frequency Dual Element Transducer

PubMed Central

Chang, Jin Ho; Kim, Hyung Ham; Lee, Jungwoo; Shung, K. Kirk

2014-01-01

This paper proposes a frequency compounding method to reduce speckle interferences, where a concentric annular type high-frequency dual element transducer is used to broaden the bandwidth of an imaging system. In frequency compounding methods, frequency division is carried out to obtain sub-band images containing uncorrelated speckles, which sacrifices axial resolution. Therefore, frequency compounding often deteriorates the target-detecting capability, quantified by the total signal-to-noise ratio (SNR), when the speckle’s SNR (SSNR) is not improved as much as the degraded axial resolution. However, this could be avoided if the effective bandwidth required for frequency compounding is increased. The primary goal of the proposed approach, hence, is to improve SSNR by a factor of two under the condition where axial resolution is degraded by a factor of less than two, which indicates the total SNR improvement to higher than 40% compared to that of an original image. Since the method here employs a dual element transducer operating at 20 and 40 MHz, the effective bandwidth necessary for frequency compounding becomes broadened. By dividing each spectrum of RF samples from both elements into two sub-bands, this method eventually enables four sets of the sub-band samples to contain uncorrelated speckles. This causes the axial resolution to be reduced by a factor of as low as 1.85, which means that this method would improve total SNR by at least 47 %. An in vitro experiment on an excised pig eye was performed to validate the proposed approach, and the results showed that the SSNR was improved from 2.081±0.365 in the original image to 4.206±0.635 in the final compounding image. PMID:19914674

Wide field fluorescence epi-microscopy behind a scattering medium enabled by speckle correlations

NASA Astrophysics Data System (ADS)

Hofer, Matthias; Soeller, Christian; Brasselet, Sophie; Bertolotti, Jacopo

2018-04-01

Fluorescence microscopy is widely used in biological imaging, however scattering from tissues strongly limits its applicability to a shallow depth. In this work we adapt a methodology inspired from stellar speckle interferometry, and exploit the optical memory effect to enable fluorescence microscopy through a turbid layer. We demonstrate efficient reconstruction of micrometer-size fluorescent objects behind a scattering medium in epi-microscopy, and study the specificities of this imaging modality (magnification, field of view, resolution) as compared to traditional microscopy. Using a modified phase retrieval algorithm to reconstruct fluorescent objects from speckle images, we demonstrate robust reconstructions even in relatively low signal to noise conditions. This modality is particularly appropriate for imaging in biological media, which are known to exhibit relatively large optical memory ranges compatible with tens of micrometers size field of views, and large spectral bandwidths compatible with emission fluorescence spectra of tens of nanometers widths.

Measuring Flow With Laser-Speckle Velocimetry

NASA Technical Reports Server (NTRS)

Smith, C. A.; Lourenco, L. M. M.; Krothapalli, A.

1988-01-01

Spatial resolution sufficient for calculation of vorticity.In laser-speckle velocimetry, pulsed or chopped laser beam expanded in one dimension by cylindrical lens to illuminate thin, fan-shaped region of flow measured. Flow seeded by small particles. Lens with optical axis perpendicular to illuminating beam forms image of illuminated particles on photographic plate. Speckle pattern of laser-illuminiated, seeded flow recorded in multiple-exposure photographs and processed to extract data on velocity field. Technique suited for study of vortical flows like those about helicopter rotor blades or airplane wings at high angles of attack.

The CHARA optical array

NASA Astrophysics Data System (ADS)

McAlister, Harold A.

1992-11-01

The Center for High Angular Resolution Astronomy (CHARA) was established in the College of Arts and Sciences at Georgia State University in 1984 with the goals of designing, constructing, and then operating a facility for very high spatial resolution astronomy. The interest in such a facility grew out of the participants' decade of activity in speckle interferometry. Although speckle interferometry continues to provide important astrophysical measurements of a variety of objects, many pressing problems require resolution far beyond that which can be expected from single aperture telescopes. In early 1986, CHARA received a grant from the National Science Foundation which has permitted a detailed exploration of the feasibility of constructing a facility which will provide a hundred-fold increase in angular resolution over what is possible by speckle interferometry at the largest existing telescopes. The design concept for the CHARA Array was developed initially with the contractural collaboration of United Technologies Optical Systems, Inc., in West Palm Beach, Florida, an arrangement that expired in August 1987. In late November 1987, the Georgia Tech Research Institute joined with CHARA to continue and complete the design concept study. Very high-resolution imaging at optical wavelengths is clearly coming of age in astronomy. The CHARA Array and other related projects will be important and necessary milestones along the way toward the development of a major national facility for high-resolution imaging--a true optical counterpart to the Very Large Array. Ground-based arrays and their scientific output will lead to high resolution facilities in space and, ultimately, on the Moon.

The Impact of a New Speckle Holography Analysis on the Galactic Center Orbits Initiative

NASA Astrophysics Data System (ADS)

Mangian, John; Ghez, Andrea; Gautam, Abhimat; Gallego, Laly; Schödel, Rainer; Lu, Jessica; Chen, Zhuo; UCLA Galactic Center Group; W.M. Keck Observatory Staff

2018-01-01

The Galactic Center Orbit Initiative has used two decades of high angular resolution imaging data from the W. M. Keck Observatory to make astrometric measurements of stellar motion around our Galaxy's central supermassive black hole. We present an analysis of a new approach to ten years of speckle imaging data (1995 - 2005) that has been processed with a new holography analysis. This analysis has (1) improved the image quality near the edge of the combined speckle frame and (2) increased the depth of the images and therefore increased the number of sources detected throughout the entire image. By directly comparing each holography analysis, we find a 41% increase in total detected sources and a 81% increase in sources further than 3" from the central black hole (SgrA*). Further, we find a 49% increase in sources of K-band magnitude greater than the old holography limiting magnitude due to the reduction of light halos surrounding bright sources.

Thermo-mechanical toner transfer for high-quality digital image correlation speckle patterns

NASA Astrophysics Data System (ADS)

Mazzoleni, Paolo; Zappa, Emanuele; Matta, Fabio; Sutton, Michael A.

2015-12-01

The accuracy and spatial resolution of full-field deformation measurements performed through digital image correlation are greatly affected by the frequency content of the speckle pattern, which can be effectively controlled using particles with well-defined and consistent shape, size and spacing. This paper introduces a novel toner-transfer technique to impress a well-defined and repeatable speckle pattern on plane and curved surfaces of metallic and cement composite specimens. The speckle pattern is numerically designed, printed on paper using a standard laser printer, and transferred onto the measurement surface via a thermo-mechanical process. The tuning procedure to compensate for the difference between designed and toner-transferred actual speckle size is presented. Based on this evidence, the applicability of the technique is discussed with respect to surface material, dimensions and geometry. Proof of concept of the proposed toner-transfer technique is then demonstrated for the case of a quenched and partitioned welded steel plate subjected to uniaxial tensile loading, and for an aluminum plate exposed to temperatures up to 70% of the melting point of aluminum and past the melting point of typical printer toner powder.

High-speed imaging using compressed sensing and wavelength-dependent scattering (Conference Presentation)

NASA Astrophysics Data System (ADS)

Shin, Jaewook; Bosworth, Bryan T.; Foster, Mark A.

2017-02-01

The process of multiple scattering has inherent characteristics that are attractive for high-speed imaging with high spatial resolution and a wide field-of-view. A coherent source passing through a multiple-scattering medium naturally generates speckle patterns with diffraction-limited features over an arbitrarily large field-of-view. In addition, the process of multiple scattering is deterministic allowing a given speckle pattern to be reliably reproduced with identical illumination conditions. Here, by exploiting wavelength dependent multiple scattering and compressed sensing, we develop a high-speed 2D time-stretch microscope. Highly chirped pulses from a 90-MHz mode-locked laser are sent through a 2D grating and a ground-glass diffuser to produce 2D speckle patterns that rapidly evolve with the instantaneous frequency of the chirped pulse. To image a scene, we first characterize the high-speed evolution of the generated speckle patterns. Subsequently we project the patterns onto the microscopic region of interest and collect the total light from the scene using a single high-speed photodetector. Thus the wavelength dependent speckle patterns serve as high-speed pseudorandom structured illumination of the scene. An image sequence is then recovered using the time-dependent signal received by the photodetector, the known speckle pattern evolution, and compressed sensing algorithms. Notably, the use of compressed sensing allows for reconstruction of a time-dependent scene using a highly sub-Nyquist number of measurements, which both increases the speed of the imager and reduces the amount of data that must be collected and stored. We will discuss our experimental demonstration of this approach and the theoretical limits on imaging speed.

Fast synchronized dual-wavelength laser speckle imaging system for monitoring hemodynamic changes in a stroke mouse model

PubMed Central

Qin, Jia; Shi, Lei; Dziennis, Suzan; Reif, Roberto; Wang, Ruikang K.

2014-01-01

In this paper, we describe a newly developed synchronized dual-wavelength laser speckle contrast imaging (SDW-LSCI) system, which contains two cameras that are synchronously triggered to acquire data. The system can acquire data at a high spatiotemporal resolution (up to 500Hz for ~1000×1000 pixels). A mouse model of stroke is used to demonstrate the capability for imaging the fast changes (within tens of milliseconds) in oxygenated and deoxygenated hemoglobin concentration, and the relative changes in blood flow in the mouse brain, through an intact cranium. This novel imaging technology will enable the study of fast hemodynamics and metabolic changes in vascular diseases. PMID:23027260

Magnetomotive laser speckle imaging

PubMed Central

Kim, Jeehyun; Oh, Junghwan; Choi, Bernard

2010-01-01

Laser speckle imaging (LSI) involves analysis of reflectance images collected during coherent optical excitation of an object to compute wide-field maps of tissue blood flow. An intrinsic limitation of LSI for resolving microvascular architecture is that its signal depends on relative motion of interrogated red blood cells. Hence, with LSI, small-diameter arterioles, venules, and capillaries are difficult to resolve due to the slow flow speeds associated with such vasculature. Furthermore, LSI characterization of subsurface blood flow is subject to blurring due to scattering, further limiting the ability of LSI to resolve or quantify blood flow in small vessels. Here, we show that magnetic activation of superparamagnetic iron oxide (SPIO) nanoparticles modulate the speckle flow index (SFI) values estimated from speckle contrast analysis of collected images. With application of an ac magnetic field to a solution of stagnant SPIO particles, an apparent increase in SFI is induced. Furthermore, with application of a focused dc magnetic field, a focal decrease in SFI values is induced. Magnetomotive LSI may enable wide-field mapping of suspicious tissue regions, enabling subsequent high-resolution optical interrogation of these regions. Similarly, subsequent photoactivation of intravascular SPIO nanoparticles could then be performed to induce selective photothermal destruction of unwanted vasculature. PMID:20210436

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

NASA Astrophysics Data System (ADS)

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.

Dynamic speckle illumination wide-field reflection phase microscopy

PubMed Central

Choi, Youngwoon; Hosseini, Poorya; Choi, Wonshik; Dasari, Ramachandra R.; So, Peter T. C.; Yaqoob, Zahid

2014-01-01

We demonstrate a quantitative reflection-phase microscope based on time-varying speckle-field illumination. Due to the short spatial coherence length of the speckle field, the proposed imaging system features superior lateral resolution, 520 nm, as well as high-depth selectivity, 1.03 µm. Off-axis interferometric detection enables wide-field and single-shot imaging appropriate for high-speed measurements. In addition, the measured phase sensitivity of this method, which is the smallest measurable axial motion, is more than 40 times higher than that available using a transmission system. We demonstrate the utility of our method by successfully distinguishing the motion of the top surface from that of the bottom in red blood cells. The proposed method will be useful for studying membrane dynamics in complex eukaryotic cells. PMID:25361156

A maximum likelihood approach to diffeomorphic speckle tracking for 3D strain estimation in echocardiography.

PubMed

Curiale, Ariel H; Vegas-Sánchez-Ferrero, Gonzalo; Bosch, Johan G; Aja-Fernández, Santiago

2015-08-01

The strain and strain-rate measures are commonly used for the analysis and assessment of regional myocardial function. In echocardiography (EC), the strain analysis became possible using Tissue Doppler Imaging (TDI). Unfortunately, this modality shows an important limitation: the angle between the myocardial movement and the ultrasound beam should be small to provide reliable measures. This constraint makes it difficult to provide strain measures of the entire myocardium. Alternative non-Doppler techniques such as Speckle Tracking (ST) can provide strain measures without angle constraints. However, the spatial resolution and the noisy appearance of speckle still make the strain estimation a challenging task in EC. Several maximum likelihood approaches have been proposed to statistically characterize the behavior of speckle, which results in a better performance of speckle tracking. However, those models do not consider common transformations to achieve the final B-mode image (e.g. interpolation). This paper proposes a new maximum likelihood approach for speckle tracking which effectively characterizes speckle of the final B-mode image. Its formulation provides a diffeomorphic scheme than can be efficiently optimized with a second-order method. The novelty of the method is threefold: First, the statistical characterization of speckle generalizes conventional speckle models (Rayleigh, Nakagami and Gamma) to a more versatile model for real data. Second, the formulation includes local correlation to increase the efficiency of frame-to-frame speckle tracking. Third, a probabilistic myocardial tissue characterization is used to automatically identify more reliable myocardial motions. The accuracy and agreement assessment was evaluated on a set of 16 synthetic image sequences for three different scenarios: normal, acute ischemia and acute dyssynchrony. The proposed method was compared to six speckle tracking methods. Results revealed that the proposed method is the most accurate method to measure the motion and strain with an average median motion error of 0.42 mm and a median strain error of 2.0 ± 0.9%, 2.1 ± 1.3% and 7.1 ± 4.9% for circumferential, longitudinal and radial strain respectively. It also showed its capability to identify abnormal segments with reduced cardiac function and timing differences for the dyssynchrony cases. These results indicate that the proposed diffeomorphic speckle tracking method provides robust and accurate motion and strain estimation. Copyright © 2015. Published by Elsevier B.V.

Rotational distortion correction in endoscopic optical coherence tomography based on speckle decorrelation

PubMed Central

Uribe-Patarroyo, Néstor; Bouma, Brett E.

2015-01-01

We present a new technique for the correction of nonuniform rotation distortion in catheter-based optical coherence tomography (OCT), based on the statistics of speckle between A-lines using intensity-based dynamic light scattering. This technique does not rely on tissue features and can be performed on single frames of data, thereby enabling real-time image correction. We demonstrate its suitability in a gastrointestinal balloon-catheter OCT system, determining the actual rotational speed with high temporal resolution, and present corrected cross-sectional and en face views showing significant enhancement of image quality. PMID:26625040

Axial resolution improvement in spectral domain optical coherence tomography using a depth-adaptive maximum-a-posterior framework

NASA Astrophysics Data System (ADS)

Boroomand, Ameneh; Tan, Bingyao; Wong, Alexander; Bizheva, Kostadinka

2015-03-01

The axial resolution of Spectral Domain Optical Coherence Tomography (SD-OCT) images degrades with scanning depth due to the limited number of pixels and the pixel size of the camera, any aberrations in the spectrometer optics and wavelength dependent scattering and absorption in the imaged object [1]. Here we propose a novel algorithm which compensates for the blurring effect of these factors of the depth-dependent axial Point Spread Function (PSF) in SDOCT images. The proposed method is based on a Maximum A Posteriori (MAP) reconstruction framework which takes advantage of a Stochastic Fully Connected Conditional Random Field (SFCRF) model. The aim is to compensate for the depth-dependent axial blur in SD-OCT images and simultaneously suppress the speckle noise which is inherent to all OCT images. Applying the proposed depth-dependent axial resolution enhancement technique to an OCT image of cucumber considerably improved the axial resolution of the image especially at higher imaging depths and allowed for better visualization of cellular membrane and nuclei. Comparing the result of our proposed method with the conventional Lucy-Richardson deconvolution algorithm clearly demonstrates the efficiency of our proposed technique in better visualization and preservation of fine details and structures in the imaged sample, as well as better speckle noise suppression. This illustrates the potential usefulness of our proposed technique as a suitable replacement for the hardware approaches which are often very costly and complicated.

Lucky imaging multiplicity studies of exoplanet host stars

NASA Astrophysics Data System (ADS)

Ginski, C.; Mugrauer, M.; Neuhäuser, R.

2014-03-01

The multiplicity of stars is an important parameter in order to understand star and planet formation. In the past decades extrasolar planets have been discovered around more than 600 stars with the radial velocity and transit techniques. Many of these systems present extreme cases of massive planetary objects at very close separations to their primary stars. To explain the configurations of such systems is hence a continued challenge in the development of formation theories. It will be very interesting to determine if there are significant differences between planets in single and multiple star systems. In our ongoing study we use high resolution imaging techniques to clarify the multiplicity status of nearby (within 250 pc) planet host stars. For targets on the northern hemisphere we employ the lucky imaging instrument Astralux at the 2.2 m telescope of the Calar Alto Observatory. The lucky imaging approach consists of taking several thousand short images with integration times shorter than the speckle coherence time, to sample the speckle variations during the observation window. We then only choose the so called "lucky shots" with a very high Strehl ratio in one of the speckles, to shift and add, resulting in a final image with the highest possible Strehl ratio and therefore highest possible angular resolution. We will present recent results of our study at the Calar Alto Observatory, as well as observations undertaken with the RTK camera at the 20 cm guiding telescope in our own observatory in Großschwabhausen.

High-Frame-Rate Speckle-Tracking Echocardiography.

PubMed

Joos, Philippe; Poree, Jonathan; Liebgott, Herve; Vray, Didier; Baudet, Mathilde; Faurie, Julia; Tournoux, Francois; Cloutier, Guy; Nicolas, Barbara; Garcia, Damien; Baudet, Mathilde; Tournoux, Francois; Joos, Philippe; Poree, Jonathan; Cloutier, Guy; Liebgott, Herve; Faurie, Julia; Vray, Didier; Nicolas, Barbara; Garcia, Damien

2018-05-01

Conventional echocardiography is the leading modality for noninvasive cardiac imaging. It has been recently illustrated that high-frame-rate echocardiography using diverging waves could improve cardiac assessment. The spatial resolution and contrast associated with this method are commonly improved by coherent compounding of steered beams. However, owing to fast tissue velocities in the myocardium, the summation process of successive diverging waves can lead to destructive interferences if motion compensation (MoCo) is not considered. Coherent compounding methods based on MoCo have demonstrated their potential to provide high-contrast B-mode cardiac images. Ultrafast speckle-tracking echocardiography (STE) based on common speckle-tracking algorithms could substantially benefit from this original approach. In this paper, we applied STE on high-frame-rate B-mode images obtained with a specific MoCo technique to quantify the 2-D motion and tissue velocities of the left ventricle. The method was first validated in vitro and then evaluated in vivo in the four-chamber view of 10 volunteers. High-contrast high-resolution B-mode images were constructed at 500 frames/s. The sequences were generated with a Verasonics scanner and a 2.5-MHz phased array. The 2-D motion was estimated with standard cross correlation combined with three different subpixel adjustment techniques. The estimated in vitro velocity vectors derived from STE were consistent with the expected values, with normalized errors ranging from 4% to 12% in the radial direction and from 10% to 20% in the cross-range direction. Global longitudinal strain of the left ventricle was also obtained from STE in 10 subjects and compared to the results provided by a clinical scanner: group means were not statistically different ( value = 0.33). The in vitro and in vivo results showed that MoCo enables preservation of the myocardial speckles and in turn allows high-frame-rate STE.

SAVI: Synthetic apertures for long-range, subdiffraction-limited visible imaging using Fourier ptychography

PubMed Central

Holloway, Jason; Wu, Yicheng; Sharma, Manoj K.; Cossairt, Oliver; Veeraraghavan, Ashok

2017-01-01

Synthetic aperture radar is a well-known technique for improving resolution in radio imaging. Extending these synthetic aperture techniques to the visible light domain is not straightforward because optical receivers cannot measure phase information. We propose to use macroscopic Fourier ptychography (FP) as a practical means of creating a synthetic aperture for visible imaging to achieve subdiffraction-limited resolution. We demonstrate the first working prototype for macroscopic FP in a reflection imaging geometry that is capable of imaging optically rough objects. In addition, a novel image space denoising regularization is introduced during phase retrieval to reduce the effects of speckle and improve perceptual quality of the recovered high-resolution image. Our approach is validated experimentally where the resolution of various diffuse objects is improved sixfold. PMID:28439550

Speckle Filtering of GF-3 Polarimetric SAR Data with Joint Restriction Principle.

PubMed

Xie, Jinwei; Li, Zhenfang; Zhou, Chaowei; Fang, Yuyuan; Zhang, Qingjun

2018-05-12

Polarimetric SAR (PolSAR) scattering characteristics of imagery are always obtained from the second order moments estimation of multi-polarization data, that is, the estimation of covariance or coherency matrices. Due to the extra-paths that signal reflected from separate scatterers within the resolution cell has to travel, speckle noise always exists in SAR images and has a severe impact on the scattering performance, especially on single look complex images. In order to achieve high accuracy in estimating covariance or coherency matrices, three aspects are taken into consideration: (1) the edges and texture of the scene are distinct after speckle filtering; (2) the statistical characteristic should be similar to the object pixel; and (3) the polarimetric scattering signature should be preserved, in addition to speckle reduction. In this paper, a joint restriction principle is proposed to meet the requirement. Three different restriction principles are introduced to the processing of speckle filtering. First, a new template, which is more suitable for the point or line targets, is designed to ensure the morphological consistency. Then, the extent sigma filter is used to restrict the pixels in the template aforementioned to have an identical statistic characteristic. At last, a polarimetric similarity factor is applied to the same pixels above, to guarantee the similar polarimetric features amongst the optional pixels. This processing procedure is named as speckle filtering with joint restriction principle and the approach is applied to GF-3 polarimetric SAR data acquired in San Francisco, CA, USA. Its effectiveness of keeping the image sharpness and preserving the scattering mechanism as well as speckle reduction is validated by the comparison with boxcar filters and refined Lee filter.

Correcting speckle contrast at small speckle size to enhance signal to noise ratio for laser speckle contrast imaging.

PubMed

Qiu, Jianjun; Li, Yangyang; Huang, Qin; Wang, Yang; Li, Pengcheng

2013-11-18

In laser speckle contrast imaging, it was usually suggested that speckle size should exceed two camera pixels to eliminate the spatial averaging effect. In this work, we show the benefit of enhancing signal to noise ratio by correcting the speckle contrast at small speckle size. Through simulations and experiments, we demonstrated that local speckle contrast, even at speckle size much smaller than one pixel size, can be corrected through dividing the original speckle contrast by the static speckle contrast. Moreover, we show a 50% higher signal to noise ratio of the speckle contrast image at speckle size below 0.5 pixel size than that at speckle size of two pixels. These results indicate the possibility of selecting a relatively large aperture to simultaneously ensure sufficient light intensity and high accuracy and signal to noise ratio, making the laser speckle contrast imaging more flexible.

Ultrasound Imaging Using Diffraction Tomography in a Cylindrical Geometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chambers, D H; Littrup, P

2002-01-24

Tomographic images of tissue phantoms and a sample of breast tissue have been produced from an acoustic synthetic array system for frequencies near 500 kHz. The images for sound speed and attenuation show millimeter resolution and demonstrate the feasibility of obtaining high-resolution tomographic images with frequencies that can deeply penetrate tissue. The image reconstruction method is based on the Born approximation to acoustic scattering and is a simplified version of a method previously used by Andre (Andre, et. al., Int. J. Imaging Systems and Technology, Vol 8, No. 1, 1997) for a circular acoustic array system. The images have comparablemore » resolution to conventional ultrasound images at much higher frequencies (3-5 MHz) but with lower speckle noise. This shows the potential of low frequency, deeply penetrating, ultrasound for high-resolution quantitative imaging.« less

Extracting and compensating dispersion mismatch in ultrahigh-resolution Fourier domain OCT imaging of the retina

PubMed Central

Choi, WooJhon; Baumann, Bernhard; Swanson, Eric A.; Fujimoto, James G.

2012-01-01

We present a numerical approach to extract the dispersion mismatch in ultrahigh-resolution Fourier domain optical coherence tomography (OCT) imaging of the retina. The method draws upon an analogy with a Shack-Hartmann wavefront sensor. By exploiting mathematical similarities between the expressions for aberration in optical imaging and dispersion mismatch in spectral / Fourier domain OCT, Shack-Hartmann principles can be extended from the two-dimensional paraxial wavevector space (or the x-y plane in the spatial domain) to the one-dimensional wavenumber space (or the z-axis in the spatial domain). For OCT imaging of the retina, different retinal layers, such as the retinal nerve fiber layer (RNFL), the photoreceptor inner and outer segment junction (IS/OS), or all the retinal layers near the retinal pigment epithelium (RPE) can be used as point source beacons in the axial direction, analogous to point source beacons used in conventional two-dimensional Shack-Hartman wavefront sensors for aberration characterization. Subtleties regarding speckle phenomena in optical imaging, which affect the Shack-Hartmann wavefront sensor used in adaptive optics, also occur analogously in this application. Using this approach and carefully suppressing speckle, the dispersion mismatch in spectral / Fourier domain OCT retinal imaging can be successfully extracted numerically and used for numerical dispersion compensation to generate sharper, ultrahigh-resolution OCT images. PMID:23187353

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

NASA Astrophysics Data System (ADS)

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.

High resolution telescope

DOEpatents

Massie, Norbert A.; Oster, Yale

1992-01-01

A large effective-aperture, low-cost optical telescope with diffraction-limited resolution enables ground-based observation of near-earth space objects. The telescope has a non-redundant, thinned-aperture array in a center-mount, single-structure space frame. It employs speckle interferometric imaging to achieve diffraction-limited resolution. The signal-to-noise ratio problem is mitigated by moving the wavelength of operation to the near-IR, and the image is sensed by a Silicon CCD. The steerable, single-structure array presents a constant pupil. The center-mount, radar-like mount enables low-earth orbit space objects to be tracked as well as increases stiffness of the space frame. In the preferred embodiment, the array has elemental telescopes with subaperture of 2.1 m in a circle-of-nine configuration. The telescope array has an effective aperture of 12 m which provides a diffraction-limited resolution of 0.02 arc seconds. Pathlength matching of the telescope array is maintained by an electro-optical system employing laser metrology. Speckle imaging relaxes pathlength matching tolerance by one order of magnitude as compared to phased arrays. Many features of the telescope contribute to substantial reduction in costs. These include eliminating the conventional protective dome and reducing on-site construction activites. The cost of the telescope scales with the first power of the aperture rather than its third power as in conventional telescopes.

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

NASA Astrophysics Data System (ADS)

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.

Laser speckle micro-rheology for biomechanical evaluation of breast tumors (Conference Presentation)

NASA Astrophysics Data System (ADS)

Hajjarian Kashany, Zeinab; Nadkarni, Seemantini K.

2016-03-01

The stiffness of the extra cellular matrix (ECM) is recognized as a key regulator of cancer cell proliferation, migration and invasion. Therefore technologies that quantify ECM stiffness with micro-scale scale resolution will likely provide important insights into neoplastic progression. Laser Speckle Micro-Rheology (LSM) is a novel optical tool for measuring tissue viscoelastic properties with micro-scale resolution. In LSM, speckle images are collected through an objective lens by a high-speed camera. Spatio-temporal correlation analysis of speckle frames yields the intensity autocorrelation function, g2(t), for each pixel, and subsequently a 2D map of viscoelastic modulus, G*(ω) is reconstructed. Here, we investigate the utility of LSM for micro-mechanical evaluation of the ECM in human breast lesions. Specimens collected 18 women undergoing lumpectomy or mastectomy were evaluated with LSM. Because collagen is the key protein associated with ECM stiffness, G*(ω) maps obtained from LSM were compared with collagen content measured by second harmonic generation (SHG) microscopy. Regions of low G*(ω), identified by LSM, corresponded to low-intensity SHG signal and adipose tissue. Likewise, regions with high G*(ω) in LSM images matched high intensity SHG signal caused by desmoplastic collagen accumulation. Quantitative regression analysis demonstrated a strong, statistically significant correlation between G*(ω) and SHG signal intensity (R=0.66 p< 0.01). These findings highlight the capability of LSM for quantifying the ECM micro-mechanics, potentially providing important insights into the biomechanical regulators of breast cancer progression.

Determination of the stacking fault density in highly defective single GaAs nanowires by means of coherent diffraction imaging

NASA Astrophysics Data System (ADS)

Davtyan, Arman; Biermanns, Andreas; Loffeld, Otmar; Pietsch, Ullrich

2016-06-01

Coherent x-ray diffraction imaging is used to measure diffraction patterns from individual highly defective nanowires, showing a complex speckle pattern instead of well-defined Bragg peaks. The approach is tested for nanowires of 500 nm diameter and 500 nm height predominately composed by zinc-blende (ZB) and twinned zinc-blende (TZB) phase domains. Phase retrieval is used to reconstruct the measured 2-dimensional intensity patterns recorded from single nanowires with 3.48 nm and 0.98 nm spatial resolution. Whereas the speckle amplitudes and distribution are perfectly reconstructed, no unique solution could be obtained for the phase structure. The number of phase switches is found to be proportional to the number of measured speckles and follows a narrow number distribution. Using data with 0.98 nm spatial resolution the mean number of phase switches is in reasonable agreement with estimates taken from TEM. However, since the resolved phase domain still is 3-4 times larger than a single GaAs bilayer we explain the non-ambiguous phase reconstruction by the fact that depending on starting phase and sequence of subroutines used during the phase retrieval the retrieved phase domain host a different sequence of randomly stacked bilayers. Modelling possible arrangements of bilayer sequences within a phase domain demonstrate that the complex speckle patterns measured can indeed be explained by the random arrangement of the ZB and TZB phase domains.

Simultaneous multispectral reflectance imaging and laser speckle flowmetry of cerebral blood flow and oxygen metabolism in focal cerebral ischemia

PubMed Central

Jones, Phill B.; Shin, Hwa Kyoung; Boas, David A.; Hyman, Bradley T.; Moskowitz, Michael A.; Ayata, Cenk; Dunn, Andrew K.

2009-01-01

Real-time investigation of cerebral blood flow (CBF), and oxy- and deoxyhemoglobin concentration (HbO, HbR) dynamics has been difficult until recently due to limited spatial and temporal resolution of techniques like laser Doppler flowmetry and magnetic resonance imaging (MRI). The combination of laser speckle flowmetry (LSF) and multispectral reflectance imaging (MSRI) yields high-resolution spatiotemporal maps of hemodynamic and metabolic changes in response to functional cortical activation. During acute focal cerebral ischemia, changes in HbO and HbR are much larger than in functional activation, resulting in the failure of the Beer-Lambert approximation to yield accurate results. We describe the use of simultaneous LSF and MSRI, using a nonlinear Monte Carlo fitting technique, to record rapid changes in CBF, HbO, HbR, and cerebral metabolic rate of oxygen (CMRO2) during acute focal cerebral ischemia induced by distal middle cerebral artery occlusion (dMCAO) and reperfusion. This technique captures CBF and CMRO2 changes during hemodynamic and metabolic events with high temporal and spatial resolution through the intact skull and demonstrates the utility of simultaneous LSF and MSRI in mouse models of cerebrovascular disease. PMID:19021335

OCT in Dermatology

NASA Astrophysics Data System (ADS)

Holmes, John; Welzel, Julia

OCT is increasingly interesting for non-invasive skin imaging in Dermatology. Due to its resolution and imaging depth, OCT is already routinely established for diagnosis of nonmelanoma skin cancer, whereas for pigmented lesions, the resolution is still not high enough. OCT has also a high value for monitoring of treatment effects, for example to control healing after non-surgical topical treatment of basal cell carcinomas. In summary, there are several indications for applications of OCT to image skin diseases, and its importance will grow in the future due to further technical developments like speckle variance OCT.

Speckle-interferometric measurement system of 3D deformation to obtain thickness changes of thin specimen under tensile loads

NASA Astrophysics Data System (ADS)

Kowarsch, Robert; Zhang, Jiajun; Sguazzo, Carmen; Hartmann, Stefan; Rembe, Christian

2017-06-01

The analysis of materials and geometries in tensile tests and the extraction of mechanic parameters is an important field in solid mechanics. Especially the measurement of thickness changes is important to obtain accurate strain information of specimens under tensile loads. Current optical measurement methods comprising 3D digital image correlation enable thickness-change measurement only with nm-resolution. We present a phase-shifting electronic speckle-pattern interferometer in combination with speckle-correlation technique to measure the 3D deformation. The phase-shift for the interferometer is introduced by fast wavelength tuning of a visible diode laser by injection current. In a post-processing step, both measurements can be combined to reconstruct the 3D deformation. In this contribution, results of a 3Ddeformation measurement for a polymer membrane are presented. These measurements show sufficient resolution for the detection of 3D deformations of thin specimen in tensile test. In future work we address the thickness changes of thin specimen under tensile loads.

Investigations of High Resolution Imaging through the Earth’s Atmosphere Using Speckle Interferometry

DTIC Science & Technology

1984-03-07

improved the SO/AFGL speckle camera for use at any conventionai`teescop" by pErv’-ion ofmicro-processor controlled " Risley prisms, shutter mechanisms...condition in the IR because of the all-reflecting system (the wedges used for mode . C are normally not used for IR work). In the 2ptical Experiments the...of pairs of •’ 16 fl**S ’ ,**S * !, S glass wedges (mode C). Beckers and Roddier (1982) used the Roddier rotation sholaring interferometer to obtain

Observing Exoplanets with High-dispersion Coronagraphy. II. Demonstration of an Active Single-mode Fiber Injection Unit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mawet, D.; Ruane, G.; Xuan, W.

2017-04-01

High-dispersion coronagraphy (HDC) optimally combines high-contrast imaging techniques such as adaptive optics/wavefront control plus coronagraphy to high spectral resolution spectroscopy. HDC is a critical pathway toward fully characterizing exoplanet atmospheres across a broad range of masses from giant gaseous planets down to Earth-like planets. In addition to determining the molecular composition of exoplanet atmospheres, HDC also enables Doppler mapping of atmosphere inhomogeneities (temperature, clouds, wind), as well as precise measurements of exoplanet rotational velocities. Here, we demonstrate an innovative concept for injecting the directly imaged planet light into a single-mode fiber, linking a high-contrast adaptively corrected coronagraph to a high-resolutionmore » spectrograph (diffraction-limited or not). Our laboratory demonstration includes three key milestones: close-to-theoretical injection efficiency, accurate pointing and tracking, and on-fiber coherent modulation and speckle nulling of spurious starlight signal coupling into the fiber. Using the extreme modal selectivity of single-mode fibers, we also demonstrated speckle suppression gains that outperform conventional image-based speckle nulling by at least two orders of magnitude.« less

Pixel-based speckle adjustment for noise reduction in Fourier-domain OCT images.

PubMed

Zhang, Anqi; Xi, Jiefeng; Sun, Jitao; Li, Xingde

2017-03-01

Speckle resides in OCT signals and inevitably effects OCT image quality. In this work, we present a novel method for speckle noise reduction in Fourier-domain OCT images, which utilizes the phase information of complex OCT data. In this method, speckle area is pre-delineated pixelwise based on a phase-domain processing method and then adjusted by the results of wavelet shrinkage of the original image. Coefficient shrinkage method such as wavelet or contourlet is applied afterwards for further suppressing the speckle noise. Compared with conventional methods without speckle adjustment, the proposed method demonstrates significant improvement of image quality.

Speckle reduction in optical coherence tomography by adaptive total variation method

NASA Astrophysics Data System (ADS)

Wu, Tong; Shi, Yaoyao; Liu, Youwen; He, Chongjun

2015-12-01

An adaptive total variation method based on the combination of speckle statistics and total variation restoration is proposed and developed for reducing speckle noise in optical coherence tomography (OCT) images. The statistical distribution of the speckle noise in OCT image is investigated and measured. With the measured parameters such as the mean value and variance of the speckle noise, the OCT image is restored by the adaptive total variation restoration method. The adaptive total variation restoration algorithm was applied to the OCT images of a volunteer's hand skin, which showed effective speckle noise reduction and image quality improvement. For image quality comparison, the commonly used median filtering method was also applied to the same images to reduce the speckle noise. The measured results demonstrate the superior performance of the adaptive total variation restoration method in terms of image signal-to-noise ratio, equivalent number of looks, contrast-to-noise ratio, and mean square error.

CHARIS Construction Status, Design, and Future Science

NASA Astrophysics Data System (ADS)

Groff, Tyler Dean; Kasdin, N. Jeremy; Peters, Mary Anne; Galvin, Michael; Knapp, Gillian R.; Brandt, Timothy; Loomis, Craig; Carr, Michael; Mede, Kyle; Jarosik, Norman; McElwain, Michael W.; Guyon, Olivier; Jovanovic, Nemanja; Takato, Naruhisa; Hayashi, Masahiko

2015-01-01

Princeton University is funded by the National Astronomical Observatory of Japan to build an integral field spectrograph (IFS) dubbed the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS). CHARIS is part of the ongoing exoplanet science effort at the Subaru Telescope, and will serve as the science imager for the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) and AO188 systems. The principal science goals are disk imaging and high contrast spectra of brown dwarfs and hot Jovian planets across J, H, and K bands. SCExAO is a coronagraphic and wavefront control system that will be capable of extreme adaptive optics and quasi-static speckle suppression. Speckle suppression is meant to reduce the residual speckle to a level that makes it possible to detect planets at very low inner working angles (~80 mas). Even so, CHARIS must mitigate spectral contamination from the residual speckle halo due to crosstalk between the closely packed spectra of the image. CHARIS mitigates crosstalk via an array of field stops behind the lenslet array and carefully toleranced relay optics. This reduces uncertainty in the measured spectrum of the exoplanets by increasing robustness of the spectrograph to nearby bright speckles. Mitigating crosstalk in hardware both improves science and reduces computational overhead. Combined with a detailed wavefront budget this improves the utility of CHARIS in the speckle control loop. Another defining feature of CHARIS is its disperser design. In addition to imaging in individual J, H, and K bands, CHARIS has a fourth mode that images across all three simultaneously. This required an improvement in the linearity of dispersion from 1.15 to 2.38 microns. To do so the CHARIS project has chosen a new high-index dispersing material and characterized its properties at cryogenic temperatures. We present the build status of the spectrograph, including status and viability of operating an H2RG detector directly using a SAM card via gigabit Ethernet over Linux. In addition to the stated and as-built specifications of the instrument hardware, we discuss the future of science impacts of CHARIS at the Subaru telescope.

Speckle perception and disturbance limit in laser based projectors

NASA Astrophysics Data System (ADS)

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

2016-04-01

We investigate the level of speckle that can be tolerated in a laser cinema projector. For this purpose, we equipped a movie theatre room with a prototype laser projector. A group of 186 participants was gathered to evaluate the speckle perception of several, short movie trailers in a subjective `Quality of Experience' experiment. This study is important as the introduction of lasers in projection systems has been hampered by the presence of speckle in projected images. 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. As is also discussed in [Verschaffelt et al., Scientific Reports 5, art. nr. 14105, 2015] we find that, for moving images, the speckle becomes disturbing if the speckle contrast becomes larger than 6.9% for the red, 6.0% for the green, and 4.8% for the blue primary colors of the projector, whereas for still images the speckle detection threshold is about 3%. As we could not independently tune the speckle contrast of each of the primary colors, this speckle disturbance limit seems to be determined by the 6.9% speckle contrast of the red color as this primary color contains the largest amount of speckle. The speckle disturbance limit for movies thus turns out to be substantially larger than that for still images, and hence is easier to attain.

Pixel-based speckle adjustment for noise reduction in Fourier-domain OCT images

PubMed Central

Zhang, Anqi; Xi, Jiefeng; Sun, Jitao; Li, Xingde

2017-01-01

Speckle resides in OCT signals and inevitably effects OCT image quality. In this work, we present a novel method for speckle noise reduction in Fourier-domain OCT images, which utilizes the phase information of complex OCT data. In this method, speckle area is pre-delineated pixelwise based on a phase-domain processing method and then adjusted by the results of wavelet shrinkage of the original image. Coefficient shrinkage method such as wavelet or contourlet is applied afterwards for further suppressing the speckle noise. Compared with conventional methods without speckle adjustment, the proposed method demonstrates significant improvement of image quality. PMID:28663860

Analysis of microvascular perfusion with multi-dimensional complete ensemble empirical mode decomposition with adaptive noise algorithm: Processing of laser speckle contrast images recorded in healthy subjects, at rest and during acetylcholine stimulation.

PubMed

Humeau-Heurtier, Anne; Marche, Pauline; Dubois, Severine; Mahe, Guillaume

2015-01-01

Laser speckle contrast imaging (LSCI) is a full-field imaging modality to monitor microvascular blood flow. It is able to give images with high temporal and spatial resolutions. However, when the skin is studied, the interpretation of the bidimensional data may be difficult. This is why an averaging of the perfusion values in regions of interest is often performed and the result is followed in time, reducing the data to monodimensional time series. In order to avoid such a procedure (that leads to a loss of the spatial resolution), we propose to extract patterns from LSCI data and to compare these patterns for two physiological states in healthy subjects: at rest and at the peak of acetylcholine-induced perfusion peak. For this purpose, the recent multi-dimensional complete ensemble empirical mode decomposition with adaptive noise (MCEEMDAN) algorithm is applied to LSCI data. The results show that the intrinsic mode functions and residue given by MCEEMDAN show different patterns for the two physiological states. The images, as bidimensional data, can therefore be processed to reveal microvascular perfusion patterns, hidden in the images themselves. This work is therefore a feasibility study before analyzing data in patients with microvascular dysfunctions.

An overview of methods to mitigate artifacts in optical coherence tomography imaging of the skin.

PubMed

Adabi, Saba; Fotouhi, Audrey; Xu, Qiuyun; Daveluy, Steve; Mehregan, Darius; Podoleanu, Adrian; Nasiriavanaki, Mohammadreza

2018-05-01

Optical coherence tomography (OCT) of skin delivers three-dimensional images of tissue microstructures. Although OCT imaging offers a promising high-resolution modality, OCT images suffer from some artifacts that lead to misinterpretation of tissue structures. Therefore, an overview of methods to mitigate artifacts in OCT imaging of the skin is of paramount importance. Speckle, intensity decay, and blurring are three major artifacts in OCT images. Speckle is due to the low coherent light source used in the configuration of OCT. Intensity decay is a deterioration of light with respect to depth, and blurring is the consequence of deficiencies of optical components. Two speckle reduction methods (one based on artificial neural network and one based on spatial compounding), an attenuation compensation algorithm (based on Beer-Lambert law) and a deblurring procedure (using deconvolution), are described. Moreover, optical properties extraction algorithm based on extended Huygens-Fresnel (EHF) principle to obtain some additional information from OCT images are discussed. In this short overview, we summarize some of the image enhancement algorithms for OCT images which address the abovementioned artifacts. The results showed a significant improvement in the visibility of the clinically relevant features in the images. The quality improvement was evaluated using several numerical assessment measures. Clinical dermatologists benefit from using these image enhancement algorithms to improve OCT diagnosis and essentially function as a noninvasive optical biopsy. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Multiscale morphological filtering for analysis of noisy and complex images

NASA Astrophysics Data System (ADS)

Kher, A.; Mitra, S.

Images acquired with passive sensing techniques suffer from illumination variations and poor local contrasts that create major difficulties in interpretation and identification tasks. On the other hand, images acquired with active sensing techniques based on monochromatic illumination are degraded with speckle noise. Mathematical morphology offers elegant techniques to handle a wide range of image degradation problems. Unlike linear filters, morphological filters do not blur the edges and hence maintain higher image resolution. Their rich mathematical framework facilitates the design and analysis of these filters as well as their hardware implementation. Morphological filters are easier to implement and are more cost effective and efficient than several conventional linear filters. Morphological filters to remove speckle noise while maintaining high resolution and preserving thin image regions that are particularly vulnerable to speckle noise were developed and applied to SAR imagery. These filters used combination of linear (one-dimensional) structuring elements in different (typically four) orientations. Although this approach preserves more details than the simple morphological filters using two-dimensional structuring elements, the limited orientations of one-dimensional elements approximate the fine details of the region boundaries. A more robust filter designed recently overcomes the limitation of the fixed orientations. This filter uses a combination of concave and convex structuring elements. Morphological operators are also useful in extracting features from visible and infrared imagery. A multiresolution image pyramid obtained with successive filtering and a subsampling process aids in the removal of the illumination variations and enhances local contrasts. A morphology-based interpolation scheme was also introduced to reduce intensity discontinuities created in any morphological filtering task. The generality of morphological filtering techniques in extracting information from a wide variety of images obtained with active and passive sensing techniques is discussed. Such techniques are particularly useful in obtaining more information from fusion of complex images by different sensors such as SAR, visible, and infrared.

Multiscale Morphological Filtering for Analysis of Noisy and Complex Images

NASA Technical Reports Server (NTRS)

Kher, A.; Mitra, S.

1993-01-01

Images acquired with passive sensing techniques suffer from illumination variations and poor local contrasts that create major difficulties in interpretation and identification tasks. On the other hand, images acquired with active sensing techniques based on monochromatic illumination are degraded with speckle noise. Mathematical morphology offers elegant techniques to handle a wide range of image degradation problems. Unlike linear filters, morphological filters do not blur the edges and hence maintain higher image resolution. Their rich mathematical framework facilitates the design and analysis of these filters as well as their hardware implementation. Morphological filters are easier to implement and are more cost effective and efficient than several conventional linear filters. Morphological filters to remove speckle noise while maintaining high resolution and preserving thin image regions that are particularly vulnerable to speckle noise were developed and applied to SAR imagery. These filters used combination of linear (one-dimensional) structuring elements in different (typically four) orientations. Although this approach preserves more details than the simple morphological filters using two-dimensional structuring elements, the limited orientations of one-dimensional elements approximate the fine details of the region boundaries. A more robust filter designed recently overcomes the limitation of the fixed orientations. This filter uses a combination of concave and convex structuring elements. Morphological operators are also useful in extracting features from visible and infrared imagery. A multiresolution image pyramid obtained with successive filtering and a subsampling process aids in the removal of the illumination variations and enhances local contrasts. A morphology-based interpolation scheme was also introduced to reduce intensity discontinuities created in any morphological filtering task. The generality of morphological filtering techniques in extracting information from a wide variety of images obtained with active and passive sensing techniques is discussed. Such techniques are particularly useful in obtaining more information from fusion of complex images by different sensors such as SAR, visible, and infrared.

Statistical model for speckle pattern optimization.

PubMed

Su, Yong; Zhang, Qingchuan; Gao, Zeren

2017-11-27

Image registration is the key technique of optical metrologies such as digital image correlation (DIC), particle image velocimetry (PIV), and speckle metrology. Its performance depends critically on the quality of image pattern, and thus pattern optimization attracts extensive attention. In this article, a statistical model is built to optimize speckle patterns that are composed of randomly positioned speckles. It is found that the process of speckle pattern generation is essentially a filtered Poisson process. The dependence of measurement errors (including systematic errors, random errors, and overall errors) upon speckle pattern generation parameters is characterized analytically. By minimizing the errors, formulas of the optimal speckle radius are presented. Although the primary motivation is from the field of DIC, we believed that scholars in other optical measurement communities, such as PIV and speckle metrology, will benefit from these discussions.

Rayleigh-maximum-likelihood bilateral filter for ultrasound image enhancement.

PubMed

Li, Haiyan; Wu, Jun; Miao, Aimin; Yu, Pengfei; Chen, Jianhua; Zhang, Yufeng

2017-04-17

Ultrasound imaging plays an important role in computer diagnosis since it is non-invasive and cost-effective. However, ultrasound images are inevitably contaminated by noise and speckle during acquisition. Noise and speckle directly impact the physician to interpret the images and decrease the accuracy in clinical diagnosis. Denoising method is an important component to enhance the quality of ultrasound images; however, several limitations discourage the results because current denoising methods can remove noise while ignoring the statistical characteristics of speckle and thus undermining the effectiveness of despeckling, or vice versa. In addition, most existing algorithms do not identify noise, speckle or edge before removing noise or speckle, and thus they reduce noise and speckle while blurring edge details. Therefore, it is a challenging issue for the traditional methods to effectively remove noise and speckle in ultrasound images while preserving edge details. To overcome the above-mentioned limitations, a novel method, called Rayleigh-maximum-likelihood switching bilateral filter (RSBF) is proposed to enhance ultrasound images by two steps: noise, speckle and edge detection followed by filtering. Firstly, a sorted quadrant median vector scheme is utilized to calculate the reference median in a filtering window in comparison with the central pixel to classify the target pixel as noise, speckle or noise-free. Subsequently, the noise is removed by a bilateral filter and the speckle is suppressed by a Rayleigh-maximum-likelihood filter while the noise-free pixels are kept unchanged. To quantitatively evaluate the performance of the proposed method, synthetic ultrasound images contaminated by speckle are simulated by using the speckle model that is subjected to Rayleigh distribution. Thereafter, the corrupted synthetic images are generated by the original image multiplied with the Rayleigh distributed speckle of various signal to noise ratio (SNR) levels and added with Gaussian distributed noise. Meanwhile clinical breast ultrasound images are used to visually evaluate the effectiveness of the method. To examine the performance, comparison tests between the proposed RSBF and six state-of-the-art methods for ultrasound speckle removal are performed on simulated ultrasound images with various noise and speckle levels. The results of the proposed RSBF are satisfying since the Gaussian noise and the Rayleigh speckle are greatly suppressed. The proposed method can improve the SNRs of the enhanced images to nearly 15 and 13 dB compared with images corrupted by speckle as well as images contaminated by speckle and noise under various SNR levels, respectively. The RSBF is effective in enhancing edge while smoothing the speckle and noise in clinical ultrasound images. In the comparison experiments, the proposed method demonstrates its superiority in accuracy and robustness for denoising and edge preserving under various levels of noise and speckle in terms of visual quality as well as numeric metrics, such as peak signal to noise ratio, SNR and root mean squared error. The experimental results show that the proposed method is effective for removing the speckle and the background noise in ultrasound images. The main reason is that it performs a "detect and replace" two-step mechanism. The advantages of the proposed RBSF lie in two aspects. Firstly, each central pixel is classified as noise, speckle or noise-free texture according to the absolute difference between the target pixel and the reference median. Subsequently, the Rayleigh-maximum-likelihood filter and the bilateral filter are switched to eliminate speckle and noise, respectively, while the noise-free pixels are unaltered. Therefore, it is implemented with better accuracy and robustness than the traditional methods. Generally, these traits declare that the proposed RSBF would have significant clinical application.

Multi-exposure speckle imaging of cerebral blood flow: a pilot clinical study (Conference Presentation)

NASA Astrophysics Data System (ADS)

Richards, Lisa M.; Kazmi, S. M. S.; Olin, Katherine E.; Waldron, James S.; Fox, Douglas J.; Dunn, Andrew K.

2017-03-01

Monitoring cerebral blood flow (CBF) during neurosurgery is essential for detecting ischemia in a timely manner for a wide range of procedures. Multiple clinical studies have demonstrated that laser speckle contrast imaging (LSCI) has high potential to be a valuable, label-free CBF monitoring technique during neurosurgery. LSCI is an optical imaging method that provides blood flow maps with high spatiotemporal resolution requiring only a coherent light source, a lens system, and a camera. However, the quantitative accuracy and sensitivity of LSCI is limited and highly dependent on the exposure time. An extension to LSCI called multi-exposure speckle imaging (MESI) overcomes these limitations, and was evaluated intraoperatively in patients undergoing brain tumor resection. This clinical study (n = 7) recorded multiple exposure times from the same cortical tissue area, and demonstrates that shorter exposure times (≤1 ms) provide the highest dynamic range and sensitivity for sampling flow rates in human neurovasculature. This study also combined exposure times using the MESI model, demonstrating high correlation with proper image calibration and acquisition. The physiological accuracy of speckle-estimated flow was validated using conservation of flow analysis on vascular bifurcations. Flow estimates were highly conserved in MESI and 1 ms exposure LSCI, with percent errors at 6.4% ± 5.3% and 7.2% ± 7.2%, respectively, while 5 ms exposure LSCI had higher errors at 21% ± 10% (n = 14 bifurcations). Results from this study demonstrate the importance of exposure time selection for LSCI, and that intraoperative MESI can be performed with high quantitative accuracy.

Speckle-reducing scale-invariant feature transform match for synthetic aperture radar image registration

NASA Astrophysics Data System (ADS)

Wang, Xianmin; Li, Bo; Xu, Qizhi

2016-07-01

The anisotropic scale space (ASS) is often used to enhance the performance of a scale-invariant feature transform (SIFT) algorithm in the registration of synthetic aperture radar (SAR) images. The existing ASS-based methods usually suffer from unstable keypoints and false matches, since the anisotropic diffusion filtering has limitations in reducing the speckle noise from SAR images while building the ASS image representation. We proposed a speckle reducing SIFT match method to obtain stable keypoints and acquire precise matches for the SAR image registration. First, the keypoints are detected in a speckle reducing anisotropic scale space constructed by the speckle reducing anisotropic diffusion, so that speckle noise is greatly reduced and prominent structures of the images are preserved, consequently the stable keypoints can be derived. Next, the probabilistic relaxation labeling approach is employed to establish the matches of the keypoints then the correct match rate of the keypoints is significantly increased. Experiments conducted on simulated speckled images and real SAR images demonstrate the effectiveness of the proposed method.

Effect of subaperture beamforming on phase coherence imaging.

PubMed

Hasegawa, Hideyuki; Kanai, Hiroshi

2014-11-01

High-frame-rate echocardiography using unfocused transmit beams and parallel receive beamforming is a promising method for evaluation of cardiac function, such as imaging of rapid propagation of vibration of the heart wall resulting from electrical stimulation of the myocardium. In this technique, high temporal resolution is realized at the expense of spatial resolution and contrast. The phase coherence factor has been developed to improve spatial resolution and contrast in ultrasonography. It evaluates the variance in phases of echo signals received by individual transducer elements after delay compensation, as in the conventional delay-andsum beamforming process. However, the phase coherence factor suppresses speckle echoes because phases of speckle echoes fluctuate as a result of interference of echoes. In the present study, the receiving aperture was divided into several subapertures, and conventional delay-and-sum beamforming was performed with respect to each subaperture to suppress echoes from scatterers except for that at a focal point. After subaperture beamforming, the phase coherence factor was obtained from beamformed RF signals from respective subapertures. By means of this procedure, undesirable echoes, which can interfere with the echo from a focal point, can be suppressed by subaperture beamforming, and the suppression of the phase coherence factor resulting from phase fluctuation caused by such interference can be avoided. In the present study, the effect of subaperture beamforming in high-frame-rate echocardiography with the phase coherence factor was evaluated using a phantom. By applying subaperture beamforming, the average intensity of speckle echoes from a diffuse scattering medium was significantly higher (-39.9 dB) than that obtained without subaperture beamforming (-48.7 dB). As for spatial resolution, the width at half-maximum of the lateral echo amplitude profile obtained without the phase coherence factor was 1.06 mm. By using the phase coherence factor, spatial resolution was improved significantly, and subaperture beamforming achieved a better spatial resolution of 0.75 mm than that of 0.78 mm obtained without subaperture beamforming.

MATLAB for laser speckle contrast analysis (LASCA): a practice-based approach

NASA Astrophysics Data System (ADS)

Postnikov, Eugene B.; Tsoy, Maria O.; Postnov, Dmitry E.

2018-04-01

Laser Speckle Contrast Analysis (LASCA) is one of the most powerful modern methods for revealing blood dynamics. The experimental design and theory for this method are well established, and the computational recipie is often regarded to be trivial. However, the achieved performance and spatial resolution may considerable differ for different implementations. We comprise a minireview of known approaches to the spatial laser speckle contrast data processing and their realization in MATLAB code providing an explicit correspondence to the mathematical representation, a discussion of available implementations. We also present the algorithm based on the 2D Haar wavelet transform, also supplied with the program code. This new method provides an opportunity to introduce horizontal, vertical and diagonal speckle contrasts; it may be used for processing highly anisotropic images of vascular trees. We provide the comparative analysis of the accuracy of vascular pattern detection and the processing times with a special attention to details of the used MATLAB procedures.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zdora, Marie-Christine; 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; Thibault, Pierre

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.

Inducible fluorescent speckle microscopy

PubMed Central

Aguiar, Paulo; Belsley, Michael; Maiato, Helder

2016-01-01

The understanding of cytoskeleton dynamics has benefited from the capacity to generate fluorescent fiducial marks on cytoskeleton components. Here we show that light-induced imprinting of three-dimensional (3D) fluorescent speckles significantly improves speckle signal and contrast relative to classic (random) fluorescent speckle microscopy. We predict theoretically that speckle imprinting using photobleaching is optimal when the laser energy and fluorophore responsivity are related by the golden ratio. This relation, which we confirm experimentally, translates into a 40% remaining signal after speckle imprinting and provides a rule of thumb in selecting the laser power required to optimally prepare the sample for imaging. This inducible speckle imaging (ISI) technique allows 3D speckle microscopy to be performed in readily available libraries of cell lines or primary tissues expressing fluorescent proteins and does not preclude conventional imaging before speckle imaging. As a proof of concept, we use ISI to measure metaphase spindle microtubule poleward flux in primary cells and explore a scaling relation connecting microtubule flux to metaphase duration. PMID:26783303

Inducible fluorescent speckle microscopy.

PubMed

Pereira, António J; Aguiar, Paulo; Belsley, Michael; Maiato, Helder

2016-01-18

The understanding of cytoskeleton dynamics has benefited from the capacity to generate fluorescent fiducial marks on cytoskeleton components. Here we show that light-induced imprinting of three-dimensional (3D) fluorescent speckles significantly improves speckle signal and contrast relative to classic (random) fluorescent speckle microscopy. We predict theoretically that speckle imprinting using photobleaching is optimal when the laser energy and fluorophore responsivity are related by the golden ratio. This relation, which we confirm experimentally, translates into a 40% remaining signal after speckle imprinting and provides a rule of thumb in selecting the laser power required to optimally prepare the sample for imaging. This inducible speckle imaging (ISI) technique allows 3D speckle microscopy to be performed in readily available libraries of cell lines or primary tissues expressing fluorescent proteins and does not preclude conventional imaging before speckle imaging. As a proof of concept, we use ISI to measure metaphase spindle microtubule poleward flux in primary cells and explore a scaling relation connecting microtubule flux to metaphase duration. © 2016 Pereira et al.

Applicability of quantitative optical imaging techniques for intraoperative perfusion diagnostics: a comparison of laser speckle contrast imaging, sidestream dark-field microscopy, and optical coherence tomography

NASA Astrophysics Data System (ADS)

Jansen, Sanne M.; de Bruin, Daniel M.; Faber, Dirk J.; Dobbe, Iwan J. G. G.; Heeg, Erik; Milstein, Dan M. J.; Strackee, Simon D.; van Leeuwen, Ton G.

2017-08-01

Patient morbidity and mortality due to hemodynamic complications are a major problem in surgery. Optical techniques can image blood flow in real-time and high-resolution, thereby enabling perfusion monitoring intraoperatively. We tested the feasibility and validity of laser speckle contrast imaging (LSCI), optical coherence tomography (OCT), and sidestream dark-field microscopy (SDF) for perfusion diagnostics in a phantom model using whole blood. Microvessels with diameters of 50, 100, and 400 μm were constructed in a scattering phantom. Perfusion was simulated by pumping heparinized human whole blood at five velocities (0 to 20 mm/s). Vessel diameter and blood flow velocity were assessed with LSCI, OCT, and SDF. Quantification of vessel diameter was feasible with OCT and SDF. LSCI could only visualize the 400-μm vessel, perfusion units scaled nonlinearly with blood velocity. OCT could assess blood flow velocity in terms of inverse OCT speckle decorrelation time. SDF was not feasible to measure blood flow; however, for diluted blood the measurements were linear with the input velocity up to 1 mm/s. LSCI, OCT, and SDF were feasible to visualize blood flow. Validated blood flow velocity measurements intraoperatively in the desired parameter (mL·g-1) remain challenging.

Speckle-learning-based object recognition through scattering media.

PubMed

Ando, Takamasa; Horisaki, Ryoichi; Tanida, Jun

2015-12-28

We experimentally demonstrated object recognition through scattering media based on direct machine learning of a number of speckle intensity images. In the experiments, speckle intensity images of amplitude or phase objects on a spatial light modulator between scattering plates were captured by a camera. We used the support vector machine for binary classification of the captured speckle intensity images of face and non-face data. The experimental results showed that speckles are sufficient for machine learning.

OBSERVATIONS OF BINARY STARS WITH THE DIFFERENTIAL SPECKLE SURVEY INSTRUMENT. IV. OBSERVATIONS OF KEPLER, CoRoT, AND HIPPARCOS STARS FROM THE GEMINI NORTH TELESCOPE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Horch, Elliott P.; Howell, Steve B.; Everett, Mark E.

2012-12-01

We present the results of 71 speckle observations of binary and unresolved stars, most of which were observed with the DSSI speckle camera at the Gemini North Telescope in 2012 July. The main purpose of the run was to obtain diffraction-limited images of high-priority targets for the Kepler and CoRoT missions, but in addition, we observed a number of close binary stars where the resolution limit of Gemini was used to better determine orbital parameters and/or confirm results obtained at or below the diffraction limit of smaller telescopes. Five new binaries and one triple system were discovered, and first orbitsmore » are calculated for other two systems. Several systems are discussed in detail.« less

The development of laser speckle or particle image displacement velocimetry. Part 1: The role of photographic parameters

NASA Technical Reports Server (NTRS)

Lourenco, L. M. M.; Krothapalli, A.

1987-01-01

One of the difficult problems in experimental fluid dynamics remains the determination of the vorticity field in fluid flows. Recently, a novel velocity measurement technique, commonly known as Laser Speckle or Particle Image Displacement Velocimetry became available. This technique permits the simultaneous visualization of the 2 dimensional streamline pattern in unsteady flows and the quantification of the velocity field. The main advantage of this new technique is that the whole 2 dimensional velocity field can be recorded with great accuracy and spatial resolution, from which the instantaneous vorticity field can be easily obtained. A apparatus used for taking particle displacement images is described. Local coherent illumination by the probe laser beam yielded Young's fringes of good quality at almost every location of the flow field. These fringes were analyzed and the velocity and vorticity fields were derived. Several conclusions drawn are discussed.

Human speckle perception threshold for still images from a laser projection system.

PubMed

Roelandt, Stijn; Meuret, Youri; Jacobs, An; Willaert, Koen; Janssens, Peter; Thienpont, Hugo; Verschaffelt, Guy

2014-10-06

We study the perception of speckle by human observers in a laser projector based on a 40 persons survey. The speckle contrast is first objectively measured making use of a well-defined speckle measurement method. We statistically analyse the results of the user quality scores, revealing that the speckle perception is not only influenced by the speckle contrast settings of the projector, but it is also strongly influenced by the type of image shown. Based on the survey, we derive a speckle contrast threshold for which speckle can be seen, and separately we investigate a speckle disturbance limit that is tolerated by the majority of test persons.

High resolution telescope including an array of elemental telescopes aligned along a common axis and supported on a space frame with a pivot at its geometric center

DOEpatents

Norbert, M.A.; Yale, O.

1992-04-28

A large effective-aperture, low-cost optical telescope with diffraction-limited resolution enables ground-based observation of near-earth space objects. The telescope has a non-redundant, thinned-aperture array in a center-mount, single-structure space frame. It employes speckle interferometric imaging to achieve diffraction-limited resolution. The signal-to-noise ratio problem is mitigated by moving the wavelength of operation to the near-IR, and the image is sensed by a Silicon CCD. The steerable, single-structure array presents a constant pupil. The center-mount, radar-like mount enables low-earth orbit space objects to be tracked as well as increases stiffness of the space frame. In the preferred embodiment, the array has elemental telescopes with subaperture of 2.1 m in a circle-of-nine configuration. The telescope array has an effective aperture of 12 m which provides a diffraction-limited resolution of 0.02 arc seconds. Pathlength matching of the telescope array is maintained by a electro-optical system employing laser metrology. Speckle imaging relaxes pathlength matching tolerance by one order of magnitude as compared to phased arrays. Many features of the telescope contribute to substantial reduction in costs. These include eliminating the conventional protective dome and reducing on-site construction activities. The cost of the telescope scales with the first power of the aperture rather than its third power as in conventional telescopes. 15 figs.

High resolution telescope including an array of elemental telescopes aligned along a common axis and supported on a space frame with a pivot at its geometric center

DOEpatents

Norbert, Massie A.; Yale, Oster

1992-01-01

A large effective-aperture, low-cost optical telescope with diffraction-limited resolution enables ground-based observation of near-earth space objects. The telescope has a non-redundant, thinned-aperture array in a center-mount, single-structure space frame. It employes speckle interferometric imaging to achieve diffraction-limited resolution. The signal-to-noise ratio problem is mitigated by moving the wavelength of operation to the near-IR, and the image is sensed by a Silicon CCD. The steerable, single-structure array presents a constant pupil. The center-mount, radar-like mount enables low-earth orbit space objects to be tracked as well as increases stiffness of the space frame. In the preferred embodiment, the array has elemental telescopes with subaperture of 2.1 m in a circle-of-nine configuration. The telescope array has an effective aperture of 12 m which provides a diffraction-limited resolution of 0.02 arc seconds. Pathlength matching of the telescope array is maintained by a electro-optical system employing laser metrology. Speckle imaging relaxes pathlength matching tolerance by one order of magnitude as compared to phased arrays. Many features of the telescope contribute to substantial reduction in costs. These include eliminating the conventional protective dome and reducing on-site construction activities. The cost of the telescope scales with the first power of the aperture rather than its third power as in conventional telescopes.

Deformation-induced speckle-pattern evolution and feasibility of correlational speckle tracking in optical coherence elastography.

PubMed

Zaitsev, Vladimir Y; Matveyev, Alexandr L; Matveev, Lev A; Gelikonov, Grigory V; Gelikonov, Valentin M; Vitkin, Alex

2015-07-01

Feasibility of speckle tracking in optical coherence tomography (OCT) based on digital image correlation (DIC) is discussed in the context of elastography problems. Specifics of applying DIC methods to OCT, compared to processing of photographic images in mechanical engineering applications, are emphasized and main complications are pointed out. Analytical arguments are augmented by accurate numerical simulations of OCT speckle patterns. In contrast to DIC processing for displacement and strain estimation in photographic images, the accuracy of correlational speckle tracking in deformed OCT images is strongly affected by the coherent nature of speckles, for which strain-induced complications of speckle “blinking” and “boiling” are typical. The tracking accuracy is further compromised by the usually more pronounced pixelated structure of OCT scans compared with digital photographic images in classical DIC applications. Processing of complex-valued OCT data (comprising both amplitude and phase) compared to intensity-only scans mitigates these deleterious effects to some degree. Criteria of the attainable speckle tracking accuracy and its dependence on the key OCT system parameters are established.

Numerical study on statistical properties of speckle pattern in laser projection display based on human eye model

NASA Astrophysics Data System (ADS)

Cui, Zhe; Wang, Anting; Ma, Qianli; Ming, Hai

2013-12-01

In this paper, the laser speckle pattern on human retina for a laser projection display is simulated. By introducing a specific eye model `Indiana Eye', the statistical properties of the laser speckle are numerical investigated. The results show that the aberrations of human eye (mostly spherical and chromatic) will decrease the speckle contrast felt by people. When the wavelength of the laser source is 550 nm (green), people will feel the strongest speck pattern and the weakest when the wavelength is 450 nm (blue). Myopia and hyperopia will decrease the speckle contrast by introducing large spherical aberrations. Although aberration is good for speckle reduction, but it will degrade the imaging capability of the eye. The results show that laser source (650 nm) will have the best image quality on the retina. At last, we compare the human eye with an aberration-free imaging system. Both the speckle contrast and the image quality appear different behavior in these two imaging systems. The results are useful when a standardized measurement procedure for speckle contrast needs to be built.

Laser Speckle Imaging to Monitor Microvascular Blood Flow: A Review.

PubMed

Vaz, Pedro G; Humeau-Heurtier, Anne; Figueiras, Edite; Correia, Carlos; Cardoso, Joao

2016-01-01

Laser speckle is a complex interference phenomenon that can easily be understood, in concept, but is difficult to predict mathematically, because it is a stochastic process. The use of laser speckle to produce images, which can carry many types of information, is called laser speckle imaging (LSI). The biomedical applications of LSI started in 1981 and, since then, many scientists have improved the laser speckle theory and developed different imaging techniques. During this process, some inconsistencies have been propagated up to now. These inconsistencies should be clarified in order to avoid errors in future works. This review presents a review of the laser speckle theory used in biomedical applications. Moreover, we also make a review of the practical concepts that are useful in the construction of laser speckle imagers. This study is not only an exposition of the concepts that can be found in the literature but also a critical analysis of the investigations presented so far. Concepts like scatterers velocity distribution, effect of static scatterers, optimal speckle size, light penetration angle, and contrast computation algorithms are discussed in detail.

Speckle averaging system for laser raster-scan image projection

DOEpatents

Tiszauer, D.H.; Hackel, L.A.

1998-03-17

The viewers` perception of laser speckle in a laser-scanned image projection system is modified or eliminated by the addition of an optical deflection system that effectively presents a new speckle realization at each point on the viewing screen to each viewer for every scan across the field. The speckle averaging is accomplished without introduction of spurious imaging artifacts. 5 figs.

Speckle averaging system for laser raster-scan image projection

DOEpatents

Tiszauer, Detlev H.; Hackel, Lloyd A.

1998-03-17

The viewers' perception of laser speckle in a laser-scanned image projection system is modified or eliminated by the addition of an optical deflection system that effectively presents a new speckle realization at each point on the viewing screen to each viewer for every scan across the field. The speckle averaging is accomplished without introduction of spurious imaging artifacts.

Prediction of venous wound healing with laser speckle imaging.

PubMed

van Vuuren, Timme Maj; Van Zandvoort, Carina; Doganci, Suat; Zwiers, Ineke; tenCate-Hoek, Arina J; Kurstjens, Ralph Lm; Wittens, Cees Ha

2017-12-01

Introduction Laser speckle imaging is used for noninvasive assessment of blood flow of cutaneous wounds. The aim of this study was to assess if laser speckle imaging can be used as a predictor of venous ulcer healing. Methods After generating the flux speckle images, three regions of interest (ROI) were identified to measure the flow. Sensitivity, specificity, negative predictive value, and positive predictive value for ulcer healing were calculated. Results In total, 17 limbs were included. A sensitivity of 92.3%, specificity of 75.0%, PPV of 80.0%, and NPV 75.0% were found in predicting wound healing based on laser speckle images. Mean flux values were lowest in the center (ROI I) and showed an increase at the wound edge (ROI II, p = 0.03). Conclusion Laser speckle imaging shows acceptable sensitivity and specificity rates in predicting venous ulcer healing. The wound edge proved to be the best probability for the prediction of wound healing.

Application of laser scanning speckle-microscopy for high-resolution express diagnostics of chlamydial infection

NASA Astrophysics Data System (ADS)

Ulyanov, Sergey; Larionova, Olga; Ulianova, Onega; Zaitsev, Sergey; Saltykov, Yury; Polyanina, Tatiana; Lyapina, Anna; Filonova, Nadezhda; Subbotina, Irina; Kalduzova, Irina; Utz, Sergey; Moiseeva, Yulia; Feodorova, Valentina

2018-04-01

Method of speckle-microscopy has been adapted to the problem of detection of Chlamydia trachomatis microbial cells in clinical samples. Prototype of laser scanning speckle-microscope has been designed. Spatial resolution and output characteristics of this microscope have been analyzed for the case of scanning of C. trachomatis bacteria inclusions - Elementary Bodies (EBs) inside the human cells, fixed on the glass. It has been demonstrated, that presence of C. trachomatis microbial cells in the sample can be easily detected using speckle microscopy.

Neighborhood binary speckle pattern for deformation measurements insensitive to local illumination variation by digital image correlation.

PubMed

Zhao, Jian; Yang, Ping; Zhao, Yue

2017-06-01

Speckle pattern-based characteristics of digital image correlation (DIC) restrict its application in engineering fields and nonlaboratory environments, since serious decorrelation effect occurs due to localized sudden illumination variation. A simple and efficient speckle pattern adjusting and optimizing approach presented in this paper is aimed at providing a novel speckle pattern robust enough to resist local illumination variation. The new speckle pattern, called neighborhood binary speckle pattern, derived from original speckle pattern, is obtained by means of thresholding the pixels of a neighborhood at its central pixel value and considering the result as a binary number. The efficiency of the proposed speckle pattern is evaluated in six experimental scenarios. Experiment results indicate that the DIC measurements based on neighborhood binary speckle pattern are able to provide reliable and accurate results, even though local brightness and contrast of the deformed images have been seriously changed. It is expected that the new speckle pattern will have more potential value in engineering applications.

Effects of red blood cell aggregates dissociation on the estimation of ultrasound speckle image velocimetry.

PubMed

Yeom, Eunseop; Nam, Kweon-Ho; Paeng, Dong-Guk; Lee, Sang-Joon

2014-08-01

Ultrasound speckle image of blood is mainly attributed by red blood cells (RBCs) which tend to form RBC aggregates. RBC aggregates are separated into individual cells when the shear force is over a certain value. The dissociation of RBC aggregates has an influence on the performance of ultrasound speckle image velocimetry (SIV) technique in which a cross-correlation algorithm is applied to the speckle images to get the velocity field information. The present study aims to investigate the effect of the dissociation of RBC aggregates on the estimation quality of SIV technique. Ultrasound B-mode images were captured from the porcine blood circulating in a mock-up flow loop with varying flow rate. To verify the measurement performance of SIV technique, the centerline velocity measured by the SIV technique was compared with that measured by Doppler spectrograms. The dissociation of RBC aggregates was estimated by using decorrelation of speckle patterns in which the subsequent window was shifted as much as the speckle displacement to compensate decorrelation caused by in-plane loss of speckle patterns. The decorrelation of speckles is considerably increased according to shear rate. Its variations are different along the radial direction. Because the dissociation of RBC aggregates changes ultrasound speckles, the estimation quality of SIV technique is significantly correlated with the decorrelation of speckles. This degradation of measurement quality may be improved by increasing the data acquisition rate. This study would be useful for simultaneous measurement of hemodynamic and hemorheological information of blood flows using only speckle images. Copyright © 2014 Elsevier B.V. All rights reserved.

Nakagami-based total variation method for speckle reduction in thyroid ultrasound images.

PubMed

Koundal, Deepika; Gupta, Savita; Singh, Sukhwinder

2016-02-01

A good statistical model is necessary for the reduction in speckle noise. The Nakagami model is more general than the Rayleigh distribution for statistical modeling of speckle in ultrasound images. In this article, the Nakagami-based noise removal method is presented to enhance thyroid ultrasound images and to improve clinical diagnosis. The statistics of log-compressed image are derived from the Nakagami distribution following a maximum a posteriori estimation framework. The minimization problem is solved by optimizing an augmented Lagrange and Chambolle's projection method. The proposed method is evaluated on both artificial speckle-simulated and real ultrasound images. The experimental findings reveal the superiority of the proposed method both quantitatively and qualitatively in comparison with other speckle reduction methods reported in the literature. The proposed method yields an average signal-to-noise ratio gain of more than 2.16 dB over the non-convex regularizer-based speckle noise removal method, 3.83 dB over the Aubert-Aujol model, 1.71 dB over the Shi-Osher model and 3.21 dB over the Rudin-Lions-Osher model on speckle-simulated synthetic images. Furthermore, visual evaluation of the despeckled images shows that the proposed method suppresses speckle noise well while preserving the textures and fine details. © IMechE 2015.

Experimental study on deformation field evolution in rock sample with en echelon faults using digital speckle correlation method

NASA Astrophysics Data System (ADS)

Ma, S.; Ma, J.; Liu, L.; Liu, P.

2007-12-01

Digital speckle correlation method (DSCM) is one kind of photomechanical deformation measurement method. DSCM could obtain continuous deformation field contactlessly by just capturing speckle images from specimen surface. Therefore, it is suitable to observe high spatial resolution deformation field in tectonophysical experiment. However, in the general DSCM experiment, the inspected surface of specimen needs to be painted to bear speckle grains in order to obtain the high quality speckle image. This also affects the realization of other measurement techniques. In this study, an improved DSCM system is developed and utilized to measure deformation field of rock specimen without surface painting. The granodiorite with high contrast nature grains is chosen to manufacture the specimen, and a specially designed DSCM algorithm is developed to analyze this kind of nature speckle images. Verification and calibration experiments show that the system could inspect a continuous (about 15Hz) high resolution displacement field (with resolution of 5μm) and strain field (with resolution of 50μɛ), dispensing with any preparation on rock specimen. Therefore, it could be conveniently utilized to study the failure of rock structure. Samples with compressive en echelon faults and extensional en echelon faults are studied on a two-direction servo-control test machine. The failure process of the samples is discussed based on the DSCM results. Experiment results show that: 1) The contours of displacement field could clearly indicate the activities of faults and new cracks. The displacement gradient adjacent to active faults and cracks is much greater than other areas. 2) Before failure of the samples, the mean strain of the jog area is largest for the compressive en echelon fault, while that is smallest for the extensional en echelon fault. This consists with the understanding that the jog area of compressive fault subjects to compression and that of extensional fault subjects to tension. 3) For the extensional en echelon sample, the dislocation across fault on load-driving end is greater than that cross fault on fixed end. Within the same fault, the dislocation across branch far from the jog area is greater than that across branch near the jog area. This indicates the restriction effect of jog area on the activity of fault. Moreover, the average dislocation across faults is much greater than that across the cracks. 4) For the compressive en echelon fault, the wing cracks initialized firstly and propagate outwards the jog area. Subsequently, a wedge strain concentration area is initialized and developed in the jog area because of the interaction of the two faults. Finally, the jog area failed when one crack propagates rapidly and connects the two ends of faults. The DSCM system used in this study could clearly show the deformation and failure process of the en echelon fault sample. The experiment using DSCM could be performed dispensing with any preparation on specimen and not affecting other inspection. Therefore, DSCM is expected to be a suitable tool for experimental study of fault samples in laboratory.

Ultrasound image filtering using the mutiplicative model

NASA Astrophysics Data System (ADS)

Navarrete, Hugo; Frery, Alejandro C.; Sanchez, Fermin; Anto, Joan

2002-04-01

Ultrasound images, as a special case of coherent images, are normally corrupted with multiplicative noise i.e. speckle noise. Speckle noise reduction is a difficult task due to its multiplicative nature, but good statistical models of speckle formation are useful to design adaptive speckle reduction filters. In this article a new statistical model, emerging from the Multiplicative Model framework, is presented and compared to previous models (Rayleigh, Rice and K laws). It is shown that the proposed model gives the best performance when modeling the statistics of ultrasound images. Finally, the parameters of the model can be used to quantify the extent of speckle formation; this quantification is applied to adaptive speckle reduction filter design. The effectiveness of the filter is demonstrated on typical in-vivo log-compressed B-scan images obtained by a clinical ultrasound system.

MuLoG, or How to Apply Gaussian Denoisers to Multi-Channel SAR Speckle Reduction?

PubMed

Deledalle, Charles-Alban; Denis, Loic; Tabti, Sonia; Tupin, Florence

2017-09-01

Speckle reduction is a longstanding topic in synthetic aperture radar (SAR) imaging. Since most current and planned SAR imaging satellites operate in polarimetric, interferometric, or tomographic modes, SAR images are multi-channel and speckle reduction techniques must jointly process all channels to recover polarimetric and interferometric information. The distinctive nature of SAR signal (complex-valued, corrupted by multiplicative fluctuations) calls for the development of specialized methods for speckle reduction. Image denoising is a very active topic in image processing with a wide variety of approaches and many denoising algorithms available, almost always designed for additive Gaussian noise suppression. This paper proposes a general scheme, called MuLoG (MUlti-channel LOgarithm with Gaussian denoising), to include such Gaussian denoisers within a multi-channel SAR speckle reduction technique. A new family of speckle reduction algorithms can thus be obtained, benefiting from the ongoing progress in Gaussian denoising, and offering several speckle reduction results often displaying method-specific artifacts that can be dismissed by comparison between results.

Differential high-speed digital micromirror device based fluorescence speckle confocal microscopy.

PubMed

Jiang, Shihong; Walker, John

2010-01-20

We report a differential fluorescence speckle confocal microscope that acquires an image in a fraction of a second by exploiting the very high frame rate of modern digital micromirror devices (DMDs). The DMD projects a sequence of predefined binary speckle patterns to the sample and modulates the intensity of the returning fluorescent light simultaneously. The fluorescent light reflecting from the DMD's "on" and "off" pixels is modulated by correlated speckle and anticorrelated speckle, respectively, to form two images on two CCD cameras in parallel. The sum of the two images recovers a widefield image, but their difference gives a near-confocal image in real time. Experimental results for both low and high numerical apertures are shown.

Overcoming turbulence-induced space-variant blur by using phase-diverse speckle.

PubMed

Thelen, Brian J; Paxman, Richard G; Carrara, David A; Seldin, John H

2009-01-01

Space-variant blur occurs when imaging through volume turbulence over sufficiently large fields of view. Space-variant effects are particularly severe in horizontal-path imaging, slant-path (air-to-ground or ground-to-air) geometries, and ground-based imaging of low-elevation satellites or astronomical objects. In these geometries, the isoplanatic angle can be comparable to or even smaller than the diffraction-limited resolution angle. We report on a postdetection correction method that seeks to correct for the effects of space-variant aberrations, with the goal of reconstructing near-diffraction-limited imagery. Our approach has been to generalize the method of phase-diverse speckle (PDS) by using a physically motivated distributed-phase-screen model. Simulation results are presented that demonstrate the reconstruction of near-diffraction-limited imagery under both matched and mismatched model assumptions. In addition, we present evidence that PDS could be used as a beaconless wavefront sensor in a multiconjugate adaptive optics system when imaging extended scenes.

Learnable despeckling framework for optical coherence tomography images

NASA Astrophysics Data System (ADS)

Adabi, Saba; Rashedi, Elaheh; Clayton, Anne; Mohebbi-Kalkhoran, Hamed; Chen, Xue-wen; Conforto, Silvia; Nasiriavanaki, Mohammadreza

2018-01-01

Optical coherence tomography (OCT) is a prevalent, interferometric, high-resolution imaging method with broad biomedical applications. Nonetheless, OCT images suffer from an artifact called speckle, which degrades the image quality. Digital filters offer an opportunity for image improvement in clinical OCT devices, where hardware modification to enhance images is expensive. To reduce speckle, a wide variety of digital filters have been proposed; selecting the most appropriate filter for an OCT image/image set is a challenging decision, especially in dermatology applications of OCT where a different variety of tissues are imaged. To tackle this challenge, we propose an expandable learnable despeckling framework, we call LDF. LDF decides which speckle reduction algorithm is most effective on a given image by learning a figure of merit (FOM) as a single quantitative image assessment measure. LDF is learnable, which means when implemented on an OCT machine, each given image/image set is retrained and its performance is improved. Also, LDF is expandable, meaning that any despeckling algorithm can easily be added to it. The architecture of LDF includes two main parts: (i) an autoencoder neural network and (ii) filter classifier. The autoencoder learns the FOM based on several quality assessment measures obtained from the OCT image including signal-to-noise ratio, contrast-to-noise ratio, equivalent number of looks, edge preservation index, and mean structural similarity index. Subsequently, the filter classifier identifies the most efficient filter from the following categories: (a) sliding window filters including median, mean, and symmetric nearest neighborhood, (b) adaptive statistical-based filters including Wiener, homomorphic Lee, and Kuwahara, and (c) edge preserved patch or pixel correlation-based filters including nonlocal mean, total variation, and block matching three-dimensional filtering.

A hybrid algorithm for speckle noise reduction of ultrasound images.

PubMed

Singh, Karamjeet; Ranade, Sukhjeet Kaur; Singh, Chandan

2017-09-01

Medical images are contaminated by multiplicative speckle noise which significantly reduce the contrast of ultrasound images and creates a negative effect on various image interpretation tasks. In this paper, we proposed a hybrid denoising approach which collaborate the both local and nonlocal information in an efficient manner. The proposed hybrid algorithm consist of three stages in which at first stage the use of local statistics in the form of guided filter is used to reduce the effect of speckle noise initially. Then, an improved speckle reducing bilateral filter (SRBF) is developed to further reduce the speckle noise from the medical images. Finally, to reconstruct the diffused edges we have used the efficient post-processing technique which jointly considered the advantages of both bilateral and nonlocal mean (NLM) filter for the attenuation of speckle noise efficiently. The performance of proposed hybrid algorithm is evaluated on synthetic, simulated and real ultrasound images. The experiments conducted on various test images demonstrate that our proposed hybrid approach outperforms the various traditional speckle reduction approaches included recently proposed NLM and optimized Bayesian-based NLM. The results of various quantitative, qualitative measures and by visual inspection of denoise synthetic and real ultrasound images demonstrate that the proposed hybrid algorithm have strong denoising capability and able to preserve the fine image details such as edge of a lesion better than previously developed methods for speckle noise reduction. The denoising and edge preserving capability of hybrid algorithm is far better than existing traditional and recently proposed speckle reduction (SR) filters. The success of proposed algorithm would help in building the lay foundation for inventing the hybrid algorithms for denoising of ultrasound images. Copyright © 2017 Elsevier B.V. All rights reserved.

Recent advances in the field of super resolved imaging and sensing

NASA Astrophysics Data System (ADS)

Zalevsky, Zeev; Borkowski, Amikam; Marom, Emanuel; Javidi, Bahram; Beiderman, Yevgeny; Micó, Vicente; García, Javier

2011-05-01

In this paper we start by presenting one recent development in the field of geometric super resolution. The new approach overcomes the reduction of resolution caused by the non ideal sampling of the image done by the spatial averaging of each pixel of the sampling array. Right after, we demonstrate a remote super sensing technique allowing monitoring, from a distance, the heart beats, blood pulse pressure and the glucose level in the blood stream of a patient by tracking the trajectory of secondary speckle patterns reflected from the skin of the wrist or from the sclera.

Speckle imaging of active galactic nuclei: NGC 1068 and NGC 4151

NASA Astrophysics Data System (ADS)

Ebstein, Steven Michael

High resolution images of NGC 1068 and NGC 4151 in the 5007 A line and the nearby continuum produced from data taken with the PAPA photon counting imaging detector using the technique of speckle imaging are presented. The images show an unresolved core of 5007 A emission in the middle of an extended emission region. The extended emission tends to lie alongside the subarcsecond radio structure. In NGC 4151, the extended emission comes from a nearly linear structure extending on both sides of the unresolved core. In NGC 1068, the extended emission is concentrated in lobes lying to the unresolved core but the emission is concentrated in lobes lying to either side of the major axis. The continuum of NGC 4151 is spatially unresolved. The continuum of NGC 1068 is extended approx. 1 in to the SW of the center of the 5007 A emission. Certain aspects of the PAPA detector are discussed, including the variable threshold discriminators that track the image intensifier pulse height and the camera artifacts. The data processing is described in detail.

Suppression of Speckles at High Adaptive Correction Using Speckle Symmetry

NASA Technical Reports Server (NTRS)

Bloemhof, Eric E.

2006-01-01

Focal-plane speckles set important sensitivity limits on ground- or space-based imagers and coronagraphs that may be used to search for faint companions, perhaps ultimately including exoplanets, around stars. As speckles vary with atmospheric fluctuations or with drifting beamtrain aberrations, they contribute speckle noise proportional to their full amplitude. Schemes to suppress speckles are thus of great interest. At high adaptive correction, speckles organize into species, represented by algebraic terms in the expansion of the phase exponential, that have distinct spatial symmetry, even or odd, under spatial inversion. Filtering speckle patterns by symmetry may eliminate a disproportionate fraction of the speckle noise while blocking (only) half of the image signal from the off-axis companion being sought. The fraction of speckle power and hence of speckle noise in each term will vary with degree of correction, and so also will the net symmetry in the speckle pattern.

Optical Logarithmic Transformation of Speckle Images with Bacteriorhodopsin Films

NASA Technical Reports Server (NTRS)

Downie, John D.

1995-01-01

The application of logarithmic transformations to speckle images is sometimes desirable in converting the speckle noise distribution into an additive, constant-variance noise distribution. The optical transmission properties of some bacteriorhodopsin films are well suited to implement such a transformation optically in a parallel fashion. I present experimental results of the optical conversion of a speckle image into a transformed image with signal-independent noise statistics, using the real-time photochromic properties of bacteriorhodopsin. The original and transformed noise statistics are confirmed by histogram analysis.

A new product for photon-limited imaging

NASA Astrophysics Data System (ADS)

Gonsiorowski, Thomas

1986-01-01

A new commercial low-light imaging detector, the Photon Digitizing Camera (PDC), is based on the PAPA detector developed at Harvard University. The PDC generates (x, y, t)-coordinate data of each detected photoevent. Because the positional address computation is performed optically, very high counting rates are achieved even at full spatial resolution. Careful optomechanical and electronic design results in a compact, rugged detector with superb performance. The PDC will be used for speckle imaging of astronomical sources and other astronomical and low-light applications.

Ultrasound-modulated optical tomography with intense acoustic bursts.

PubMed

Zemp, Roger J; Kim, Chulhong; Wang, Lihong V

2007-04-01

Ultrasound-modulated optical tomography (UOT) detects ultrasonically modulated light to spatially localize multiply scattered photons in turbid media with the ultimate goal of imaging the optical properties in living subjects. A principal challenge of the technique is weak modulated signal strength. We discuss ways to push the limits of signal enhancement with intense acoustic bursts while conforming to optical and ultrasonic safety standards. A CCD-based speckle-contrast detection scheme is used to detect acoustically modulated light by measuring changes in speckle statistics between ultrasound-on and ultrasound-off states. The CCD image capture is synchronized with the ultrasound burst pulse sequence. Transient acoustic radiation force, a consequence of bursts, is seen to produce slight signal enhancement over pure ultrasonic-modulation mechanisms for bursts and CCD exposure times of the order of milliseconds. However, acoustic radiation-force-induced shear waves are launched away from the acoustic sample volume, which degrade UOT spatial resolution. By time gating the CCD camera to capture modulated light before radiation force has an opportunity to accumulate significant tissue displacement, we reduce the effects of shear-wave image degradation, while enabling very high signal-to-noise ratios. Additionally, we maintain high-resolution images representative of optical and not mechanical contrast. Signal-to-noise levels are sufficiently high so as to enable acquisition of 2D images of phantoms with one acoustic burst per pixel.

Flux or speed? Examining speckle contrast imaging of vascular flows

PubMed Central

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

2015-01-01

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

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

PubMed

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.

Compensation for the signal processing characteristics of ultrasound B-mode scanners in adaptive speckle reduction.

PubMed

Crawford, D C; Bell, D S; Bamber, J C

1993-01-01

A systematic method to compensate for nonlinear amplification of individual ultrasound B-scanners has been investigated in order to optimise performance of an adaptive speckle reduction (ASR) filter for a wide range of clinical ultrasonic imaging equipment. Three potential methods have been investigated: (1) a method involving an appropriate selection of the speckle recognition feature was successful when the scanner signal processing executes simple logarithmic compressions; (2) an inverse transform (decompression) of the B-mode image was effective in correcting for the measured characteristics of image data compression when the algorithm was implemented in full floating point arithmetic; (3) characterising the behaviour of the statistical speckle recognition feature under conditions of speckle noise was found to be the method of choice for implementation of the adaptive speckle reduction algorithm in limited precision integer arithmetic. In this example, the statistical features of variance and mean were investigated. The third method may be implemented on commercially available fast image processing hardware and is also better suited for transfer into dedicated hardware to facilitate real-time adaptive speckle reduction. A systematic method is described for obtaining ASR calibration data from B-mode images of a speckle producing phantom.

Study on diagnosis of micro-biomechanical structure using optical coherence tomography

NASA Astrophysics Data System (ADS)

Saeki, Souichi; Hashimoto, Youhei; Saito, Takashi; Hiro, Takafumi; Matsuzaki, Masunori

2007-02-01

Acute coronary syndromes, e.g. myocardial infarctions, are caused by the rupture of unstable plaques on coronary arteries. The stability of plaque, which depends on biomechanical properties of fibrous cap, should be diagnosed crucially. Recently, Optical Coherence Tomography (OCT) has been developed as a cross-sectional imaging method of microstructural biological tissue with high resolution 1~10 μm. Multi-functional OCT system has been promising, e.g. an estimator of biomechanical characteristics. It has been, however, difficult to estimate biomechanical characteristics, because OCT images have just speckle patterns by back-scattering light from tissue. In this study, presented is Optical Coherence Straingraphy (OCS) on the basis of OCT system, which can diagnose tissue strain distribution. This is basically composed of Recursive Cross-correlation technique (RC), which can provide a displacement vector distribution with high resolution. Furthermore, Adjacent Cross-correlation Multiplication (ACM) is introduced as a speckle noise reduction method. Multiplying adjacent correlation maps can eliminate anomalies from speckle noise, and then can enhance S/N in the determination of maximum correlation coefficient. Error propagation also can be further prevented by introducing to the recursive algorithm (RC). In addition, the spatial vector interpolation by local least square method is introduced to remove erroneous vectors and smooth the vector distribution. This was numerically applied to compressed elastic heterogeneous tissue samples to carry out the accuracy verifications. Consequently, it was quantitatively confirmed that its accuracy of displacement vectors and strain matrix components could be enhanced, comparing with the conventional method. Therefore, the proposed method was validated by the identification of different elastic objects with having nearly high resolution for that defined by optical system.

Comparison of Filters Dedicated to Speckle Suppression in SAR Images

NASA Astrophysics Data System (ADS)

Kupidura, P.

2016-06-01

This paper presents the results of research on the effectiveness of different filtering methods dedicated to speckle suppression in SAR images. The tests were performed on RadarSat-2 images and on an artificial image treated with simulated speckle noise. The research analysed the performance of particular filters related to the effectiveness of speckle suppression and to the ability to preserve image details and edges. Speckle is a phenomenon inherent to radar images - a deterministic noise connected with land cover type, but also causing significant changes in digital numbers of pixels. As a result, it may affect interpretation, classification and other processes concerning radar images. Speckle, resembling "salt and pepper" noise, has the form of a set of relatively small groups of pixels of values markedly different from values of other pixels representing the same type of land cover. Suppression of this noise may also cause suppression of small image details, therefore the ability to preserve the important parts of an image, was analysed as well. In the present study, selected filters were tested, and methods dedicated particularly to speckle noise suppression: Frost, Gamma-MAP, Lee, Lee-Sigma, Local Region, general filtering methods which might be effective in this respect: Mean, Median, in addition to morphological filters (alternate sequential filters with multiple structuring element and by reconstruction). The analysis presented in this paper compared the effectiveness of different filtering methods. It proved that some of the dedicated radar filters are efficient tools for speckle suppression, but also demonstrated a significant efficiency of the morphological approach, especially its ability to preserve image details.

Visual based laser speckle pattern recognition method for structural health monitoring

NASA Astrophysics Data System (ADS)

Park, Kyeongtaek; Torbol, Marco

2017-04-01

This study performed the system identification of a target structure by analyzing the laser speckle pattern taken by a camera. The laser speckle pattern is generated by the diffuse reflection of the laser beam on a rough surface of the target structure. The camera, equipped with a red filter, records the scattered speckle particles of the laser light in real time and the raw speckle image of the pixel data is fed to the graphic processing unit (GPU) in the system. The algorithm for laser speckle contrast analysis (LASCA) computes: the laser speckle contrast images and the laser speckle flow images. The k-mean clustering algorithm is used to classify the pixels in each frame and the clusters' centroids, which function as virtual sensors, track the displacement between different frames in time domain. The fast Fourier transform (FFT) and the frequency domain decomposition (FDD) compute the modal properties of the structure: natural frequencies and damping ratios. This study takes advantage of the large scale computational capability of GPU. The algorithm is written in Compute Unifies Device Architecture (CUDA C) that allows the processing of speckle images in real time.

A novel speckle pattern—Adaptive digital image correlation approach with robust strain calculation

NASA Astrophysics Data System (ADS)

Cofaru, Corneliu; Philips, Wilfried; Van Paepegem, Wim

2012-02-01

Digital image correlation (DIC) has seen widespread acceptance and usage as a non-contact method for the determination of full-field displacements and strains in experimental mechanics. The advances of imaging hardware in the last decades led to high resolution and speed cameras being more affordable than in the past making large amounts of data image available for typical DIC experimental scenarios. The work presented in this paper is aimed at maximizing both the accuracy and speed of DIC methods when employed with such images. A low-level framework for speckle image partitioning which replaces regularly shaped blocks with image-adaptive cells in the displacement calculation is introduced. The Newton-Raphson DIC method is modified to use the image pixels of the cells and to perform adaptive regularization to increase the spatial consistency of the displacements. Furthermore, a novel robust framework for strain calculation based also on the Newton-Raphson algorithm is introduced. The proposed methods are evaluated in five experimental scenarios, out of which four use numerically deformed images and one uses real experimental data. Results indicate that, as the desired strain density increases, significant computational gains can be obtained while maintaining or improving accuracy and rigid-body rotation sensitivity.

Ultrasound-Mediated Biophotonic Imaging: A Review of Acousto-Optical Tomography and Photo-Acoustic Tomography

PubMed Central

Wang, Lihong V.

2004-01-01

This article reviews two types of ultrasound-mediated biophotonic imaging–acousto-optical tomography (AOT, also called ultrasound-modulated optical tomography) and photo-acoustic tomography (PAT, also called opto-acoustic or thermo-acoustic tomography)–both of which are based on non-ionizing optical and ultrasonic waves. The goal of these technologies is to combine the contrast advantage of the optical properties and the resolution advantage of ultrasound. In these two technologies, the imaging contrast is based primarily on the optical properties of biological tissues, and the imaging resolution is based primarily on the ultrasonic waves that either are provided externally or produced internally, within the biological tissues. In fact, ultrasonic mediation overcomes both the resolution disadvantage of pure optical imaging in thick tissues and the contrast and speckle disadvantages of pure ultrasonic imaging. In our discussion of AOT, the relationship between modulation depth and acoustic amplitude is clarified. Potential clinical applications of ultrasound-mediated biophotonic imaging include early cancer detection, functional imaging, and molecular imaging. PMID:15096709

Laser speckle imaging allows real-time intraoperative blood flow assessment during neurosurgical procedures.

PubMed

Hecht, Nils; Woitzik, Johannes; König, Susanne; Horn, Peter; Vajkoczy, Peter

2013-07-01

Currently, there is no adequate technique for intraoperative monitoring of cerebral blood flow (CBF). To evaluate laser speckle imaging (LSI) for assessment of relative CBF, LSI was performed in 30 patients who underwent direct surgical revascularization for treatment of arteriosclerotic cerebrovascular disease (ACVD), Moyamoya disease (MMD), or giant aneurysms, and in 8 control patients who underwent intracranial surgery for reasons other than hemodynamic compromise. The applicability and sensitivity of LSI was investigated through baseline perfusion and CO2 reactivity testing. The dynamics of LSI were assessed during bypass test occlusion and flow initiation procedures. Laser speckle imaging permitted robust (pseudo-) quantitative assessment of relative microcirculatory flow and standard bypass grafting resulted in significantly higher postoperative baseline perfusion values in ACVD and MMD. The applicability and sensitivity of LSI was shown by a significantly reduced CO2 reactivity in ACVD (9.6±9%) and MMD (8.5±8%) compared with control (31.2±5%; P<0.0001). In high- and intermediate-flow bypass patients, LSI was characterized by a dynamic real-time response to acute perfusion changes and ultimately confirmed a sufficient flow substitution through the bypass graft. Thus, LSI can be used for sensitive and continuous, non-invasive real-time visualization and measurement of relative cortical CBF in excellent spatial-temporal resolution.

Enhanced tagging of light utilizing acoustic radiation force with speckle pattern analysis

NASA Astrophysics Data System (ADS)

Vakili, Ali; Hollmann, Joseph L.; Holt, R. Glynn; DiMarzio, Charles A.

2017-10-01

In optical imaging, the depth and resolution are limited due to scattering. Unlike light, scattering of ultrasound (US) waves in tissue is negligible. Hybrid imaging methods such as US-modulated optical tomography (UOT) use the advantages of both modalities. UOT tags light by inducing phase change caused by modulating the local index of refraction of the medium. The challenge in UOT is detecting the small signal. The displacement induced by the acoustic radiation force (ARF) is another US effect that can be utilized to tag the light. It induces greater phase change, resulting in a stronger signal. Moreover, the absorbed acoustic energy generates heat, resulting in change in the index of refraction and a strong phase change. The speckle pattern is governed by the phase of the interfering scattered waves; hence, speckle pattern analysis can obtain information about displacement and temperature changes. We have presented a model to simulate the insonation processes. Simulation results based on fixed-particle Monte Carlo and experimental results show that the signal acquired by utilizing ARF is stronger compared to UOT. The introduced mean irradiance change (MIC) signal reveals both thermal and mechanical effects of the focused US beam in different timescales. Simulation results suggest that variation in the MIC signal can be used to generate a displacement image of the medium.

Speckle tracking and speckle content based composite strain imaging for solid and fluid filled lesions.

PubMed

Rabbi, Md Shifat-E; Hasan, Md Kamrul

2017-02-01

Strain imaging though for solid lesions provides an effective way for determining their pathologic condition by displaying the tissue stiffness contrast, for fluid filled lesions such an imaging is yet an open problem. In this paper, we propose a novel speckle content based strain imaging technique for visualization and classification of fluid filled lesions in elastography after automatic identification of the presence of fluid filled lesions. Speckle content based strain, defined as a function of speckle density based on the relationship between strain and speckle density, gives an indirect strain value for fluid filled lesions. To measure the speckle density of the fluid filled lesions, two new criteria based on oscillation count of the windowed radio frequency signal and local variance of the normalized B-mode image are used. An improved speckle tracking technique is also proposed for strain imaging of the solid lesions and background. A wavelet-based integration technique is then proposed for combining the strain images from these two techniques for visualizing both the solid and fluid filled lesions from a common framework. The final output of our algorithm is a high quality composite strain image which can effectively visualize both solid and fluid filled breast lesions in addition to the speckle content of the fluid filled lesions for their discrimination. The performance of our algorithm is evaluated using the in vivo patient data and compared with recently reported techniques. The results show that both the solid and fluid filled lesions can be better visualized using our technique and the fluid filled lesions can be classified with good accuracy. Copyright © 2016 Elsevier B.V. All rights reserved.

A New Feature-Enhanced Speckle Reduction Method Based on Multiscale Analysis for Ultrasound B-Mode Imaging.

PubMed

Kang, Jinbum; Lee, Jae Young; Yoo, Yangmo

2016-06-01

Effective speckle reduction in ultrasound B-mode imaging is important for enhancing the image quality and improving the accuracy in image analysis and interpretation. In this paper, a new feature-enhanced speckle reduction (FESR) method based on multiscale analysis and feature enhancement filtering is proposed for ultrasound B-mode imaging. In FESR, clinical features (e.g., boundaries and borders of lesions) are selectively emphasized by edge, coherence, and contrast enhancement filtering from fine to coarse scales while simultaneously suppressing speckle development via robust diffusion filtering. In the simulation study, the proposed FESR method showed statistically significant improvements in edge preservation, mean structure similarity, speckle signal-to-noise ratio, and contrast-to-noise ratio (CNR) compared with other speckle reduction methods, e.g., oriented speckle reducing anisotropic diffusion (OSRAD), nonlinear multiscale wavelet diffusion (NMWD), the Laplacian pyramid-based nonlinear diffusion and shock filter (LPNDSF), and the Bayesian nonlocal means filter (OBNLM). Similarly, the FESR method outperformed the OSRAD, NMWD, LPNDSF, and OBNLM methods in terms of CNR, i.e., 10.70 ± 0.06 versus 9.00 ± 0.06, 9.78 ± 0.06, 8.67 ± 0.04, and 9.22 ± 0.06 in the phantom study, respectively. Reconstructed B-mode images that were developed using the five speckle reduction methods were reviewed by three radiologists for evaluation based on each radiologist's diagnostic preferences. All three radiologists showed a significant preference for the abdominal liver images obtained using the FESR methods in terms of conspicuity, margin sharpness, artificiality, and contrast, p<0.0001. For the kidney and thyroid images, the FESR method showed similar improvement over other methods. However, the FESR method did not show statistically significant improvement compared with the OBNLM method in margin sharpness for the kidney and thyroid images. These results demonstrate that the proposed FESR method can improve the image quality of ultrasound B-mode imaging by enhancing the visualization of lesion features while effectively suppressing speckle noise.

SAR Speckle Noise Reduction Using Wiener Filter

NASA Technical Reports Server (NTRS)

Joo, T. H.; Held, D. N.

1983-01-01

Synthetic aperture radar (SAR) images are degraded by speckle. A multiplicative speckle noise model for SAR images is presented. Using this model, a Wiener filter is derived by minimizing the mean-squared error using the known speckle statistics. Implementation of the Wiener filter is discussed and experimental results are presented. Finally, possible improvements to this method are explored.

Solving the inverse scattering problem in reflection-mode dynamic speckle-field phase microscopy (Conference Presentation)

NASA Astrophysics Data System (ADS)

Zhou, Renjie; So, Peter T. C.; Yaqoob, Zahid; Jin, Di; Hosseini, Poorya; Kuang, Cuifang; Singh, Vijay Raj; Kim, Yang-Hyo; Dasari, Ramachandra R.

2017-02-01

Most of the quantitative phase microscopy systems are unable to provide depth-resolved information for measuring complex biological structures. Optical diffraction tomography provides a non-trivial solution to it by 3D reconstructing the object with multiple measurements through different ways of realization. Previously, our lab developed a reflection-mode dynamic speckle-field phase microscopy (DSPM) technique, which can be used to perform depth resolved measurements in a single shot. Thus, this system is suitable for measuring dynamics in a layer of interest in the sample. DSPM can be also used for tomographic imaging, which promises to solve the long-existing "missing cone" problem in 3D imaging. However, the 3D imaging theory for this type of system has not been developed in the literature. Recently, we have developed an inverse scattering model to rigorously describe the imaging physics in DSPM. Our model is based on the diffraction tomography theory and the speckle statistics. Using our model, we first precisely calculated the defocus response and the depth resolution in our system. Then, we further calculated the 3D coherence transfer function to link the 3D object structural information with the axially scanned imaging data. From this transfer function, we found that in the reflection mode excellent sectioning effect exists in the low lateral spatial frequency region, thus allowing us to solve the "missing cone" problem. Currently, we are working on using this coherence transfer function to reconstruct layered structures and complex cells.

Imaging in laser spectroscopy by a single-pixel camera based on speckle patterns

NASA Astrophysics Data System (ADS)

Žídek, K.; Václavík, J.

2016-11-01

Compressed sensing (CS) is a branch of computational optics able to reconstruct an image (or any other information) from a reduced number of measurements - thus significantly saving measurement time. It relies on encoding the detected information by a random pattern and consequent mathematical reconstruction. CS can be the enabling step to carry out imaging in many time-consuming measurements. The critical step in CS experiments is the method to invoke encoding by a random mask. Complex devices and relay optics are commonly used for the purpose. We present a new approach of creating the random mask by using laser speckles from coherent laser light passing through a diffusor. This concept is especially powerful in laser spectroscopy, where it does not require any complicated modification of the current techniques. The main advantage consist in the unmatched simplicity of the random pattern generation and a versatility of the pattern resolution. Unlike in the case of commonly used random masks, here the pattern fineness can be adjusted by changing the laser spot size being diffused. We demonstrate the pattern tuning together with the connected changes in the pattern statistics. In particular, the issue of patterns orthogonality, which is important for the CS applications, is discussed. Finally, we demonstrate on a set of 200 acquired speckle patterns that the concept can be successfully employed for single-pixel camera imaging. We discuss requirements on detector noise for the image reconstruction.

High Resolution Astrophysical Observations Using Speckle Imaging

DTIC Science & Technology

1986-04-11

2. J.L.C. Sanz and T.S. ’uang, "Unified HIlbert space approach to iterative least-squares signal restoration," JOSA 73, p. 1455 (83). 3. V.T. Tom...Tinbergen, J., Greenberg , J.M., and de Jager, C. 1981, Astr. Ap., 95, 215. Tsuji, T. 1978, Pub. Astr. Soc. Japan, 30, 435. Van der Hucht, K.A

Speckle temporal stability in XAO coronagraphic images. II. Refine model for quasi-static speckle temporal evolution for VLT/SPHERE

NASA Astrophysics Data System (ADS)

Martinez, P.; Kasper, M.; Costille, A.; Sauvage, J. F.; Dohlen, K.; Puget, P.; Beuzit, J. L.

2013-06-01

Context. Observing sequences have shown that the major noise source limitation in high-contrast imaging is the presence of quasi-static speckles. The timescale on which quasi-static speckles evolve is determined by various factors, mechanical or thermal deformations, among others. Aims: Understanding these time-variable instrumental speckles and, especially, their interaction with other aberrations, referred to as the pinning effect, is paramount for the search for faint stellar companions. The temporal evolution of quasi-static speckles is, for instance, required for quantifying the gain expected when using angular differential imaging (ADI) and to determining the interval on which speckle nulling techniques must be carried out. Methods: Following an early analysis of a time series of adaptively corrected, coronagraphic images obtained in a laboratory condition with the high-order test bench (HOT) at ESO Headquarters, we confirm our results with new measurements carried out with the SPHERE instrument during its final test phase in Europe. The analysis of the residual speckle pattern in both direct and differential coronagraphic images enables the characterization of the temporal stability of quasi-static speckles. Data were obtained in a thermally actively controlled environment reproducing realistic conditions encountered at the telescope. Results: The temporal evolution of the quasi-static wavefront error exhibits a linear power law, which can be used to model quasi-static speckle evolution in the context of forthcoming high-contrast imaging instruments, with implications for instrumentation (design, observing strategies, data reduction). Such a model can be used for instance to derive the timescale on which non-common path aberrations must be sensed and corrected. We found in our data that quasi-static wavefront error increases with ~0.7 Å per minute.

Laser speckle imaging in the spatial frequency domain

PubMed Central

Mazhar, Amaan; Cuccia, David J.; Rice, Tyler B.; Carp, Stefan A.; Durkin, Anthony J.; Boas, David A.; Choi, Bernard; Tromberg, Bruce J.

2011-01-01

Laser Speckle Imaging (LSI) images interference patterns produced by coherent addition of scattered laser light to map subsurface tissue perfusion. However, the effect of longer path length photons is typically unknown and poses a limitation towards absolute quantification. In this work, LSI is integrated with spatial frequency domain imaging (SFDI) to suppress multiple scattering and absorption effects. First, depth sensitive speckle contrast is shown in phantoms by separating a deep source (4 mm) from a shallow source (2 mm) of speckle contrast by using a high spatial frequency of illumination (0.24 mm−1). We develop an SFD adapted correlation diffusion model and show that with high frequency (0.24 mm−1) illumination, doubling of absorption contrast results in only a 1% change in speckle contrast versus 25% change using a planar unmodulated (0 mm−1) illumination. Similar absorption change is mimicked in vivo imaging a finger occlusion and the relative speckle contrast change from baseline is 10% at 0.26 mm−1 versus 60% at 0 mm−1 during a finger occlusion. These results underscore the importance of path length and optical properties in determining speckle contrast. They provide an integrated approach for simultaneous mapping of blood flow (speckle contrast) and oxygenation (optical properties) which can be used to inform tissue metabolism. PMID:21698018

Instruments at the Lowell Observatory Discovery Channel Telescope (DCT)

NASA Astrophysics Data System (ADS)

Jacoby, George H.; Bida, Thomas A.; Fischer, Debra; Horch, Elliott; Kutyrev, Alexander; Mace, Gregory N.; Massey, Philip; Roe, Henry G.; Prato, Lisa A.

2017-01-01

The Lowell Observatory Discovery Channel Telescope (DCT) has been in full science operation for 2 years (2015 and 2016). Five instruments have been commissioned during that period, and two additional instruments are planned for 2017. These include:+ Large Monolithic Imager (LMI) - a CCD imager (12.6 arcmin FoV)+ DeVeny - a general purpose optical spectrograph (2 arcmin slit length, 10 grating choices)+ NIHTS - a low resolution (R=160) YJHK spectrograph (1.3 arcmin slit)+ DSSI - a two-channel optical speckle imager (5 arcsec FoV)+ IGRINS - a high resolution (45,000) HK spectrograph, on loan from the University of Texas.In the upcoming year, instruments will be delivered from the University of Maryland (RIMAS - a YJHK imager/spectrograph) and from Yale University (EXPRES - a very high resolution stabilized optical echelle for PRV).Each of these instruments will be described, along with their primary science goals.

Noise adaptive wavelet thresholding for speckle noise removal in optical coherence tomography.

PubMed

Zaki, Farzana; Wang, Yahui; Su, Hao; Yuan, Xin; Liu, Xuan

2017-05-01

Optical coherence tomography (OCT) is based on coherence detection of interferometric signals and hence inevitably suffers from speckle noise. To remove speckle noise in OCT images, wavelet domain thresholding has demonstrated significant advantages in suppressing noise magnitude while preserving image sharpness. However, speckle noise in OCT images has different characteristics in different spatial scales, which has not been considered in previous applications of wavelet domain thresholding. In this study, we demonstrate a noise adaptive wavelet thresholding (NAWT) algorithm that exploits the difference of noise characteristics in different wavelet sub-bands. The algorithm is simple, fast, effective and is closely related to the physical origin of speckle noise in OCT image. Our results demonstrate that NAWT outperforms conventional wavelet thresholding.

Speckle noise attenuation in optical coherence tomography by compounding images acquired at different positions of the sample

NASA Astrophysics Data System (ADS)

Popescu, Dan P.; Hewko, Mark D.; Sowa, Michael G.

2007-01-01

This study demonstrates a simple method for attenuating the speckle noise generated by coherent multiple-scattered photons in optical-coherence tomography images. The method could be included among the space-diversity techniques used for speckle reduction. It relies on displacing the sample along a weakly focused beam in the sample arm of the interferometer, acquiring a coherent image for each sample position and adding the individual images to form a compounded image. It is proven that the compounded image displays a reduction in the speckle noise generated by multiple scattered photons and an enhancement in the intensity signal caused by single-backscattered photons. To evaluate its potential biomedical applications, the method is used to investigate in vitro a caries lesion affecting the enamel layer of a wisdom tooth. Because of the uncorrelated nature of the speckle noise the compounded image provides a better mapping of the lesion compared to a single (coherent) image.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsantis, Stavros; Spiliopoulos, Stavros; Karnabatidis, Dimitrios

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 totalmore » 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 new wavelet-based EFCM clustering model was introduced toward noise reduction and detail preservation. The proposed method improves the overall US image quality, which in turn could affect the decision-making on whether additional imaging and/or intervention is needed.« less

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

PubMed

Tsantis, Stavros; Spiliopoulos, Stavros; Skouroliakou, Aikaterini; Karnabatidis, Dimitrios; Hazle, John D; Kagadis, George C

2014-07-01

Speckle suppression in ultrasound (US) images of various anatomic structures via a novel speckle noise reduction algorithm. 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. 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. A new wavelet-based EFCM clustering model was introduced toward noise reduction and detail preservation. The proposed method improves the overall US image quality, which in turn could affect the decision-making on whether additional imaging and/or intervention is needed.

Extracting built-up areas from TerraSAR-X data using object-oriented classification method

NASA Astrophysics Data System (ADS)

Wang, SuYun; Sun, Z. C.

2017-02-01

Based on single-polarized TerraSAR-X, the approach generates homogeneous segments on an arbitrary number of scale levels by applying a region-growing algorithm which takes the intensity of backscatter and shape-related properties into account. The object-oriented procedure consists of three main steps: firstly, the analysis of the local speckle behavior in the SAR intensity data, leading to the generation of a texture image; secondly, a segmentation based on the intensity image; thirdly, the classification of each segment using the derived texture file and intensity information in order to identify and extract build-up areas. In our research, the distribution of BAs in Dongying City is derived from single-polarized TSX SM image (acquired on 17th June 2013) with average ground resolution of 3m using our proposed approach. By cross-validating the random selected validation points with geo-referenced field sites, Quick Bird high-resolution imagery, confusion matrices with statistical indicators are calculated and used for assessing the classification results. The results demonstrate that an overall accuracy 92.89 and a kappa coefficient of 0.85 could be achieved. We have shown that connect texture information with the analysis of the local speckle divergence, combining texture and intensity of construction extraction is feasible, efficient and rapid.

Video surveillance with speckle imaging

DOEpatents

Carrano, Carmen J [Livermore, CA; Brase, James M [Pleasanton, CA

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.

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

NASA Astrophysics Data System (ADS)

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.

Effects of photon noise on speckle image reconstruction with the Knox-Thompson algorithm. [in astronomy

NASA Technical Reports Server (NTRS)

Nisenson, P.; Papaliolios, C.

1983-01-01

An analysis of the effects of photon noise on astronomical speckle image reconstruction using the Knox-Thompson algorithm is presented. It is shown that the quantities resulting from the speckle average arre biased, but that the biases are easily estimated and compensated. Calculations are also made of the convergence rate for the speckle average as a function of the source brightness. An illustration of the effects of photon noise on the image recovery process is included.

Fine Resolution Imaging of Space Objects.

DTIC Science & Technology

1982-02-01

Figur einschliesst," J. reine agnew. Math. 123, 241 (1901). 5. J. Christou, "Imaging of Star Clusters from Speckle Inter- ferometry," Opt. Commun...Also, at any point x, by definition g.+,(x) is the near- est value to gMx ) that satisfies the object-domain constraints. Therefore, at all...the point gk(x) rather than from g^(x) since presumably gMx ) is closer to the solution than gk(x). After using Eq. (40), one would employ Eq. (35

Fractality of pulsatile flow in speckle images

NASA Astrophysics Data System (ADS)

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.

Multiresolution generalized N dimension PCA for ultrasound image denoising

PubMed Central

2014-01-01

Background Ultrasound images are usually affected by speckle noise, which is a type of random multiplicative noise. Thus, reducing speckle and improving image visual quality are vital to obtaining better diagnosis. Method In this paper, a novel noise reduction method for medical ultrasound images, called multiresolution generalized N dimension PCA (MR-GND-PCA), is presented. In this method, the Gaussian pyramid and multiscale image stacks on each level are built first. GND-PCA as a multilinear subspace learning method is used for denoising. Each level is combined to achieve the final denoised image based on Laplacian pyramids. Results The proposed method is tested with synthetically speckled and real ultrasound images, and quality evaluation metrics, including MSE, SNR and PSNR, are used to evaluate its performance. Conclusion Experimental results show that the proposed method achieved the lowest noise interference and improved image quality by reducing noise and preserving the structure. Our method is also robust for the image with a much higher level of speckle noise. For clinical images, the results show that MR-GND-PCA can reduce speckle and preserve resolvable details. PMID:25096917

Reflective ghost imaging through turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hardy, Nicholas D.; Shapiro, Jeffrey H.

2011-12-15

Recent work has indicated that ghost imaging may have applications in standoff sensing. However, most theoretical work has addressed transmission-based ghost imaging. To be a viable remote-sensing system, the ghost imager needs to image rough-surfaced targets in reflection through long, turbulent optical paths. We develop, within a Gaussian-state framework, expressions for the spatial resolution, image contrast, and signal-to-noise ratio of such a system. We consider rough-surfaced targets that create fully developed speckle in their returns and Kolmogorov-spectrum turbulence that is uniformly distributed along all propagation paths. We address both classical and nonclassical optical sources, as well as a computational ghostmore » imager.« less

Speckle disturbance limit in laser-based cinema projection systems

PubMed Central

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

2015-01-01

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. PMID:26370531

Speckle disturbance limit in laser-based cinema projection systems.

PubMed

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

2015-09-15

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.

Speckle disturbance limit in laser-based cinema projection systems

NASA Astrophysics Data System (ADS)

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.

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

PubMed

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.

Performance evaluation of spatial compounding in the presence of aberration and adaptive imaging

NASA Astrophysics Data System (ADS)

Dahl, Jeremy J.; Guenther, Drake; Trahey, Gregg E.

2003-05-01

Spatial compounding has been used for years to reduce speckle in ultrasonic images and to resolve anatomical features hidden behind the grainy appearance of speckle. Adaptive imaging restores image contrast and resolution by compensating for beamforming errors caused by tissue-induced phase errors. Spatial compounding represents a form of incoherent imaging, whereas adaptive imaging attempts to maintain a coherent, diffraction-limited aperture in the presence of aberration. Using a Siemens Antares scanner, we acquired single channel RF data on a commercially available 1-D probe. Individual channel RF data was acquired on a cyst phantom in the presence of a near field electronic phase screen. Simulated data was also acquired for both a 1-D and a custom built 8x96, 1.75-D probe (Tetrad Corp.). The data was compounded using a receive spatial compounding algorithm; a widely used algorithm because it takes advantage of parallel beamforming to avoid reductions in frame rate. Phase correction was also performed by using a least mean squares algorithm to estimate the arrival time errors. We present simulation and experimental data comparing the performance of spatial compounding to phase correction in contrast and resolution tasks. We evaluate spatial compounding and phase correction, and combinations of the two methods, under varying aperture sizes, aperture overlaps, and aberrator strength to examine the optimum configuration and conditions in which spatial compounding will provide a similar or better result than adaptive imaging. We find that, in general, phase correction is hindered at high aberration strengths and spatial frequencies, whereas spatial compounding is helped by these aberrators.

Cartography of asteroids and comet nuclei from low resolution data

NASA Technical Reports Server (NTRS)

Stooke, Philip J.

1992-01-01

High resolution images of non-spherical objects, such as Viking images of Phobos and the anticipated Galileo images of Gaspra, lend themselves to conventional planetary cartographic procedures: control network analysis, stereophotogrammetry, image mosaicking in 2D or 3D, and airbrush mapping. There remains the problem of a suitable map projection for bodies which are extremely elongated or irregular in shape. Many bodies will soon be seen at lower resolution (5-30 pixels across the disk) in images from speckle interferometry, the Hubble Space Telescope, ground-based radar, distinct spacecraft encounters, and closer images degraded by smear. Different data with similar effective resolutions are available from stellar occultations, radar or lightcurve convex hulls, lightcurve modeling of albedo variations, and cometary jet modeling. With such low resolution, conventional methods of shape determination will be less useful or will fail altogether, leaving limb and terminator topography as the principal sources of topographic information. A method for shape determination based on limb and terminator topography was developed. It has been applied to the nucleus of Comet Halley and the jovian satellite Amalthea. The Amalthea results are described to give an example of the cartographic possibilities and problems of anticipated data sets.

SECM half-inch tethered endoscopic capsule (HITEC) for esophageal imaging (Conference Presentation)

NASA Astrophysics Data System (ADS)

Kang, DongKyun; Kim, Minkyu; Carruth, Robert W.; Lu, Weina; Wu, Tao; Alali, Sanaz; Do, Dukho; Soomro, Amna R.; Grant, Catriona N.; Tiernan, Aubrey R.; Rosenberg, Mireille; Nishioka, Norman S.; Tearney, Guillermo J.

2016-03-01

Spectrally encoded confocal microscopy (SECM) is a high-speed confocal endomicroscopy technology that can image extremely large regions of human tissue at cellular resolution within a short imaging time. Previously, we have developed a 7-mm-diameter SECM endoscopic capsule and successfully demonstrated imaging of human esophagus in vivo. Even though we were able to successfully capture images with the previous capsule, it suffered from two limitations: (1) the capsule had a small diameter, which provided a limited contact between SECM capsule and esophagus; and (2) speckle noise in SECM images made it challenging to appreciate cellular features. In this paper, we present a new SECM capsule, termed SECM half-inch tethered endoscopic capsule (HITEC), which addresses the two aforementioned technical challenges. With the SECM HITEC, a dual-clad fiber was used to reduce the speckle noise. Miniature GRIN optics was used to increase the NA of the fiber from 0.09 to 0.25, which made it possible to build a SECM capsule with large diameter (12.7 mm) while maintaining a short rigid length (22 mm). A water-immersion objective lens was custom designed and manufactured to provide high NA of 0.7. We have manufactured the SECM HITEC catheter and tested its optical and mechanical performance. Lateral and axial resolution was measured as 1.2 µm and 13 µm, respectively. We have imaged swine esophageal tissues ex vivo, and SECM images clearly visualized cell nuclei. Non-uniform rotational distortion (NURD) was small, less than 5%. Preliminary results suggest that SECM HITEC provides sufficient optical and mechanical performance for tissue imaging. In a future clinical study, we will test the feasibility of utilizing SECM HITEC for improved cellular imaging human of the human esophagus in vivo.

Variance based joint sparsity reconstruction of synthetic aperture radar data for speckle reduction

NASA Astrophysics Data System (ADS)

Scarnati, Theresa; Gelb, Anne

2018-04-01

In observing multiple synthetic aperture radar (SAR) images of the same scene, it is apparent that the brightness distributions of the images are not smooth, but rather composed of complicated granular patterns of bright and dark spots. Further, these brightness distributions vary from image to image. This salt and pepper like feature of SAR images, called speckle, reduces the contrast in the images and negatively affects texture based image analysis. This investigation uses the variance based joint sparsity reconstruction method for forming SAR images from the multiple SAR images. In addition to reducing speckle, the method has the advantage of being non-parametric, and can therefore be used in a variety of autonomous applications. Numerical examples include reconstructions of both simulated phase history data that result in speckled images as well as the images from the MSTAR T-72 database.

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.

PubMed

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-dimensional data, and was used to determine the changes in cochlear blood flow with single vessel resolution. It was demonstrated that during a hypoxic challenge there was an increase in the concentrations of Hb, a decrease in the concentrations of HbO and cochlear blood flow, and a slight decrease in the concentration of HbT. Also, the rate of change in the concentrations of Hb and HbO was quantified during and after the hypoxic challenge. The ability to simultaneously measure these ischemic parameters with high spatio-temporal resolution will allow the detailed quantitative analysis of several hearing disorders, and will be useful for diagnosing and developing treatments.

Advances in indirect detector systems for ultra high-speed hard X-ray imaging with synchrotron light

NASA Astrophysics Data System (ADS)

Olbinado, M. P.; Grenzer, J.; Pradel, P.; De Resseguier, T.; Vagovic, P.; Zdora, M.-C.; Guzenko, V. A.; David, C.; Rack, A.

2018-04-01

We report on indirect X-ray detector systems for various full-field, ultra high-speed X-ray imaging methodologies, such as X-ray phase-contrast radiography, diffraction topography, grating interferometry and speckle-based imaging performed at the hard X-ray imaging beamline ID19 of the European Synchrotron—ESRF. Our work highlights the versatility of indirect X-ray detectors to multiple goals such as single synchrotron pulse isolation, multiple-frame recording up to millions frames per second, high efficiency, and high spatial resolution. Besides the technical advancements, potential applications are briefly introduced and discussed.

[Laser speckle suppression due to dynamic multiple scattering scheme introduced by oblique incidence].

PubMed

Xu, Mei-fang; Gao, Wen-hong; Shi, Yun-bo; Wang, Hao-quan; Du, Bin-bin

2014-06-01

Speckle suppression has been the research focus in laser display technology. In the present paper, the relation between multiple scattering and the size of speckle grains is established by analyzing the properties of speckle generated by the laser beam through SiO2 suspension. Combined with dynamic light scattering theory, laser speckle suppression due to dynamic multiple scattering scheme introduced by oblique incidence is proposed. A speckle suppression element consists of a static diffuser and a light pipe containing the water suspension of SiO2 microspheres with a diameter of 300 nm and a molar concentration of 3.0 x 10(-4) μm3, which is integrated with the laser display system. The laser beam with different incident angles into the SiO2 suspension affecting the contrast of the speckle images is analyzed by the experiments. The results demonstrate that the contrast of the speckle image can be reduced to 0.067 from 0.43 when the beam with the incident angle of approximately 8 degrees illuminates into the SiO2 suspension. The spatial average of speckle granules and the temporal average of speckle images were achieved by the proposed method, which improved the effect of speckle suppression. The proposed element for speckle suppression improved the reliability and reduced the cost of laser projection system, since no mechanical vibration is needed and it is convenient to integrate the element with the existing projection system.

Quantitative laser speckle flowmetry of the in vivo microcirculation using sidestream dark field microscopy

PubMed Central

Nadort, Annemarie; Woolthuis, Rutger G.; van Leeuwen, Ton G.; Faber, Dirk J.

2013-01-01

We present integrated Laser Speckle Contrast Imaging (LSCI) and Sidestream Dark Field (SDF) flowmetry to provide real-time, non-invasive and quantitative measurements of speckle decorrelation times related to microcirculatory flow. Using a multi exposure acquisition scheme, precise speckle decorrelation times were obtained. Applying SDF-LSCI in vitro and in vivo allows direct comparison between speckle contrast decorrelation and flow velocities, while imaging the phantom and microcirculation architecture. This resulted in a novel analysis approach that distinguishes decorrelation due to flow from other additive decorrelation sources. PMID:24298399

Analyzing speckle contrast for HiLo microscopy optimization.

PubMed

Mazzaferri, J; Kunik, D; Belisle, J M; Singh, K; Lefrançois, S; Costantino, S

2011-07-18

HiLo microscopy is a recently developed technique that provides both optical sectioning and fast imaging with a simple implementation and at a very low cost. The methodology combines widefield and speckled illumination images to obtain one optically sectioned image. Hence, the characteristics of such speckle illumination ultimately determine the quality of HiLo images and the overall performance of the method. In this work, we study how speckle contrast influence local variations of fluorescence intensity and brightness profiles of thick samples. We present this article as a guide to adjust the parameters of the system for optimizing the capabilities of this novel technology.

Analyzing speckle contrast for HiLo microscopy optimization

NASA Astrophysics Data System (ADS)

Mazzaferri, J.; Kunik, D.; Belisle, J. M.; Singh, K.; Lefrançois, S.; Costantino, S.

2011-07-01

HiLo microscopy is a recently developed technique that provides both optical sectioning and fast imaging with a simple implementation and at a very low cost. The methodology combines widefield and speckled illumination images to obtain one optically sectioned image. Hence, the characteristics of such speckle illumination ultimately determine the quality of HiLo images and the overall performance of the method. In this work, we study how speckle contrast influence local variations of fluorescence intensity and brightness profiles of thick samples. We present this article as a guide to adjust the parameters of the system for optimizing the capabilities of this novel technology.

Wavefront control methods for high-contrast integral field spectroscopy

NASA Astrophysics Data System (ADS)

Groff, Tyler D.; Mejia Prada, Camilo; Cady, Eric; Rizzo, Maxime J.; Mandell, Avi; Gong, Qian; McElwain, Michael; Zimmerman, Neil; Saxena, Prabal; Guyon, Olivier

2017-09-01

Direct Imaging of exoplanets using a coronagraph has become a major field of research both on the ground and in space. Key to the science of direct imaging is the spectroscopic capabilities of the instrument, our ability to fit spectra, and understanding the composition of the observed planets. Direct imaging instruments generally use an integral field spectrograph (IFS), which encodes the spectrum into a two-dimensional image on the detector. This results in more efficient detection and characterization of targets, and the spectral information is critical to achieving detection limits below the speckle floor of the imager. The most mature application of these techniques is at more modest contrast ratios on ground-based telescopes, achieving approximately 5-6 orders of magnitude suppression. In space, where we are attempting to detect Earth-analogs, the contrast requirements are more severe and the IFS must be incorporated into the wavefront control loop to reach 1e-10 detection limits required for Earth-like planet detection. We present the objectives and application of IFS imagery for both a speckle control loop and post-processing of images. Results, tested methodologies, and the future work using the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) and the Prototype Imaging Spectrograph for Coronagraphic Exoplanet Studies (PISCES) at the JPL High Contrast Imaging Testbed are presented.

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

PubMed

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. Copyright © 2016 Elsevier Inc. All rights reserved.

Statistical characterization of speckle noise in coherent imaging systems

NASA Astrophysics Data System (ADS)

Yaroslavsky, Leonid; Shefler, A.

2003-05-01

Speckle noise imposes fundamental limitation on image quality in coherent radiation based imaging and optical metrology systems. Speckle noise phenomena are associated with properties of objects to diffusely scatter irradiation and with the fact that in recording the wave field, a number of signal distortions inevitably occur due to technical limitations inherent to hologram sensors. The statistical theory of speckle noise was developed with regard to only limited resolving power of coherent imaging devices. It is valid only asymptotically as much as the central limit theorem of the probability theory can be applied. In applications this assumption is not always applicable. Moreover, in treating speckle noise problem one should also consider other sources of the hologram deterioration. In the paper, statistical properties of speckle due to the limitation of hologram size, dynamic range and hologram signal quantization are studied by Monte-Carlo simulation for holograms recorded in near and far diffraction zones. The simulation experiments have shown that, for limited resolving power of the imaging system, widely accepted opinion that speckle contrast is equal to one holds only for rather severe level of the hologram size limitation. For moderate limitations, speckle contrast changes gradually from zero for no limitation to one for limitation to less than about 20% of hologram size. The results obtained for the limitation of the hologram sensor"s dynamic range and hologram signal quantization reveal that speckle noise due to these hologram signal distortions is not multiplicative and is directly associated with the severity of the limitation and quantization. On the base of the simulation results, analytical models are suggested.

Speckle reduction in optical coherence tomography images based on wave atoms

PubMed Central

Du, Yongzhao; Liu, Gangjun; Feng, Guoying; Chen, Zhongping

2014-01-01

Abstract. Optical coherence tomography (OCT) is an emerging noninvasive imaging technique, which is based on low-coherence interferometry. OCT images suffer from speckle noise, which reduces image contrast. A shrinkage filter based on wave atoms transform is proposed for speckle reduction in OCT images. Wave atoms transform is a new multiscale geometric analysis tool that offers sparser expansion and better representation for images containing oscillatory patterns and textures than other traditional transforms, such as wavelet and curvelet transforms. Cycle spinning-based technology is introduced to avoid visual artifacts, such as Gibbs-like phenomenon, and to develop a translation invariant wave atoms denoising scheme. The speckle suppression degree in the denoised images is controlled by an adjustable parameter that determines the threshold in the wave atoms domain. The experimental results show that the proposed method can effectively remove the speckle noise and improve the OCT image quality. The signal-to-noise ratio, contrast-to-noise ratio, average equivalent number of looks, and cross-correlation (XCOR) values are obtained, and the results are also compared with the wavelet and curvelet thresholding techniques. PMID:24825507

Optically Sectioned Imaging of Microvasculature of In-Vivo and Ex-Vivo Thick Tissue Models with Speckle-illumination HiLo Microscopy and HiLo Image Processing Implementation in MATLAB Architecture

NASA Astrophysics Data System (ADS)

Suen, Ricky Wai

The work described in this thesis covers the conversion of HiLo image processing into MATLAB architecture and the use of speckle-illumination HiLo microscopy for use of ex-vivo and in-vivo imaging of thick tissue models. HiLo microscopy is a wide-field fluorescence imaging technique and has been demonstrated to produce optically sectioned images comparable to confocal in thin samples. The imaging technique was developed by Jerome Mertz and the Boston University Biomicroscopy Lab and has been implemented in our lab as a stand-alone optical setup and a modification to a conventional fluorescence microscope. Speckle-illumination HiLo microscopy combines two images taken under speckle-illumination and standard uniform-illumination to generate an optically sectioned image that reject out-of-focus fluorescence. The evaluated speckle contrast in the images is used as a weighting function where elements that move out-of-focus have a speckle contrast that decays to zero. The experiments shown here demonstrate the capability of our HiLo microscopes to produce optically-sectioned images of the microvasculature of ex-vivo and in-vivo thick tissue models. The HiLo microscope were used to image the microvasculature of ex-vivo mouse heart sections prepared for optical histology and the microvasculature of in-vivo rodent dorsal window chamber models. Studies in label-free surface profiling with HiLo microscopy is also presented.

Software phantom with realistic speckle modeling for validation of image analysis methods in echocardiography

NASA Astrophysics Data System (ADS)

Law, Yuen C.; Tenbrinck, Daniel; Jiang, Xiaoyi; Kuhlen, Torsten

2014-03-01

Computer-assisted processing and interpretation of medical ultrasound images is one of the most challenging tasks within image analysis. Physical phenomena in ultrasonographic images, e.g., the characteristic speckle noise and shadowing effects, make the majority of standard methods from image analysis non optimal. Furthermore, validation of adapted computer vision methods proves to be difficult due to missing ground truth information. There is no widely accepted software phantom in the community and existing software phantoms are not exible enough to support the use of specific speckle models for different tissue types, e.g., muscle and fat tissue. In this work we propose an anatomical software phantom with a realistic speckle pattern simulation to _ll this gap and provide a exible tool for validation purposes in medical ultrasound image analysis. We discuss the generation of speckle patterns and perform statistical analysis of the simulated textures to obtain quantitative measures of the realism and accuracy regarding the resulting textures.

Speckle tracking as a method to measure hemidiaphragm excursion.

PubMed

Goutman, Stephen A; Hamilton, James D; Swihart, Blake; Foerster, Bradley; Feldman, Eva L; Rubin, Jonathan M

2017-01-01

Diaphragm excursion measured via ultrasound may be an important imaging outcome measure of respiratory function. We developed a new method for measuring diaphragm movement and compared it to the more traditional M-mode method. Ultrasound images of the right and left hemidiaphragms were collected to compare speckle tracking and M-mode measurements of diaphragm excursion. Speckle tracking was performed using EchoInsight (Epsilon Imaging, Ann Arbor, Michigan). Six healthy subjects without a history of pulmonary diseases were included in this proof-of-concept study. Speckle tracking of the diaphragm is technically possible. Unlike M-mode, speckle tracking carries the advantage of reliable visualization and measurement of the left hemidiaphragm. Speckle tracking accounted for diaphragm movement simultaneously in the cephalocaudad and mediolateral directions, unlike M-mode, which is 1-dimensional. Diaphragm speckle tracking may represent a novel, more robust method for measuring diaphragm excursion, especially for the left hemidiaphragm. Muscle Nerve 55: 125-127, 2017. © 2016 Wiley Periodicals, Inc.

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

NASA Astrophysics Data System (ADS)

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.

Transesophageal Speckle-Tracking Echocardiography Improves Right Ventricular Systolic Function Assessment in the Perioperative Setting.

PubMed

Markin, Nicholas W; Chamsi-Pasha, Mohammed; Luo, Jiangtao; Thomas, Walker R; Brakke, Tara R; Porter, Thomas R; Shillcutt, Sasha K

2017-02-01

Perioperative evaluation of right ventricular (RV) systolic function is important to follow intraoperative changes, but it is often not possible to assess with transthoracic echocardiographic (TTE) imaging, because of surgical field constraints. Echocardiographic RV quantification is most commonly performed using tricuspid annular plane systolic excursion (TAPSE), but it is not clear whether this method works with transesophageal echocardiographic (TEE) imaging. This study was performed to evaluate the relationship between TTE and TEE TAPSE distances measured with M-mode imaging and in comparison with speckle-tracking TTE and TEE measurements. Prospective observational TTE and TEE imaging was performed during elective cardiac surgical procedures in 100 subjects. Speckle-tracking echocardiographic TAPSE distances were determined and compared with the TTE M-mode TAPSE standard. Both an experienced and an inexperienced user of the speckle-tracking echocardiographic software evaluated the images, to enable interobserver assessment in 84 subjects. The comparison between TTE M-mode TAPSE and TEE M-mode TAPSE demonstrated significant variability, with a Spearman correlation of 0.5 and a mean variance in measurement of 6.5 mm. There was equivalence within data pairs and correlations between TTE M-mode TAPSE and both speckle-tracking TTE and speckle-tracking TEE TAPSE, with Spearman correlations of 0.65 and 0.65, respectively. The average variance in measurement was 0.6 mm for speckle-tracking TTE TAPSE and 1.5 mm for speckle-tracking TEE TAPSE. Using TTE M-mode TAPSE as a control, TEE M-mode TAPSE results are not accurate and should not be used clinically to evaluate RV systolic function. The relationship between speckle-tracking echocardiographic TAPSE and TTE M-mode TAPSE suggests that in the perioperative setting, speckle-tracking TEE TAPSE might be used to quantitatively evaluate RV systolic function in the absence of TTE imaging. Copyright © 2016 American Society of Echocardiography. Published by Elsevier Inc. All rights reserved.

Towards non-contact photo-acoustic endoscopy using speckle pattern analysis

NASA Astrophysics Data System (ADS)

Lengenfelder, Benjamin; Mehari, Fanuel; Tang, Yuqi; Klämpfl, Florian; Zalevsky, Zeev; Schmidt, Michael

2017-03-01

Photoacoustic Tomography combines the advantages of optical and acoustic imaging as it makes use of the high optical contrast of tissue and the high resolution of ultrasound. Furthermore, high penetration depths in tissue in the order of several centimeters can be achieved by the combination of these modalities. Extensive research is being done in the field of miniaturization of photoacoustic devices, as photoacoustic imaging could be of significant benefits for the physician during endoscopic interventions. All the existing miniature systems are based on contact transducers for signal detection that are placed at the distal end of an endoscopic device. This makes the manufacturing process difficult and impedance matching to the inspected surface a requirement. The requirement for contact limits the view of the physician during the intervention. Consequently, a fiber based non-contact optical sensing technique would be highly beneficial for the development of miniaturized photoacoustic endoscopic devices. This work demonstrates the feasibility of surface displacement detection using remote speckle-sensing using a high speed camera and an imaging fiber bundle that is used in commercially available video endoscopes. The feasibility of displacement sensing is demonstrated by analysis of phantom vibrations which are induced by loudspeaker membrane oscillations. Since the usability of the remote speckle-sensing for photo-acoustic signal detection was already demonstrated, the fiber bundle approach demonstrates the potential for non-contact photoacoustic detections during endoscopy.

Using Ultrasonic Speckle Velocimetry to Detect Fluid Instabilities in a Surfactant Solution

NASA Astrophysics Data System (ADS)

Bice, Jason E.

Rheometry is a leading technology used to define material properties of multi-phase viscoelastic fluid-like materials, such as the shear modulus and viscosity. However, traditional rheometry relies on a mechanical response from a rotating or oscillating rotor of various geometries which does not allow for any spatial or temporal quantification of the material characteristics. Further, the setup operates under the assumption of a uniform and homogeneous flow. Thus, only qualitative deductions can be realized when a complex fluid displays inhomogeneous behavior, such as wall slip or shear banding. Due to this lack of capability, non-intrusive imaging is required to define and quantify behavior that occurs in a complex fluid under shear conditions. This thesis outlines the design, fabrication, and experimental examples of an adapted ultrasonic speckle velocimetry device, which enables spatial and temporal resolution of inhomogeneous fluid behavior using ultrasound acoustics. For the experimental example, a commercial surfactant mixture (hair shampoo) was tested to show the utility and precision that ultrasonic speckle velocimetry possesses.

Tracking quasi-stationary flow of weak fluorescent signals by adaptive multi-frame correlation.

PubMed

Ji, L; Danuser, G

2005-12-01

We have developed a novel cross-correlation technique to probe quasi-stationary flow of fluorescent signals in live cells at a spatial resolution that is close to single particle tracking. By correlating image blocks between pairs of consecutive frames and integrating their correlation scores over multiple frame pairs, uncertainty in identifying a globally significant maximum in the correlation score function has been greatly reduced as compared with conventional correlation-based tracking using the signal of only two consecutive frames. This approach proves robust and very effective in analysing images with a weak, noise-perturbed signal contrast where texture characteristics cannot be matched between only a pair of frames. It can also be applied to images that lack prominent features that could be utilized for particle tracking or feature-based template matching. Furthermore, owing to the integration of correlation scores over multiple frames, the method can handle signals with substantial frame-to-frame intensity variation where conventional correlation-based tracking fails. We tested the performance of the method by tracking polymer flow in actin and microtubule cytoskeleton structures labelled at various fluorophore densities providing imagery with a broad range of signal modulation and noise. In applications to fluorescent speckle microscopy (FSM), where the fluorophore density is sufficiently low to reveal patterns of discrete fluorescent marks referred to as speckles, we combined the multi-frame correlation approach proposed above with particle tracking. This hybrid approach allowed us to follow single speckles robustly in areas of high speckle density and fast flow, where previously published FSM analysis methods were unsuccessful. Thus, we can now probe cytoskeleton polymer dynamics in living cells at an entirely new level of complexity and with unprecedented detail.

(Non-) homomorphic approaches to denoise intensity SAR images with non-local means and stochastic distances

NASA Astrophysics Data System (ADS)

Penna, Pedro A. A.; Mascarenhas, Nelson D. A.

2018-02-01

The development of new methods to denoise images still attract researchers, who seek to combat the noise with the minimal loss of resolution and details, like edges and fine structures. Many algorithms have the goal to remove additive white Gaussian noise (AWGN). However, it is not the only type of noise which interferes in the analysis and interpretation of images. Therefore, it is extremely important to expand the filters capacity to different noise models present in li-terature, for example the multiplicative noise called speckle that is present in synthetic aperture radar (SAR) images. The state-of-the-art algorithms in remote sensing area work with similarity between patches. This paper aims to develop two approaches using the non local means (NLM), developed for AWGN. In our research, we expanded its capacity for intensity SAR ima-ges speckle. The first approach is grounded on the use of stochastic distances based on the G0 distribution without transforming the data to the logarithm domain, like homomorphic transformation. It takes into account the speckle and backscatter to estimate the parameters necessary to compute the stochastic distances on NLM. The second method uses a priori NLM denoising with a homomorphic transformation and applies the inverse Gamma distribution to estimate the parameters that were used into NLM with stochastic distances. The latter method also presents a new alternative to compute the parameters for the G0 distribution. Finally, this work compares and analyzes the synthetic and real results of the proposed methods with some recent filters of the literature.

AMBER-NACO aperture-synthesis imaging of the half-obscured central star and the edge-on disk of the red giant L2 Puppis

NASA Astrophysics Data System (ADS)

Ohnaka, K.; Schertl, D.; Hofmann, K.-H.; Weigelt, G.

2015-09-01

Aims: The red giant L2 Pup started a dimming event in 1994, which is considered to be caused by the ejection of dust clouds. We present near-IR aperture-synthesis imaging of L2 Pup achieved by combining data from VLT/NACO and the AMBER instrument of the Very Large Telescope Interferometer (VLTI). Our aim is to spatially resolve the innermost region of the circumstellar environment. Methods: We carried out speckle interferometric observations at 2.27 μm with VLT/NACO and long-baseline interferometric observations with VLTI/AMBER at 2.2-2.35 μm with baselines of 15-81 m. We also extracted an 8.7 μm image from the mid-IR VLTI instrument MIDI. Results: The diffraction-limited image obtained by bispectrum speckle interferometry with NACO with a spatial resolution of 57 mas shows an elongated component. The aperture-synthesis imaging combining the NACO speckle data and AMBER data with a spatial resolution of 5.6 × 7.3 mas further resolves not only this elongated component, but also the central star. The reconstructed image reveals that the elongated component is a nearly edge-on disk with a size of ~180 × 50 mas lying in the E-W direction, and furthermore, that the southern hemisphere of the central star is severely obscured by the equatorial dust lane of the disk. The angular size of the disk is consistent with the distance that the dust clouds that were ejected at the onset of the dimming event should have traveled by the time of our observations, if we assume that the dust clouds moved radially. This implies that the formation of the disk may be responsible for the dimming event. The 8.7 μm image with a spatial resolution of 220 mas extracted from the MIDI data taken in 2004 (seven years before the AMBER and NACO observations) shows an approximately spherical envelope without a signature of the disk. This suggests that the mass loss before the dimming event may have been spherical. Based on AMBER, NACO, and MIDI observations made with the Very Large Telescope and Very Large Telescope Interferometer of the European Southern Observatory. Program ID: 074.D-0075(A), 074.D-0101(A), 074.D-0198(B), 088.D-0150(A/B), and 288.D-5041(A). Appendices are available in electronic form at http://www.aanda.org

Enhanced spectral domain optical coherence tomography for pathological and functional studies

NASA Astrophysics Data System (ADS)

Yuan, Zhijia

Optical coherence tomography (OCT) is a novel technique that enables noninvasive or minimally invasive, cross-sectional imaging of biological tissue at sub-10mum spatial resolution and up to 2-3mm imaging depth. Numerous technological advances have emerged in recent years that have shown great potential to develop OCT into a powerful imaging and diagnostic tools. In particular, the implementation of Fourier-domain OCT (FDOCT) is a major step forward that leads to greatly improved imaging rate and image fidelity of OCT. This dissertation summarizes the work that focuses on enhancing the performances and functionalities of spectral radar based FDOCT (SDOCT) for pathological and functional applications. More specifically, chapters 1-4 emphasize on the development of SDOCT and its utility in pathological studies, including cancer diagnosis. The principle of SDOCT is first briefly outlined, followed by the design of our bench-top SDOCT systems with emphasis on spectral linear interpolation, calibration and system dispersion compensation. For ultrahigh-resolution SDOCT, time-lapse image registration and frame averaging is introduced to effectively reduce speckle noise and uncover subcellular details, showing great promise for enhancing the diagnosis of carcinoma in situ. To overcome the image depth limitation of OCT, a dual-modal imaging method combing SDOCT with high-frequency ultrasound is proposed and examined in animal cancer models to enhance the sensitivity and staging capabilities for bladder cancer diagnosis. Chapters 5-7 summarize the work on developing Doppler SDOCT for functional studies. Digital-frequency-ramping OCT (DFR-OCT) is developed in the study, which has demonstrated the ability to significantly improve the signal-to-noise ratio and thus sensitivity for retrieving subsurface blood flow imaging. New DFR algorithms and imaging processing methods are discussed to further enhance cortical CBF imaging. Applications of DFR-OCT for brain functional studies are presented and laser speckle imaging is combined to enable quantitative cerebral blood flow (CBF) imaging at high spatiotemporal resolutions. An angiography-enhanced Doppler optical coherence tomography (aDFR-OCT) was also demonstrated to enable quantitative imaging of capillary changes for brain functional studies. Lastly, future work on technological development and potential biomedical applications is briefly outlined.

Speckle noise suppression method in holographic display using time multiplexing

NASA Astrophysics Data System (ADS)

Liu, Su-Juan; Wang, Di; Li, Song-Jie; Wang, Qiong-Hua

2017-06-01

We propose a method to suppress the speckle noise in holographic display using time multiplexing. The diffractive optical elements (DOEs) and the subcomputer-generated holograms (sub-CGHs) are generated, respectively. The final image is reconstructed using time multiplexing of the subimages and the final subimages. Meanwhile, the speckle noise of the final image is suppressed by reducing the coherence of the reconstructed light and separating the adjacent image points in space. Compared with the pixel separation method, the experiments demonstrate that the proposed method suppresses the speckle noise effectively with less calculation burden and lower demand for frame rate of the spatial light modulator. In addition, with increases of the DOEs and the sub-CGHs, the speckle noise is further suppressed.

Digital 3D holographic display using scattering layers for enhanced viewing angle and image size

NASA Astrophysics Data System (ADS)

Yu, Hyeonseung; Lee, KyeoReh; Park, Jongchan; Park, YongKeun

2017-05-01

In digital 3D holographic displays, the generation of realistic 3D images has been hindered by limited viewing angle and image size. Here we demonstrate a digital 3D holographic display using volume speckle fields produced by scattering layers in which both the viewing angle and the image size are greatly enhanced. Although volume speckle fields exhibit random distributions, the transmitted speckle fields have a linear and deterministic relationship with the input field. By modulating the incident wavefront with a digital micro-mirror device, volume speckle patterns are controlled to generate 3D images of micrometer-size optical foci with 35° viewing angle in a volume of 2 cm × 2 cm × 2 cm.

A novel method for repeatedly generating speckle patterns used in digital image correlation

NASA Astrophysics Data System (ADS)

Zhang, Juan; Sweedy, Ahmed; Gitzhofer, François; Baroud, Gamal

2018-01-01

Speckle patterns play a key role in Digital Image Correlation (DIC) measurement, and generating an optimal speckle pattern has been the goal for decades now. The usual method of generating a speckle pattern is by manually spraying the paint on the specimen. However, this makes it difficult to reproduce the optimal pattern for maintaining identical testing conditions and achieving consistent DIC results. This study proposed and evaluated a novel method using an atomization system to repeatedly generate speckle patterns. To verify the repeatability of the speckle patterns generated by this system, simulation and experimental studies were systematically performed. The results from both studies showed that the speckle patterns and, accordingly, the DIC measurements become highly accurate and repeatable using the proposed atomization system.

Estimation of reactogenicity of preparations produced on the basis of photoinactivated live vaccines against brucellosis and tularaemia on the organismic level.2. Using the method of speckle-microscopy with high spatial resolution

NASA Astrophysics Data System (ADS)

Ulianova, O. V.; Uianov, S. S.; Li, Pengcheng; Luo, Qingming

2011-04-01

The method of speckle microscopy was adapted to estimate the reactogenicity of the prototypes of vaccine preparations against extremely dangerous infections. The theory is proposed to describe the mechanism of formation of the output signal from the super-high spatial resolution speckle microscope. The experimental studies show that bacterial suspensions, irradiated in different regimes of inactivation, do not exert negative influence on the blood microcirculations in laboratory animals.

Multimodal optical imaging system for in vivo investigation of cerebral oxygen delivery and energy metabolism

PubMed Central

Yaseen, Mohammad A.; Srinivasan, Vivek J.; Gorczynska, Iwona; Fujimoto, James G.; Boas, David A.; Sakadžić, Sava

2015-01-01

Improving our understanding of brain function requires novel tools to observe multiple physiological parameters with high resolution in vivo. We have developed a multimodal imaging system for investigating multiple facets of cerebral blood flow and metabolism in small animals. The system was custom designed and features multiple optical imaging capabilities, including 2-photon and confocal lifetime microscopy, optical coherence tomography, laser speckle imaging, and optical intrinsic signal imaging. Here, we provide details of the system’s design and present in vivo observations of multiple metrics of cerebral oxygen delivery and energy metabolism, including oxygen partial pressure, microvascular blood flow, and NADH autofluorescence. PMID:26713212

Optical Processing of Speckle Images with Bacteriorhodopsin for Pattern Recognition

NASA Technical Reports Server (NTRS)

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.

Improving the visualization of 3D ultrasound data with 3D filtering

NASA Astrophysics Data System (ADS)

Shamdasani, Vijay; Bae, Unmin; Managuli, Ravi; Kim, Yongmin

2005-04-01

3D ultrasound imaging is quickly gaining widespread clinical acceptance as a visualization tool that allows clinicians to obtain unique views not available with traditional 2D ultrasound imaging and an accurate understanding of patient anatomy. The ability to acquire, manipulate and interact with the 3D data in real time is an important feature of 3D ultrasound imaging. Volume rendering is often used to transform the 3D volume into 2D images for visualization. Unlike computed tomography (CT) and magnetic resonance imaging (MRI), volume rendering of 3D ultrasound data creates noisy images in which surfaces cannot be readily discerned due to speckles and low signal-to-noise ratio. The degrading effect of speckles is especially severe when gradient shading is performed to add depth cues to the image. Several researchers have reported that smoothing the pre-rendered volume with a 3D convolution kernel, such as 5x5x5, can significantly improve the image quality, but at the cost of decreased resolution. In this paper, we have analyzed the reasons for the improvement in image quality with 3D filtering and determined that the improvement is due to two effects. The filtering reduces speckles in the volume data, which leads to (1) more accurate gradient computation and better shading and (2) decreased noise during compositing. We have found that applying a moderate-size smoothing kernel (e.g., 7x7x7) to the volume data before gradient computation combined with some smoothing of the volume data (e.g., with a 3x3x3 lowpass filter) before compositing yielded images with good depth perception and no appreciable loss in resolution. Providing the clinician with the flexibility to control both of these effects (i.e., shading and compositing) independently could improve the visualization of the 3D ultrasound data. Introducing this flexibility into the ultrasound machine requires 3D filtering to be performed twice on the volume data, once before gradient computation and again before compositing. 3D filtering of an ultrasound volume containing millions of voxels requires a large amount of computation, and doing it twice decreases the number of frames that can be visualized per second. To address this, we have developed several techniques to make computation efficient. For example, we have used the moving average method to filter a 128x128x128 volume with a 3x3x3 boxcar kernel in 17 ms on a single MAP processor running at 400 MHz. The same methods reduced the computing time on a Pentium 4 running at 3 GHz from 110 ms to 62 ms. We believe that our proposed method can improve 3D ultrasound visualization without sacrificing resolution and incurring an excessive computing time.

Statistical Analysis of speckle noise reduction techniques for echocardiographic Images

NASA Astrophysics Data System (ADS)

Saini, Kalpana; Dewal, M. L.; Rohit, Manojkumar

2011-12-01

Echocardiography is the safe, easy and fast technology for diagnosing the cardiac diseases. As in other ultrasound images these images also contain speckle noise. In some cases this speckle noise is useful such as in motion detection. But in general noise removal is required for better analysis of the image and proper diagnosis. Different Adaptive and anisotropic filters are included for statistical analysis. Statistical parameters such as Signal-to-Noise Ratio (SNR), Peak Signal-to-Noise Ratio (PSNR), and Root Mean Square Error (RMSE) calculated for performance measurement. One more important aspect that there may be blurring during speckle noise removal. So it is prefered that filter should be able to enhance edges during noise removal.

Development of Multiple-Frequency Ultrasonic Imaging System Using Multiple Resonance Piezoelectric Transducer

NASA Astrophysics Data System (ADS)

Akiyama, Iwaki; Yoshizumi, Natsuki; Saito, Shigemi; Wada, Yuji; Koyama, Daisuke; Nakamura, Kentaro

2012-07-01

The authors have developed a multiple frequency imaging system using a multiple resonance transducer (MRT) consisting of 1-3 composite materials with a low mechanical quality factor Q bonded together. The MRT has a structure consisting of thin and thick piezoelectric plates, two matching layers, and a backing layer. This makes it possible to obtain B-mode images of satisfactory resolution using ultrasonic pulses owing to their short duration. In this paper, the vibration property of the MRT derived through equivalent-circuit analysis is first shown. By utilizing the result, an MRT capable of transmitting ultrasonic pulses for generation of the images of biological tissues with satisfactory resolution is designed and prototyped. Setting the prototype transducer in the mechanical sector probe of commercial ultrasonic diagnosis equipment, the speckle reduction effect is demonstrated using images of various phantoms to mimic biological tissues and a human thyroid.

High-resolution image reconstruction technique applied to the optical testing of ground-based astronomical telescopes

NASA Astrophysics Data System (ADS)

Jin, Zhenyu; Lin, Jing; Liu, Zhong

2008-07-01

By study of the classical testing techniques (such as Shack-Hartmann Wave-front Sensor) adopted in testing the aberration of ground-based astronomical optical telescopes, we bring forward two testing methods on the foundation of high-resolution image reconstruction technology. One is based on the averaged short-exposure OTF and the other is based on the Speckle Interferometric OTF by Antoine Labeyrie. Researches made by J.Ohtsubo, F. Roddier, Richard Barakat and J.-Y. ZHANG indicated that the SITF statistical results would be affected by the telescope optical aberrations, which means the SITF statistical results is a function of optical system aberration and the atmospheric Fried parameter (seeing). Telescope diffraction-limited information can be got through two statistics methods of abundant speckle images: by the first method, we can extract the low frequency information such as the full width at half maximum (FWHM) of the telescope PSF to estimate the optical quality; by the second method, we can get a more precise description of the telescope PSF with high frequency information. We will apply the two testing methods to the 2.4m optical telescope of the GMG Observatory, in china to validate their repeatability and correctness and compare the testing results with that of the Shack-Hartmann Wave-Front Sensor got. This part will be described in detail in our paper.

The application of infrared speckle interferometry to the imaging of remote galaxies and AGN

NASA Technical Reports Server (NTRS)

Olivares, Robert O.

1995-01-01

A 1.5 meter reflector, used for both infrared and optical astronomy, is also being used for infrared speckle interferometry and CCD imaging. The application of these imaging techniques to remote galaxies and active galactic nuclei are discussed. A simple model for the origin of speckle in coherent imaging systems is presented. Very careful photometry of the continuum of the galaxy M31 is underway using CCD images. It involves extremely intensive data reduction because the object itself is very large and has low surface brightness.

High-contrast multilayer imaging of biological organisms through dark-field digital refocusing.

PubMed

Faridian, Ahmad; Pedrini, Giancarlo; Osten, Wolfgang

2013-08-01

We have developed an imaging system to extract high contrast images from different layers of biological organisms. Utilizing a digital holographic approach, the system works without scanning through layers of the specimen. In dark-field illumination, scattered light has the main contribution in image formation, but in the case of coherent illumination, this creates a strong speckle noise that reduces the image quality. To remove this restriction, the specimen has been illuminated with various speckle-fields and a hologram has been recorded for each speckle-field. Each hologram has been analyzed separately and the corresponding intensity image has been reconstructed. The final image has been derived by averaging over the reconstructed images. A correlation approach has been utilized to determine the number of speckle-fields required to achieve a desired contrast and image quality. The reconstructed intensity images in different object layers are shown for different sea urchin larvae. Two multimedia files are attached to illustrate the process of digital focusing.

Speckle noise reduction in ultrasound images using a discrete wavelet transform-based image fusion technique.

PubMed

Choi, Hyun Ho; Lee, Ju Hwan; Kim, Sung Min; Park, Sung Yun

2015-01-01

Here, the speckle noise in ultrasonic images is removed using an image fusion-based denoising method. To optimize the denoising performance, each discrete wavelet transform (DWT) and filtering technique was analyzed and compared. In addition, the performances were compared in order to derive the optimal input conditions. To evaluate the speckle noise removal performance, an image fusion algorithm was applied to the ultrasound images, and comparatively analyzed with the original image without the algorithm. As a result, applying DWT and filtering techniques caused information loss and noise characteristics, and did not represent the most significant noise reduction performance. Conversely, an image fusion method applying SRAD-original conditions preserved the key information in the original image, and the speckle noise was removed. Based on such characteristics, the input conditions of SRAD-original had the best denoising performance with the ultrasound images. From this study, the best denoising technique proposed based on the results was confirmed to have a high potential for clinical application.

Ultrasonic backscatter imaging by shear-wave-induced echo phase encoding of target locations.

PubMed

McAleavey, Stephen

2011-01-01

We present a novel method for ultrasound backscatter image formation wherein lateral resolution of the target is obtained by using traveling shear waves to encode the lateral position of targets in the phase of the received echo. We demonstrate that the phase modulation as a function of shear wavenumber can be expressed in terms of a Fourier transform of the lateral component of the target echogenicity. The inverse transform, obtained by measurements of the phase modulation over a range of shear wave spatial frequencies, yields the lateral scatterer distribution. Range data are recovered from time of flight as in conventional ultrasound, yielding a B-mode-like image. In contrast to conventional ultrasound imaging, where mechanical or electronic focusing is used and lateral resolution is determined by aperture size and wavelength, we demonstrate that lateral resolution using the proposed method is independent of the properties of the aperture. Lateral resolution of the target is achieved using a stationary, unfocused, single-element transducer. We present simulated images of targets of uniform and non-uniform shear modulus. Compounding for speckle reduction is demonstrated. Finally, we demonstrate image formation with an unfocused transducer in gelatin phantoms of uniform shear modulus.

Compact divided-pupil line-scanning confocal microscope for investigation of human tissues

NASA Astrophysics Data System (ADS)

Glazowski, Christopher; Peterson, Gary; Rajadhyaksha, Milind

2013-03-01

Divided-pupil line-scanning confocal microscopy (DPLSCM) can provide a simple and low-cost approach for imaging of human tissues with pathology-like nuclear and cellular detail. Using results from a multidimensional numerical model of DPLSCM, we found optimal pupil configurations for improved axial sectioning, as well as control of speckle noise in the case of reflectance imaging. The modeling results guided the design and construction of a simple (10 component) microscope, packaged within the footprint of an iPhone, and capable of cellular resolution. We present the optical design with experimental video-images of in-vivo human tissues.

High Resolution Active Optics Observations from the Kepler Follow-up Observation Program

NASA Astrophysics Data System (ADS)

Gautier, Thomas N.; Ciardi, D. R.; Marcy, G. W.; Hirsch, L.

2014-01-01

The ground based follow-up observation program for candidate exoplanets discovered with the Kepler observatory has supported a major effort for high resolution imaging of candidate host stars using adaptive optics wave-front correction (AO), speckle imaging and lucky imaging. These images allow examination of the sky as close as a few tenths of an arcsecond from the host stars to detect background objects that might be the source of the Kepler transit signal instead of the host star. This poster reports on the imaging done with AO cameras on the Keck, Palomar 5m and Shane 3m (Lick Observatory) which have been used to obtain high resolution images of over 500 Kepler Object of Interest (KOI) exoplanet candidate host stars. All observations were made at near infrared wavelengths in the J, H and K bands, mostly using the host target star as the AO guide star. Details of the sensitivity to background objects actually attained by these observations and the number of background objects discovered are presented. Implications to the false positive rate of the Kepler candidates are discussed.

Digital micromirror device-based laser-illumination Fourier ptychographic microscopy

PubMed Central

Kuang, Cuifang; Ma, Ye; Zhou, Renjie; Lee, Justin; Barbastathis, George; Dasari, Ramachandra R.; Yaqoob, Zahid; So, Peter T. C.

2015-01-01

We report a novel approach to Fourier ptychographic microscopy (FPM) by using a digital micromirror device (DMD) and a coherent laser source (532 nm) for generating spatially modulated sample illumination. Previously demonstrated FPM systems are all based on partially-coherent illumination, which offers limited throughput due to insufficient brightness. Our FPM employs a high power coherent laser source to enable shot-noise limited high-speed imaging. For the first time, a digital micromirror device (DMD), imaged onto the back focal plane of the illumination objective, is used to generate spatially modulated sample illumination field for ptychography. By coding the on/off states of the micromirrors, the illumination plane wave angle can be varied at speeds more than 4 kHz. A set of intensity images, resulting from different oblique illuminations, are used to numerically reconstruct one high-resolution image without obvious laser speckle. Experiments were conducted using a USAF resolution target and a fiber sample, demonstrating high-resolution imaging capability of our system. We envision that our approach, if combined with a coded-aperture compressive-sensing algorithm, will further improve the imaging speed in DMD-based FPM systems. PMID:26480361

Digital micromirror device-based laser-illumination Fourier ptychographic microscopy.

PubMed

Kuang, Cuifang; Ma, Ye; Zhou, Renjie; Lee, Justin; Barbastathis, George; Dasari, Ramachandra R; Yaqoob, Zahid; So, Peter T C

2015-10-19

We report a novel approach to Fourier ptychographic microscopy (FPM) by using a digital micromirror device (DMD) and a coherent laser source (532 nm) for generating spatially modulated sample illumination. Previously demonstrated FPM systems are all based on partially-coherent illumination, which offers limited throughput due to insufficient brightness. Our FPM employs a high power coherent laser source to enable shot-noise limited high-speed imaging. For the first time, a digital micromirror device (DMD), imaged onto the back focal plane of the illumination objective, is used to generate spatially modulated sample illumination field for ptychography. By coding the on/off states of the micromirrors, the illumination plane wave angle can be varied at speeds more than 4 kHz. A set of intensity images, resulting from different oblique illuminations, are used to numerically reconstruct one high-resolution image without obvious laser speckle. Experiments were conducted using a USAF resolution target and a fiber sample, demonstrating high-resolution imaging capability of our system. We envision that our approach, if combined with a coded-aperture compressive-sensing algorithm, will further improve the imaging speed in DMD-based FPM systems.

Stellar Companions of Exoplanet Host Stars in K2

NASA Astrophysics Data System (ADS)

Matson, Rachel; Howell, Steve; Horch, Elliott; Everett, Mark

2018-01-01

Stellar multiplicity has significant implications for the detection and characterization of exoplanets. A stellar companion can mimic the signal of a transiting planet or distort the true planetary radii, leading to improper density estimates and over-predicting the occurrence rates of Earth-sized planets. Determining the fraction of exoplanet host stars that are also binaries allows us to better determine planetary characteristics as well as establish the relationship between binarity and planet formation. Using high-resolution speckle imaging to obtain diffraction limited images of K2 planet candidate host stars we detect stellar companions within one arcsec and up to six magnitudes fainter than the host star. By comparing our observed companion fraction to TRILEGAL star count simulations, and using the known detection limits of speckle imaging, we find the binary fraction of K2 planet host stars to be similar to that of Kepler host stars and solar-type field stars. Accounting for stellar companions in exoplanet studies is therefore essential for deriving true stellar and planetary properties as well as maximizing the returns for TESS and future exoplanet missions.

Effect of Non-speckle Echo Signals on Tissue Characteristics for Liver Fibrosis using Probability Density Function of Ultrasonic B-mode image

NASA Astrophysics Data System (ADS)

Mori, Shohei; Hirata, Shinnosuke; Yamaguchi, Tadashi; Hachiya, Hiroyuki

To develop a quantitative diagnostic method for liver fibrosis using an ultrasound B-mode image, a probability imaging method of tissue characteristics based on a multi-Rayleigh model, which expresses a probability density function of echo signals from liver fibrosis, has been proposed. In this paper, an effect of non-speckle echo signals on tissue characteristics estimated from the multi-Rayleigh model was evaluated. Non-speckle signals were determined and removed using the modeling error of the multi-Rayleigh model. The correct tissue characteristics of fibrotic tissue could be estimated with the removal of non-speckle signals.

Reflectance Speckle of Retinal Nerve Fiber Layer Reveals Axonal Activity

PubMed Central

Huang, Xiang-Run; Knighton, Robert W.; Zhou, Ye; Zhao, Xiao-Peng

2013-01-01

Purpose. This study investigated the retinal nerve fiber layer (RNFL) reflectance speckle and tested the hypothesis that temporal change of RNFL speckle reveals axonal dynamic activity. Methods. RNFL reflectance speckle of isolated rat retinas was studied with monochromatic illumination. A series of reflectance images was collected every 5 seconds for approximately 15 minutes. Correlation coefficients (CC) of selected areas between a reference and subsequent images were calculated and plotted as a function of the time intervals between images. An exponential function fit to the time course was used to evaluate temporal change of speckle pattern. To relate temporal change of speckle to axonal activity, in vitro living retina perfused at a normal (34°C) and a lower (24°C) temperature, paraformaldehyde-fixed retina, and retina treated with microtubule depolymerization were used. Results. RNFL reflectance was not uniform; rather nerve fiber bundles had a speckled texture that changed with time. In normally perfused retina, the time constant of the CC change was 0.56 ± 0.26 minutes. In retinas treated with lower temperature and microtubule depolymerization, the time constants increased by two to four times, indicating that the speckle pattern changed more slowly. The speckled texture in fixed retina was stationary. Conclusions. Fixation stops axonal activity; treatments with either lower temperature or microtubule depolymerization are known to decrease axonal transport. The results obtained in this study suggest that temporal change of RNFL speckle reveals structural change due to axonal activity. Assessment of RNFL reflectance speckle may offer a new means of evaluating axonal function. PMID:23532525

Estimation of reactogenicity of preparations produced on the basis of photoinactivated live vaccines against brucellosis and tularaemia on the organismic level. 2. Using the method of speckle-microscopy with high spatial resolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ulianova, O V; Uianov, S S; Li Pengcheng

2011-04-30

The method of speckle microscopy was adapted to estimate the reactogenicity of the prototypes of vaccine preparations against extremely dangerous infections. The theory is proposed to describe the mechanism of formation of the output signal from the super-high spatial resolution speckle microscope. The experimental studies show that bacterial suspensions, irradiated in different regimes of inactivation, do not exert negative influence on the blood microcirculations in laboratory animals. (optical technologies in biophysics and medicine)

Shift-Invariant Image Reconstruction of Speckle-Degraded Images Using Bispectrum Estimation

DTIC Science & Technology

1990-05-01

process with the requisite negative exponential pelf. I call this model the Negative Exponential Model ( NENI ). The NENI flowchart is seen in Figure 6...Figure ]3d-g. Statistical Histograms and Phase for the RPj NG EXP FDF MULT METHOD FILuteC 14a. Truth Object Speckled Via the NENI HISTOGRAM OF SPECKLE

Optimized digital speckle patterns for digital image correlation by consideration of both accuracy and efficiency.

PubMed

Chen, Zhenning; Shao, Xinxing; Xu, Xiangyang; He, Xiaoyuan

2018-02-01

The technique of digital image correlation (DIC), which has been widely used for noncontact deformation measurements in both the scientific and engineering fields, is greatly affected by the quality of speckle patterns in terms of its performance. This study was concerned with the optimization of the digital speckle pattern (DSP) for DIC in consideration of both the accuracy and efficiency. The root-mean-square error of the inverse compositional Gauss-Newton algorithm and the average number of iterations were used as quality metrics. Moreover, the influence of subset sizes and the noise level of images, which are the basic parameters in the quality assessment formulations, were also considered. The simulated binary speckle patterns were first compared with the Gaussian speckle patterns and captured DSPs. Both the single-radius and multi-radius DSPs were optimized. Experimental tests and analyses were conducted to obtain the optimized and recommended DSP. The vector diagram of the optimized speckle pattern was also uploaded as reference.

Speckle patterns produced by an optical vortex and its application to surface roughness measurements.

PubMed

Passos, M H M; Lemos, M R; Almeida, S R; Balthazar, W F; da Silva, L; Huguenin, J A O

2017-01-10

In this work, we report on the analysis of speckle patterns produced by illuminating different rough surfaces with an optical vortex, a first-order (l=1) Laguerre-Gaussian beam. The generated speckle patterns were observed in the normal direction exploring four different planes: the diffraction plane, image plane, focal plane, and exact Fourier transform plane. The digital speckle patterns were analyzed using the Hurst exponent of digital images, an interesting tool used to study surface roughness. We show a proof of principle that the Hurst exponent of a digital speckle pattern is more sensitive with respect to the surface roughness when the speckle pattern is produced by an optical vortex and observed at a focal plane. We also show that Hurst exponents are not so sensitive with respect to the topological charge l. These results open news possibilities of investigation into speckle metrology once we have several techniques that use speckle patterns for different applications.

Color quality improvement of reconstructed images in color digital holography using speckle method and spectral estimation

NASA Astrophysics Data System (ADS)

Funamizu, Hideki; Onodera, Yusei; Aizu, Yoshihisa

2018-05-01

In this study, we report color quality improvement of reconstructed images in color digital holography using the speckle method and the spectral estimation. In this technique, an object is illuminated by a speckle field and then an object wave is produced, while a plane wave is used as a reference wave. For three wavelengths, the interference patterns of two coherent waves are recorded as digital holograms on an image sensor. Speckle fields are changed by moving a ground glass plate in an in-plane direction, and a number of holograms are acquired to average the reconstructed images. After the averaging process of images reconstructed from multiple holograms, we use the Wiener estimation method for obtaining spectral transmittance curves in reconstructed images. The color reproducibility in this method is demonstrated and evaluated using a Macbeth color chart film and staining cells of onion.

Exploiting physical constraints for multi-spectral exo-planet detection

NASA Astrophysics Data System (ADS)

Thiébaut, Éric; Devaney, Nicholas; Langlois, Maud; Hanley, Kenneth

2016-07-01

We derive a physical model of the on-axis PSF for a high contrast imaging system such as GPI or SPHERE. This model is based on a multi-spectral Taylor series expansion of the diffraction pattern and predicts that the speckles should be a combination of spatial modes with deterministic chromatic magnification and weighting. We propose to remove most of the residuals by fitting this model on a set of images at multiple wavelengths and times. On simulated data, we demonstrate that our approach achieves very good speckle suppression without additional heuristic parameters. The residual speckles1, 2 set the most serious limitation in the detection of exo-planets in high contrast coronographic images provided by instruments such as SPHERE3 at the VLT, GPI4, 5 at Gemini, or SCExAO6 at Subaru. A number of post-processing methods have been proposed to remove as much as possible of the residual speckles while preserving the signal from the planets. These methods exploit the fact that the speckles and the planetary signal have different temporal and spectral behaviors. Some methods like LOCI7 are based on angular differential imaging8 (ADI), spectral differential imaging9, 10 (SDI), or on a combination of ADI and SDI.11 Instead of working on image differences, we propose to tackle the exo-planet detection as an inverse problem where a model of the residual speckles is fit on the set of multi-spectral images and, possibly, multiple exposures. In order to reduce the number of degrees of freedom, we impose specific constraints on the spatio-spectral distribution of stellar speckles. These constraints are deduced from a multi-spectral Taylor series expansion of the diffraction pattern for an on-axis source which implies that the speckles are a combination of spatial modes with deterministic chromatic magnification and weighting. Using simulated data, the efficiency of speckle removal by fitting the proposed multi-spectral model is compared to the result of using an approximation based on the singular value decomposition of the rescaled images. We show how the difficult problem to fitting a bilinear model on the can be solved in practise. The results are promising for further developments including application to real data and joint planet detection in multi-variate data (multi-spectral and multiple exposures images).

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

NASA Astrophysics Data System (ADS)

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.

Lagrangian speckle model and tissue-motion estimation--theory.

PubMed

Maurice, R L; Bertrand, M

1999-07-01

It is known that when a tissue is subjected to movements such as rotation, shearing, scaling, etc., changes in speckle patterns that result act as a noise source, often responsible for most of the displacement-estimate variance. From a modeling point of view, these changes can be thought of as resulting from two mechanisms: one is the motion of the speckles and the other, the alterations of their morphology. In this paper, we propose a new tissue-motion estimator to counteract these speckle decorrelation effects. The estimator is based on a Lagrangian description of the speckle motion. This description allows us to follow local characteristics of the speckle field as if they were a material property. This method leads to an analytical description of the decorrelation in a way which enables the derivation of an appropriate inverse filter for speckle restoration. The filter is appropriate for linear geometrical transformation of the scattering function (LT), i.e., a constant-strain region of interest (ROI). As the LT itself is a parameter of the filter, a tissue-motion estimator can be formulated as a nonlinear minimization problem, seeking the best match between the pre-tissue-motion image and a restored-speckle post-motion image. The method is tested, using simulated radio-frequency (RF) images of tissue undergoing axial shear.

Determination of the effect of source intensity profile on speckle contrast using coherent spatial frequency domain imaging

PubMed Central

Rice, Tyler B.; Konecky, Soren D.; Owen, Christopher; Choi, Bernard; Tromberg, Bruce J.

2012-01-01

Laser Speckle Imaging (LSI) is fast, noninvasive technique to image particle dynamics in scattering media such as biological tissue. While LSI measurements are independent of the overall intensity of the laser source, we find that spatial variations in the laser source profile can impact measured flow rates. This occurs due to differences in average photon path length across the profile, and is of significant concern because all lasers have some degree of natural Gaussian profile in addition to artifacts potentially caused by projecting optics. Two in vivo measurement are performed to show that flow rates differ based on location with respect to the beam profile. A quantitative analysis is then done through a speckle contrast forward model generated within a coherent Spatial Frequency Domain Imaging (cSFDI) formalism. The model predicts remitted speckle contrast as a function of spatial frequency, optical properties, and scattering dynamics. Comparison with experimental speckle contrast images were done using liquid phantoms with known optical properties for three common beam shapes. cSFDI is found to accurately predict speckle contrast for all beam shapes to within 5% root mean square error. Suggestions for improving beam homogeneity are given, including a widening of the natural beam Gaussian, proper diffusing glass spreading, and flat top shaping using microlens arrays. PMID:22741080

Edge Probability and Pixel Relativity-Based Speckle Reducing Anisotropic Diffusion.

PubMed

Mishra, Deepak; Chaudhury, Santanu; Sarkar, Mukul; Soin, Arvinder Singh; Sharma, Vivek

2018-02-01

Anisotropic diffusion filters are one of the best choices for speckle reduction in the ultrasound images. These filters control the diffusion flux flow using local image statistics and provide the desired speckle suppression. However, inefficient use of edge characteristics results in either oversmooth image or an image containing misinterpreted spurious edges. As a result, the diagnostic quality of the images becomes a concern. To alleviate such problems, a novel anisotropic diffusion-based speckle reducing filter is proposed in this paper. A probability density function of the edges along with pixel relativity information is used to control the diffusion flux flow. The probability density function helps in removing the spurious edges and the pixel relativity reduces the oversmoothing effects. Furthermore, the filtering is performed in superpixel domain to reduce the execution time, wherein a minimum of 15% of the total number of image pixels can be used. For performance evaluation, 31 frames of three synthetic images and 40 real ultrasound images are used. In most of the experiments, the proposed filter shows a better performance as compared to the state-of-the-art filters in terms of the speckle region's signal-to-noise ratio and mean square error. It also shows a comparative performance for figure of merit and structural similarity measure index. Furthermore, in the subjective evaluation, performed by the expert radiologists, the proposed filter's outputs are preferred for the improved contrast and sharpness of the object boundaries. Hence, the proposed filtering framework is suitable to reduce the unwanted speckle and improve the quality of the ultrasound images.

Ultrasound speckle reduction based on fractional order differentiation.

PubMed

Shao, Dangguo; Zhou, Ting; Liu, Fan; Yi, Sanli; Xiang, Yan; Ma, Lei; Xiong, Xin; He, Jianfeng

2017-07-01

Ultrasound images show a granular pattern of noise known as speckle that diminishes their quality and results in difficulties in diagnosis. To preserve edges and features, this paper proposes a fractional differentiation-based image operator to reduce speckle in ultrasound. An image de-noising model based on fractional partial differential equations with balance relation between k (gradient modulus threshold that controls the conduction) and v (the order of fractional differentiation) was constructed by the effective combination of fractional calculus theory and a partial differential equation, and the numerical algorithm of it was achieved using a fractional differential mask operator. The proposed algorithm has better speckle reduction and structure preservation than the three existing methods [P-M model, the speckle reducing anisotropic diffusion (SRAD) technique, and the detail preserving anisotropic diffusion (DPAD) technique]. And it is significantly faster than bilateral filtering (BF) in producing virtually the same experimental results. Ultrasound phantom testing and in vivo imaging show that the proposed method can improve the quality of an ultrasound image in terms of tissue SNR, CNR, and FOM values.

Laser speckle-imaging of blood microcirculation in the brain cortex of laboratory rats in stress

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vilensky, M A; Semyachkina-Glushkovskaya, Oxana V; Timoshina, P A

2012-06-30

The results of experimental approbation of the method of laser full-field speckle-imaging for monitoring the changes in blood microcirculation state of the brain cortex of laboratory rats under the conditions of developing stroke and administration of vasodilating and vasoconstrictive agents are presented. The studies aimed at the choice of the optimal conditions of speckle-image formation and recording were performed and the software implementing an adaptive algorithm for processing the data of measurements was created. The transfer of laser radiation to the probed region of the biotissue was implemented by means of a silica-polymer optical fibre. The problems and prospects ofmore » speckle-imaging of cerebral microcirculation of blood in laboratory and clinical conditions are discussed.« less

Kitt Peak Speckle Interferometry of Close Visual Binary Stars (Abstract)

NASA Astrophysics Data System (ADS)

Gener, R.; Rowe, D.; Smith, T. C.; Teiche, A.; Harshaw, R.; Wallace, D.; Weise, E.; Wiley, E.; Boyce, G.; Boyce, P.; Branston, D.; Chaney, K.; Clark, R. K.; Estrada, C.; Estrada, R.; Frey, T.; Green, W. L.; Haurberg, N.; Jones, G.; Kenney, J.; Loftin, S.; McGieson, I.; Patel, R.; Plummer, J.; Ridgely, J.; Trueblood, M.; Westergren, D.; Wren, P.

2014-12-01

(Abstract only) Speckle interferometry can be used to overcome normal seeing limitations by taking many very short exposures at high magnification and analyzing the resulting speckles to obtain the position angles and separations of close binary stars. A typical speckle observation of a close binary consists of 1,000 images, each 20 milliseconds in duration. The images are stored as a multi-plane FITS cube. A portable speckle interferometry system that features an electron-multiplying CCD camera was used by the authors during two week-long observing runs on the 2.1-meter telescope at Kitt Peak National Observatory to obtain some 1,000 data cubes of close binaries selected from a dozen different research programs. Many hundreds of single reference stars were also observed and used in deconvolution to remove undesirable atmospheric and telescope optical effects. The database of well over one million images was reduced with the Speckle Interferometry Tool of platesolve3. A few sample results are provided. During the second Kitt Peak run, the McMath-Pierce 1.6- and 0.8-meter solar telescopes were evaluated for nighttime speckle interferometry, while the 0.8-meter Coude feed was used to obtain differential radial velocities of short arc binaries.

Kitt Peak Speckle Interferometry of Close Visual Binary Stars

NASA Astrophysics Data System (ADS)

Genet, Russell M.; Rowe, David; Smith, Thomas C.; Teiche, Alex; Harshaw, Richard; Wallace, Daniel; Weise, Eric; Wiley, Edward; Boyce, Grady; Boyce, Patrick; Branston, Detrick; Chaney, Kayla; Clark, R. Kent; Estrada, Chris; Frey, Thomas; Estrada, Reed; Green, Wayne; Haurberg, Nathalie; Kenney, John; Jones, Greg; Loftin, Sheri; McGieson, Izak; Patel, Rikita; Plummer, Josh; Ridgely, John; Trueblood, Mark; Westergren, Donald; Wren, Paul

2015-09-01

Speckle interferometry can be used to overcome normal seeing limitations by taking many very short exposures at high magnification and analyzing the resulting speckles to obtain the position angles and separations of close binary stars. A typical speckle observation of a close binary consists of 1000 images, each 20 milliseconds in duration. The images are stored as a multi-plane FITS cube. A portable speckle interferometry system that features an electronmultiplying CCD camera was used by the authors during two week-long observing runs on the 2.1-meter telescope at Kitt Peak National Observatory to obtain some 1000 data cubes of close binaries selected from a dozen different research programs. Many hundreds of single reference stars were also observed and used in deconvolution to remove undesirable atmospheric and telescope optical effects. The data base of well over one million images was reduced with the Speckle Interferometry Tool of PlateSolve 3. A few sample results are provided. During the second Kitt Peak run, the McMath-Pierce 1.6- and 0.8-meter solar telescopes were evaluated for nighttime speckle interferometry, while the 0.8-meter Coude feed was used to obtain differential radial velocities of short arc binaries.

Early monitoring of cerebral hypoperfusion in rats by laser speckle imaging and functional photoacoustic microscopy

NASA Astrophysics Data System (ADS)

Wang, Hui; Yang, Xiaoquan; Wang, Zhen; Deng, Zilin; Gong, Hui; Luo, Qingming

2012-06-01

Because cerebral hypoperfusion brings damage to the brain, prevention of cerebrovascular diseases correlative to hypoperfusion by studying animal models makes great sense. Since complicated cerebrovascular adaptive changes in hypoperfusion could not be revealed only by cerebral blood flow (CBF) velocity imaging, we performed multi-parameter imaging by combining laser speckle imaging and functional photoacoustic microscopy. The changes in CBF, hemoglobin oxygen saturation (SO2), and total hemoglobin concentration (HbT) in single blood vessels of ipsilateral cortex were observed during transient cerebral hypoperfusion by ligating the unilateral common carotid artery in rats. CBF, SO2, and HbT, respectively, decreased to 37+/-3%, 71+/-7.5%, and 92+/-1.3% of baseline in 6 s immediately after occlusion, and then recovered to 77+/-4.8%, 84+/-8%, and 96+/-2% of baseline in 60 s. These parameters presented the decrease with different degree and the following recovery over time after ligation, the recovery of SO2 lagged behind those of CBF and HbT, which had the similar response. The results demonstrated that complete monitoring of both cerebral hemodynamic response and oxygen metabolic changes occurred at the earliest period of cerebral hypoperfusion was possible by using the two image modalities with high temporal and spatial resolution.

High resolution solar observations in the context of space weather prediction

NASA Astrophysics Data System (ADS)

Yang, Guo

Space weather has a great impact on the Earth and human life. It is important to study and monitor active regions on the solar surface and ultimately to predict space weather based on the Sun's activity. In this study, a system that uses the full power of speckle masking imaging by parallel processing to obtain high-spatial resolution images of the solar surface in near real-time has been developed and built. The application of this system greatly improves the ability to monitor the evolution of solar active regions and to predict the adverse effects of space weather. The data obtained by this system have also been used to study fine structures on the solar surface and their effects on the upper solar atmosphere. A solar active region has been studied using high resolution data obtained by speckle masking imaging. Evolution of a pore in an active region presented. Formation of a rudimentary penumbra is studied. The effects of the change of the magnetic fields on the upper level atmosphere is discussed. Coronal Mass Ejections (CMEs) have a great impact on space weather. To study the relationship between CMEs and filament disappearance, a list of 431 filament and prominence disappearance events has been compiled. Comparison of this list with CME data obtained by satellite has shown that most filament disappearances seem to have no corresponding CME events. Even for the limb events, only thirty percent of filament disappearances are associated with CMEs. A CME event that was observed on March 20, 2000 has been studied in detail. This event did not show the three-parts structure of typical CMEs. The kinematical and morphological properties of this event were examined.

Expanding applications, accuracy, and interpretation of laser speckle contrast imaging of cerebral blood flow

PubMed Central

Kazmi, S M Shams; Richards, Lisa M; Schrandt, Christian J; Davis, Mitchell A; Dunn, Andrew K

2015-01-01

Laser speckle contrast imaging (LSCI) provides a rapid characterization of cortical flow dynamics for functional monitoring of the microcirculation. The technique stems from interactions of laser light with moving particles. These interactions encode the encountered Doppler phenomena within a random interference pattern imaged in widefield, known as laser speckle. Studies of neurovascular function and coupling with LSCI have benefited from the real-time characterization of functional dynamics in the laboratory setting through quantification of perfusion dynamics. While the technique has largely been relegated to acute small animal imaging, its scalability is being assessed and characterized for both chronic and clinical neurovascular imaging. PMID:25944593

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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.

Three Dimensional Imaging with Multiple Wavelength Speckle Interferometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

2014-05-28

We present the design, modeling, construction, and results of a three-dimensional imager based upon multiple-wavelength speckle interferometry. A surface under test is illuminated with tunable laser light in a Michelson interferometer configuration while a speckled image is acquired at each laser frequency step. The resulting hypercube is Fourier transformed in the frequency dimension and the beat frequencies that result map the relative offsets of surface features. Synthetic wavelengths resulting from the laser tuning can probe features ranging from 18 microns to hundreds of millimeters. Three dimensional images will be presented along with modeling results.

Speckle noise reduction in digital holography by slightly rotating the object

NASA Astrophysics Data System (ADS)

Herrera-Ramirez, Jorge; Hincapie-Zuluaga, Diego Andrés; Garcia-Sucerquia, Jorge

2016-12-01

This work shows the realization of speckle reduction in the numerical reconstruction of digitally recorded holograms by the superposition of multiple slightly rotated digital holographic images of the object. The superposition of T uncorrelated holographic images reduces the contrast of the speckle noise of the image following the expected 1/√{T} law. The effect of the method on the borders of the resulting image is evaluated by quantifying the utilization of the dynamic range or the contrast between the white and black areas of a regular die. Experimental results validate the feasibility of the proposed method.

Quantitative, depth-resolved determination of particle motion using multi-exposure, spatial frequency domain laser speckle imaging.

PubMed

Rice, Tyler B; Kwan, Elliott; Hayakawa, Carole K; Durkin, Anthony J; Choi, Bernard; Tromberg, Bruce J

2013-01-01

Laser Speckle Imaging (LSI) is a simple, noninvasive technique for rapid imaging of particle motion in scattering media such as biological tissue. LSI is generally used to derive a qualitative index of relative blood flow due to unknown impact from several variables that affect speckle contrast. These variables may include optical absorption and scattering coefficients, multi-layer dynamics including static, non-ergodic regions, and systematic effects such as laser coherence length. In order to account for these effects and move toward quantitative, depth-resolved LSI, we have developed a method that combines Monte Carlo modeling, multi-exposure speckle imaging (MESI), spatial frequency domain imaging (SFDI), and careful instrument calibration. Monte Carlo models were used to generate total and layer-specific fractional momentum transfer distributions. This information was used to predict speckle contrast as a function of exposure time, spatial frequency, layer thickness, and layer dynamics. To verify with experimental data, controlled phantom experiments with characteristic tissue optical properties were performed using a structured light speckle imaging system. Three main geometries were explored: 1) diffusive dynamic layer beneath a static layer, 2) static layer beneath a diffuse dynamic layer, and 3) directed flow (tube) submerged in a dynamic scattering layer. Data fits were performed using the Monte Carlo model, which accurately reconstructed the type of particle flow (diffusive or directed) in each layer, the layer thickness, and absolute flow speeds to within 15% or better.

Speckle imaging techniques of the turbulence degraded images

NASA Astrophysics Data System (ADS)

Liu, Jin; Huang, Zongfu; Mao, Hongjun; Liang, Yonghui

2018-03-01

We propose a speckle imaging algorithm in which we use the improved form of spectral ratio to obtain the Fried parameter, we also use a filter to reduce the high frequency noise effects. Our algorithm makes an improvement in the quality of the reconstructed images. The performance is illustrated by computer simulations.

Interference in astronomical speckle patterns

NASA Technical Reports Server (NTRS)

Breckinridge, J. B.

1976-01-01

Astronomical speckle patterns are examined in an atmospheric-optics context in order to determine what kind of image quality is to be expected from several different imaging techniques. The model used to describe the instantaneous complex field distribution across the pupil of a large telescope regards the pupil as a deep phase grating with a periodicity given by the size of the cell of uniform phase or the refractive index structure function. This model is used along with an empirical formula derived purely from the physical appearance of the speckle patterns to discuss the orders of interference in astronomical speckle patterns.

Optimization of camera exposure durations for multi-exposure speckle imaging of the microcirculation

PubMed Central

Kazmi, S. M. Shams; Balial, Satyajit; Dunn, Andrew K.

2014-01-01

Improved Laser Speckle Contrast Imaging (LSCI) blood flow analyses that incorporate inverse models of the underlying laser-tissue interaction have been used to develop more quantitative implementations of speckle flowmetry such as Multi-Exposure Speckle Imaging (MESI). In this paper, we determine the optimal camera exposure durations required for obtaining flow information with comparable accuracy with the prevailing MESI implementation utilized in recent in vivo rodent studies. A looping leave-one-out (LOO) algorithm was used to identify exposure subsets which were analyzed for accuracy against flows obtained from analysis with the original full exposure set over 9 animals comprising n = 314 regional flow measurements. From the 15 original exposures, 6 exposures were found using the LOO process to provide comparable accuracy, defined as being no more than 10% deviant, with the original flow measurements. The optimal subset of exposures provides a basis set of camera durations for speckle flowmetry studies of the microcirculation and confers a two-fold faster acquisition rate and a 28% reduction in processing time without sacrificing accuracy. Additionally, the optimization process can be used to identify further reductions in the exposure subsets for tailoring imaging over less expansive flow distributions to enable even faster imaging. PMID:25071956

Relationship between analysis of laser speckle image and Knoop hardness on softening enamel.

PubMed

Koshoji, Nelson H; Prates, Renato A; Bussadori, Sandra K; Bortoletto, Carolina C; de Miranda Junior, Walter G; Librantz, André F H; Leal, Cintia Raquel Lima; Oliveira, Marcelo T; Deana, Alessandro M

2016-09-01

In this study is presented the correlation between laser speckle images and enamel hardness loss. In order to shift the enamel hardness, a dental demineralization model was applied to 32 samples of vestibular bovine teeth. After they were cleaned, cut and polished, the samples were divided into 4 groups and immersed in 30ml of a cola-based soft drink for 10, 20, 30 and 40min twice a day for 7 consecutive days with half the surface protected by two layers of nail polish. Each sample was analyzed by Knoop hardness and laser speckle imaging. Pearson's correlation analysis demonstrated that the laser speckle image technique presents a strong correlation with the hardness loss of the enamel (r=0.7085, p<0.0001). This finding is corroborated by Blend & Altman analysis, in which the data presented a constant behavior throughout the whole interval. For both analyses, more than 95% of the data is within the confidence interval, as expected. This work demonstrates, for the first time to our knowledge, an empirical model for correlating laser speckle images with the loss of tooth enamel hardness. Copyright © 2016. Published by Elsevier B.V.

Measurement of eye aberrations in a speckle field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Larichev, A V; Ivanov, P V; Iroshnikov, N G

2001-12-31

The influence of speckles on the performance of a Shark-Hartmann wavefront sensor is investigated in the eye aberration studies. The dependence of the phase distortion measurement error on the characteristic speckle size is determined experimentally. Scanning of the reference source was used to suppress the speckle structure of the laser beam scattered by the retina. The technique developed by us made it possible to study the time dependence of the human eye aberrations with a resolution of 30 ms. (laser applications and other topics in quantum electronics)

Artificial Incoherent Speckles Enable Precision Astrometry and Photometry in High-contrast Imaging

NASA Astrophysics Data System (ADS)

Jovanovic, N.; Guyon, O.; Martinache, F.; Pathak, P.; Hagelberg, J.; Kudo, T.

2015-11-01

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 from 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 of the Subaru Coronagraphic Extreme Adaptive Optics system to generate a field of speckles for the purposes of calibration. Speckles can be placed up to 22.5 λ/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 π, during a long science integration renders these speckles effectively incoherent with the underlying halo. We quantitatively show for the first time that this incoherence, in turn, increases the robustness and stability of the adaptive speckles, which will improve the precision of astrometric and photometric calibration procedures. This technique will be valuable for high-contrast imaging observations with imagers and integral field spectrographs alike.

Development of a multi-exposure speckle imaging for mice brain imaging

NASA Astrophysics Data System (ADS)

Soleimanzad, Haleh; Gurden, Hirac; Pain, Frédéric

2017-02-01

In the last decade, Laser Speckle Contrast Imaging (LSCI) has been proposed and validated for imaging cerebral blood flow at the rodent brain surface in vivo. The technique relies on the calculation of the spatial speckle contrast, which is related to the velocity of scatterers (red blood cells). The implementation of the technique requires a partial craniotomy so that the brain tissues of interest can be illuminated with a laser diode. However, the studies of changes in the microcirculation during disease progression or treatment require longitudinal studies (i.e. imaging is done repeatedly over weeks or even months). Practically, the less invasive way to obtain such data is to image through the thinned skull without a craniotomy. However the presence of static scatterers (skull) will affect the speckle calculation and produce a bias in the estimation of the microcirculation changes. An extension to LSCI, termed Multi-Exposure Speckle Imaging (MESI) was proposed and validated a few years ago that address these limitations. It relies on a model of the speckle contrast as a function of the exposure time and the proportion of static scatterers. Here, we used MESI with the aim of repeatedly imaging the olfactory bulb of mice models of obesity. First, we have developed a MESI set up which was characterized on microfluidic flow phantoms with different flow-rates and channel diameters to simulate blood flow in animal model characteristics. Second, we show that MESI can discriminate flows in the presence of static scatterers and it can measure flow changes consistently. Finally we provide an in vivo validation of the technique in mice with and without a craniotomy.

High-Resolution Surface Reconstruction from Imagery for Close Range Cultural Heritage Applications

NASA Astrophysics Data System (ADS)

Wenzel, K.; Abdel-Wahab, M.; Cefalu, A.; Fritsch, D.

2012-07-01

The recording of high resolution point clouds with sub-mm resolution is a demanding and cost intensive task, especially with current equipment like handheld laser scanners. We present an image based approached, where techniques of image matching and dense surface reconstruction are combined with a compact and affordable rig of off-the-shelf industry cameras. Such cameras provide high spatial resolution with low radiometric noise, which enables a one-shot solution and thus an efficient data acquisition while satisfying high accuracy requirements. However, the largest drawback of image based solutions is often the acquisition of surfaces with low texture where the image matching process might fail. Thus, an additional structured light projector is employed, represented here by the pseudo-random pattern projector of the Microsoft Kinect. Its strong infrared-laser projects speckles of different sizes. By using dense image matching techniques on the acquired images, a 3D point can be derived for almost each pixel. The use of multiple cameras enables the acquisition of a high resolution point cloud with high accuracy for each shot. For the proposed system up to 3.5 Mio. 3D points with sub-mm accuracy can be derived per shot. The registration of multiple shots is performed by Structure and Motion reconstruction techniques, where feature points are used to derive the camera positions and rotations automatically without initial information.

Dynamic imaging of cerebral blood flow in rat reperfused mini-stroke model using laser speckle temporal contrast analysis

NASA Astrophysics Data System (ADS)

Wang, Zhen; Luo, Weihua; Li, Pengcheng; Zeng, Shaoqun; Luo, Qingming

2007-05-01

Laser speckle temporal contrast analysis (LSTCA) was used to image the cerebral blood flow (CBF) of ischemic area in reperfused mini-stroke model in rats. Focal cortical ischemia in male Sprague-Dawley rats (n=20) was induced by deliberate ligation of multiple branches of the middle cerebral artery (MCA) together with a nylon ring and the dura. LSTCA was used to monitor the spatio-temporal characteristics of cerebral blood flow dynamics in the rat somatosensory cortex in the ischemic and reperfused stages. The infarction volume was measured by 2, 3, 5- triphenyltetrazolium chloride (TTC) staining 24 hours after reperfusion. The distribution of changes in cerebral blood flow which outlined by the laser speckle imaging represented the relative CBF gradient (21.98+/-1.96%, 67.2+/-1.67 %, 107.24+/-4.71 % of the baseline) from ischemic core, penumbra zone to normal tissue immediately after cortical ischemia, in which a central ischemic core had little or no perfusion surrounded by a penumbral region with reduced perfusion, in addition, we had shown the existence of a surrounding region of hyperemic tissue; Thereafter a postrecanalization hyperperfusion occurred in the same infarct core since 24 hours after reperfusion (242.62+/-18.52% of the baseline). Histology of the ischemic regions at 24 hours after reperfusion revealed small focal infarcts that were typically 3~4 mm in diameter, approximately equal to the nylon ring in size and position and essentially accordant with the spatial distribution of the ischemic cortex with below 30% residual CBF of the pre-ischemic baseline. It was demonstrated that this technique of LSTCA was easy to implement and availably used to image the spatial and temporal evolution of CBF changes with high resolution in rat reperfused mini-stroke model.

Speckle: Friend or foe?

NASA Astrophysics Data System (ADS)

Goodman, Joseph W.

2013-05-01

Speckle appears whenever coherent radiation of any kind is used. We review here the basic properties of speckle, the negative effects it has on imaging systems of various kinds, and the positive benefits it offers in certain nondestructive testing and metrology problems.

The NN-explore Exoplanet Stellar Speckle Imager: Instrument Description and Preliminary Results

NASA Astrophysics Data System (ADS)

Scott, Nicholas J.; Howell, Steve B.; Horch, Elliott P.; Everett, Mark E.

2018-05-01

A new speckle and wide-field imaging instrument for the WIYN telescope called NN-EXPLORE Exoplanet Stellar Speckle Imager (NESSI) is described. NESSI offers simultaneous two-color diffraction-limited imaging and wide-field traditional imaging for validation and characterization of transit and precision RV exoplanet studies. Many exoplanet targets will come from the NASA K2 and Transiting Exoplanet Survey Satellite (TESS) missions. NESSI is capable of resolving close binaries at sub-arcsecond separations down to the diffraction limit and >6 mag contrast difference in the visible band on targets as faint as 14th mag. Preliminary results from the instrument commissioning at WIYN and demonstrations of the instrument’s capabilities are presented.

Laser speckle imaging to improve clinical outcomes for patients with trigeminal neuralgia undergoing radiofrequency thermocoagulation.

PubMed

Ringkamp, Matthias; Wooten, Matthew; Carson, Benjamin S; Lim, Michael; Hartke, Timothy; Guarnieri, Michael

2016-02-01

Percutaneous treatments for trigeminal neuralgia are safe, simple, and effective for achieving good pain control. Procedural risks could be minimized by using noninvasive imaging techniques to improve the placement of the radiofrequency thermocoagulation probe into the trigeminal ganglion. Positioning of a probe is crucial to maximize pain relief and to minimize unwanted side effects, such as denervation in unaffected areas. This investigation examined the use of laser speckle imaging during probe placement in an animal model. This preclinical safety study used nonhuman primates, Macaca nemestrina (pigtail monkeys), to examine whether real-time imaging of blood flow in the face during the positioning of a coagulation probe could monitor the location and guide the positioning of the probe within the trigeminal ganglion. Data from 6 experiments in 3 pigtail monkeys support the hypothesis that laser imaging is safe and improves the accuracy of probe placement. Noninvasive laser speckle imaging can be performed safely in nonhuman primates. Because improved probe placement may reduce morbidity associated with percutaneous rhizotomies, efficacy trials of laser speckle imaging should be conducted in humans.

A Pixel Correlation Technique for Smaller Telescopes to Measure Doubles

NASA Astrophysics Data System (ADS)

Wiley, E. O.

2013-04-01

Pixel correlation uses the same reduction techniques as speckle imaging but relies on autocorrelation among captured pixel hits rather than true speckles. A video camera operating at speeds (8-66 milliseconds) similar to lucky imaging to capture 400-1,000 video frames. The AVI files are converted to bitmap images and analyzed using the interferometric algorithms in REDUC using all frames. This results in a series of corellograms from which theta and rho can be measured. Results using a 20 cm (8") Dall-Kirkham working at f22.5 are presented for doubles with separations between 1" to 5.7" under average seeing conditions. I conclude that this form of visualizing and analyzing visual double stars is a viable alternative to lucky imaging that can be employed by telescopes that are too small in aperture to capture a sufficient number of speckles for true speckle interferometry.

Optical imaging through dynamic turbid media using the Fourier-domain shower-curtain effect

PubMed Central

Edrei, Eitan; Scarcelli, Giuliano

2016-01-01

Several phenomena have been recently exploited to circumvent scattering and have succeeded in imaging or focusing light through turbid layers. However, the requirement for the turbid medium to be steady during the imaging process remains a fundamental limitation of these methods. Here we introduce an optical imaging modality that overcomes this challenge by taking advantage of the so-called shower-curtain effect, adapted to the spatial-frequency domain via speckle correlography. We present high resolution imaging of objects hidden behind millimeter-thick tissue or dense lens cataracts. We demonstrate our imaging technique to be insensitive to rapid medium movements (> 5 m/s) beyond any biologically-relevant motion. Furthermore, we show this method can be extended to several contrast mechanisms and imaging configurations. PMID:27347498

Half-quadratic variational regularization methods for speckle-suppression and edge-enhancement in SAR complex image

NASA Astrophysics Data System (ADS)

Zhao, Xia; Wang, Guang-xin

2008-12-01

Synthetic aperture radar (SAR) is an active remote sensing sensor. It is a coherent imaging system, the speckle is its inherent default, which affects badly the interpretation and recognition of the SAR targets. Conventional methods of removing the speckle is studied usually in real SAR image, which reduce the edges of the images at the same time as depressing the speckle. Morever, Conventional methods lost the information about images phase. Removing the speckle and enhancing the target and edge simultaneously are still a puzzle. To suppress the spckle and enhance the targets and the edges simultaneously, a half-quadratic variational regularization method in complex SAR image is presented, which is based on the prior knowledge of the targets and the edge. Due to the non-quadratic and non- convex quality and the complexity of the cost function, a half-quadratic variational regularization variation is used to construct a new cost function,which is solved by alternate optimization. In the proposed scheme, the construction of the model, the solution of the model and the selection of the model peremeters are studied carefully. In the end, we validate the method using the real SAR data.Theoretic analysis and the experimental results illustrate the the feasibility of the proposed method. Further more, the proposed method can preserve the information about images phase.

Airplane wing deformation and flight flutter detection method by using three-dimensional speckle image correlation technology.

PubMed

Wu, Jun; Yu, Zhijing; Wang, Tao; Zhuge, Jingchang; Ji, Yue; Xue, Bin

2017-06-01

Airplane wing deformation is an important element of aerodynamic characteristics, structure design, and fatigue analysis for aircraft manufacturing, as well as a main test content of certification regarding flutter for airplanes. This paper presents a novel real-time detection method for wing deformation and flight flutter detection by using three-dimensional speckle image correlation technology. Speckle patterns whose positions are determined through the vibration characteristic of the aircraft are coated on the wing; then the speckle patterns are imaged by CCD cameras which are mounted inside the aircraft cabin. In order to reduce the computation, a matching technique based on Geodetic Systems Incorporated coded points combined with the classical epipolar constraint is proposed, and a displacement vector map for the aircraft wing can be obtained through comparing the coordinates of speckle points before and after deformation. Finally, verification experiments containing static and dynamic tests by using an aircraft wing model demonstrate the accuracy and effectiveness of the proposed method.

Laser speckle contrast imaging: monitoring blood flow dynamics and vascular structure of photodynamic therapy

NASA Astrophysics Data System (ADS)

Liu, Qian; Zhou, Sibo; Zhang, Zhihong; Luo, Qingming

2005-01-01

Laser speckle contrast imaging (LSCI) is a noninvasive optical image technique that has been developed for imaging in vivo blood flow dynamics and vascular structure with high spatial and temporal resolution. It records the full-field spatio-temporal characteristics of microcirculation in real time without the need of laser beam flying. In this paper applications of this technique for monitoring changes of blood flow and vascular structure following photodynamic therapy (PDT) in vivo model were demonstrated. In this study, an in vivo model of chick chorioallantoic membrane (CAM) at embryo age (EA) of 10~13 days, was observed following PDT irradiated by a power tunable laser diode (λ = 656.5 nm). Laser intensity incident on the treatment site was maintained at 40 mW/cm2 and photosensitizer of Pyropheophorbide Acid (Pyro-Acid) was used. CAM was adopted in PDT since it is a transparent in vivo model and the irradiated lights of laser can penetrate tumor with greater depth. The laser delivered through fiber bundle to the treatment site in PDT also acted as the coherent light source of LSCI. This study shows that LSCI can be used to assess the efficacy of peripheral vessels damage of tumor in PDT by monitoring changes of blood flow and vascular structure.

Vessel packaging effect in laser speckle contrast imaging and laser Doppler imaging.

PubMed

Fredriksson, Ingemar; Larsson, Marcus

2017-10-01

Laser speckle-based techniques are frequently used to assess microcirculatory blood flow. Perfusion estimates are calculated either by analyzing the speckle fluctuations over time as in laser Doppler flowmetry (LDF), or by analyzing the speckle contrast as in laser speckle contrast imaging (LSCI). The perfusion estimates depend on the amount of blood and its speed distribution. However, the perfusion estimates are commonly given in arbitrary units as they are nonlinear and depend on the magnitude and the spatial distribution of the optical properties in the tissue under investigation. We describe how the spatial confinement of blood to vessels, called the vessel packaging effect, can be modeled in LDF and LSCI, which affect the Doppler power spectra and speckle contrast, and the underlying bio-optical mechanisms for these effects. As an example, the perfusion estimate is reduced by 25% for LDF and often more than 50% for LSCI when blood is located in vessels with an average diameter of 40  μm, instead of being homogeneously distributed within the tissue. This significant effect can be compensated for only with knowledge of the average diameter of the vessels in the tissue. (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Coherence switching of a vertical-cavity semiconductor-laser for multimode biomedical imaging (Conference Presentation)

NASA Astrophysics Data System (ADS)

Cao, Hui; Knitter, Sebastian; Liu, Changgeng; Redding, Brandon; Khokha, Mustafa Kezar; Choma, Michael Andrew

2017-02-01

Speckle formation is a limiting factor when using coherent sources for imaging and sensing, but can provide useful information about the motion of an object. Illumination sources with tunable spatial coherence are therefore desirable as they can offer both speckled and speckle-free images. Efficient methods of coherence switching have been achieved with a solid-state degenerate laser, and here we demonstrate a semiconductor-based degenerate laser system that can be switched between a large number of mutually incoherent spatial modes and few-mode operation. Our system is designed around a semiconductor gain element, and overcomes barriers presented by previous low spatial coherence lasers. The gain medium is an electrically-pumped vertical external cavity surface emitting laser (VECSEL) with a large active area. The use of a degenerate external cavity enables either distributing the laser emission over a large ( 1000) number of mutually incoherent spatial modes or concentrating emission to few modes by using a pinhole in the Fourier plane of the self-imaging cavity. To demonstrate the unique potential of spatial coherence switching for multimodal biomedical imaging, we use both low and high spatial coherence light generated by our VECSEL-based degenerate laser for imaging embryo heart function in Xenopus, an important animal model of heart disease. The low-coherence illumination is used for high-speed (100 frames per second) speckle-free imaging of dynamic heart structure, while the high-coherence emission is used for laser speckle contrast imaging of the blood flow.

Image Quality in High-resolution and High-cadence Solar Imaging

NASA Astrophysics Data System (ADS)

Denker, C.; Dineva, E.; Balthasar, H.; Verma, M.; Kuckein, C.; Diercke, A.; González Manrique, S. J.

2018-03-01

Broad-band imaging and even imaging with a moderate bandpass (about 1 nm) provides a photon-rich environment, where frame selection (lucky imaging) becomes a helpful tool in image restoration, allowing us to perform a cost-benefit analysis on how to design observing sequences for imaging with high spatial resolution in combination with real-time correction provided by an adaptive optics (AO) system. This study presents high-cadence (160 Hz) G-band and blue continuum image sequences obtained with the High-resolution Fast Imager (HiFI) at the 1.5-meter GREGOR solar telescope, where the speckle-masking technique is used to restore images with nearly diffraction-limited resolution. The HiFI employs two synchronized large-format and high-cadence sCMOS detectors. The median filter gradient similarity (MFGS) image-quality metric is applied, among others, to AO-corrected image sequences of a pore and a small sunspot observed on 2017 June 4 and 5. A small region of interest, which was selected for fast-imaging performance, covered these contrast-rich features and their neighborhood, which were part of Active Region NOAA 12661. Modifications of the MFGS algorithm uncover the field- and structure-dependency of this image-quality metric. However, MFGS still remains a good choice for determining image quality without a priori knowledge, which is an important characteristic when classifying the huge number of high-resolution images contained in data archives. In addition, this investigation demonstrates that a fast cadence and millisecond exposure times are still insufficient to reach the coherence time of daytime seeing. Nonetheless, the analysis shows that data acquisition rates exceeding 50 Hz are required to capture a substantial fraction of the best seeing moments, significantly boosting the performance of post-facto image restoration.

Improving high resolution retinal image quality using speckle illumination HiLo imaging

PubMed Central

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 illumination microscopes and produce pseudo-confocal images with significantly improved image quality. In this work, we adopted the HiLo technique to a flood AO ophthalmoscope and performed AO imaging in both (physical) model and live rat eyes. The improvement in image quality from HiLo imaging is shown both qualitatively and quantitatively by using spatial spectral analysis. PMID:25136486

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

PubMed

Zhou, Xiaolin; Bedggood, Phillip; Metha, Andrew

2014-08-01

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 illumination microscopes and produce pseudo-confocal images with significantly improved image quality. In this work, we adopted the HiLo technique to a flood AO ophthalmoscope and performed AO imaging in both (physical) model and live rat eyes. The improvement in image quality from HiLo imaging is shown both qualitatively and quantitatively by using spatial spectral analysis.

Phase object retrieval through scattering medium

NASA Astrophysics Data System (ADS)

Zhao, Ming; Zhao, Meijing; Wu, Houde; Xu, Wenhai

2018-05-01

Optical imaging through a scattering medium has been an interesting and important research topic, especially in the field of biomedical imaging. However, it is still a challenging task due to strong scattering. This paper proposes to recover the phase object behind the scattering medium from one single-shot speckle intensity image using calibrated transmission matrices (TMs). We construct the forward model as a non-linear mapping, since the intensity image loses the phase information, and then a generalized phase retrieval algorithm is employed to recover the hidden object. Moreover, we show that a phase object can be reconstructed with a small portion of the speckle image captured by the camera. The simulation is performed to demonstrate our scheme and test its performance. Finally, a real experiment is set up, we measure the TMs from the scattering medium, and then use it to reconstruct the hidden object. We show that a phase object of size 32 × 32 is retrieved from 150 × 150 speckle grains, which is only 1/50 of the speckles area. We believe our proposed method can benefit the community of imaging through the scattering medium.

A spatially-variant deconvolution method based on total variation for optical coherence tomography images

NASA Astrophysics Data System (ADS)

Almasganj, Mohammad; Adabi, Saba; Fatemizadeh, Emad; Xu, Qiuyun; Sadeghi, Hamid; Daveluy, Steven; Nasiriavanaki, Mohammadreza

2017-03-01

Optical Coherence Tomography (OCT) has a great potential to elicit clinically useful information from tissues due to its high axial and transversal resolution. In practice, an OCT setup cannot reach to its theoretical resolution due to imperfections of its components, which make its images blurry. The blurriness is different alongside regions of image; thus, they cannot be modeled by a unique point spread function (PSF). In this paper, we investigate the use of solid phantoms to estimate the PSF of each sub-region of imaging system. We then utilize Lucy-Richardson, Hybr and total variation (TV) based iterative deconvolution methods for mitigating occurred spatially variant blurriness. It is shown that the TV based method will suppress the so-called speckle noise in OCT images better than the two other approaches. The performance of proposed algorithm is tested on various samples, including several skin tissues besides the test image blurred with synthetic PSF-map, demonstrating qualitatively and quantitatively the advantage of TV based deconvolution method using spatially-variant PSF for enhancing image quality.

Application of full field optical studies for pulsatile flow in a carotid artery phantom

PubMed Central

Nemati, M.; Loozen, G. B.; van der Wekken, N.; van de Belt, G.; Urbach, H. P.; Bhattacharya, N.; Kenjeres, S.

2015-01-01

A preliminary comparative measurement between particle imaging velocimetry (PIV) and laser speckle contrast analysis (LASCA) to study pulsatile flow using ventricular assist device in a patient-specific carotid artery phantom is reported. These full-field optical techniques have both been used to study flow and extract complementary parameters. We use the high spatial resolution of PIV to generate a full velocity map of the flow field and the high temporal resolution of LASCA to extract the detailed frequency spectrum of the fluid pulses. Using this combination of techniques a complete study of complex pulsatile flow in an intricate flow network can be studied. PMID:26504652

Multimodal ophthalmic imaging using swept source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography

NASA Astrophysics Data System (ADS)

Malone, Joseph D.; El-Haddad, Mohamed T.; Tye, Logan A.; Majeau, Lucas; Godbout, Nicolas; Rollins, Andrew M.; Boudoux, Caroline; Tao, Yuankai K.

2016-03-01

Scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT) benefit clinical diagnostic imaging in ophthalmology by enabling in vivo noninvasive en face and volumetric visualization of retinal structures, respectively. Spectrally encoding methods enable confocal imaging through fiber optics and reduces system complexity. Previous applications in ophthalmic imaging include spectrally encoded confocal scanning laser ophthalmoscopy (SECSLO) and a combined SECSLO-OCT system for image guidance, tracking, and registration. However, spectrally encoded imaging suffers from speckle noise because each spectrally encoded channel is effectively monochromatic. Here, we demonstrate in vivo human retinal imaging using a swept source spectrally encoded scanning laser ophthalmoscope and OCT (SSSESLO- OCT) at 1060 nm. SS-SESLO-OCT uses a shared 100 kHz Axsun swept source, shared scanner and imaging optics, and are detected simultaneously on a shared, dual channel high-speed digitizer. SESLO illumination and detection was performed using the single mode core and multimode inner cladding of a double clad fiber coupler, respectively, to preserve lateral resolution while improving collection efficiency and reducing speckle contrast at the expense of confocality. Concurrent en face SESLO and cross-sectional OCT images were acquired with 1376 x 500 pixels at 200 frames-per-second. Our system design is compact and uses a shared light source, imaging optics, and digitizer, which reduces overall system complexity and ensures inherent co-registration between SESLO and OCT FOVs. En face SESLO images acquired concurrent with OCT cross-sections enables lateral motion tracking and three-dimensional volume registration with broad applications in multivolume OCT averaging, image mosaicking, and intraoperative instrument tracking.

Speckle reduction in laser projection using a dynamic deformable mirror.

PubMed

Tran, Thi-Kim-Trinh; Chen, Xuyuan; Svensen, Øyvind; Akram, Muhammad Nadeem

2014-05-05

Despite of much effort and significant progress in recent years, speckle removal is still a challenge for laser projection technology. In this paper, speckle reduction by dynamic deformable mirror was investigated. Time varying independent speckle patterns were generated due to the angle diversity introduced by the dynamic mirror, and these speckle patterns were averaged out by the camera or human eyes, thus reducing speckle contrast in the final image. The speckle reduction by the wavelength diversity of the lasers was also studied. Both broadband lasers and narrowband laser were used for experiment. It is experimentally shown that speckle suppression can be attained by the widening of the spectrum of the lasers. Lower speckle contrast reduction was attained by the wavelength diversity for narrowband laser compared to the broadband lasers. This method of speckle reduction is suitable in laser projectors for wide screen applications where high power laser illumination is needed.

Report on the ESO Workshop ''Astronomy at High Angular Resolution''

NASA Astrophysics Data System (ADS)

Boffin, H.; Schmidtobreick, L.; Hussain, G.; Berger, J.-Ph.

2015-03-01

A workshop took place in Brussels in 2000 on astrotomography, a generic term for indirect mapping techniques that can be applied to a huge variety of astrophysical systems, ranging from planets, single stars and binaries to active galactic nuclei. It appeared to be timely to revisit the topic given the many past, recent and forthcoming improvements in telescopes and instrumentation. We therefore decided to repeat the astrotomography workshop, but to put it into the much broader context of high angular resolution astronomy. Many techniques, from lucky and speckle imaging, adaptive optics to interferometry, are now widely employed to achieve high angular resolution and they have led to an amazing number of new discoveries. A summary of the workshop themes is presented.

The usability of the optical parametric amplification of light for high-angular-resolution imaging and fast astrometry

NASA Astrophysics Data System (ADS)

Kurek, A. R.; Stachowski, A.; Banaszek, K.; Pollo, A.

2018-05-01

High-angular-resolution imaging is crucial for many applications in modern astronomy and astrophysics. The fundamental diffraction limit constrains the resolving power of both ground-based and spaceborne telescopes. The recent idea of a quantum telescope based on the optical parametric amplification (OPA) of light aims to bypass this limit for the imaging of extended sources by an order of magnitude or more. We present an updated scheme of an OPA-based device and a more accurate model of the signal amplification by such a device. The semiclassical model that we present predicts that the noise in such a system will form so-called light speckles as a result of light interference in the optical path. Based on this model, we analysed the efficiency of OPA in increasing the angular resolution of the imaging of extended targets and the precise localization of a distant point source. According to our new model, OPA offers a gain in resolved imaging in comparison to classical optics. For a given time-span, we found that OPA can be more efficient in localizing a single distant point source than classical telescopes.

Iterative Self-Dual Reconstruction on Radar Image Recovery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martins, Charles; Medeiros, Fatima; Ushizima, Daniela

2010-05-21

Imaging systems as ultrasound, sonar, laser and synthetic aperture radar (SAR) are subjected to speckle noise during image acquisition. Before analyzing these images, it is often necessary to remove the speckle noise using filters. We combine properties of two mathematical morphology filters with speckle statistics to propose a signal-dependent noise filter to multiplicative noise. We describe a multiscale scheme that preserves sharp edges while it smooths homogeneous areas, by combining local statistics with two mathematical morphology filters: the alternating sequential and the self-dual reconstruction algorithms. The experimental results show that the proposed approach is less sensitive to varying window sizesmore » when applied to simulated and real SAR images in comparison with standard filters.« less

The Speckle Toolbox: A Powerful Data Reduction Tool for CCD Astrometry

NASA Astrophysics Data System (ADS)

Harshaw, Richard; Rowe, David; Genet, Russell

2017-01-01

Recent advances in high-speed low-noise CCD and CMOS cameras, coupled with breakthroughs in data reduction software that runs on desktop PCs, has opened the domain of speckle interferometry and high-accuracy CCD measurements of double stars to amateurs, allowing them to do useful science of high quality. This paper describes how to use a speckle interferometry reduction program, the Speckle Tool Box (STB), to achieve this level of result. For over a year the author (Harshaw) has been using STB (and its predecessor, Plate Solve 3) to obtain measurements of double stars based on CCD camera technology for pairs that are either too wide (the stars not sharing the same isoplanatic patch, roughly 5 arc-seconds in diameter) or too faint to image in the coherence time required for speckle (usually under 40ms). This same approach - using speckle reduction software to measure CCD pairs with greater accuracy than possible with lucky imaging - has been used, it turns out, for several years by the U. S. Naval Observatory.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zdora, Marie-Christine, E-mail: marie-christine.zdora@diamond.ac.uk; Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE; Department of Physics & Astronomy, University College London, London WC1E 6BT

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 specklemore » tracking. This study is particularly important for further implementations and developments of coherent speckle-based techniques at laboratory x-ray sources.« less

Differential speckle and wide-field imaging for the Gemini-North and WIYN telescopes

NASA Astrophysics Data System (ADS)

Scott, Nicholas J.; Howell, Steve B.; Horch, Elliott P.

2016-07-01

Two new instruments are currently being built for the Gemini-North and WIYN telescopes. They are based on the existing DSSI (Differential Speckle Survey Instrument), but the new dual-channel instruments will have both speckle and "wide-field" imaging capabilities. Nearly identical copies of the instrument will be installed as a public access permanent loan at the Gemini-N and WIYN telescopes. Many exoplanet targets will come from the NASA K2 and TESS missions. The faint limiting magnitude, for speckle observations, will remain around 16 to 17th magnitude depending on observing conditions, while wide-field, high speed imaging should be able to go to 21+. For Gemini, the instrument will be remotely operable from either the mid-level facility at Hale Pohaku or the remote operations base in Hilo.

Wavelet tree structure based speckle noise removal for optical coherence tomography

NASA Astrophysics Data System (ADS)

Yuan, Xin; Liu, Xuan; Liu, Yang

2018-02-01

We report a new speckle noise removal algorithm in optical coherence tomography (OCT). Though wavelet domain thresholding algorithms have demonstrated superior advantages in suppressing noise magnitude and preserving image sharpness in OCT, the wavelet tree structure has not been investigated in previous applications. In this work, we propose an adaptive wavelet thresholding algorithm via exploiting the tree structure in wavelet coefficients to remove the speckle noise in OCT images. The threshold for each wavelet band is adaptively selected following a special rule to retain the structure of the image across different wavelet layers. Our results demonstrate that the proposed algorithm outperforms conventional wavelet thresholding, with significant advantages in preserving image features.

Detection of white spot lesions by segmenting laser speckle images using computer vision methods.

PubMed

Gavinho, Luciano G; Araujo, Sidnei A; Bussadori, Sandra K; Silva, João V P; Deana, Alessandro M

2018-05-05

This paper aims to develop a method for laser speckle image segmentation of tooth surfaces for diagnosis of early stages caries. The method, applied directly to a raw image obtained by digital photography, is based on the difference between the speckle pattern of a carious lesion tooth surface area and that of a sound area. Each image is divided into blocks which are identified in a working matrix by their χ 2 distance between block histograms of the analyzed image and the reference histograms previously obtained by K-means from healthy (h_Sound) and lesioned (h_Decay) areas, separately. If the χ 2 distance between a block histogram and h_Sound is greater than the distance to h_Decay, this block is marked as decayed. The experiments showed that the method can provide effective segmentation for initial lesions. We used 64 images to test the algorithm and we achieved 100% accuracy in segmentation. Differences between the speckle pattern of a sound tooth surface region and a carious region, even in the early stage, can be evidenced by the χ 2 distance between histograms. This method proves to be more effective for segmenting the laser speckle image, which enhances the contrast between sound and lesioned tissues. The results were obtained with low computational cost. The method has the potential for early diagnosis in a clinical environment, through the development of low-cost portable equipment.

Speckle measuring instrument based on biological characteristics of the human eyes and speckle reduction with advanced electromagnetic micro-scanning mirror

NASA Astrophysics Data System (ADS)

Yuan, Yuan; Fang, Tao; Sun, Min Yuan; Gao, Wei Nan; Zhang, Shuo; Bi, Yong

2018-07-01

Laser speckle is a major issue for laser projection displays. In various techniques of speckle reduction, speckle is quantified with a speckle contrast value. However, the measured speckle contrast is poorly suited for the subjective speckle perception of a human observer. Here, we investigate the characteristics of human eyes and propose a simplified optical transfer function of human eyes. Accordingly, two human-eye-modeled speckle measuring sets are configured. Based on the experimental set, an advanced electromagnetic micro-scanning mirror (EM-MSM) is exploited; which is of 6.5 mm in diameter and its half angle is 7.8° for a horizontal scan and 6.53° for a vertical scan. Finally, we quantitatively show that images generated with an EM-MSM exhibit superior quality. By providing human-eye-modeled speckle measuring instruments and an EM-MSM for speckle reduction, it has a promising promotion to laser projector development.

The role of photographic parameters in laser speckle or particle image displacement velocimetry

NASA Technical Reports Server (NTRS)

Lourenco, L.; Krothapalli, A.

1987-01-01

The parameters involved in obtaining the multiple exposure photographs in the laser speckle velocimetry method (to record the light scattering by the seeding particles) were optimized. The effects of the type, concentration, and dimensions of the tracer, the exposure conditions (time between exposures, exposure time, and number of exposures), and the sensitivity and resolution of the film on the quality of the final results were investigated, photographing an experimental flow behind an impulsively started circular cylinder. The velocity data were acquired by digital processing of Young's fringes, produced by point-by-point scanning of a photographic negative. Using the optimal photographing conditions, the errors involved in the estimation of the fringe angle and spacing were of the order of 1 percent for the spacing and +/1 deg for the fringe orientation. The resulting accuracy in the velocity was of the order of 2-3 percent of the maximum velocity in the field.

SPECKLE NOISE SUBTRACTION AND SUPPRESSION WITH ADAPTIVE OPTICS CORONAGRAPHIC IMAGING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ren Deqing; Dou Jiangpei; Zhang Xi

2012-07-10

Future ground-based direct imaging of exoplanets depends critically on high-contrast coronagraph and wave-front manipulation. A coronagraph is designed to remove most of the unaberrated starlight. Because of the wave-front error, which is inherit from the atmospheric turbulence from ground observations, a coronagraph cannot deliver its theoretical performance, and speckle noise will limit the high-contrast imaging performance. Recently, extreme adaptive optics, which can deliver an extremely high Strehl ratio, is being developed for such a challenging mission. In this publication, we show that barely taking a long-exposure image does not provide much gain for coronagraphic imaging with adaptive optics. We furthermore » discuss a speckle subtraction and suppression technique that fully takes advantage of the high contrast provided by the coronagraph, as well as the wave front corrected by the adaptive optics. This technique works well for coronagraphic imaging with conventional adaptive optics with a moderate Strehl ratio, as well as for extreme adaptive optics with a high Strehl ratio. We show how to substrate and suppress speckle noise efficiently up to the third order, which is critical for future ground-based high-contrast imaging. Numerical simulations are conducted to fully demonstrate this technique.« less

Lensless Photoluminescence Hyperspectral Camera Employing Random Speckle Patterns.

PubMed

Žídek, Karel; Denk, Ondřej; Hlubuček, Jiří

2017-11-10

We propose and demonstrate a spectrally-resolved photoluminescence imaging setup based on the so-called single pixel camera - a technique of compressive sensing, which enables imaging by using a single-pixel photodetector. The method relies on encoding an image by a series of random patterns. In our approach, the image encoding was maintained via laser speckle patterns generated by an excitation laser beam scattered on a diffusor. By using a spectrometer as the single-pixel detector we attained a realization of a spectrally-resolved photoluminescence camera with unmatched simplicity. We present reconstructed hyperspectral images of several model scenes. We also discuss parameters affecting the imaging quality, such as the correlation degree of speckle patterns, pattern fineness, and number of datapoints. Finally, we compare the presented technique to hyperspectral imaging using sample scanning. The presented method enables photoluminescence imaging for a broad range of coherent excitation sources and detection spectral areas.

Intelligent estimation of noise and blur variances using ANN for the restoration of ultrasound images.

PubMed

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

2016-11-01

Ultrasound (US) imaging is a widely used clinical diagnostic tool in medical imaging techniques. It is a comparatively safe, economical, painless, portable, and noninvasive real-time tool compared to the other imaging modalities. However, the image quality of US imaging is severely affected by the presence of speckle noise and blur during the acquisition process. In order to ensure a high-quality clinical diagnosis, US images must be restored by reducing their speckle noise and blur. In general, speckle noise is modeled as a multiplicative noise following a Rayleigh distribution and blur as a Gaussian function. Hereto, we propose an intelligent estimator based on artificial neural networks (ANNs) to estimate the variances of noise and blur, which, in turn, are used to obtain an image without discernible distortions. A set of statistical features computed from the image and its complex wavelet sub-bands are used as input to the ANN. In the proposed method, we solve the inverse Rayleigh function numerically for speckle reduction and use the Richardson-Lucy algorithm for de-blurring. The performance of this method is compared with that of the traditional methods by applying them to a synthetic, physical phantom and clinical data, which confirms better restoration results by the proposed method.

Skull optical clearing for assessing to cerebral hemodynamics with high contrast and resolution (Conference Presentation)

NASA Astrophysics Data System (ADS)

Zhu, Dan

2017-03-01

The tissue optical clearing technique could significantly enhance the biomedical optical imaging depth, but current investigations are mainly limited to in vitro studies. In vivo tissue optical clearing method should be enough rapid, transparent and safe, which makes it more difficult, especially, for hard tissue. During the past years, we developed skull optical clearing methods for in vivo cortical imaging. This presentation will report recent progress in skull optical clearing method, including their efficacy, safety, and applications. The skull optical clearing method is proved to be effective for adult mice ages in different month and permit various imaging techniques to monitor cortical blood flow, blood oxygen, and vascular with high resolution and contrast, not only for local cortex, but also for whole cortex. The long-term and short-term observation show that there is no obvious effect on cortical vascular function when laser speckle contrast imaging and hyperspectral imaging are used to repeatedly image the cortical blood flow, blood oxygen. Finally, we will demonstrate some applications for physiological or pathological situation, including monitoring the anoxia, drug-induced cortical response, et al.

Use of kurtosis for locating deep blood vessels in raw speckle imaging using a homogeneity representation.

PubMed

Peregrina-Barreto, Hayde; Perez-Corona, Elizabeth; Rangel-Magdaleno, Jose; Ramos-Garcia, Ruben; Chiu, Roger; Ramirez-San-Juan, Julio C

2017-06-01

Visualization of deep blood vessels in speckle images is an important task as it is used to analyze the dynamics of the blood flow and the health status of biological tissue. Laser speckle imaging is a wide-field optical technique to measure relative blood flow speed based on the local speckle contrast analysis. However, it has been reported that this technique is limited to certain deep blood vessels (about ? = 300 ?? ? m ) because of the high scattering of the sample; beyond this depth, the quality of the vessel’s image decreases. The use of a representation based on homogeneity values, computed from the co-occurrence matrix, is proposed as it provides an improved vessel definition and its corresponding diameter. Moreover, a methodology is proposed for automatic blood vessel location based on the kurtosis analysis. Results were obtained from the different skin phantoms, showing that it is possible to identify the vessel region for different morphologies, even up to 900 ?? ? m in depth.

Noncontact 3-D Speckle Contrast Diffuse Correlation Tomography of Tissue Blood Flow Distribution.

PubMed

Huang, Chong; Irwin, Daniel; Zhao, Mingjun; Shang, Yu; Agochukwu, Nneamaka; Wong, Lesley; Yu, Guoqiang

2017-10-01

Recent advancements in near-infrared diffuse correlation techniques and instrumentation have opened the path for versatile deep tissue microvasculature blood flow imaging systems. Despite this progress there remains a need for a completely noncontact, noninvasive device with high translatability from small/testing (animal) to large/target (human) subjects with trivial application on both. Accordingly, we discuss our newly developed setup which meets this demand, termed noncontact speckle contrast diffuse correlation tomography (nc_scDCT). The nc_scDCT provides fast, continuous, portable, noninvasive, and inexpensive acquisition of 3-D tomographic deep (up to 10 mm) tissue blood flow distributions with straightforward design and customization. The features presented include a finite-element-method implementation for incorporating complex tissue boundaries, fully noncontact hardware for avoiding tissue compression and interactions, rapid data collection with a diffuse speckle contrast method, reflectance-based design promoting experimental translation, extensibility to related techniques, and robust adjustable source and detector patterns and density for high resolution measurement with flexible regions of interest enabling unique application-specific setups. Validation is shown in the detection and characterization of both high and low contrasts in flow relative to the background using tissue phantoms with a pump-connected tube (high) and phantom spheres (low). Furthermore, in vivo validation of extracting spatiotemporal 3-D blood flow distributions and hyperemic response during forearm cuff occlusion is demonstrated. Finally, the success of instrument feasibility in clinical use is examined through the intraoperative imaging of mastectomy skin flap.

Coherent diffraction imaging analysis of shape-controlled nanoparticles with focused hard X-ray free-electron laser pulses.

PubMed

Takahashi, Yukio; Suzuki, Akihiro; Zettsu, Nobuyuki; Oroguchi, Tomotaka; Takayama, Yuki; Sekiguchi, Yuki; Kobayashi, Amane; Yamamoto, Masaki; Nakasako, Masayoshi

2013-01-01

We report the first demonstration of the coherent diffraction imaging analysis of nanoparticles using focused hard X-ray free-electron laser pulses, allowing us to analyze the size distribution of particles as well as the electron density projection of individual particles. We measured 1000 single-shot coherent X-ray diffraction patterns of shape-controlled Ag nanocubes and Au/Ag nanoboxes and estimated the edge length from the speckle size of the coherent diffraction patterns. We then reconstructed the two-dimensional electron density projection with sub-10 nm resolution from selected coherent diffraction patterns. This method enables the simultaneous analysis of the size distribution of synthesized nanoparticles and the structures of particles at nanoscale resolution to address correlations between individual structures of components and the statistical properties in heterogeneous systems such as nanoparticles and cells.

Local scattering property scales flow speed estimation in laser speckle contrast imaging

NASA Astrophysics Data System (ADS)

Miao, Peng; Chao, Zhen; Feng, Shihan; Yu, Hang; Ji, Yuanyuan; Li, Nan; Thakor, Nitish V.

2015-07-01

Laser speckle contrast imaging (LSCI) has been widely used in in vivo blood flow imaging. However, the effect of local scattering property (scattering coefficient µ s ) on blood flow speed estimation has not been well investigated. In this study, such an effect was quantified and involved in relation between speckle autocorrelation time τ c and flow speed v based on simulation flow experiments. For in vivo blood flow imaging, an improved estimation strategy was developed to eliminate the estimation bias due to the inhomogeneous distribution of the scattering property. Compared to traditional LSCI, a new estimation method significantly suppressed the imaging noise and improves the imaging contrast of vasculatures. Furthermore, the new method successfully captured the blood flow changes and vascular constriction patterns in rats’ cerebral cortex from normothermia to mild and moderate hypothermia.

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

NASA Astrophysics Data System (ADS)

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.

Correcting for motion artifact in handheld laser speckle images

NASA Astrophysics Data System (ADS)

Lertsakdadet, Ben; Yang, Bruce Y.; Dunn, Cody E.; Ponticorvo, Adrien; Crouzet, Christian; Bernal, Nicole; Durkin, Anthony J.; Choi, Bernard

2018-03-01

Laser speckle imaging (LSI) is a wide-field optical technique that enables superficial blood flow quantification. LSI is normally performed in a mounted configuration to decrease the likelihood of motion artifact. However, mounted LSI systems are cumbersome and difficult to transport quickly in a clinical setting for which portability is essential in providing bedside patient care. To address this issue, we created a handheld LSI device using scientific grade components. To account for motion artifact of the LSI device used in a handheld setup, we incorporated a fiducial marker (FM) into our imaging protocol and determined the difference between highest and lowest speckle contrast values for the FM within each data set (Kbest and Kworst). The difference between Kbest and Kworst in mounted and handheld setups was 8% and 52%, respectively, thereby reinforcing the need for motion artifact quantification. When using a threshold FM speckle contrast value (KFM) to identify a subset of images with an acceptable level of motion artifact, mounted and handheld LSI measurements of speckle contrast of a flow region (KFLOW) in in vitro flow phantom experiments differed by 8%. Without the use of the FM, mounted and handheld KFLOW values differed by 20%. To further validate our handheld LSI device, we compared mounted and handheld data from an in vivo porcine burn model of superficial and full thickness burns. The speckle contrast within the burn region (KBURN) of the mounted and handheld LSI data differed by <4 % when accounting for motion artifact using the FM, which is less than the speckle contrast difference between superficial and full thickness burns. Collectively, our results suggest the potential of handheld LSI with an FM as a suitable alternative to mounted LSI, especially in challenging clinical settings with space limitations such as the intensive care unit.

Methods to Enhance Laser Speckle Imaging of High-Flow and Low-Flow Vasculature

PubMed Central

Choi, Bernard; Ringold, Tyson L.; Kim, Jeehyun

2012-01-01

The objective of this paper is to present two methods to extend the response range of laser speckle imaging (LSI). We report on the use of two methods (image exposure time control and magnetomotive actuation of exogenous contrast agents) to enhance characterization of high- and low-flow vasculature, respectively. With an exposure time of 10 and 0.01 ms, the linear response range extended to 10 and 280 mm/s, respectively. With application of an AC magnetic field to a solution of stagnant SPIO particles, an apparent increase of ~3× in speckle flow index was induced. PMID:19964103

Speckle interferometry of asteroids

NASA Technical Reports Server (NTRS)

Drummond, Jack D.; Hege, E. Keith

1989-01-01

Steward Observatory's two-dimensional power spectrum signature analysis of speckle interferometry observations is summarized. Results for six asteroids are presented. The poles and triaxial ellipsoid dimensions of 4 Vesta, 433 Eros, 511 Davida, and 532 Herculina have been previously reported. New results for 2 Pallas and 29 Amphitrite are given, as well as further results for Vesta. Image reconstruction is ultimately required to minimize biasing effects of asteroid surface features on the simpler power spectrum analysis. Preliminary imaging results have been achieved for Vesta and Eros, and images for these two are displayed. Speckle interferometry and radiometry diameters are compared, and diameters from the two occultations of Pallas are addressed.

Differences between time domain and Fourier domain optical coherence tomography in imaging tissues.

PubMed

Gao, W; Wu, X

2017-11-01

It has been numerously demonstrated that both time domain and Fourier domain optical coherence tomography (OCT) can generate high-resolution depth-resolved images of living tissues and cells. In this work, we compare the common points and differences between two methods when the continuous and random properties of live tissue are taken into account. It is found that when relationships that exist between the scattered light and tissue structures are taken into account, spectral interference measurements in Fourier domain OCT (FDOCT) is more advantageous than interference fringe envelope measurements in time domain OCT (TDOCT) in the cases where continuous property of tissue is taken into account. It is also demonstrated that when random property of tissue is taken into account FDOCT measures the Fourier transform of the spatial correlation function of the refractive index and speckle phenomena will limit the effective limiting imaging resolution in both TDOCT and FDOCT. Finally, the effective limiting resolution of both TDOCT and FDOCT are given which can be used to estimate the effective limiting resolution in various practical applications. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

Adaptive optics and the eye (super resolution OCT).

PubMed

Miller, D T; Kocaoglu, O P; Wang, Q; Lee, S

2011-03-01

The combination of adaptive optics (AO) and optical coherence tomography (OCT) was first reported 8 years ago and has undergone tremendous technological advances since then. The technical benefits of adding AO to OCT (increased lateral resolution, smaller speckle, and enhanced sensitivity) increase the imaging capability of OCT in ways that make it well suited for three-dimensional (3D) cellular imaging in the retina. Today, AO-OCT systems provide ultrahigh 3D resolution (3 × 3 × 3 μm³) and ultrahigh speed (up to an order of magnitude faster than commercial OCT). AO-OCT systems have been used to capture volume images of retinal structures, previously only visible with histology, and are being used for studying clinical conditions. Here, we present representative examples of cellular structures that can be visualized with AO-OCT. We overview three studies from our laboratory that used ultrahigh-resolution AO-OCT to measure the cross-sectional profiles of individual bundles in the retinal nerve fiber layer; the diameters of foveal capillaries that define the terminal rim of the foveal avascular zone; and the spacing and length of individual cone photoreceptor outer segments as close as 0.5° from the fovea center.

Speckle statistics in adaptive optics images at visible wavelengths

NASA Astrophysics Data System (ADS)

Stangalini, Marco; Pedichini, Fernando; Ambrosino, Filippo; Centrone, Mauro; Del Moro, Dario

2016-07-01

Residual speckles in adaptive optics (AO) images represent a well known limitation to the achievement of the contrast needed for faint stellar companions detection. Speckles in AO imagery can be the result of either residual atmospheric aberrations, not corrected by the AO, or slowly evolving aberrations induced by the optical system. In this work we take advantage of new high temporal cadence (1 ms) data acquired by the SHARK forerunner experiment at the Large Binocular Telescope (LBT), to characterize the AO residual speckles at visible waveleghts. By means of an automatic identification of speckles, we study the main statistical properties of AO residuals. In addition, we also study the memory of the process, and thus the clearance time of the atmospheric aberrations, by using information Theory. These information are useful for increasing the realism of numerical simulations aimed at assessing the instrumental performances, and for the application of post-processing techniques on AO imagery.

Laser Speckle Imaging of Blood Flow Beneath Static Scattering Media

NASA Astrophysics Data System (ADS)

Regan, Caitlin Anderson

Laser speckle imaging (LSI) is a wide-field optical imaging technique that provides information about the movement of scattering particles in biological samples. LSI is used to create maps of relative blood flow and perfusion in samples such as the skin, brain, teeth, gingiva, and other biological tissues. The presence of static, or non-moving, optical scatterers affects the ability of LSI to provide true quantitative and spatially resolved measurements of blood flow. With in vitro experiments using tissue-simulating phantoms, we determined that temporal analysis of raw speckle image sequences improved the quantitative accuracy of LSI to measure flow beneath a static scattering layer. We then applied the temporal algorithm to assess the potential of LSI to monitor oral health. We designed and tested two generations of miniature LSI devices to measure flow in the pulpal chamber of teeth and in the gingiva. Our preliminary clinical pilot data indicated that speckle contrast may correlate with gingival health. To improve visualization of subsurface blood vessels, we developed a technique called photothermal LSI. We applied a short pulse of laser energy to selectively perturb the motion of red blood cells, increasing the signal from vasculature relative to the surroundings. To study the spectral and depth dependence of laser speckle contrast, we developed a Monte Carlo model of light and momentum transport to simulate speckle contrast. With an increase in the thickness of the overlying static-scattering layer, we observed a quadratic decrease in the quantity of dynamically scattered light collected by the detector. We next applied the model to study multi-exposure speckle imaging (MESI), a method that purportedly improves quantitative accuracy of subsurface blood flow measurements. We unexpectedly determined that MESI faced similar depth limitations as conventional LSI, findings that were supported by in vitro experimental data. Finally, we used the model to study the effects of epidermal melanin absorption on LSI, and demonstrated that speckle contrast is less sensitive to varying melanin content than reflectance. We then proposed a two-wavelength measurement protocol that may enable melanin-independent LSI measurements of blood flow in patients with varying skin types. In conclusion, through in vitro and in silico experiments, we were able to further the understanding of the depth dependent origins of laser speckle contrast as well as the inherent limitations of this technology.

Digital Correlation In Laser-Speckle Velocimetry

NASA Technical Reports Server (NTRS)

Gilbert, John A.; Mathys, Donald R.

1992-01-01

Periodic recording helps to eliminate spurious results. Improved digital-correlation process extracts velocity field of two-dimensional flow from laser-speckle images of seed particles distributed sparsely in flow. Method which involves digital correlation of images recorded at unequal intervals, completely automated and has potential to be fastest yet.

Adaptive nonlinear L2 and L3 filters for speckled image processing

NASA Astrophysics Data System (ADS)

Lukin, Vladimir V.; Melnik, Vladimir P.; Chemerovsky, Victor I.; Astola, Jaakko T.

1997-04-01

Here we propose adaptive nonlinear filters based on calculation and analysis of two or three order statistics in a scanning window. They are designed for processing images corrupted by severe speckle noise with non-symmetrical. (Rayleigh or one-side exponential) distribution laws; impulsive noise can be also present. The proposed filtering algorithms provide trade-off between impulsive noise can be also present. The proposed filtering algorithms provide trade-off between efficient speckle noise suppression, robustness, good edge/detail preservation, low computational complexity, preservation of average level for homogeneous regions of images. Quantitative evaluations of the characteristics of the proposed filter are presented as well as the results of the application to real synthetic aperture radar and ultrasound medical images.

Integration of instrumentation and processing software of a laser speckle contrast imaging system

NASA Astrophysics Data System (ADS)

Carrick, Jacob J.

Laser speckle contrast imaging (LSCI) has the potential to be a powerful tool in medicine, but more research in the field is required so it can be used properly. To help in the progression of Michigan Tech's research in the field, a graphical user interface (GUI) was designed in Matlab to control the instrumentation of the experiments as well as process the raw speckle images into contrast images while they are being acquired. The design of the system was successful and is currently being used by Michigan Tech's Biomedical Engineering department. This thesis describes the development of the LSCI GUI as well as offering a full introduction into the history, theory and applications of LSCI.

Laser speckle imaging identification of increases in cortical microcirculatory blood flow induced by motor activity during awake craniotomy.

PubMed

Klijn, Eva; Hulscher, Hester C; Balvers, Rutger K; Holland, Wim P J; Bakker, Jan; Vincent, Arnaud J P E; Dirven, Clemens M F; Ince, Can

2013-02-01

The goal of awake neurosurgery is to maximize resection of brain lesions with minimal injury to functional brain areas. Laser speckle imaging (LSI) is a noninvasive macroscopic technique with high spatial and temporal resolution used to monitor changes in capillary perfusion. In this study, the authors hypothesized that LSI can be useful as a noncontact method of functional brain mapping during awake craniotomy for tumor removal. Such a modality would be an advance in this type of neurosurgery since current practice involves the application of invasive intraoperative single-point electrocortical (electrode) stimulation and measurements. After opening the dura mater, patients were woken up, and LSI was set up to image the exposed brain area. Patients were instructed to follow a rest-activation-rest protocol in which activation consisted of the hand-clenching motor task. Subsequently, exposed brain areas were mapped for functional motor areas by using standard electrocortical stimulation (ECS). Changes in the LSI signal were analyzed offline and compared with the results of ECS. In functional motor areas of the hand mapped with ECS, cortical blood flow measured using LSI significantly increased from 2052 ± 818 AU to 2471 ± 675 AU during hand clenching, whereas capillary blood flow did not change in the control regions (areas mapped using ECS with no functional activity). The main finding of this study was that changes in laser speckle perfusion as a measure of cortical microvascular blood flow when performing a motor task with the hand relate well to the ECS map. The authors have shown the feasibility of using LSI for direct visualization of cortical microcirculatory blood flow changes during neurosurgery.

Real time laser speckle imaging monitoring vascular targeted photodynamic therapy

NASA Astrophysics Data System (ADS)

Goldschmidt, Ruth; Vyacheslav, Kalchenko; Scherz, Avigdor

2017-02-01

Laser speckle imaging is a technique that has been developed to non-invasively monitor in vivo blood flow dynamics and vascular structure, at high spatial and temporal resolution. It can record the full-field spatio-temporal characteristics of microcirculation and has therefore, often been used to study the blood flow in tumors after photodynamic therapy (PDT). Yet, there is a paucity of reports on real-time laser speckle imaging (RTLSI) during PDT. Vascular-targeted photodynamic therapy (VTP) with WST11, a water-soluble bacteriochlorophyll derivative, achieves tumor ablation through rapid occlusion of the tumor vasculature followed by a cascade of events that actively kill the tumor cells. WST11-VTP has been already approved for treatment of early/intermediate prostate cancer at a certain drug dose, time and intensity of illumination. Application to other cancers may require different light dosage. However, incomplete vascular occlusion at lower light dose may result in cancer cell survival and tumor relapse while excessive light dose may lead to toxicity of nearby healthy tissues. Here we provide evidence for the feasibility of concomitant RTLSI of the blood flow dynamics in the tumor and surrounding normal tissues during and after WST11-VTP. Fast decrease in the blood flow is followed by partial mild reperfusion and a complete flow arrest within the tumor by the end of illumination. While the primary occlusion of the tumor feeding arteries and draining veins agrees with previous data published by our group, the late effects underscore the significance of light dose control to minimize normal tissue impairment. In conclusion- RTSLI application should allow to optimize VTP efficacy vs toxicity in both the preclinical and clinical arenas.

Speckle interferometry of asteroids

NASA Technical Reports Server (NTRS)

Drummond, Jack

1988-01-01

By studying the image two-dimensional power spectra or autocorrelations projected by an asteroid as it rotates, it is possible to locate its rotational pole and derive its three axes dimensions through speckle interferometry under certain assumptions of uniform, geometric scattering, and triaxial ellipsoid shape. However, in cases where images can be reconstructed, the need for making the assumptions is obviated. Furthermore, the ultimate goal for speckle interferometry of image reconstruction will lead to mapping albedo features (if they exist) as impact areas or geological units. The first glimpses of the surface of an asteroid were obtained from images of 4 Vesta reconstructed from speckle interferometric observations. These images reveal that Vesta is quite Moon-like in having large hemispheric-scale albedo features. All of its lightcurves can be produced from a simple model developed from the images. Although undoubtedly more intricate than the model, Vesta's lightcurves can be matched by a model with three dark and four bright spots. The dark areas so dominate one hemisphere that a lightcurve minimum occurs when the maximum cross-section area is visible. The triaxial ellipsoid shape derived for Vesta is not consistent with the notion that the asteroid has an equilibrium shape in spite of its having apparently been differentiated.

Edge Preserved Speckle Noise Reduction Using Integrated Fuzzy Filters

PubMed Central

Dewal, M. L.; Rohit, Manoj Kumar

2014-01-01

Echocardiographic images are inherent with speckle noise which makes visual reading and analysis quite difficult. The multiplicative speckle noise masks finer details, necessary for diagnosis of abnormalities. A novel speckle reduction technique based on integration of geometric, wiener, and fuzzy filters is proposed and analyzed in this paper. The denoising applications of fuzzy filters are studied and analyzed along with 26 denoising techniques. It is observed that geometric filter retains noise and, to address this issue, wiener filter is embedded into the geometric filter during iteration process. The performance of geometric-wiener filter is further enhanced using fuzzy filters and the proposed despeckling techniques are called integrated fuzzy filters. Fuzzy filters based on moving average and median value are employed in the integrated fuzzy filters. The performances of integrated fuzzy filters are tested on echocardiographic images and synthetic images in terms of image quality metrics. It is observed that the performance parameters are highest in case of integrated fuzzy filters in comparison to fuzzy and geometric-fuzzy filters. The clinical validation reveals that the output images obtained using geometric-wiener, integrated fuzzy, nonlocal means, and details preserving anisotropic diffusion filters are acceptable. The necessary finer details are retained in the denoised echocardiographic images. PMID:27437499

Application of shift-and-add algorithms for imaging objects within biological media

NASA Astrophysics Data System (ADS)

Aizert, Avishai; Moshe, Tomer; Abookasis, David

2017-01-01

The Shift-and-Add (SAA) technique is a simple mathematical operation developed to reconstruct, at high spatial resolution, atmospherically degraded solar images obtained from stellar speckle interferometry systems. This method shifts and assembles individual degraded short-exposure images into a single average image with significantly improved contrast and detail. Since the inhomogeneous refractive indices of biological tissue causes light scattering similar to that induced by optical turbulence in the atmospheric layers, we assume that SAA methods can be successfully implemented to reconstruct the image of an object within a scattering biological medium. To test this hypothesis, five SAA algorithms were evaluated for reconstructing images acquired from multiple viewpoints. After successfully retrieving the hidden object's shape, quantitative image quality metrics were derived, enabling comparison of imaging error across a spectrum of layer thicknesses, demonstrating the relative efficacy of each SAA algorithm for biological imaging.

Online biospeckle assessment without loss of definition and resolution by motion history image

NASA Astrophysics Data System (ADS)

Godinho, R. P.; Silva, M. M.; Nozela, J. R.; Braga, R. A.

2012-03-01

The application of the dynamic laser speckle as a reliable instrument to achieve maps of activity in biological material is available in literature optics and laser. The application, particularly in live specimens, such as animals and human beings necessitated some approaches to avoid the kinking of the bodies, which creates changes in the patterns undermining the biological activity under monitoring. The adoption of online techniques circumvented the noise generated by the kinking, however, with considerable reduction in the resolution and definition of the activity maps. This work presents a feasible alternative to the routine online methods based on the Motion History Image (MHI) methodology. The adoption of MHI was tested in biological and non-biological samples and compared with online as well as offline procedures of biospeckle image analysis. Tests on paint drying was associated to alcohol volatilization, and tests on a maize seed and on growing of roots confirmed the hypothesis that the MHI would be able to implement an online approach without the reduction of resolution and definition on the resultant images, thereby presenting in some cases results that were comparable to the offline procedures.

Simulation of speckle patterns with pre-defined correlation distributions.

PubMed

Song, Lipei; Zhou, Zhen; Wang, Xueyan; Zhao, Xing; Elson, Daniel S

2016-03-01

We put forward a method to easily generate a single or a sequence of fully developed speckle patterns with pre-defined correlation distribution by utilizing the principle of coherent imaging. The few-to-one mapping between the input correlation matrix and the correlation distribution between simulated speckle patterns is realized and there is a simple square relationship between the values of these two correlation coefficient sets. This method is demonstrated both theoretically and experimentally. The square relationship enables easy conversion from any desired correlation distribution. Since the input correlation distribution can be defined by a digital matrix or a gray-scale image acquired experimentally, this method provides a convenient way to simulate real speckle-related experiments and to evaluate data processing techniques.

Simulation of speckle patterns with pre-defined correlation distributions

PubMed Central

Song, Lipei; Zhou, Zhen; Wang, Xueyan; Zhao, Xing; Elson, Daniel S.

2016-01-01

We put forward a method to easily generate a single or a sequence of fully developed speckle patterns with pre-defined correlation distribution by utilizing the principle of coherent imaging. The few-to-one mapping between the input correlation matrix and the correlation distribution between simulated speckle patterns is realized and there is a simple square relationship between the values of these two correlation coefficient sets. This method is demonstrated both theoretically and experimentally. The square relationship enables easy conversion from any desired correlation distribution. Since the input correlation distribution can be defined by a digital matrix or a gray-scale image acquired experimentally, this method provides a convenient way to simulate real speckle-related experiments and to evaluate data processing techniques. PMID:27231589

Potential accuracy of translation estimation between radar and optical images

NASA Astrophysics Data System (ADS)

Uss, M.; Vozel, B.; Lukin, V.; Chehdi, K.

2015-10-01

This paper investigates the potential accuracy achievable for optical to radar image registration by area-based approach. The analysis is carried out mainly based on the Cramér-Rao Lower Bound (CRLB) on translation estimation accuracy previously proposed by the authors and called CRLBfBm. This bound is now modified to take into account radar image speckle noise properties: spatial correlation and signal-dependency. The newly derived theoretical bound is fed with noise and texture parameters estimated for the co-registered pair of optical Landsat 8 and radar SIR-C images. It is found that difficulty of optical to radar image registration stems more from speckle noise influence than from dissimilarity of the considered kinds of images. At finer scales (and higher speckle noise level), probability of finding control fragments (CF) suitable for registration is low (1% or less) but overall number of such fragments is high thanks to image size. Conversely, at the coarse scale, where speckle noise level is reduced, probability of finding CFs suitable for registration can be as high as 40%, but overall number of such CFs is lower. Thus, the study confirms and supports area-based multiresolution approach for optical to radar registration where coarse scales are used for fast registration "lock" and finer scales for reaching higher registration accuracy. The CRLBfBm is found inaccurate for the main scale due to intensive speckle noise influence. For other scales, the validity of the CRLBfBm bound is confirmed by calculating statistical efficiency of area-based registration method based on normalized correlation coefficient (NCC) measure that takes high values of about 25%.

Ultrasound speckle tracking for radial, longitudinal and circumferential strain estimation of the carotid artery--an in vitro validation via sonomicrometry using clinical and high-frequency ultrasound.

PubMed

Larsson, Matilda; Heyde, Brecht; Kremer, Florence; Brodin, Lars-Åke; D'hooge, Jan

2015-02-01

Ultrasound speckle tracking for carotid strain assessment has in the past decade gained interest in studies of arterial stiffness and cardiovascular diseases. The aim of this study was to validate and directly contrast carotid strain assessment by speckle tracking applied on clinical and high-frequency ultrasound images in vitro. Four polyvinyl alcohol phantoms mimicking the carotid artery were constructed with different mechanical properties and connected to a pump generating carotid flow profiles. Gray-scale ultrasound long- and short-axis images of the phantoms were obtained using a standard clinical ultrasound system, Vivid 7 (GE Healthcare, Horten, Norway) and a high-frequency ultrasound system, Vevo 2100 (FUJIFILM, VisualSonics, Toronto, Canada) with linear-array transducers (12L/MS250). Radial, longitudinal and circumferential strains were estimated using an in-house speckle tracking algorithm and compared with reference strain acquired by sonomicrometry. Overall, the estimated strain corresponded well with the reference strain. The correlation between estimated peak strain in clinical ultrasound images and reference strain was 0.91 (p<0.001) for radial strain, 0.73 (p<0.001) for longitudinal strain and 0.90 (p<0.001) for circumferential strain and for high-frequency ultrasound images 0.95 (p<0.001) for radial strain, 0.93 (p<0.001) for longitudinal strain and 0.90 (p<0.001) for circumferential strain. A significant larger bias and root mean square error was found for circumferential strain estimation on clinical ultrasound images compared to high frequency ultrasound images, but no significant difference in bias and root mean square error was found for radial and longitudinal strain when comparing estimation on clinical and high-frequency ultrasound images. The agreement between sonomicrometry and speckle tracking demonstrates that carotid strain assessment by ultrasound speckle tracking is feasible. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

Speckle tracking imaging in inflammatory heart diseases.

PubMed

Leitman, Marina; Vered, Zvi; Tyomkin, Vladimir; Macogon, Boris; Moravsky, Gil; Peleg, Eli; Copel, Laurian

2018-05-01

Accurate diagnosis of acute myocarditis is important for the prognosis and risk stratification of these patients. Cardiac magnetic resonance (CMR) has become a major modality for diagnosis of myocarditis, but not widely available. In this study, we tried to evaluate regional and global longitudinal strain by speckle tracking echocardiography in patients with acute inflammatory myocardial diseases in correlation with CMR. Patients with suspected acute myocarditis were recruited prospectively. Clinical diagnosis was established based on clinical, electrocardiographic, laboratory and conventional echocardiographic data. All patients underwent CMR and repeat echocardiographic examination within 24 h of CMR. Echocardiographic examinations were analyzed offline with speckle tracking imaging software. Thirty-two patients with acute perimyocarditis and myopericarditis were included. Mean age was 29 ± 8, 30 males. All patients presented with chest pain and an abnormal electrocardiogram, in 28 ST elevation was found. Troponin was elevated in 30 and was 0.7 ± 0.5 ng/ml. Creatine kinase was 487 ± 319 U. LVEF was 56 ± 5%. Wall motion abnormalities were present in postero-lateral (53%), and inferior wall (21%). Delayed enhancement on CMR was found in 29 patients. Echocardiographic EF based on speckle tracking imaging correlated with CMR calculated EF. There was a positive correlation between the amplitude of regional strain and delayed enhancement, r = 0.52. Sensitivity and specificity of regional strain for prediction of delayed enhancement was 85 and 73% respectively. Speckle tracking imaging can help in the diagnosis of acute myocarditis when CMR is not readily available. Speckle tracking imaging based EF correlates with CMR calculated LVEF and with global strain.

Shunt flow evaluation in congenital heart disease based on two-dimensional speckle tracking.

PubMed

Fadnes, Solveig; Nyrnes, Siri Ann; Torp, Hans; Lovstakken, Lasse

2014-10-01

High-frame-rate ultrasound speckle tracking was used for quantification of peak velocity in shunt flows resulting from septal defects in congenital heart disease. In a duplex acquisition scheme implemented on a research scanner, unfocused transmit beams and full parallel receive beamforming were used to achieve a frame rate of 107 frames/s for full field-of-view flow images with high accuracy, while also ensuring high-quality focused B-mode tissue imaging. The setup was evaluated in vivo for neonates with atrial and ventricular septal defects. The shunt position was automatically tracked in B-mode images and further used in blood speckle tracking to obtain calibrated shunt flow velocities throughout the cardiac cycle. Validation toward color flow imaging and pulsed wave Doppler with manual angle correction indicated that blood speckle tracking could provide accurate estimates of shunt flow velocities. The approach was less biased by clutter filtering compared with color flow imaging and was able to provide velocity estimates beyond the Nyquist range. Possible placements of sample volumes (and angle corrections) for conventional Doppler resulted in a peak shunt velocity variations of 0.49-0.56 m/s for the ventricular septal defect of patient 1 and 0.38-0.58 m/s for the atrial septal defect of patient 2. In comparison, the peak velocities found from speckle tracking were 0.77 and 0.33 m/s for patients 1 and 2, respectively. Results indicated that complex intraventricular flow velocity patterns could be quantified using high-frame-rate speckle tracking of both blood and tissue movement. This could potentially help increase diagnostic accuracy and decrease inter-observer variability when measuring peak velocity in shunt flows. Copyright © 2014 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Effect of incidence/observation angles and angular diversity on speckle reduction by wavelength diversity in laser projection systems.

PubMed

Yamada, Hirotaka; Moriyasu, Kengo; Sato, Hiroto; Hatanaka, Hidekazu

2017-12-11

The speckle reduction for laser projectors has been vigorously studied because speckle causes a serious deterioration in image quality. Most speckle reduction methods can be categorized into wavelength diversity, angular diversity and polarization diversity, which are usually treated independently. In this paper, it is shown that the effect of wavelength diversity and angular diversity on speckle reduction is not independent, and that the effect of wavelength also depends on incidence and observation angles on screen. The speckle reduction effect by wavelength diversity is smaller when the angular diversity is larger. Also, the speckle reduction effect is investigated on various screens including matte and silver screens, and it is shown that the effect of wavelength diversity is larger on matte screen than on silver screen.

On the appropriate feature for general SAR image registration

NASA Astrophysics Data System (ADS)

Li, Dong; Zhang, Yunhua

2012-09-01

An investigation to the appropriate feature for SAR image registration is conducted. The commonly-used features such as tie points, Harris corner, the scale invariant feature transform (SIFT), and the speeded up robust feature (SURF) are comprehensively evaluated in terms of several criteria such as the geometrical invariance of feature, the extraction speed, the localization accuracy, the geometrical invariance of descriptor, the matching speed, the robustness to decorrelation, and the flexibility to image speckling. It is shown that SURF outperforms others. It is particularly indicated that SURF has good flexibility to image speckling because the Fast-Hessian detector of SURF has a potential relation with the refined Lee filter. It is recommended to perform SURF on the oversampled image with unaltered sampling step so as to improve the subpixel registration accuracy and speckle immunity. Thus SURF is more appropriate and competent for general SAR image registration.

Advanced Methods in Fluorescence Microscopy

PubMed Central

Fritzky, Luke; Lagunoff, David

2013-01-01

It requires a good deal of will power to resist hyperbole in considering the advances that have been achieved in fluorescence microscopy in the last 25 years. Our effort has been to survey the modalities of microscopic fluorescence imaging available to cell biologists and perhaps useful for diagnostic pathologists. The gamut extends from established confocal laser scanning through multiphoton and TIRF to the emerging technologies of super-resolution microscopy that breech the Abbé limit of resolution. Also considered are the recent innovations in structured and light sheet illumination, the use of FRET and molecular beacons that exploit specific characteristics of designer fluorescent proteins, fluorescence speckles, and second harmonic generation for native anisometric structures like collagen, microtubules and sarcomeres. PMID:23271142

Advanced methods in fluorescence microscopy.

PubMed

Fritzky, Luke; Lagunoff, David

2013-01-01

It requires a good deal of will power to resist hyperbole in considering the advances that have been achieved in fluorescence microscopy in the last 25 years. Our effort has been to survey the modalities of microscopic fluorescence imaging available to cell biologists and perhaps useful for diagnostic pathologists. The gamut extends from established confocal laser scanning through multiphoton and TIRF to the emerging technologies of super-resolution microscopy that breech the Abbe limit of resolution. Also considered are the recent innovations in structured and light sheet illumination, the use of FRET and molecular beacons that exploit specific characteristics of designer fluorescent proteins, fluorescence speckles, and second harmonic generation for native anisometric structures like collagen, microtubules and sarcomeres.

Advanced methods in fluorescence microscopy.

PubMed

Fritzky, Luke; Lagunoff, David

2013-01-01

It requires a good deal of will power to resist hyperbole in considering the advances that have been achieved in fluorescence microscopy in the last 25 years. Our effort has been to survey the modalities of microscopic fluorescence imaging available to cell biologists and perhaps useful for diagnostic pathologists. The gamut extends from established confocal laser scanning through multiphoton and TIRF to the emerging technologies of super-resolution microscopy that breech the Abbé limit of resolution. Also considered are the recent innovations in structured and light sheet illumination, the use of FRET and molecular beacons that exploit specific characteristics of designer fluorescent proteins, fluorescence speckles, and second harmonic generation for native anisometric structures like collagen, microtubules and sarcomeres.

Atherosclerotic plaque characterization by spatial and temporal speckle pattern analysis

NASA Astrophysics Data System (ADS)

Tearney, Guillermo J.; Bouma, Brett E.

2002-04-01

Improved methods are needed to identify the vulnerable coronary plaques responsible for acute myocardial infraction or sudden cardiac death. We describe a method for characterizing the structure and biomechanical properties of atherosclerotic plaques based on speckle pattern fluctuations. Near-field speckle images were acquired from five human aortic specimens ex vivo. The speckle decorrelation time constant varied significantly for vulnerable aortic plaques (τ = 40 ms) versus stable plaques (τ = 400 ms) and normal aorta (τ = 500 ms). These initial results indicate that different atherosclerotic plaque types may be distinguished by analysis of temporal and spatial speckle pattern fluctuations.

Techniques of noninvasive optical tomographic imaging

NASA Astrophysics Data System (ADS)

Rosen, Joseph; Abookasis, David; Gokhler, Mark

2006-01-01

Recently invented methods of optical tomographic imaging through scattering and absorbing media are presented. In one method, the three-dimensional structure of an object hidden between two biological tissues is recovered from many noisy speckle pictures obtained on the output of a multi-channeled optical imaging system. Objects are recovered from many speckled images observed by a digital camera through two stereoscopic microlens arrays. Each microlens in each array generates a speckle image of the object buried between the layers. In the computer each image is Fourier transformed jointly with an image of the speckled point-like source captured under the same conditions. A set of the squared magnitudes of the Fourier-transformed pictures is accumulated to form a single average picture. This final picture is again Fourier transformed, resulting in the three-dimensional reconstruction of the hidden object. In the other method, the effect of spatial longitudinal coherence is used for imaging through an absorbing layer with different thickness, or different index of refraction, along the layer. The technique is based on synthesis of multiple peak spatial degree of coherence. This degree of coherence enables us to scan simultaneously different sample points on different altitudes, and thus decreases the acquisition time. The same multi peak degree of coherence is also used for imaging through the absorbing layer. Our entire experiments are performed with a quasi-monochromatic light source. Therefore problems of dispersion and inhomogeneous absorption are avoided.

Low-cost, high-resolution, single-structure array telescopes for imaging of low-earth-orbit satellites

NASA Technical Reports Server (NTRS)

Massie, N. A.; Oster, Yale; Poe, Greg; Seppala, Lynn; Shao, Mike

1992-01-01

Telescopes that are designed for the unconventional imaging of near-earth satellites must follow unique design rules. The costs must be reduced substantially over those of the conventional telescope designs, and the design must accommodate a technique to circumvent atmospheric distortion of the image. Apertures of 12 m and more along with altitude-altitude mounts that provide high tracking rates are required. A novel design for such a telescope, optimized for speckle imaging, has been generated. Its mount closely resembles a radar mount, and it does not use the conventional dome. Costs for this design are projected to be considerably lower than those for the conventional designs. Results of a design study are presented with details of the electro-optical and optical designs.

Optimal detection pinhole for lowering speckle noise while maintaining adequate optical sectioning in confocal reflectance microscopes

PubMed Central

Rajadhyaksha, Milind

2012-01-01

Abstract. Coherent speckle influences the resulting image when narrow spectral line-width and single spatial mode illumination are used, though these are the same light-source properties that provide the best radiance-to-cost ratio. However, a suitable size of the detection pinhole can be chosen to maintain adequate optical sectioning while making the probability density of the speckle noise more normal and reducing its effect. The result is a qualitatively better image with improved contrast, which is easier to read. With theoretical statistics and experimental results, we show that the detection pinhole size is a fundamental parameter for designing imaging systems for use in turbid media. PMID:23224184

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

NASA Astrophysics Data System (ADS)

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.

Comparison of texture synthesis methods for content generation in ultrasound simulation for training

NASA Astrophysics Data System (ADS)

Mattausch, Oliver; Ren, Elizabeth; Bajka, Michael; Vanhoey, Kenneth; Goksel, Orcun

2017-03-01

Navigation and interpretation of ultrasound (US) images require substantial expertise, the training of which can be aided by virtual-reality simulators. However, a major challenge in creating plausible simulated US images is the generation of realistic ultrasound speckle. Since typical ultrasound speckle exhibits many properties of Markov Random Fields, it is conceivable to use texture synthesis for generating plausible US appearance. In this work, we investigate popular classes of texture synthesis methods for generating realistic US content. In a user study, we evaluate their performance for reproducing homogeneous tissue regions in B-mode US images from small image samples of similar tissue and report the best-performing synthesis methods. We further show that regression trees can be used on speckle texture features to learn a predictor for US realism.

Assessing Impact of High-Dose Pitavastatin on Carotid Artery Elasticity with Speckle-Tracking Strain Imaging.

PubMed

Kim, Chee Hae; Wang, Shuang; Park, Jun-Bean; Jung, Keun-Hwa; Yoon, Yeonyee E; Lee, Seung-Pyo; Kim, Hyung-Kwan; Kim, Yong-Jin; Cho, Goo-Yeong; Sohn, Dae-Won

2018-03-07

Speckle-tracking imaging has been introduced for the precise assessment of vessel mechanics. However, there are no data on the role of this imaging tool in assessing the changes in vasculature with statin therapy, which is known to enhance vascular elasticity. This study was a prospective study including 48 statin-naïve patients (age, 58.2±8.4 years; 29.2% male) with hypercholesterolemia. Circumferential carotid artery strain (CAS) and stiffness index (β 2 ) were measured using speckle-tracking imaging before and after 3 months of high-dose pitavastatin treatment (4 mg daily). For the comparison, we measured conventional carotid elasticity parameters and intima-media thickness using B-mode ultrasound at the same time points. Compared with baseline, there was significant improvement in circumferential CAS (2.98%±1.18% to 3.40%±1.43%, p=0.008) and β 2 (0.19±0.07 to 0.17±0.08, p=0.047) after statin therapy. Contrariwise, there were no significant changes in all conventional carotid elasticity metrics and intima-media thickness. When stratifying patients into two subgroups by 10 year atherosclerotic cardiovascular disease (ASCVD) risk, speckle-tracking-derived circumferential CAS and β 2 improved significantly only in patients with ASCVD risk ≥ 7.5%. Short-term treatment with high-dose pitavastatin improved carotid artery elasticity measured by speckle-tracking method, but not conventional parameters by B-mode ultrasound. Speckle-tracking-based measurements may allow the early noninvasive assessment of statin effects on vascular function in hypercholesterolemic patients.

In vivo lateral blood flow velocity measurement using speckle size estimation.

PubMed

Xu, Tiantian; Hozan, Mohsen; Bashford, Gregory R

2014-05-01

In previous studies, we proposed blood measurement using speckle size estimation, which estimates the lateral component of blood flow within a single image frame based on the observation that the speckle pattern corresponding to blood reflectors (typically red blood cells) stretches (i.e., is "smeared") if blood flow is in the same direction as the electronically controlled transducer line selection in a 2-D image. In this observational study, the clinical viability of ultrasound blood flow velocity measurement using speckle size estimation was investigated and compared with that of conventional spectral Doppler of carotid artery blood flow data collected from human patients in vivo. Ten patients (six male, four female) were recruited. Right carotid artery blood flow data were collected in an interleaved fashion (alternating Doppler and B-mode A-lines) with an Antares Ultrasound Imaging System and transferred to a PC via the Axius Ultrasound Research Interface. The scanning velocity was 77 cm/s, and a 4-s interval of flow data were collected from each subject to cover three to five complete cardiac cycles. Conventional spectral Doppler data were collected simultaneously to compare with estimates made by speckle size estimation. The results indicate that the peak systolic velocities measured with the two methods are comparable (within ±10%) if the scan velocity is greater than or equal to the flow velocity. When scan velocity is slower than peak systolic velocity, the speckle stretch method asymptotes to the scan velocity. Thus, the speckle stretch method is able to accurately measure pure lateral flow, which conventional Doppler cannot do. In addition, an initial comparison of the speckle size estimation and color Doppler methods with respect to computational complexity and data acquisition time indicated potential time savings in blood flow velocity estimation using speckle size estimation. Further studies are needed for calculation of the speckle stretch method across a field of view and combination with an appropriate axial flow estimator. Copyright © 2014 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Fourier ptychographic reconstruction using Poisson maximum likelihood and truncated Wirtinger gradient.

PubMed

Bian, Liheng; Suo, Jinli; Chung, Jaebum; Ou, Xiaoze; Yang, Changhuei; Chen, Feng; Dai, Qionghai

2016-06-10

Fourier ptychographic microscopy (FPM) is a novel computational coherent imaging technique for high space-bandwidth product imaging. Mathematically, Fourier ptychographic (FP) reconstruction can be implemented as a phase retrieval optimization process, in which we only obtain low resolution intensity images corresponding to the sub-bands of the sample's high resolution (HR) spatial spectrum, and aim to retrieve the complex HR spectrum. In real setups, the measurements always suffer from various degenerations such as Gaussian noise, Poisson noise, speckle noise and pupil location error, which would largely degrade the reconstruction. To efficiently address these degenerations, we propose a novel FP reconstruction method under a gradient descent optimization framework in this paper. The technique utilizes Poisson maximum likelihood for better signal modeling, and truncated Wirtinger gradient for effective error removal. Results on both simulated data and real data captured using our laser-illuminated FPM setup show that the proposed method outperforms other state-of-the-art algorithms. Also, we have released our source code for non-commercial use.

Wavelet median denoising of ultrasound images

NASA Astrophysics Data System (ADS)

Macey, Katherine E.; Page, Wyatt H.

2002-05-01

Ultrasound images are contaminated with both additive and multiplicative noise, which is modeled by Gaussian and speckle noise respectively. Distinguishing small features such as fallopian tubes in the female genital tract in the noisy environment is problematic. A new method for noise reduction, Wavelet Median Denoising, is presented. Wavelet Median Denoising consists of performing a standard noise reduction technique, median filtering, in the wavelet domain. The new method is tested on 126 images, comprised of 9 original images each with 14 levels of Gaussian or speckle noise. Results for both separable and non-separable wavelets are evaluated, relative to soft-thresholding in the wavelet domain, using the signal-to-noise ratio and subjective assessment. The performance of Wavelet Median Denoising is comparable to that of soft-thresholding. Both methods are more successful in removing Gaussian noise than speckle noise. Wavelet Median Denoising outperforms soft-thresholding for a larger number of cases of speckle noise reduction than of Gaussian noise reduction. Noise reduction is more successful using non-separable wavelets than separable wavelets. When both methods are applied to ultrasound images obtained from a phantom of the female genital tract a small improvement is seen; however, a substantial improvement is required prior to clinical use.

Simultaneous imaging of oxygen tension and blood flow in animals using a digital micromirror device.

PubMed

Ponticorvo, Adrien; Dunn, Andrew K

2010-04-12

In this study we present a novel imaging method that combines high resolution cerebral blood flow imaging with a highly flexible map of absolute pO(2). In vivo measurements of pO(2) in animals using phosphorescence quenching is a well established method, and is preferable over electrical probes which are inherently invasive and are limited to single point measurements. However, spatially resolved pO(2) measurements using phosphorescence lifetime quenching typically require expensive cameras to obtain images of pO(2) and often suffer from poor signal to noise. Our approach enables us to retain the high temporal resolution and sensitivity of single point detection of phosphorescence by using a digital micromirror device (DMD) to selectively illuminate arbitrarily shaped regions of tissue. In addition, by simultaneously using Laser Speckle Contrast Imaging (LSCI) to measure relative blood flow, we can better examine the relationship between blood flow and absolute pO(2). We successfully used this instrument to study changes that occur during ischemic conditions in the brain with enough spatial resolution to clearly distinguish different regions. This novel instrument will provide researchers with an inexpensive and improved technique to examine multiple hemodynamic parameters simultaneously in the brain as well as other tissues.

Deviations from Rayleigh statistics in ultrasonic speckle.

PubMed

Tuthill, T A; Sperry, R H; Parker, K J

1988-04-01

The statistics of speckle patterns in ultrasound images have potential for tissue characterization. In "fully developed speckle" from many random scatterers, the amplitude is widely recognized as possessing a Rayleigh distribution. This study examines how scattering populations and signal processing can produce non-Rayleigh distributions. The first order speckle statistics are shown to depend on random scatterer density and the amplitude and spacing of added periodic scatterers. Envelope detection, amplifier compression, and signal bandwidth are also shown to cause distinct changes in the signal distribution.

A Multi Directional Perfect Reconstruction Filter Bank Designed with 2-D Eigenfilter Approach: Application to Ultrasound Speckle Reduction.

PubMed

Nagare, Mukund B; Patil, Bhushan D; Holambe, Raghunath S

2017-02-01

B-Mode ultrasound images are degraded by inherent noise called Speckle, which creates a considerable impact on image quality. This noise reduces the accuracy of image analysis and interpretation. Therefore, reduction of speckle noise is an essential task which improves the accuracy of the clinical diagnostics. In this paper, a Multi-directional perfect-reconstruction (PR) filter bank is proposed based on 2-D eigenfilter approach. The proposed method used for the design of two-dimensional (2-D) two-channel linear-phase FIR perfect-reconstruction filter bank. In this method, the fan shaped, diamond shaped and checkerboard shaped filters are designed. The quadratic measure of the error function between the passband and stopband of the filter has been used an objective function. First, the low-pass analysis filter is designed and then the PR condition has been expressed as a set of linear constraints on the corresponding synthesis low-pass filter. Subsequently, the corresponding synthesis filter is designed using the eigenfilter design method with linear constraints. The newly designed 2-D filters are used in translation invariant pyramidal directional filter bank (TIPDFB) for reduction of speckle noise in ultrasound images. The proposed 2-D filters give better symmetry, regularity and frequency selectivity of the filters in comparison to existing design methods. The proposed method is validated on synthetic and real ultrasound data which ensures improvement in the quality of ultrasound images and efficiently suppresses the speckle noise compared to existing methods.

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.

PubMed

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

2016-09-01

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%; 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.

Quantitative X-ray dark-field and phase tomography using single directional speckle scanning technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hongchang, E-mail: hongchang.wang@diamond.ac.uk; Kashyap, Yogesh; Sawhney, Kawal

2016-03-21

X-ray dark-field contrast tomography can provide important supplementary information inside a sample to the conventional absorption tomography. Recently, the X-ray speckle based technique has been proposed to provide qualitative two-dimensional dark-field imaging with a simple experimental arrangement. In this letter, we deduce a relationship between the second moment of scattering angle distribution and cross-correlation degradation of speckle and establish a quantitative basis of X-ray dark-field tomography using single directional speckle scanning technique. In addition, the phase contrast images can be simultaneously retrieved permitting tomographic reconstruction, which yields enhanced contrast in weakly absorbing materials. Such complementary tomography technique can allow systematicmore » investigation of complex samples containing both soft and hard materials.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berenguer de la Cuesta, Felisa; Wenger, Marco P.E.; Bean, Richard J.

Coherent X-ray diffraction has been applied in the imaging of inorganic materials with great success. However, its application to biological specimens has been limited to some notable exceptions, due to the induced radiation damage and the extended nature of biological samples, the last limiting the application of most part of the phasing algorithms. X-ray ptychography, still under development, is a good candidate to overcome such difficulties and become a powerful imaging method for biology. We describe herein the feasibility of applying ptychography to the imaging of biological specimens, in particular collagen rich samples. We report here speckles in diffraction patternsmore » from soft animal tissue, obtained with an optimized small angle X-ray setup that exploits the natural coherence of the beam. By phasing these patterns, dark field images of collagen within tendon, skin, bone, or cornea will eventually be obtained with a resolution of 60-70 nm. We present simulations of the contrast mechanism in collagen based on atomic force microscope images of the samples. Simulations confirmed the 'speckled' nature of the obtained diffraction patterns. Once inverted, the patterns will show the disposition and orientation of the fibers within the tissue, by enhancing the phase contrast between protein and no protein regions of the sample. Our work affords the application of the most innovative coherent X-ray diffraction tools to the study of biological specimens, and this approach will have a significant impact in biology and medicine because it overcomes many of the limits of current microscopy techniques.« less

Coherent X-ray diffraction from collagenous soft tissues.

PubMed

Berenguer de la Cuesta, Felisa; Wenger, Marco P E; Bean, Richard J; Bozec, Laurent; Horton, Michael A; Robinson, Ian K

2009-09-08

Coherent X-ray diffraction has been applied in the imaging of inorganic materials with great success. However, its application to biological specimens has been limited to some notable exceptions, due to the induced radiation damage and the extended nature of biological samples, the last limiting the application of most part of the phasing algorithms. X-ray ptychography, still under development, is a good candidate to overcome such difficulties and become a powerful imaging method for biology. We describe herein the feasibility of applying ptychography to the imaging of biological specimens, in particular collagen rich samples. We report here speckles in diffraction patterns from soft animal tissue, obtained with an optimized small angle X-ray setup that exploits the natural coherence of the beam. By phasing these patterns, dark field images of collagen within tendon, skin, bone, or cornea will eventually be obtained with a resolution of 60-70 nm. We present simulations of the contrast mechanism in collagen based on atomic force microscope images of the samples. Simulations confirmed the 'speckled' nature of the obtained diffraction patterns. Once inverted, the patterns will show the disposition and orientation of the fibers within the tissue, by enhancing the phase contrast between protein and no protein regions of the sample. Our work affords the application of the most innovative coherent X-ray diffraction tools to the study of biological specimens, and this approach will have a significant impact in biology and medicine because it overcomes many of the limits of current microscopy techniques.

Infrared speckle interferometry and spectroscopy of Io

NASA Technical Reports Server (NTRS)

Howell, Robert R.

1991-01-01

The goal during the last year was to continue the speckle monitoring of volcanic hot spots on Io, and to begin observations of the 1991 series of mutual events between Io and Europa. The former provide a time history of the volcanic activity, while the latter give the highest spatial resolution and the best sensitivity to faint spots. A minor component of the program is lunar occultation observations of young T Tauri stars. The occultations provide milliarcsecond resolution which let us search for circumstellar material and determine which systems are multiple.

Speckle Noise in Highly Corrected Coronagraphs

NASA Technical Reports Server (NTRS)

Bloemhof, Eric E.

2004-01-01

Speckles in a highly corrected adaptive optic imaging system have been studied through numerical simulations and through analytic and algebraic investigations of the Fourier-optical expressions connecting pupil plane and focal plane, which simplify at high Strehl ratio. Significant insights into the behavior of speckles, and the speckle noise caused when they vary over time, have thus been gained. Such speckle noise is expected to set key limits on the sensitivity of searches for companions around other stars, including extrasolar planets. In most cases, it is advantageous to use a coronagraph of some kind to suppress the bright primary star and so enhance the dynamic range of companion searches. In the current paper, I investigate speckle behavior and its impact on speckle noise in some common coronagraphic architectures, including the classical Lyot coronagraph and the new four quadrant phase mask (FQPM) concept.

Adaptive mesh optimization and nonrigid motion recovery based image registration for wide-field-of-view ultrasound imaging.

PubMed

Tan, Chaowei; Wang, Bo; Liu, Paul; Liu, Dong

2008-01-01

Wide field of view (WFOV) imaging mode obtains an ultrasound image over an area much larger than the real time window normally available. As the probe is moved over the region of interest, new image frames are combined with prior frames to form a panorama image. Image registration techniques are used to recover the probe motion, eliminating the need for a position sensor. Speckle patterns, which are inherent in ultrasound imaging, change, or become decorrelated, as the scan plane moves, so we pre-smooth the image to reduce the effects of speckle in registration, as well as reducing effects from thermal noise. Because we wish to track the movement of features such as structural boundaries, we use an adaptive mesh over the entire smoothed image to home in on areas with feature. Motion estimation using blocks centered at the individual mesh nodes generates a field of motion vectors. After angular correction of motion vectors, we model the overall movement between frames as a nonrigid deformation. The polygon filling algorithm for precise, persistence-based spatial compounding constructs the final speckle reduced WFOV image.

Intraoperative laser speckle contrast imaging with retrospective motion correction for quantitative assessment of cerebral blood flow

PubMed Central

Richards, Lisa M.; Towle, Erica L.; Fox, Douglas J.; Dunn, Andrew K.

2014-01-01

Abstract. Although multiple intraoperative cerebral blood flow (CBF) monitoring techniques are currently available, a quantitative method that allows for continuous monitoring and that can be easily integrated into the surgical workflow is still needed. Laser speckle contrast imaging (LSCI) is an optical imaging technique with a high spatiotemporal resolution that has been recently demonstrated as feasible and effective for intraoperative monitoring of CBF during neurosurgical procedures. This study demonstrates the impact of retrospective motion correction on the quantitative analysis of intraoperatively acquired LSCI images. LSCI images were acquired through a surgical microscope during brain tumor resection procedures from 10 patients under baseline conditions and after a cortical stimulation in three of those patients. The patient’s electrocardiogram (ECG) was recorded during acquisition for postprocess correction of pulsatile artifacts. Automatic image registration was retrospectively performed to correct for tissue motion artifacts, and the performance of rigid and nonrigid transformations was compared. In baseline cases, the original images had 25%±27% noise across 16 regions of interest (ROIs). ECG filtering moderately reduced the noise to 20%±21%, while image registration resulted in a further noise reduction of 15%±4%. Combined ECG filtering and image registration significantly reduced the noise to 6.2%±2.6% (p<0.05). Using the combined motion correction, accuracy and sensitivity to small changes in CBF were improved in cortical stimulation cases. There was also excellent agreement between rigid and nonrigid registration methods (15/16 ROIs with <3% difference). Results from this study demonstrate the importance of motion correction for improved visualization of CBF changes in clinical LSCI images. PMID:26157974

Measurement potential of laser speckle velocimetry

NASA Technical Reports Server (NTRS)

Adrian, R. J.

1982-01-01

Laser speckle velocimetry, the measurement of fluid velocity by measuring the translation of speckle pattern or individual particles that are moving with the fluid, is described. The measurement is accomplished by illuminating the fluid with consecutive pulses of Laser Light and recording the images of the particles or the speckles on a double exposed photographic plate. The plate contains flow information throughout the image plane so that a single double exposure may provide data at hundreds or thousands of points in the illuminated region of the fluid. Conventional interrogation of the specklegram involves illuminating the plate to form Young's fringes, whose spacing is inversely proportional to the speckle separation. Subsequently the fringes are digitized and analyzed in a computer to determine their frequency and orientation, yielding the velocity magnitude and orientation. The Young's fringe technique is equivalent to performing a 2-D spatial correlation of the double exposed specklegram intensity pattern, and this observation suggests that correlation should be considered as an alternative processing method. The principle of the correlation technique is examined.

Speckle dynamics under ergodicity breaking

NASA Astrophysics Data System (ADS)

Sdobnov, Anton; Bykov, Alexander; Molodij, Guillaume; Kalchenko, Vyacheslav; Jarvinen, Topias; Popov, Alexey; Kordas, Krisztian; Meglinski, Igor

2018-04-01

Laser speckle contrast imaging (LSCI) is a well-known and versatile approach for the non-invasive visualization of flows and microcirculation localized in turbid scattering media, including biological tissues. In most conventional implementations of LSCI the ergodic regime is typically assumed valid. However, most composite turbid scattering media, especially biological tissues, are non-ergodic, containing a mixture of dynamic and static centers of light scattering. In the current study, we examined the speckle contrast in different dynamic conditions with the aim of assessing limitations in the quantitative interpretation of speckle contrast images. Based on a simple phenomenological approach, we introduced a coefficient of speckle dynamics to quantitatively assess the ratio of the dynamic part of a scattering medium to the static one. The introduced coefficient allows one to distinguish real changes in motion from the mere appearance of static components in the field of view. As examples of systems with static/dynamic transitions, thawing and heating of Intralipid samples were studied by the LSCI approach.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

O’Shea, T; Bamber, J; Harris, E

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 templatemore » 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 would also be prudent. This work is support by Cancer Research UK Programme Grant C33589/A19727.« less

An improved triangulation laser rangefinder using a custom CMOS HDR linear image sensor

NASA Astrophysics Data System (ADS)

Liscombe, Michael

3-D triangulation laser rangefinders are used in many modern applications, from terrain mapping to biometric identification. Although a wide variety of designs have been proposed, laser speckle noise still provides a fundamental limitation on range accuracy. These works propose a new triangulation laser rangefinder designed specifically to mitigate the effects of laser speckle noise. The proposed rangefinder uses a precision linear translator to laterally reposition the imaging system (e.g., image sensor and imaging lens). For a given spatial location of the laser spot, capturing N spatially uncorrelated laser spot profiles is shown to improve range accuracy by a factor of N . This technique has many advantages over past speckle-reduction technologies, such as a fixed system cost and form factor, and the ability to virtually eliminate laser speckle noise. These advantages are made possible through spatial diversity and come at the cost of increased acquisition time. The rangefinder makes use of the ICFYKWG1 linear image sensor, a custom CMOS sensor developed at the Vision Sensor Laboratory (York University). Tests are performed on the image sensor's innovative high dynamic range technology to determine its effects on range accuracy. As expected, experimental results have shown that the sensor provides a trade-off between dynamic range and range accuracy.

Overview of Single-Molecule Speckle (SiMS) Microscopy and Its Electroporation-Based Version with Efficient Labeling and Improved Spatiotemporal Resolution.

PubMed

Yamashiro, Sawako; Watanabe, Naoki

2017-07-06

Live-cell single-molecule imaging was introduced more than a decade ago, and has provided critical information on remodeling of the actin cytoskeleton, the motion of plasma membrane proteins, and dynamics of molecular motor proteins. Actin remodeling has been the best target for this approach because actin and its associated proteins stop diffusing when assembled, allowing visualization of single-molecules of fluorescently-labeled proteins in a state specific manner. The approach based on this simple principle is called Single-Molecule Speckle (SiMS) microscopy. For instance, spatiotemporal regulation of actin polymerization and lifetime distribution of actin filaments can be monitored directly by tracking actin SiMS. In combination with fluorescently labeled probes of various actin regulators, SiMS microscopy has contributed to clarifying the processes underlying recycling, motion and remodeling of the live-cell actin network. Recently, we introduced an electroporation-based method called eSiMS microscopy, with high efficiency, easiness and improved spatiotemporal precision. In this review, we describe the application of live-cell single-molecule imaging to cellular actin dynamics and discuss the advantages of eSiMS microscopy over previous SiMS microscopy.

SAR image filtering based on the heavy-tailed Rayleigh model.

PubMed

Achim, Alin; Kuruoğlu, Ercan E; Zerubia, Josiane

2006-09-01

Synthetic aperture radar (SAR) images are inherently affected by a signal dependent noise known as speckle, which is due to the radar wave coherence. In this paper, we propose a novel adaptive despeckling filter and derive a maximum a posteriori (MAP) estimator for the radar cross section (RCS). We first employ a logarithmic transformation to change the multiplicative speckle into additive noise. We model the RCS using the recently introduced heavy-tailed Rayleigh density function, which was derived based on the assumption that the real and imaginary parts of the received complex signal are best described using the alpha-stable family of distribution. We estimate model parameters from noisy observations by means of second-kind statistics theory, which relies on the Mellin transform. Finally, we compare the proposed algorithm with several classical speckle filters applied on actual SAR images. Experimental results show that the homomorphic MAP filter based on the heavy-tailed Rayleigh prior for the RCS is among the best for speckle removal.

Improved cardiac motion detection from ultrasound images using TDIOF: a combined B-mode/ tissue Doppler approach

NASA Astrophysics Data System (ADS)

Tavakoli, Vahid; Stoddard, Marcus F.; Amini, Amir A.

2013-03-01

Quantitative motion analysis of echocardiographic images helps clinicians with the diagnosis and therapy of patients suffering from cardiac disease. Quantitative analysis is usually based on TDI (Tissue Doppler Imaging) or speckle tracking. These methods are based on two independent techniques - the Doppler Effect and image registration, respectively. In order to increase the accuracy of the speckle tracking technique and cope with the angle dependency of TDI, herein, a combined approach dubbed TDIOF (Tissue Doppler Imaging Optical Flow) is proposed. TDIOF is formulated based on the combination of B-mode and Doppler energy terms in an optical flow framework and minimized using algebraic equations. In this paper, we report on validations with simulated, physical cardiac phantom, and in-vivo patient data. It is shown that the additional Doppler term is able to increase the accuracy of speckle tracking, the basis for several commercially available echocardiography analysis techniques.

Guided SAR image despeckling with probabilistic non local weights

NASA Astrophysics Data System (ADS)

Gokul, Jithin; Nair, Madhu S.; Rajan, Jeny

2017-12-01

SAR images are generally corrupted by granular disturbances called speckle, which makes visual analysis and detail extraction a difficult task. Non Local despeckling techniques with probabilistic similarity has been a recent trend in SAR despeckling. To achieve effective speckle suppression without compromising detail preservation, we propose an improvement for the existing Generalized Guided Filter with Bayesian Non-Local Means (GGF-BNLM) method. The proposed method (Guided SAR Image Despeckling with Probabilistic Non Local Weights) replaces parametric constants based on heuristics in GGF-BNLM method with dynamically derived values based on the image statistics for weight computation. Proposed changes make GGF-BNLM method adaptive and as a result, significant improvement is achieved in terms of performance. Experimental analysis on SAR images shows excellent speckle reduction without compromising feature preservation when compared to GGF-BNLM method. Results are also compared with other state-of-the-art and classic SAR depseckling techniques to demonstrate the effectiveness of the proposed method.

A Nonlinear Diffusion Equation-Based Model for Ultrasound Speckle Noise Removal

NASA Astrophysics Data System (ADS)

Zhou, Zhenyu; Guo, Zhichang; Zhang, Dazhi; Wu, Boying

2018-04-01

Ultrasound images are contaminated by speckle noise, which brings difficulties in further image analysis and clinical diagnosis. In this paper, we address this problem in the view of nonlinear diffusion equation theories. We develop a nonlinear diffusion equation-based model by taking into account not only the gradient information of the image, but also the information of the gray levels of the image. By utilizing the region indicator as the variable exponent, we can adaptively control the diffusion type which alternates between the Perona-Malik diffusion and the Charbonnier diffusion according to the image gray levels. Furthermore, we analyze the proposed model with respect to the theoretical and numerical properties. Experiments show that the proposed method achieves much better speckle suppression and edge preservation when compared with the traditional despeckling methods, especially in the low gray level and low-contrast regions.

Using the auxiliary camera for system calibration of 3D measurement by digital speckle

NASA Astrophysics Data System (ADS)

Xue, Junpeng; Su, Xianyu; Zhang, Qican

2014-06-01

The study of 3D shape measurement by digital speckle temporal sequence correlation have drawn a lot of attention by its own advantages, however, the measurement mainly for depth z-coordinate, horizontal physical coordinate (x, y) are usually marked as image pixel coordinate. In this paper, a new approach for the system calibration is proposed. With an auxiliary camera, we made up the temporary binocular vision system, which are used for the calibration of horizontal coordinates (mm) while the temporal sequence reference-speckle-sets are calibrated. First, the binocular vision system has been calibrated using the traditional method. Then, the digital speckles are projected on the reference plane, which is moved by equal distance in the direction of depth, temporal sequence speckle images are acquired with camera as reference sets. When the reference plane is in the first position and final position, crossed fringe pattern are projected to the plane respectively. The control points of pixel coordinates are extracted by Fourier analysis from the images, and the physical coordinates are calculated by the binocular vision. The physical coordinates corresponding to each pixel of the images are calculated by interpolation algorithm. Finally, the x and y corresponding to arbitrary depth value z are obtained by the geometric formula. Experiments prove that our method can fast and flexibly measure the 3D shape of an object as point cloud.

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

PubMed

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.

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

PubMed Central

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

Enhanced diagnostic of skin conditions by polarized laser speckles: phantom studies and computer modeling

NASA Astrophysics Data System (ADS)

Tchvialeva, Lioudmila; Lee, Tim K.; Markhvida, Igor; Zeng, Haishan; Doronin, Alexander; Meglinski, Igor

2014-03-01

The incidence of the skin melanoma, the most commonly fatal form of skin cancer, is increasing faster than any other potentially preventable cancer. Clinical practice is currently hampered by the lack of the ability to rapidly screen the functional and morphological properties of tissues. In our previous study we show that the quantification of scattered laser light polarization provides a useful metrics for diagnostics of the malignant melanoma. In this study we exploit whether the image speckle could improve skin cancer diagnostic in comparison with the previously used free-space speckle. The study includes skin phantom measurements and computer modeling. To characterize the depolarization of light we measure the spatial distribution of speckle patterns and analyse their depolarization ratio taken into account radial symmetry. We examine the dependences of depolarization ratio vs. roughness for phantoms which optical properties are of the order of skin lesions. We demonstrate that the variation in bulk optical properties initiates the assessable changes in the depolarization ratio. We show that image speckle differentiates phantoms significantly better than free-space speckle. The results of experimental measurements are compared with the results of Monte Carlo simulation.

Intrinsic speckle noise in in-line particle holography due to polydisperse and continuous particle sizes

NASA Astrophysics Data System (ADS)

Edwards, Philip J.; Hobson, Peter R.; Rodgers, G. J.

2000-08-01

In-line particle holography is subject to image deterioration due to intrinsic speckle noise. The resulting reduction in the signal to noise ratio (SNR) of the replayed image can become critical for applications such as holographic particle velocimetry (HPV) and 3D visualisation of marine plankton. Work has been done to extend the mono-disperse model relevant to HPV to include poly-disperse particle fields appropriate for the visualisation of marine plankton. Continuous and discrete particle fields are both considered. It is found that random walk statistics still apply for the poly-disperse case. The speckle field is simply the summation of the individual speckle patters due to each scatter size. Therefor the characteristic speckle parameter (which encompasses particle diameter, concentration and sample depth) is alos just the summation of the individual speckle parameters. This reduces the SNR calculation to the same form as for the mono-disperse case. For the continuous situation three distributions, power, exponential and Gaussian are discussed with the resulting SNR calcuated. The work presented here was performed as part of the Holomar project to produce a working underwater holographic camera for recording plankton.

Correcting for motion artifact in handheld laser speckle images.

PubMed

Lertsakdadet, Ben; Yang, Bruce Y; Dunn, Cody E; Ponticorvo, Adrien; Crouzet, Christian; Bernal, Nicole; Durkin, Anthony J; Choi, Bernard

2018-03-01

Laser speckle imaging (LSI) is a wide-field optical technique that enables superficial blood flow quantification. LSI is normally performed in a mounted configuration to decrease the likelihood of motion artifact. However, mounted LSI systems are cumbersome and difficult to transport quickly in a clinical setting for which portability is essential in providing bedside patient care. To address this issue, we created a handheld LSI device using scientific grade components. To account for motion artifact of the LSI device used in a handheld setup, we incorporated a fiducial marker (FM) into our imaging protocol and determined the difference between highest and lowest speckle contrast values for the FM within each data set (Kbest and Kworst). The difference between Kbest and Kworst in mounted and handheld setups was 8% and 52%, respectively, thereby reinforcing the need for motion artifact quantification. When using a threshold FM speckle contrast value (KFM) to identify a subset of images with an acceptable level of motion artifact, mounted and handheld LSI measurements of speckle contrast of a flow region (KFLOW) in in vitro flow phantom experiments differed by 8%. Without the use of the FM, mounted and handheld KFLOW values differed by 20%. To further validate our handheld LSI device, we compared mounted and handheld data from an in vivo porcine burn model of superficial and full thickness burns. The speckle contrast within the burn region (KBURN) of the mounted and handheld LSI data differed by <4  %   when accounting for motion artifact using the FM, which is less than the speckle contrast difference between superficial and full thickness burns. Collectively, our results suggest the potential of handheld LSI with an FM as a suitable alternative to mounted LSI, especially in challenging clinical settings with space limitations such as the intensive care unit. (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Use of speckle for determining the response characteristics of Doppler imaging radars

NASA Technical Reports Server (NTRS)

Tilley, D. G.

1986-01-01

An optical model is developed for imaging optical radars such as the SAR on Seasat and the Shuttle Imaging Radar (SIR-B) by analyzing the Doppler shift of individual speckles in the image. The signal received at the spacecraft is treated in terms of a Fresnel-Kirchhoff integration over all backscattered radiation within a Huygen aperture at the earth. Account is taken of the movement of the spacecraft along the orbital path between emission and reception. The individual points are described by integration of the point source amplitude with a Green's function scattering kernel. Doppler data at each point furnishes the coordinates for visual representations. A Rayleigh-Poisson model of the surface scattering characteristics is used with Monte Carlo methods to generate simulations of Doppler radar speckle that compare well with Seasat SAR data SIR-B data.

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

NASA Astrophysics Data System (ADS)

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.

Investigations of High Resolution Imaging through the Earth’s Atmosphere Using Speckle Interferometry.

DTIC Science & Technology

1987-03-15

previous studies based on surfact- integrated measures alone./ - "o % 10- ’% Py ",". , [. ... T.T; 3 i...19 ’S,, IL 644 L %% 5%;-Si N’S’ a . W-i W’U U1 1 Introduction The M2 lab supergiant a Orionis has been one of the most frequently studied ...level of the ’ maxima in three of folur cases . rhe 1978 lightcurve wasit causes us to severely underestimate the the only one obtained when the sub

Texture Feature Analysis for Different Resolution Level of Kidney Ultrasound Images

NASA Astrophysics Data System (ADS)

Kairuddin, Wan Nur Hafsha Wan; Mahmud, Wan Mahani Hafizah Wan

2017-08-01

Image feature extraction is a technique to identify the characteristic of the image. The objective of this work is to discover the texture features that best describe a tissue characteristic of a healthy kidney from ultrasound (US) image. Three ultrasound machines that have different specifications are used in order to get a different quality (different resolution) of the image. Initially, the acquired images are pre-processed to de-noise the speckle to ensure the image preserve the pixels in a region of interest (ROI) for further extraction. Gaussian Low- pass Filter is chosen as the filtering method in this work. 150 of enhanced images then are segmented by creating a foreground and background of image where the mask is created to eliminate some unwanted intensity values. Statistical based texture features method is used namely Intensity Histogram (IH), Gray-Level Co-Occurance Matrix (GLCM) and Gray-level run-length matrix (GLRLM).This method is depends on the spatial distribution of intensity values or gray levels in the kidney region. By using One-Way ANOVA in SPSS, the result indicated that three features (Contrast, Difference Variance and Inverse Difference Moment Normalized) from GLCM are not statistically significant; this concludes that these three features describe a healthy kidney characteristics regardless of the ultrasound image quality.

Continuum generation in optical fibers for high-resolution holographic coherence domain imaging application

NASA Astrophysics Data System (ADS)

Li, Linghui; Gruzdev, Vitaly; Yu, Ping; Chen, J. K.

2009-02-01

High pulse energy continuum generation in conventional multimode optical fibers has been studied for potential applications to a holographic optical coherence imaging system. As a new imaging modality for the biological tissue imaging, high-resolution holographic optical coherence imaging requires a broadband light source with a high brightness, a relatively low spatial coherence and a high stability. A broadband femtosecond laser can not be used as the light source of holographic imaging system since the laser creates a lot of speckle patterns. By coupling high peak power femtosecond laser pulses into a multimode optical fiber, nonlinear optical effects cause a continuum generation that can be served as a super-bright and broadband light source. In our experiment, an amplified femtosecond laser was coupled into the fiber through a microscopic objective. We measured the FWHM of the continuum generation as a function of incident pulse energy from 80 nJ to 800 μJ. The maximum FWHM is about 8 times higher than that of the input pulses. The stability was analyzed at different pump energies, integration times and fiber lengths. The spectral broadening and peak position show that more than two processes compete in the fiber.

Some comments on particle image displacement velocimetry

NASA Technical Reports Server (NTRS)

Lourenco, L. M.

1988-01-01

Laser speckle velocimetry (LSV) or particle image displacement velocimetry, is introduced. This technique provides the simultaneous visualization of the two-dimensional streamline pattern in unsteady flows as well as the quantification of the velocity field over an entire plane. The advantage of this technique is that the velocity field can be measured over an entire plane of the flow field simultaneously, with accuracy and spatial resolution. From this the instantaneous vorticity field can be easily obtained. This constitutes a great asset for the study of a variety of flows that evolve stochastically in both space and time. The basic concept of LSV; methods of data acquisition and reduction, examples of its use, and parameters that affect its utilization are described.

GF-3 SAR Image Despeckling Based on the Improved Non-Local Means Using Non-Subsampled Shearlet Transform

NASA Astrophysics Data System (ADS)

Shi, R.; Sun, Z.

2018-04-01

GF-3 synthetic aperture radar (SAR) images are rich in information and have obvious sparse features. However, the speckle appears in the GF-3 SAR images due to the coherent imaging system and it hinders the interpretation of images seriously. Recently, Shearlet is applied to the image processing with its best sparse representation. A new Shearlet-transform-based method is proposed in this paper based on the improved non-local means. Firstly, the logarithmic operation and the non-subsampled Shearlet transformation are applied to the GF-3 SAR image. Secondly, in order to solve the problems that the image details are smoothed overly and the weight distribution is affected by the speckle, a new non-local means is used for the transformed high frequency coefficient. Thirdly, the Shearlet reconstruction is carried out. Finally, the final filtered image is obtained by an exponential operation. Experimental results demonstrate that, compared with other despeckling methods, the proposed method can suppress the speckle effectively in homogeneous regions and has better capability of edge preserving.

The agreement between 3D, standard 2D and triplane 2D speckle tracking: effects of image quality and 3D volume rate.

PubMed

Trache, Tudor; Stöbe, Stephan; Tarr, Adrienn; Pfeiffer, Dietrich; Hagendorff, Andreas

2014-12-01

Comparison of 3D and 2D speckle tracking performed on standard 2D and triplane 2D datasets of normal and pathological left ventricular (LV) wall-motion patterns with a focus on the effect that 3D volume rate (3DVR), image quality and tracking artifacts have on the agreement between 2D and 3D speckle tracking. 37 patients with normal LV function and 18 patients with ischaemic wall-motion abnormalities underwent 2D and 3D echocardiography, followed by offline speckle tracking measurements. The values of 3D global, regional and segmental strain were compared with the standard 2D and triplane 2D strain values. Correlation analysis with the LV ejection fraction (LVEF) was also performed. The 3D and 2D global strain values correlated good in both normally and abnormally contracting hearts, though systematic differences between the two methods were observed. Of the 3D strain parameters, the area strain showed the best correlation with the LVEF. The numerical agreement of 3D and 2D analyses varied significantly with the volume rate and image quality of the 3D datasets. The highest correlation between 2D and 3D peak systolic strain values was found between 3D area and standard 2D longitudinal strain. Regional wall-motion abnormalities were similarly detected by 2D and 3D speckle tracking. 2DST of triplane datasets showed similar results to those of conventional 2D datasets. 2D and 3D speckle tracking similarly detect normal and pathological wall-motion patterns. Limited image quality has a significant impact on the agreement between 3D and 2D numerical strain values.

A pilot study to image the vascular network of small melanocytic choroidal tumors with speckle noise-free 1050-nm swept source optical coherence tomography (OCT choroidal angiography).

PubMed

Maloca, Peter; Gyger, Cyrill; Hasler, Pascal W

2016-06-01

To visualize and measure the vascular network of melanocytic choroidal tumors with speckle noise-free swept source optical coherence tomography (SS-OCT choroidal angiography). Melanocytic choroidal tumors from 24 eyes were imaged with 1050-nm optical coherence tomography (Topcon DRI OCT-1 Atlantis). A semi-automated algorithm was developed to remove speckle noise and to extract and measure the volume of the choroidal vessels from the obtained OCT data. In all cases, analysis of the choroidal vessels could be performed with SS-OCT without the need for pupillary dilation. The proposed method allows speckle noise-free, structure-guided visualization and measurement of the larger choroidal vessels in three dimensions. The obtained data suggest that speckle noise-free OCT may be more effective at identifying choroidal structures than traditional OCT methods. The measured volume of the extracted choroidal vessels of Haller's layer and Sattler's layer in the examined tumorous eyes was on average 0.982463955 mm(3) /982463956 μm(3) (range of 0.209764406 mm(3) /209764405.9 μm(3)to 1.78105544 mm(3) /1781055440 μm(3)). Full thickness obstruction of the choroidal vasculature by the tumor was found in 18 cases (72 %). In seven cases (18 %), choroidal vessel architecture did not show pronounced morphological abnormalities (18 %). Speckle noise-free OCT may serve as a new illustrative imaging technology and enhance visualization of the choroidal vessels without the need for dye injection. OCT can be used to identify and evaluate the choroidal vessels of melanocytic choroidal tumors, and may represent a potentially useful tool for imaging and monitoring of choroidal nevi and melanoma.

Dynamic laser speckle for non-destructive quality evaluation of bread

NASA Astrophysics Data System (ADS)

Stoykova, E.; Ivanov, B.; Shopova, M.; Lyubenova, T.; Panchev, I.; Sainov, V.

2010-10-01

Coherent illumination of a diffuse object yields a randomly varying interference pattern, which changes over time at any modification of the object. This phenomenon can be used for detection and visualization of physical or biological activity in various objects (e.g. fruits, seeds, coatings) through statistical description of laser speckle dynamics. The present report aims at non-destructive full-field evaluation of bread by spatial-temporal characterization of laser speckle. The main purpose of the conducted experiments was to prove the ability of the dynamic speckle method to indicate activity within the studied bread samples. In the set-up for acquisition and storage of dynamic speckle patterns an expanded beam from a DPSS laser (532 nm and 100mW) illuminated the sample through a ground glass diffuser. A CCD camera, adjusted to focus the sample, recorded regularly a sequence of images (8 bits and 780 x 582 squared pixels, sized 8.1 × 8.1 μm) at sampling frequency 0.25 Hz. A temporal structure function was calculated to evaluate activity of the bread samples in time using the full images in the sequence. In total, 7 samples of two types of bread were monitored during a chemical and physical process of bread's staling. Segmentation of images into matrixes of isometric fragments was also utilized. The results proved the potential of dynamic speckle as effective means for monitoring the process of bread staling and ability of this approach to differentiate between different types of bread.

Kitt Peak speckle camera

NASA Technical Reports Server (NTRS)

Breckinridge, J. B.; Mcalister, H. A.; Robinson, W. G.

1979-01-01

The speckle camera in regular use at Kitt Peak National Observatory since 1974 is described in detail. The design of the atmospheric dispersion compensation prisms, the use of film as a recording medium, the accuracy of double star measurements, and the next generation speckle camera are discussed. Photographs of double star speckle patterns with separations from 1.4 sec of arc to 4.7 sec of arc are shown to illustrate the quality of image formation with this camera, the effects of seeing on the patterns, and to illustrate the isoplanatic patch of the atmosphere.

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

PubMed Central

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%; 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. PMID:27599202

Digital Speckle Photography of Subpixel Displacements of Speckle Structures Based on Analysis of Their Spatial Spectra

NASA Astrophysics Data System (ADS)

Maksimova, L. A.; Ryabukho, P. V.; Mysina, N. Yu.; Lyakin, D. V.; Ryabukho, V. P.

2018-04-01

We have investigated the capabilities of the method of digital speckle interferometry for determining subpixel displacements of a speckle structure formed by a displaceable or deformable object with a scattering surface. An analysis of spatial spectra of speckle structures makes it possible to perform measurements with a subpixel accuracy and to extend the lower boundary of the range of measurements of displacements of speckle structures to the range of subpixel values. The method is realized on the basis of digital recording of the images of undisplaced and displaced speckle structures, their spatial frequency analysis using numerically specified constant phase shifts, and correlation analysis of spatial spectra of speckle structures. Transformation into the frequency range makes it possible to obtain quantities to be measured with a subpixel accuracy from the shift of the interference-pattern minimum in the diffraction halo by introducing an additional phase shift into the complex spatial spectrum of the speckle structure or from the slope of the linear plot of the function of accumulated phase difference in the field of the complex spatial spectrum of the displaced speckle structure. The capabilities of the method have been investigated in natural experiment.

Laboratory test of a polarimetry imaging subtraction system for the high-contrast imaging

NASA Astrophysics Data System (ADS)

Dou, Jiangpei; Ren, Deqing; Zhu, Yongtian; Zhang, Xi; Li, Rong

2012-09-01

We propose a polarimetry imaging subtraction test system that can be used for the direct imaging of the reflected light from exoplanets. Such a system will be able to remove the speckle noise scattered by the wave-front error and thus can enhance the high-contrast imaging. In this system, we use a Wollaston Prism (WP) to divide the incoming light into two simultaneous images with perpendicular linear polarizations. One of the images is used as the reference image. Then both the phase and geometric distortion corrections have been performed on the other image. The corrected image is subtracted with the reference image to remove the speckles. The whole procedure is based on an optimization algorithm and the target function is to minimize the residual speckles after subtraction. For demonstration purpose, here we only use a circular pupil in the test without integrating of our apodized-pupil coronagraph. It is shown that best result can be gained by inducing both phase and distortion corrections. Finally, it has reached an extra contrast gain of 50-times improvement in average, which is promising to be used for the direct imaging of exoplanets.

Near Real-Time Image Reconstruction

NASA Astrophysics Data System (ADS)

Denker, C.; Yang, G.; Wang, H.

2001-08-01

In recent years, post-facto image-processing algorithms have been developed to achieve diffraction-limited observations of the solar surface. We present a combination of frame selection, speckle-masking imaging, and parallel computing which provides real-time, diffraction-limited, 256×256 pixel images at a 1-minute cadence. Our approach to achieve diffraction limited observations is complementary to adaptive optics (AO). At the moment, AO is limited by the fact that it corrects wavefront abberations only for a field of view comparable to the isoplanatic patch. This limitation does not apply to speckle-masking imaging. However, speckle-masking imaging relies on short-exposure images which limits its spectroscopic applications. The parallel processing of the data is performed on a Beowulf-class computer which utilizes off-the-shelf, mass-market technologies to provide high computational performance for scientific calculations and applications at low cost. Beowulf computers have a great potential, not only for image reconstruction, but for any kind of complex data reduction. Immediate access to high-level data products and direct visualization of dynamic processes on the Sun are two of the advantages to be gained.

Color speckle in laser displays

NASA Astrophysics Data System (ADS)

Kuroda, Kazuo

2015-07-01

At the beginning of this century, lighting technology has been shifted from discharge lamps, fluorescent lamps and electric bulbs to solid-state lighting. Current solid-state lighting is based on the light emitting diodes (LED) technology, but the laser lighting technology is developing rapidly, such as, laser cinema projectors, laser TVs, laser head-up displays, laser head mounted displays, and laser headlamps for motor vehicles. One of the main issues of laser displays is the reduction of speckle noise1). For the monochromatic laser light, speckle is random interference pattern on the image plane (retina for human observer). For laser displays, RGB (red-green-blue) lasers form speckle patterns independently, which results in random distribution of chromaticity, called color speckle2).

Gaussian pre-filtering for uncertainty minimization in digital image correlation using numerically-designed speckle patterns

NASA Astrophysics Data System (ADS)

Mazzoleni, Paolo; Matta, Fabio; Zappa, Emanuele; Sutton, Michael A.; Cigada, Alfredo

2015-03-01

This paper discusses the effect of pre-processing image blurring on the uncertainty of two-dimensional digital image correlation (DIC) measurements for the specific case of numerically-designed speckle patterns having particles with well-defined and consistent shape, size and spacing. Such patterns are more suitable for large measurement surfaces on large-scale specimens than traditional spray-painted random patterns without well-defined particles. The methodology consists of numerical simulations where Gaussian digital filters with varying standard deviation are applied to a reference speckle pattern. To simplify the pattern application process for large areas and increase contrast to reduce measurement uncertainty, the speckle shape, mean size and on-center spacing were selected to be representative of numerically-designed patterns that can be applied on large surfaces through different techniques (e.g., spray-painting through stencils). Such 'designer patterns' are characterized by well-defined regions of non-zero frequency content and non-zero peaks, and are fundamentally different from typical spray-painted patterns whose frequency content exhibits near-zero peaks. The effect of blurring filters is examined for constant, linear, quadratic and cubic displacement fields. Maximum strains between ±250 and ±20,000 με are simulated, thus covering a relevant range for structural materials subjected to service and ultimate stresses. The robustness of the simulation procedure is verified experimentally using a physical speckle pattern subjected to constant displacements. The stability of the relation between standard deviation of the Gaussian filter and measurement uncertainty is assessed for linear displacement fields at varying image noise levels, subset size, and frequency content of the speckle pattern. It is shown that bias error as well as measurement uncertainty are minimized through Gaussian pre-filtering. This finding does not apply to typical spray-painted patterns without well-defined particles, for which image blurring is only beneficial in reducing bias errors.

Potential use of combining the diffusion equation with the free Shrödinger equation to improve the Optical Coherence Tomography image analysis

NASA Astrophysics Data System (ADS)

Cabrera Fernandez, Delia; Salinas, Harry M.; Somfai, Gabor; Puliafito, Carmen A.

2006-03-01

Optical coherence tomography (OCT) is a rapidly emerging medical imaging technology. In ophthalmology, OCT is a powerful tool because it enables visualization of the cross sectional structure of the retina and anterior eye with higher resolutions than any other non-invasive imaging modality. Furthermore, OCT image information can be quantitatively analyzed, enabling objective assessment of features such as macular edema and diabetes retinopathy. We present specific improvements in the quantitative analysis of the OCT system, by combining the diffusion equation with the free Shrödinger equation. In such formulation, important features of the image can be extracted by extending the analysis from the real axis to the complex domain. Experimental results indicate that our proposed novel approach has good performance in speckle noise removal, enhancement and segmentation of the various cellular layers of the retina using the OCT system.

First Results of the Near Real-Time Imaging Reconstruction System at Big Bear Solar Observatory

NASA Astrophysics Data System (ADS)

Yang, G.; Denker, C.; Wang, H.

2003-05-01

The Near Real-Time Imaging Reconstruction system (RTIR) at Big Bear Solar Observatory (BBSO) is designed to obtain high spatial resolution solar images at a cadence of 1 minute utilizing the power of parallel processing. With this system, we can compute near diffraction-limited images without saving huge amounts of data that are involved in the speckle masking reconstruction algorithm. It enables us to monitor active regions and give fast response to the solar activity. In this poster we present the first results of our new 32-CPU Beowulf cluster system. The images are 1024 x 1024 and the field of view (FOV) is 80'' x 80''. Our target is an active region with complex magnetic configuration. We focus on pores and small spots in the active region with the goal of better understanding the formation of penumbra structure. In addition we expect to study evolution of active regions during solar flares.

DMD-based LED-illumination super-resolution and optical sectioning microscopy.

PubMed

Dan, Dan; Lei, Ming; Yao, Baoli; Wang, Wen; Winterhalder, Martin; Zumbusch, Andreas; Qi, Yujiao; Xia, Liang; Yan, Shaohui; Yang, Yanlong; Gao, Peng; Ye, Tong; Zhao, Wei

2013-01-01

Super-resolution three-dimensional (3D) optical microscopy has incomparable advantages over other high-resolution microscopic technologies, such as electron microscopy and atomic force microscopy, in the study of biological molecules, pathways and events in live cells and tissues. We present a novel approach of structured illumination microscopy (SIM) by using a digital micromirror device (DMD) for fringe projection and a low-coherence LED light for illumination. The lateral resolution of 90 nm and the optical sectioning depth of 120 μm were achieved. The maximum acquisition speed for 3D imaging in the optical sectioning mode was 1.6×10(7) pixels/second, which was mainly limited by the sensitivity and speed of the CCD camera. In contrast to other SIM techniques, the DMD-based LED-illumination SIM is cost-effective, ease of multi-wavelength switchable and speckle-noise-free. The 2D super-resolution and 3D optical sectioning modalities can be easily switched and applied to either fluorescent or non-fluorescent specimens.

DMD-based LED-illumination Super-resolution and optical sectioning microscopy

PubMed Central

Dan, Dan; Lei, Ming; Yao, Baoli; Wang, Wen; Winterhalder, Martin; Zumbusch, Andreas; Qi, Yujiao; Xia, Liang; Yan, Shaohui; Yang, Yanlong; Gao, Peng; Ye, Tong; Zhao, Wei

2013-01-01

Super-resolution three-dimensional (3D) optical microscopy has incomparable advantages over other high-resolution microscopic technologies, such as electron microscopy and atomic force microscopy, in the study of biological molecules, pathways and events in live cells and tissues. We present a novel approach of structured illumination microscopy (SIM) by using a digital micromirror device (DMD) for fringe projection and a low-coherence LED light for illumination. The lateral resolution of 90 nm and the optical sectioning depth of 120 μm were achieved. The maximum acquisition speed for 3D imaging in the optical sectioning mode was 1.6×107 pixels/second, which was mainly limited by the sensitivity and speed of the CCD camera. In contrast to other SIM techniques, the DMD-based LED-illumination SIM is cost-effective, ease of multi-wavelength switchable and speckle-noise-free. The 2D super-resolution and 3D optical sectioning modalities can be easily switched and applied to either fluorescent or non-fluorescent specimens. PMID:23346373

Separated Component-Based Restoration of Speckled SAR Images

DTIC Science & Technology

2014-01-01

One of the simplest approaches for speckle noise reduction is known as multi-look processing. It involves non-coherently summing the independent...image is assumed to be piecewise smooth [21], [22], [23]. It has been shown that TV regular- ization often yields images with the stair -casing effect...as a function f , is to be decomposed into a sum of two components f = u+ v, where u represents the cartoon or geometric (i.e. piecewise smooth

Measurement of in-plane displacements using the phase singularities generated by directional wavelet transforms of speckle pattern images.

PubMed

Vadnjal, Ana Laura; Etchepareborda, Pablo; Federico, Alejandro; Kaufmann, Guillermo H

2013-03-20

We present a method to determine micro and nano in-plane displacements based on the phase singularities generated by application of directional wavelet transforms to speckle pattern images. The spatial distribution of the obtained phase singularities by the wavelet transform configures a network, which is characterized by two quasi-orthogonal directions. The displacement value is determined by identifying the intersection points of the network before and after the displacement produced by the tested object. The performance of this method is evaluated using simulated speckle patterns and experimental data. The proposed approach is compared with the optical vortex metrology and digital image correlation methods in terms of performance and noise robustness, and the advantages and limitations associated to each method are also discussed.

Laser speckle contrast imaging of cerebral autoregulation in rats at a macro- and microcirculation level

NASA Astrophysics Data System (ADS)

Semyachkina-Glushkovskaya, O. V.; Abdurashitov, A. S.; Sindeev, S. S.; Tuchin, V. V.

2016-06-01

Using the method of laser speckle imaging for the simultaneous study of macro- and microcirculation in cerebral vessels of healthy rats, we show that the mechanisms underlying cerebral autoregulation depend on the initial condition of the organism and the sex of individual animals. The pharmacological dose-dependent stimulation of the peripheral arterial pressure increase is not accompanied by the cerebral circulation responses of analogous intensity, but manifests itself as 'compensating' reactions, namely, the redistribution of the blood flow at the level of macro- (in females) and microcirculation (in females and males). The obtained results extend our understanding of the capabilities of laser speckle imaging technique in neurophysiological studies of reserve abilities of cerebral circulation autoregulation under the conditions of hypertensive status formation.

X-ray phase contrast tomography by tracking near field speckle

PubMed Central

Wang, Hongchang; Berujon, Sebastien; Herzen, Julia; Atwood, Robert; Laundy, David; Hipp, Alexander; Sawhney, Kawal

2015-01-01

X-ray imaging techniques that capture variations in the x-ray phase can yield higher contrast images with lower x-ray dose than is possible with conventional absorption radiography. However, the extraction of phase information is often more difficult than the extraction of absorption information and requires a more sophisticated experimental arrangement. We here report a method for three-dimensional (3D) X-ray phase contrast computed tomography (CT) which gives quantitative volumetric information on the real part of the refractive index. The method is based on the recently developed X-ray speckle tracking technique in which the displacement of near field speckle is tracked using a digital image correlation algorithm. In addition to differential phase contrast projection images, the method allows the dark-field images to be simultaneously extracted. After reconstruction, compared to conventional absorption CT images, the 3D phase CT images show greatly enhanced contrast. This new imaging method has advantages compared to other X-ray imaging methods in simplicity of experimental arrangement, speed of measurement and relative insensitivity to beam movements. These features make the technique an attractive candidate for material imaging such as in-vivo imaging of biological systems containing soft tissue. PMID:25735237

Measurement of absolute regional lung air volumes from near-field x-ray speckles.

PubMed

Leong, Andrew F T; Paganin, David M; Hooper, Stuart B; Siew, Melissa L; Kitchen, Marcus J

2013-11-18

Propagation-based phase contrast x-ray (PBX) imaging yields high contrast images of the lung where airways that overlap in projection coherently scatter the x-rays, giving rise to a speckled intensity due to interference effects. Our previous works have shown that total and regional changes in lung air volumes can be accurately measured from two-dimensional (2D) absorption or phase contrast images when the subject is immersed in a water-filled container. In this paper we demonstrate how the phase contrast speckle patterns can be used to directly measure absolute regional lung air volumes from 2D PBX images without the need for a water-filled container. We justify this technique analytically and via simulation using the transport-of-intensity equation and calibrate the technique using our existing methods for measuring lung air volume. Finally, we show the full capabilities of this technique for measuring regional differences in lung aeration.

Optically Phase-Locked Electronic Speckle Pattern Interferometer (OPL-ESPI)

NASA Astrophysics Data System (ADS)

Moran, Steven E.; Law, Robert L.; Craig, Peter N.; Goldberg, Warren M.

1986-10-01

This report describes the design, theory, operation, and characteristics of the OPL-ESPI, which generates real time equal Doppler speckle contours of vibrating objects from unstable sensor platforms with a Doppler resolution of 30 Hz and a maximum tracking range of + or - 5 HMz. The optical phase locked loop compensates for the deleterious effects of ambient background vibration and provides the bases for a new ESPI video signal processing technique, which produces high contrast speckle contours. The OPL-ESPI system has local oscillator phase modulation capability, offering the potential for detection of vibrations with the amplitudes less than lambda/100.

Comparison of Indocyanine Green Angiography and Laser Speckle Contrast Imaging for the Assessment of Vasculature Perfusion

PubMed Central

Towle, Erica L.; Richards, Lisa M.; Kazmi, S. M. Shams; Fox, Douglas J.; Dunn, Andrew K.

2013-01-01

BACKGROUND Assessment of the vasculature is critical for overall success in cranial vascular neurological surgery procedures. Although several methods of monitoring cortical perfusion intraoperatively are available, not all are appropriate or convenient in a surgical environment. Recently, 2 optical methods of care have emerged that are able to obtain high spatial resolution images with easily implemented instrumentation: indocyanine green (ICG) angiography and laser speckle contrast imaging (LSCI). OBJECTIVE To evaluate the usefulness of ICG and LSCI in measuring vessel perfusion. METHODS An experimental setup was developed that simultaneously collects measurements of ICG fluorescence and LSCI in a rodent model. A 785-nm laser diode was used for both excitation of the ICG dye and the LSCI illumination. A photothrombotic clot model was used to occlude specific vessels within the field of view to enable comparison of the 2 methods for monitoring vessel perfusion. RESULTS The induced blood flow change demonstrated that ICG is an excellent method for visualizing the volume and type of vessel at a single point in time; however, it is not always an accurate representation of blood flow. In contrast, LSCI provides a continuous and accurate measurement of blood flow changes without the need of an external contrast agent. CONCLUSION These 2 methods should be used together to obtain a complete understanding of tissue perfusion. PMID:22843129

Improving image-quality of interference fringes of out-of-plane vibration using temporal speckle pattern interferometry and standard deviation for piezoelectric plates.

PubMed

Chien-Ching Ma; Ching-Yuan Chang

2013-07-01

Interferometry provides a high degree of accuracy in the measurement of sub-micrometer deformations; however, the noise associated with experimental measurement undermines the integrity of interference fringes. This study proposes the use of standard deviation in the temporal domain to improve the image quality of patterns obtained from temporal speckle pattern interferometry. The proposed method combines the advantages of both mean and subtractive methods to remove background noise and ambient disturbance simultaneously, resulting in high-resolution images of excellent quality. The out-of-plane vibration of a thin piezoelectric plate is the main focus of this study, providing information useful to the development of energy harvesters. First, ten resonant states were measured using the proposed method, and both mode shape and resonant frequency were investigated. We then rebuilt the phase distribution of the first resonant mode based on the clear interference patterns obtained using the proposed method. This revealed instantaneous deformations in the dynamic characteristics of the resonant state. The proposed method also provides a frequency-sweeping function, facilitating its practical application in the precise measurement of resonant frequency. In addition, the mode shapes and resonant frequencies obtained using the proposed method were recorded and compared with results obtained using finite element method and laser Doppler vibrometery, which demonstrated close agreement.

Full-field speckle interferometry for non-contact photoacoustic tomography.

PubMed

Horstmann, Jens; Spahr, Hendrik; Buj, Christian; Münter, Michael; Brinkmann, Ralf

2015-05-21

A full-field speckle interferometry method for non-contact and prospectively high speed Photoacoustic Tomography is introduced and evaluated as proof of concept. Thermoelastic pressure induced changes of the objects topography are acquired in a repetitive mode without any physical contact to the object. In order to obtain high acquisition speed, the object surface is illuminated by laser pulses and imaged onto a high speed camera chip. In a repetitive triple pulse mode, surface displacements can be acquired with nanometre sensitivity and an adjustable sampling rate of e.g. 20 MHz with a total acquisition time far below one second using kHz repetition rate lasers. Due to recurring interferometric referencing, the method is insensitive to thermal drift of the object due to previous pulses or other motion. The size of the investigated area and the spatial and temporal resolution of the detection are scalable. In this study, the approach is validated by measuring a silicone phantom and a porcine skin phantom with embedded silicone absorbers. The reconstruction of the absorbers is presented in 2D and 3D. The sensitivity of the measurement with respect to the photoacoustic detection is discussed. Potentially, Photoacoustic Imaging can be brought a step closer towards non-anaesthetized in vivo imaging and new medical applications not allowing acoustic contact, such as neurosurgical monitoring or burnt skin investigation.

Longitudinal spatial coherence gated high-resolution tomography and quantitative phase microscopy of biological cells and tissues with uniform illumination

NASA Astrophysics Data System (ADS)

Mehta, Dalip Singh; Ahmad, Azeem; Dubey, Vishesh; Singh, Veena; Butola, Ankit; Mohanty, Tonmoy; Nandi, Sreyankar

2018-02-01

We report longitudinal spatial coherence (LSC) gated high-resolution tomography and quantitative phase microscopy of biological cells and tissues with uniform illumination using laser as a light source. To accomplish this a pseudo thermal light source was synthesized by passing laser beams through an optical system, which is basically a speckle reduction system with combined effect of spatial, temporal, angular and polarisation diversity. The longitudinal spatial coherence length of such light was significantly reduced by synthesizing a pseudo thermal source with the combined effect of spatial, angular and temporal diversity. This results in a low spatially coherent (i.e., broad angular frequency spectrum) light source with narrow temporal frequency spectrum. Light from such a pseudo thermal light source was passed through an interference microscope with varying magnification, such as, 10X and 50X. The interference microscope was used for full-field OCT imaging of multilayer objects and topography of industrial objects. Experimental results of optical sectioning of multilayer biological objects with high axial-resolution less than 10μm was achieved which is comparable to broadband white light source. The synthesized light source with reduced speckles having uniform illumination on the sample, which can be very useful for fluorescence microscopy as well as quantitative phase microscopy with less phase noise. The present system does not require any dispersion compensation optical system for biological samples as a highly monochromatic light source is used.

Speckle-based three-dimensional velocity measurement using spatial filtering velocimetry.

PubMed

Iversen, Theis F Q; Jakobsen, Michael L; Hanson, Steen G

2011-04-10

We present an optical method for measuring the real-time three-dimensional (3D) translational velocity of a diffusely scattering rigid object observed through an imaging system. The method is based on a combination of the motion of random speckle patterns and regular fringe patterns. The speckle pattern is formed in the observation plane of the imaging system due to reflection from an area of the object illuminated by a coherent light source. The speckle pattern translates in response to in-plane translation of the object, and the presence of an angular offset reference wave coinciding with the speckle pattern in the observation plane gives rise to interference, resulting in a fringe pattern that translates in response to the out-of-plane translation of the object. Numerical calculations are performed to evaluate the dynamic properties of the intensity distribution and the response of realistic spatial filters designed to measure the three components of the object's translational velocity. Furthermore, experimental data are presented that demonstrate full 3D velocity measurement. © 2011 Optical Society of America

Quantitative model of diffuse speckle contrast analysis for flow measurement.

PubMed

Liu, Jialin; Zhang, Hongchao; Lu, Jian; Ni, Xiaowu; Shen, Zhonghua

2017-07-01

Diffuse speckle contrast analysis (DSCA) is a noninvasive optical technique capable of monitoring deep tissue blood flow. However, a detailed study of the speckle contrast model for DSCA has yet to be presented. We deduced the theoretical relationship between speckle contrast and exposure time and further simplified it to a linear approximation model. The feasibility of this linear model was validated by the liquid phantoms which demonstrated that the slope of this linear approximation was able to rapidly determine the Brownian diffusion coefficient of the turbid media at multiple distances using multiexposure speckle imaging. Furthermore, we have theoretically quantified the influence of optical property on the measurements of the Brownian diffusion coefficient which was a consequence of the fact that the slope of this linear approximation was demonstrated to be equal to the inverse of correlation time of the speckle.

Polychromatic wave-optics models for image-plane speckle. 2. Unresolved objects.

PubMed

Van Zandt, Noah R; Spencer, Mark F; Steinbock, Michael J; Anderson, Brian M; Hyde, Milo W; Fiorino, Steven T

2018-05-20

Polychromatic laser light can reduce speckle noise in many wavefront-sensing and imaging applications. To help quantify the achievable reduction in speckle noise, this study investigates the accuracy of three polychromatic wave-optics models under the specific conditions of an unresolved object. Because existing theory assumes a well-resolved object, laboratory experiments are used to evaluate model accuracy. The three models use Monte-Carlo averaging, depth slicing, and spectral slicing, respectively, to simulate the laser-object interaction. The experiments involve spoiling the temporal coherence of laser light via a fiber-based, electro-optic modulator. After the light scatters off of the rough object, speckle statistics are measured. The Monte-Carlo method is found to be highly inaccurate, while depth-slicing error peaks at 7.8% but is generally much lower in comparison. The spectral-slicing method is the most accurate, always producing results within the error bounds of the experiment.

Effects of the source, surface, and sensor couplings and colorimetric of laser speckle pattern on the performance of optical imaging system

NASA Astrophysics Data System (ADS)

Darwiesh, M.; El-Sherif, Ashraf F.; El-Ghandour, Hatem; Aly, Hussein A.; Mokhtar, A. M.

2011-03-01

Optical imaging systems are widely used in different applications include tracking for portable scanners; input pointing devices for laptop computers, cell phones, and cameras, fingerprint-identification scanners, optical navigation for target tracking, and in optical computer mouse. We presented an experimental work to measure and analyze the laser speckle pattern (LSP) produced from different optical sources (i.e. various color LEDs, 3 mW diode laser, and 10mW He-Ne laser) with different produced operating surfaces (Gabor hologram diffusers), and how they affects the performance of the optical imaging systems; speckle size and signal-to-noise ratio (signal is represented by the patches of the speckles that contain or carry information, and noise is represented by the whole remaining part of the selected image). The theoretical and experimental studies of the colorimetry (color correction is done in the color images captured by the optical imaging system to produce realistic color images which contains most of the information in the image by selecting suitable gray scale which contains most of the informative data in the image, this is done by calculating the accurate Red-Green-Blue (RGB) color components making use of the measured spectrum for light sources, and color matching functions of International Telecommunication Organization (ITU-R709) for CRT phosphorus, Tirinton-SONY Model ) for the used optical sources are investigated and introduced to present the relations between the signal-to-noise ratios with different diffusers for each light source. The source surface coupling has been discussed and concludes that the performance of the optical imaging system for certain source varies from worst to best based on the operating surface. The sensor /surface coupling has been studied and discussed for the case of He-Ne laser and concludes the speckle size is ranged from 4.59 to 4.62 μm, which are slightly different or approximately the same for all produced diffusers (which satisfies the fact that the speckle size is independent on the illuminating surface). But, the calculated value of signal-tonoise ratio takes different values ranged from 0.71 to 0.92 for different diffuser. This means that the surface texture affects the performance of the optical sensor because, all images captured for all diffusers under the same conditions [same source (He-Ne laser), same distances of the experimental set-up, and the same sensor (CCD camera)].

Polarization-multiplexing ghost imaging

NASA Astrophysics Data System (ADS)

Dongfeng, Shi; Jiamin, Zhang; Jian, Huang; Yingjian, Wang; Kee, Yuan; Kaifa, Cao; Chenbo, Xie; Dong, Liu; Wenyue, Zhu

2018-03-01

A novel technique for polarization-multiplexing ghost imaging is proposed to simultaneously obtain multiple polarimetric information by a single detector. Here, polarization-division multiplexing speckles are employed for object illumination. The light reflected from the objects is detected by a single-pixel detector. An iterative reconstruction method is used to restore the fused image containing the different polarimetric information by using the weighted sum of the multiplexed speckles based on the correlation coefficients obtained from the detected intensities. Next, clear images of the different polarimetric information are recovered by demultiplexing the fused image. The results clearly demonstrate that the proposed method is effective.

Understanding the exposure-time effect on speckle contrast measurements for laser displays

NASA Astrophysics Data System (ADS)

Suzuki, Koji; Kubota, Shigeo

2018-02-01

To evaluate the influence of exposure time on speckle noise for laser displays, speckle contrast measurement method was developed observable at a human eye response time using a high-sensitivity camera which has a signal multiplying function. The nonlinearity of camera light sensitivity was calibrated to measure accurate speckle contrasts, and the measuring lower limit noise of speckle contrast was improved by applying spatial-frequency low pass filter to the captured images. Three commercially available laser displays were measured over a wide range of exposure times from tens of milliseconds to several seconds without adjusting the brightness of laser displays. The speckle contrast of raster-scanned mobile projector without any speckle-reduction device was nearly constant over various exposure times. On the contrary to this, in full-frame projection type laser displays equipped with a temporally-averaging speckle-reduction device, some of their speckle contrasts close to the lower limits noise were slightly increased at the shorter exposure time due to the noise. As a result, the exposure-time effect of speckle contrast could not be observed in our measurements, although it is more reasonable to think that the speckle contrasts of laser displays, which are equipped with the temporally-averaging speckle-reduction device, are dependent on the exposure time. This discrepancy may be attributed to the underestimation of temporal averaging factor. We expected that this method is useful for evaluating various laser displays and clarify the relationship between the speckle noise and the exposure time for a further verification of speckle reduction.

Wide-area mapping of resting state hemodynamic correlations at microvascular resolution with multi-contrast optical imaging (Conference Presentation)

NASA Astrophysics Data System (ADS)

Senarathna, Janaka; Hadjiabadi, Darian; Gil, Stacy; Thakor, Nitish V.; Pathak, Arvind P.

2017-02-01

Different brain regions exhibit complex information processing even at rest. Therefore, assessing temporal correlations between regions permits task-free visualization of their `resting state connectivity'. Although functional MRI (fMRI) is widely used for mapping resting state connectivity in the human brain, it is not well suited for `microvascular scale' imaging in rodents because of its limited spatial resolution. Moreover, co-registered cerebral blood flow (CBF) and total hemoglobin (HbT) data are often unavailable in conventional fMRI experiments. Therefore, we built a customized system that combines laser speckle contrast imaging (LSCI), intrinsic optical signal (IOS) imaging and fluorescence imaging (FI) to generate multi-contrast functional connectivity maps at a spatial resolution of 10 μm. This system comprised of three illumination sources: a 632 nm HeNe laser (for LSCI), a 570 nm ± 5 nm filtered white light source (for IOS), and a 473 nm blue laser (for FI), as well as a sensitive CCD camera operating at 10 frames per second for image acquisition. The acquired data enabled visualization of changes in resting state neurophysiology at microvascular spatial scales. Moreover, concurrent mapping of CBF and HbT-based temporal correlations enabled in vivo mapping of how resting brain regions were linked in terms of their hemodynamics. Additionally, we complemented this approach by exploiting the transit times of a fluorescent tracer (Dextran-FITC) to distinguish arterial from venous perfusion. Overall, we demonstrated the feasibility of wide area mapping of resting state connectivity at microvascular resolution and created a new toolbox for interrogating neurovascular function.

Imaging human brain cyto- and myelo-architecture with quantitative OCT (Conference Presentation)

NASA Astrophysics Data System (ADS)

Boas, David A.; Wang, Hui; Konukoglu, Ender; Fischl, Bruce; Sakadzic, Sava; Magnain, Caroline V.

2017-02-01

No current imaging technology allows us to directly and without significant distortion visualize the microscopic and defining anatomical features of the human brain. Ex vivo histological techniques can yield exquisite planar images, but the cutting, mounting and staining that are required components of this type of imaging induce distortions that are different for each slice, introducing cross-slice differences that prohibit true 3D analysis. We are overcoming this issue by utilizing Optical Coherence Tomography (OCT) with the goal to image whole human brain cytoarchitectural and laminar properties with potentially 3.5 µm resolution in block-face without the need for exogenous staining. From the intrinsic scattering contrast of the brain tissue, OCT gives us images that are comparable to Nissl stains, but without the distortions introduced in standard histology as the OCT images are acquired from the block face prior to slicing and thus without the need for subsequent staining and mounting. We have shown that laminar and cytoarchitectural properties of the brain can be characterized with OCT just as well as with Nissl staining. We will present our recent advances to improve the axial resolution while maintaining contrast; improvements afforded by speckle reduction procedures; and efforts to obtain quantitative maps of the optical scattering coefficient, an intrinsic property of the tissue.

Speckle interferometry of asteroids

NASA Technical Reports Server (NTRS)

Drummond, Jack

1988-01-01

This final report for NASA Contract NAGw-867 consists of abstracts of the first three papers in a series of four appearing in Icarus that were funded by the preceding contract NAGw-224: (1) Speckle Interferometry of Asteroids I. 433 Eros; (2) Speckle Interferometry of Asteroids II. 532 Herculina; (3) Speckle Interferometry of Asteroids III. 511 Davida and its Photometry; and the fourth abstract attributed to NAGw-867, (4) Speckle Interferometry of Asteroids IV. Reconstructed images of 4 Vesta; and a review of the results from the asteroid interferometry program at Steward Observatory prepared for the Asteroids II book, (5) Speckle Interferometry of Asteroids. Two papers on asteroids, indirectly related to speckle interferometry, were written in part under NAGw-867. One is in press and its abstract is included here: Photometric Geodesy of Main-Belt Asteroids. II. Analysis of Lightcurves for Poles, Periods and Shapes; and the other paper, Triaxial Ellipsoid Dimensions and Rotational Pole of 2 Pallas from Two Stellar Occultations, is included in full.

In vivo burn diagnosis by camera-phone diffuse reflectance laser speckle detection.

PubMed

Ragol, S; Remer, I; Shoham, Y; Hazan, S; Willenz, U; Sinelnikov, I; Dronov, V; Rosenberg, L; Bilenca, A

2016-01-01

Burn diagnosis using laser speckle light typically employs widefield illumination of the burn region to produce two-dimensional speckle patterns from light backscattered from the entire irradiated tissue volume. Analysis of speckle contrast in these time-integrated patterns can then provide information on burn severity. Here, by contrast, we use point illumination to generate diffuse reflectance laser speckle patterns of the burn. By examining spatiotemporal fluctuations in these time-integrated patterns along the radial direction from the incident point beam, we show the ability to distinguish partial-thickness burns in a porcine model in vivo within the first 24 hours post-burn. Furthermore, our findings suggest that time-integrated diffuse reflectance laser speckle can be useful for monitoring burn healing over time post-burn. Unlike conventional diffuse reflectance laser speckle detection systems that utilize scientific or industrial-grade cameras, our system is designed with a camera-phone, demonstrating the potential for burn diagnosis with a simple imager.

In vivo burn diagnosis by camera-phone diffuse reflectance laser speckle detection

PubMed Central

Ragol, S.; Remer, I.; Shoham, Y.; Hazan, S.; Willenz, U.; Sinelnikov, I.; Dronov, V.; Rosenberg, L.; Bilenca, A.

2015-01-01

Burn diagnosis using laser speckle light typically employs widefield illumination of the burn region to produce two-dimensional speckle patterns from light backscattered from the entire irradiated tissue volume. Analysis of speckle contrast in these time-integrated patterns can then provide information on burn severity. Here, by contrast, we use point illumination to generate diffuse reflectance laser speckle patterns of the burn. By examining spatiotemporal fluctuations in these time-integrated patterns along the radial direction from the incident point beam, we show the ability to distinguish partial-thickness burns in a porcine model in vivo within the first 24 hours post-burn. Furthermore, our findings suggest that time-integrated diffuse reflectance laser speckle can be useful for monitoring burn healing over time post-burn. Unlike conventional diffuse reflectance laser speckle detection systems that utilize scientific or industrial-grade cameras, our system is designed with a camera-phone, demonstrating the potential for burn diagnosis with a simple imager. PMID:26819831

Speckle Tracking Imaging in Normal Stress Echocardiography.

PubMed

Leitman, Marina; Tyomkin, Vladimir; Peleg, Eli; Zyssman, Izhak; Rosenblatt, Simcha; Sucher, Edgar; Gercenshtein, Vered; Vered, Zvi

2017-04-01

Exercise stress echocardiography is a widely used modality for the diagnosis and follow-up of patients with coronary artery disease. During the last decade, speckle tracking imaging has been used increasingly for accurate evaluation of cardiac function. This work aimed to assess speckle-tracking imaging parameters during nonischemic exercise stress echocardiography. During 2011 to 2014 we studied 46 patients without history of coronary artery disease, who completed exercise stress echocardiography protocol, had normal left ventricular function, a nonischemic response, and satisfactory image quality. These exams were analyzed with speckle-tracking imaging software at rest and at peak exercise. Peak strain and time-to-peak strain were measured at rest and after exercise. Clinical follow-up included a telephone contact 1 to 3 years after stress echo exam, confirming freedom from coronary events during this time. Global and regional peak strain increased following exercise. Time-to-peak global and regional strain and time-to-peak strain adjusted to the heart rate were significantly shorter in all segments after exercise. Rest-to-stress ratio of time-to-peak strain adjusted to the heart rate was 2.0 to 2.8. Global and regional peak strain rise during normal exercise echocardiography. Peak global and regional strain occur before or shortly after aortic valve closure at rest and after exercise, and the delay is more apparent at the basal segments. Time-to-peak strain normally shortens significantly during exercise; after adjustment to heart rate it shortens by a ratio of 2.0 to 2.8. These data may be useful for interpretation of future exercise stress speckle-tracking echocardiography studies. © 2016 by the American Institute of Ultrasound in Medicine.

Long-range and depth-selective imaging of macroscopic targets using low-coherence and wide-field interferometry (Conference Presentation)

NASA Astrophysics Data System (ADS)

Woo, Sungsoo; Kang, Sungsam; Yoon, Changhyeong; Choi, Wonshik

2016-03-01

With the advancement of 3D display technology, 3D imaging of macroscopic objects has drawn much attention as they provide the contents to display. The most widely used imaging methods include a depth camera, which measures time of flight for the depth discrimination, and various structured illumination techniques. However, these existing methods have poor depth resolution, which makes imaging complicated structures a difficult task. In order to resolve this issue, we propose an imaging system based upon low-coherence interferometry and off-axis digital holographic imaging. By using light source with coherence length of 200 micro, we achieved the depth resolution of 100 micro. In order to map the macroscopic objects with this high axial resolution, we installed a pair of prisms in the reference beam path for the long-range scanning of the optical path length. Specifically, one prism was fixed in position, and the other prism was mounted on a translation stage and translated in parallel to the first prism. Due to the multiple internal reflections between the two prisms, the overall path length was elongated by a factor of 50. In this way, we could cover a depth range more than 1 meter. In addition, we employed multiple speckle illuminations and incoherent averaging of the acquired holographic images for reducing the specular reflections from the target surface. Using this newly developed system, we performed imaging targets with multiple different layers and demonstrated imaging targets hidden behind the scattering layers. The method was also applied to imaging targets located around the corner.

FOCAL PLANE WAVEFRONT SENSING USING RESIDUAL ADAPTIVE OPTICS SPECKLES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Codona, Johanan L.; Kenworthy, Matthew, E-mail: jlcodona@gmail.com

2013-04-20

Optical imperfections, misalignments, aberrations, and even dust can significantly limit sensitivity in high-contrast imaging systems such as coronagraphs. An upstream deformable mirror (DM) in the pupil can be used to correct or compensate for these flaws, either to enhance the Strehl ratio or suppress the residual coronagraphic halo. Measurement of the phase and amplitude of the starlight halo at the science camera is essential for determining the DM shape that compensates for any non-common-path (NCP) wavefront errors. Using DM displacement ripples to create a series of probe and anti-halo speckles in the focal plane has been proposed for space-based coronagraphsmore » and successfully demonstrated in the lab. We present the theory and first on-sky demonstration of a technique to measure the complex halo using the rapidly changing residual atmospheric speckles at the 6.5 m MMT telescope using the Clio mid-IR camera. The AO system's wavefront sensor measurements are used to estimate the residual wavefront, allowing us to approximately compute the rapidly evolving phase and amplitude of speckle halo. When combined with relatively short, synchronized science camera images, the complex speckle estimates can be used to interferometrically analyze the images, leading to an estimate of the static diffraction halo with NCP effects included. In an operational system, this information could be collected continuously and used to iteratively correct quasi-static NCP errors or suppress imperfect coronagraphic halos.« less

Fluorescence endoscopy using fiber speckle illumination

NASA Astrophysics Data System (ADS)

Nakano, Shuhei; Katagiri, Takashi; Matsuura, Yuji

2018-02-01

An endoscopic fluorescence imaging system based on fiber speckle illumination is proposed. In this system, a multimode fiber for transmission of excitation laser light and collection of fluorescence is inserted into a conventional flexible endoscope. Since the excitation laser light has random speckle structure, one can detect fluorescence signal corresponding to the irradiation pattern if the sample contains fluorophores. The irradiation pattern can be captured by the endoscope camera when the excitation wavelength is within the sensitivity range of the camera. By performing multiple measurements while changing the irradiation pattern, a fluorescence image is reconstructed by solving a norm minimization problem. The principle of our method was experimentally demonstrated. A 2048 pixels image of quantum dots coated on a frosted glass was successfully reconstructed by 32 measurements. We also confirmed that our method can be applied on biological tissues.

Feasibility of speckle variance OCT for imaging cutaneous microvasculature regeneration during healing of wounds in diabetic mice

NASA Astrophysics Data System (ADS)

Sharma, P.; Kumawat, J.; Kumar, S.; Sahu, K.; Verma, Y.; Gupta, P. K.; Rao, K. D.

2018-02-01

We report on a study to assess the feasibility of a swept source-based speckle variance optical coherence tomography setup for monitoring cutaneous microvasculature. Punch wounds created in the ear pinnae of diabetic mice were monitored at different times post wounding to assess the structural and vascular changes. It was observed that the epithelium thickness increases post wounding and continues to be thick even after healing. Also, the wound size assessed by vascular images is larger than the physical wound size. The results show that the developed speckle variance optical coherence tomography system can be used to monitor vascular regeneration during wound healing in diabetic mice.

Single-shot speckle reduction in numerical reconstruction of digitally recorded holograms.

PubMed

Hincapie, Diego; Herrera-Ramírez, Jorge; Garcia-Sucerquia, Jorge

2015-04-15

A single-shot method to reduce the speckle noise in the numerical reconstructions of electronically recorded holograms is presented. A recorded hologram with the dimensions N×M is split into S=T×T sub-holograms. The uncorrelated superposition of the individually reconstructed sub-holograms leads to an image with the speckle noise reduced proportionally to the 1/S law. The experimental results are presented to support the proposed methodology.

Close Binary Star Speckle Interferometry on the McMath-Pierce 0.8-Meter Solar Telescope

NASA Astrophysics Data System (ADS)

Wiley, Edward; Harshaw, Richard; Jones, Gregory; Branston, Detrick; Boyce, Patrick; Rowe, David; Ridgely, John; Estrada, Reed; Genet, Russell

2015-09-01

Observations were made in April 2014 to assess the utility of the 0.8-meter solar telescope at the McMath-Pierce Solar Observatory at Kitt Peak National Observatory for performing speckle interferometry observations of close binary stars. Several configurations using science cameras, acquisition cameras, eyepieces, and flip mirrors were evaluated. Speckle images were obtained and recommendations for further improvement of the acquisition system are presented.

Accuracy concerns in digital speckle photography combined with Fresnel digital holographic interferometry

NASA Astrophysics Data System (ADS)

Zhao, Yuchen; Zemmamouche, Redouane; Vandenrijt, Jean-François; Georges, Marc P.

2018-05-01

A combination of digital holographic interferometry (DHI) and digital speckle photography (DSP) allows in-plane and out-of-plane displacement measurement between two states of an object. The former can be determined by correlating the two speckle patterns whereas the latter is given by the phase difference obtained from DHI. We show that the amplitude of numerically reconstructed object wavefront obtained from Fresnel in-line digital holography (DH), in combination with phase shifting techniques, can be used as speckle patterns in DSP. The accuracy of in-plane measurement is improved after correcting the phase errors induced by reference wave during reconstruction process. Furthermore, unlike conventional imaging system, Fresnel DH offers the possibility to resize the pixel size of speckle patterns situated on the reconstruction plane under the same optical configuration simply by zero-padding the hologram. The flexibility of speckle size adjustment in Fresnel DH ensures the accuracy of estimation result using DSP.

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

NASA Astrophysics Data System (ADS)

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.

Improved cancer diagnostics by different image processing techniques on OCT images

NASA Astrophysics Data System (ADS)

Kanawade, Rajesh; Lengenfelder, Benjamin; Marini Menezes, Tassiana; Hohmann, Martin; Kopfinger, Stefan; Hohmann, Tim; Grabiec, Urszula; Klämpfl, Florian; Gonzales Menezes, Jean; Waldner, Maximilian; Schmidt, Michael

2015-07-01

Optical-coherence tomography (OCT) is a promising non-invasive, high-resolution imaging modality which can be used for cancer diagnosis and its therapeutic assessment. However, speckle noise makes detection of cancer boundaries and image segmentation problematic and unreliable. Therefore, to improve the image analysis for a precise cancer border detection, the performance of different image processing algorithms such as mean, median, hybrid median filter and rotational kernel transformation (RKT) for this task is investigated. This is done on OCT images acquired from an ex-vivo human cancerous mucosa and in vitro by using cultivated tumour applied on organotypical hippocampal slice cultures. The preliminary results confirm that the border between the healthy and the cancer lesions can be identified precisely. The obtained results are verified with fluorescence microscopy. This research can improve cancer diagnosis and the detection of borders between healthy and cancerous tissue. Thus, it could also reduce the number of biopsies required during screening endoscopy by providing better guidance to the physician.

Influence of ultrasound speckle tracking strategies for motion and strain estimation.

PubMed

Curiale, Ariel H; Vegas-Sánchez-Ferrero, Gonzalo; Aja-Fernández, Santiago

2016-08-01

Speckle Tracking is one of the most prominent techniques used to estimate the regional movement of the heart based on ultrasound acquisitions. Many different approaches have been proposed, proving their suitability to obtain quantitative and qualitative information regarding myocardial deformation, motion and function assessment. New proposals to improve the basic algorithm usually focus on one of these three steps: (1) the similarity measure between images and the speckle model; (2) the transformation model, i.e. the type of motion considered between images; (3) the optimization strategies, such as the use of different optimization techniques in the transformation step or the inclusion of structural information. While many contributions have shown their good performance independently, it is not always clear how they perform when integrated in a whole pipeline. Every step will have a degree of influence over the following and hence over the final result. Thus, a Speckle Tracking pipeline must be analyzed as a whole when developing novel methods, since improvements in a particular step might be undermined by the choices taken in further steps. This work presents two main contributions: (1) We provide a complete analysis of the influence of the different steps in a Speckle Tracking pipeline over the motion and strain estimation accuracy. (2) The study proposes a methodology for the analysis of Speckle Tracking systems specifically designed to provide an easy and systematic way to include other strategies. We close the analysis with some conclusions and recommendations that can be used as an orientation of the degree of influence of the models for speckle, the transformation models, interpolation schemes and optimization strategies over the estimation of motion features. They can be further use to evaluate and design new strategy into a Speckle Tracking system. Copyright © 2016 Elsevier B.V. All rights reserved.

Quantitative imaging of heterogeneous dynamics in drying and aging paints

PubMed Central

van der Kooij, Hanne M.; Fokkink, Remco; van der Gucht, Jasper; Sprakel, Joris

2016-01-01

Drying and aging paint dispersions display a wealth of complex phenomena that make their study fascinating yet challenging. To meet the growing demand for sustainable, high-quality paints, it is essential to unravel the microscopic mechanisms underlying these phenomena. Visualising the governing dynamics is, however, intrinsically difficult because the dynamics are typically heterogeneous and span a wide range of time scales. Moreover, the high turbidity of paints precludes conventional imaging techniques from reaching deep inside the paint. To address these challenges, we apply a scattering technique, Laser Speckle Imaging, as a versatile and quantitative tool to elucidate the internal dynamics, with microscopic resolution and spanning seven decades of time. We present a toolbox of data analysis and image processing methods that allows a tailored investigation of virtually any turbid dispersion, regardless of the geometry and substrate. Using these tools we watch a variety of paints dry and age with unprecedented detail. PMID:27682840

Computational efficient unsupervised coastline detection from single-polarization 1-look SAR images of complex coastal environments

NASA Astrophysics Data System (ADS)

Garzelli, Andrea; Zoppetti, Claudia; Pinelli, Gianpaolo

2017-10-01

Coastline detection in synthetic aperture radar (SAR) images is crucial in many application fields, from coastal erosion monitoring to navigation, from damage assessment to security planning for port facilities. The backscattering difference between land and sea is not always documented in SAR imagery, due to the severe speckle noise, especially in 1-look data with high spatial resolution, high sea state, or complex coastal environments. This paper presents an unsupervised, computationally efficient solution to extract the coastline acquired by only one single-polarization 1-look SAR image. Extensive tests on Spotlight COSMO-SkyMed images of complex coastal environments and objective assessment demonstrate the validity of the proposed procedure which is compared to state-of-the-art methods through visual results and with an objective evaluation of the distance between the detected and the true coastline provided by regional authorities.

Principal Component Analysis in the Spectral Analysis of the Dynamic Laser Speckle Patterns

NASA Astrophysics Data System (ADS)

Ribeiro, K. M.; Braga, R. A., Jr.; Horgan, G. W.; Ferreira, D. D.; Safadi, T.

2014-02-01

Dynamic laser speckle is a phenomenon that interprets an optical patterns formed by illuminating a surface under changes with coherent light. Therefore, the dynamic change of the speckle patterns caused by biological material is known as biospeckle. Usually, these patterns of optical interference evolving in time are analyzed by graphical or numerical methods, and the analysis in frequency domain has also been an option, however involving large computational requirements which demands new approaches to filter the images in time. Principal component analysis (PCA) works with the statistical decorrelation of data and it can be used as a data filtering. In this context, the present work evaluated the PCA technique to filter in time the data from the biospeckle images aiming the reduction of time computer consuming and improving the robustness of the filtering. It was used 64 images of biospeckle in time observed in a maize seed. The images were arranged in a data matrix and statistically uncorrelated by PCA technique, and the reconstructed signals were analyzed using the routine graphical and numerical methods to analyze the biospeckle. Results showed the potential of the PCA tool in filtering the dynamic laser speckle data, with the definition of markers of principal components related to the biological phenomena and with the advantage of fast computational processing.

Real-time acquisition and display of flow contrast using speckle variance optical coherence tomography in a graphics processing unit.

PubMed

Xu, Jing; Wong, Kevin; Jian, Yifan; Sarunic, Marinko V

2014-02-01

In this report, we describe a graphics processing unit (GPU)-accelerated processing platform for real-time acquisition and display of flow contrast images with Fourier domain optical coherence tomography (FDOCT) in mouse and human eyes in vivo. Motion contrast from blood flow is processed using the speckle variance OCT (svOCT) technique, which relies on the acquisition of multiple B-scan frames at the same location and tracking the change of the speckle pattern. Real-time mouse and human retinal imaging using two different custom-built OCT systems with processing and display performed on GPU are presented with an in-depth analysis of performance metrics. The display output included structural OCT data, en face projections of the intensity data, and the svOCT en face projections of retinal microvasculature; these results compare projections with and without speckle variance in the different retinal layers to reveal significant contrast improvements. As a demonstration, videos of real-time svOCT for in vivo human and mouse retinal imaging are included in our results. The capability of performing real-time svOCT imaging of the retinal vasculature may be a useful tool in a clinical environment for monitoring disease-related pathological changes in the microcirculation such as diabetic retinopathy.

Hylemetry versus Biometry: a new method to certificate the lithography authenticity

NASA Astrophysics Data System (ADS)

Schirripa Spagnolo, Giuseppe; Cozzella, Lorenzo; Simonetti, Carla

2011-06-01

When we buy an artwork object a certificate of authenticity contain specific details about the artwork. Unfortunately, these certificates are often exchanged between similar artworks: the same document is supplied by the seller to certificate the originality. In this way the buyer will have a copy of an original certificate to attest that the "not original artwork" is an original one. A solution for this problem would be to insert a system that links together the certificate and a specific artwork. To do this it is necessary, for a single artwork, to find unique, unrepeatable, and unchangeable characteristics. In this paper we propose a new lithography certification based on the color spots distribution, which compose the lithography itself. Due to the high resolution acquisition media available today, it is possible using analysis method typical of speckle metrology. In particular, in verification phase it is only necessary acquiring the same portion of lithography, extracting the verification information, using the private key to obtain the same information from the certificate and confronting the two information using a comparison threshold. Due to the possible rotation and translation it is applied image correlation solutions, used in speckle metrology, to determine translation and rotation error and correct allow to verifying extracted and acquired images in the best situation, for granting correct originality verification.

Nonlocal means-based speckle filtering for ultrasound images

PubMed Central

Coupé, Pierrick; Hellier, Pierre; Kervrann, Charles; Barillot, Christian

2009-01-01

In image processing, restoration is expected to improve the qualitative inspection of the image and the performance of quantitative image analysis techniques. In this paper, an adaptation of the Non Local (NL-) means filter is proposed for speckle reduction in ultrasound (US) images. Originally developed for additive white Gaussian noise, we propose to use a Bayesian framework to derive a NL-means filter adapted to a relevant ultrasound noise model. Quantitative results on synthetic data show the performances of the proposed method compared to well-established and state-of-the-art methods. Results on real images demonstrate that the proposed method is able to preserve accurately edges and structural details of the image. PMID:19482578

Optoelectronic imaging of speckle using image processing method

NASA Astrophysics Data System (ADS)

Wang, Jinjiang; Wang, Pengfei

2018-01-01

A detailed image processing of laser speckle interferometry is proposed as an example for the course of postgraduate student. Several image processing methods were used together for dealing with optoelectronic imaging system, such as the partial differential equations (PDEs) are used to reduce the effect of noise, the thresholding segmentation also based on heat equation with PDEs, the central line is extracted based on image skeleton, and the branch is removed automatically, the phase level is calculated by spline interpolation method, and the fringe phase can be unwrapped. Finally, the imaging processing method was used to automatically measure the bubble in rubber with negative pressure which could be used in the tire detection.

Extended sources near-field processing of experimental aperture synthesis data and application of the Gerchberg method for enhancing radiometric three-dimensional millimetre-wave images in security screening portals

NASA Astrophysics Data System (ADS)

Salmon, Neil A.

2017-10-01

Aperture synthesis for passive millimetre wave imaging provides a means to screen people for concealed threats in the extreme near-field configuration of a portal, a regime where the imager to subject distance is of the order of both the required depth-of-field and the field-of-view. Due to optical aberrations, focal plane array imagers cannot deliver the large depth-of-fields and field-of-views required in this regime. Active sensors on the other hand can deliver these but face challenges of illumination, speckle and multi-path issues when imaging canyon regions of the body. Fortunately an aperture synthesis passive millimetre wave imaging system can deliver large depth-of-fields and field-of-views, whilst having no speckle effects, as the radiometric emission from the human body is spatially incoherent. Furthermore, as in portal security screening scenarios the aperture synthesis imaging technique delivers a half-wavelength spatial resolution, it can effectively screen the whole of the human body. Some recent measurements are presented that demonstrate the three-dimensional imaging capability of extended sources using a 22 GHz aperture synthesis system. A comparison is made between imagery generated via the analytic Fourier transform and a gridding fast Fourier transform method. The analytic Fourier transform enables aliasing in the imagery to be more clearly identified. Some initial results are also presented of how the Gerchberg technique, an image enhancement algorithm used in radio astronomy, is adapted for three-dimensional imaging in security screening. This technique is shown to be able to improve the quality of imagery, without adding extra receivers to the imager. The requirements of a walk through security screening system for use at entrances to airport departure lounges are discussed, concluding that these can be met by an aperture synthesis imager.

[Elastic registration method to compute deformation functions for mitral valve].

PubMed

Yang, Jinyu; Zhang, Wan; Yin, Ran; Deng, Yuxiao; Wei, Yunfeng; Zeng, Junyi; Wen, Tong; Ding, Lu; Liu, Xiaojian; Li, Yipeng

2014-10-01

Mitral valve disease is one of the most popular heart valve diseases. Precise positioning and displaying of the valve characteristics is necessary for the minimally invasive mitral valve repairing procedures. This paper presents a multi-resolution elastic registration method to compute the deformation functions constructed from cubic B-splines in three dimensional ultrasound images, in which the objective functional to be optimized was generated by maximum likelihood method based on the probabilistic distribution of the ultrasound speckle noise. The algorithm was then applied to register the mitral valve voxels. Numerical results proved the effectiveness of the algorithm.

Study on the Classification of GAOFEN-3 Polarimetric SAR Images Using Deep Neural Network

NASA Astrophysics Data System (ADS)

Zhang, J.; Zhang, J.; Zhao, Z.

2018-04-01

Polarimetric Synthetic Aperture Radar (POLSAR) imaging principle determines that the image quality will be affected by speckle noise. So the recognition accuracy of traditional image classification methods will be reduced by the effect of this interference. Since the date of submission, Deep Convolutional Neural Network impacts on the traditional image processing methods and brings the field of computer vision to a new stage with the advantages of a strong ability to learn deep features and excellent ability to fit large datasets. Based on the basic characteristics of polarimetric SAR images, the paper studied the types of the surface cover by using the method of Deep Learning. We used the fully polarimetric SAR features of different scales to fuse RGB images to the GoogLeNet model based on convolution neural network Iterative training, and then use the trained model to test the classification of data validation.First of all, referring to the optical image, we mark the surface coverage type of GF-3 POLSAR image with 8m resolution, and then collect the samples according to different categories. To meet the GoogLeNet model requirements of 256 × 256 pixel image input and taking into account the lack of full-resolution SAR resolution, the original image should be pre-processed in the process of resampling. In this paper, POLSAR image slice samples of different scales with sampling intervals of 2 m and 1 m to be trained separately and validated by the verification dataset. Among them, the training accuracy of GoogLeNet model trained with resampled 2-m polarimetric SAR image is 94.89 %, and that of the trained SAR image with resampled 1 m is 92.65 %.

Comment on Vaknine, R. and Lorenz, W.J. Lateral filtering of medical ultrasonic B-scans before image generation.

PubMed

Dickinson, R J

1985-04-01

In a recent paper, Vaknine and Lorenz discuss the merits of lateral deconvolution of demodulated B-scans. While this technique will decrease the lateral blurring of single discrete targets, such as the diaphragm in their figure 3, it is inappropriate to apply the method to the echoes arising from inhomogeneous structures such as soft tissue. In this latter case, the echoes from individual scatterers within the resolution cell of the transducer interfere to give random fluctuations in received echo amplitude termed speckle. Although his process can be modeled as a linear convolution similar to that of conventional image formation theory, the process of demodulation is a nonlinear process which loses the all-important phase information, and prevents the subsequent restoration of the image by Wiener filtering, itself a linear process.

AN IMPROVED DISTANCE AND MASS ESTIMATE FOR SGR A* FROM A MULTISTAR ORBIT ANALYSIS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boehle, A.; Ghez, A. M.; Meyer, L.

2016-10-10

We present new, more precise measurements of the mass and distance of our Galaxy’s central supermassive black hole, Sgr A*. These results stem from a new analysis that more than doubles the time baseline for astrometry of faint stars orbiting Sgr A*, combining 2 decades of speckle imaging and adaptive optics data. Specifically, we improve our analysis of the speckle images by using information about a star’s orbit from the deep adaptive optics data (2005–2013) to inform the search for the star in the speckle years (1995–2005). When this new analysis technique is combined with the first complete re-reduction ofmore » Keck Galactic Center speckle images using speckle holography, we are able to track the short-period star S0-38 ( K -band magnitude = 17, orbital period = 19 yr) through the speckle years. We use the kinematic measurements from speckle holography and adaptive optics to estimate the orbits of S0-38 and S0-2 and thereby improve our constraints of the mass ( M {sub bh}) and distance ( R {sub o} ) of Sgr A*: M {sub bh} = (4.02 ± 0.16 ± 0.04) × 10{sup 6} M {sub ⊙} and 7.86 ± 0.14 ± 0.04 kpc. The uncertainties in M {sub bh} and R {sub o} as determined by the combined orbital fit of S0-2 and S0-38 are improved by a factor of 2 and 2.5, respectively, compared to an orbital fit of S0-2 alone and a factor of ∼2.5 compared to previous results from stellar orbits. This analysis also limits the extended dark mass within 0.01 pc to less than 0.13 × 10{sup 6} M {sub ⊙} at 99.7% confidence, a factor of 3 lower compared to prior work.« less

Impact of transducer frequency setting on speckle tracking measures.

PubMed

Olsen, Flemming Javier; Svendsen, Jesper Hastrup; Køber, Lars; Højberg, Søren; Haugan, Ketil; Jensen, Jan Skov; Biering-Sørensen, Tor

2018-03-01

Speckle tracking echocardiography is an emerging technique, which is currently being included in clinical guidelines. We sought to investigate the impact of transducer frequency settings on speckle tracking derived measures. The study comprised of 22 subjects prospectively enrolled for a randomized controlled trial (LOOP-study, Clinicaltrials.gov:NCT02036450). Patients were above 70 years of age with increased risk of stroke, and had an echocardiogram performed, which included focused images of the left ventricle. Focused images were obtained with the transducer frequency set at both 1.7/3.3 and 1.5/3.0 MHz. The images were obtained immediately after each other at the exact same position for the two settings. Speckle tracking was performed in three apical projections, allowing for acquisition of layered global longitudinal strain (GLS) and strain rate measures. Concordance between the frequency settings was tested for endo-, mid-, and epicardial GLS and strain rates by coefficients of variation, bias coefficients and visually displayed by Bland-Altman plots. Bland-Altman plots did not reveal any significant over- or underestimation of any speckle tracking measure. Bias coefficients showed that none of the measurements differed significantly between the two settings (bias for GLS endo  = - 0.07 ± 2.94, p = 0.91; GLS mid  = 0.02 ± 2.70, p = 0.98, GLS epi  = 0.07 ± 2.53, p = 0.90). Coefficients of variation were as follows: GLS endo  = 15.11%, GLS mid  = 15.28%, GLS epi  = 17.26%, systolic strain rate = 15.66%, early diastolic strain rate = 38.46%, late diastolic strain rate = 11%. Changing between transducer frequency settings does not systematically derange speckle tracking measures. One can safely reduce the transducer frequency without compromising the validity of speckle tracking derived measures.

The CHARIS IFS for high contrast imaging at Subaru

NASA Technical Reports Server (NTRS)

Groff, Tyler D.; Kasdin, N. Jeremy; Limbach, Mary Anne; Galvin, Michael; Carr, Michael A.; Knapp, Gillian; Brandt, Timothy; Loomis, Craig; Jarosik, Norman; Mede, Kyle;

Tethered SECM endoscopic capsule for the diagnosis of eosinophilic esophagitis (Conference Presentation)

NASA Astrophysics Data System (ADS)

Do, Dukho; Kang, DongKyun; Tabatabaei, Nima; Grant, Catriona N.; Nishioka, Norman S.; Rosenberg, Mireille; Hesterberg, Paul E.; Yuan, Qian; Garber, John J.; Katz, Aubrey J.; Shreffler, Wayne G.; Tearney, Guillermo J.

2017-02-01

Eosinophilic Esophagitis (EoE) is an inflammatory disease caused by inhaled or ingested food allergies, and characterized by the infiltration of eosinophils in the esophagus. The gold standard for diagnosing EoE is to conduct endoscopy and obtain multiple biopsy specimens from different portions of the esophagus; an exam is considered positive if more than 15 eosinophils per high power field (HPF) in any of the biopsies. This method of diagnosis is problematic because endoscopic biopsy is expensive and poorly tolerated and the esophageal eosinophil burden needs to be monitored frequently during the course of the disease. Spectrally encoded confocal microscopy (SECM) is a high-speed confocal microscopy technology that can visualize individual eosinophils in large microscopic images of the human esophagus, equivalent to more than 30,000 HPF. Previously, we have demonstrated that tethered capsule SECM can be conducted in unsedated subjects with diagnosed EoE. However, speckle noise and the relatively low resolution in images obtained with the first capsule prototypes made it challenging to distinguish eosinophils from other cells. In this work, we present a next-generation tethered SECM capsule, which has been modified to significantly improve image quality. First, we substituted the single mode fiber with a dual-clad fiber to reduce speckle noise. A gradient-index multimode fiber was fusion spliced at the tip of the dual-clad fiber to increase the effective numerical aperture of the fiber from 0.09 to 0.15, expanding the beam more rapidly to increase the illumination aperture at the objective. These modifications enabled the new SECM capsule to achieve a lateral resolution of 1.8 µm and an axial resolution of 16.1 µm, which substantially improves the capacity of this probe to visualize cellular features in human tissue. The total size of the SECM capsule remained 6.75 mm in diameter and 31 mm in length. We are now in the process of testing this new SECM capsule in humans. Early results using this new SECM capsule suggest that this technology has the potential to be an effective tool for the diagnosis of EoE.

Modeling envelope statistics of blood and myocardium for segmentation of echocardiographic images.

PubMed

Nillesen, Maartje M; Lopata, Richard G P; Gerrits, Inge H; Kapusta, Livia; Thijssen, Johan M; de Korte, Chris L

2008-04-01

The objective of this study was to investigate the use of speckle statistics as a preprocessing step for segmentation of the myocardium in echocardiographic images. Three-dimensional (3D) and biplane image sequences of the left ventricle of two healthy children and one dog (beagle) were acquired. Pixel-based speckle statistics of manually segmented blood and myocardial regions were investigated by fitting various probability density functions (pdf). The statistics of heart muscle and blood could both be optimally modeled by a K-pdf or Gamma-pdf (Kolmogorov-Smirnov goodness-of-fit test). Scale and shape parameters of both distributions could differentiate between blood and myocardium. Local estimation of these parameters was used to obtain parametric images, where window size was related to speckle size (5 x 2 speckles). Moment-based and maximum-likelihood estimators were used. Scale parameters were still able to differentiate blood from myocardium; however, smoothing of edges of anatomical structures occurred. Estimation of the shape parameter required a larger window size, leading to unacceptable blurring. Using these parameters as an input for segmentation resulted in unreliable segmentation. Adaptive mean squares filtering was then introduced using the moment-based scale parameter (sigma(2)/mu) of the Gamma-pdf to automatically steer the two-dimensional (2D) local filtering process. This method adequately preserved sharpness of the edges. In conclusion, a trade-off between preservation of sharpness of edges and goodness-of-fit when estimating local shape and scale parameters is evident for parametric images. For this reason, adaptive filtering outperforms parametric imaging for the segmentation of echocardiographic images.

A generalized gamma mixture model for ultrasonic tissue characterization.

PubMed

Vegas-Sanchez-Ferrero, Gonzalo; Aja-Fernandez, Santiago; Palencia, Cesar; Martin-Fernandez, Marcos

2012-01-01

Several statistical models have been proposed in the literature to describe the behavior of speckles. Among them, the Nakagami distribution has proven to very accurately characterize the speckle behavior in tissues. However, it fails when describing the heavier tails caused by the impulsive response of a speckle. The Generalized Gamma (GG) distribution (which also generalizes the Nakagami distribution) was proposed to overcome these limitations. Despite the advantages of the distribution in terms of goodness of fitting, its main drawback is the lack of a closed-form maximum likelihood (ML) estimates. Thus, the calculation of its parameters becomes difficult and not attractive. In this work, we propose (1) a simple but robust methodology to estimate the ML parameters of GG distributions and (2) a Generalized Gama Mixture Model (GGMM). These mixture models are of great value in ultrasound imaging when the received signal is characterized by a different nature of tissues. We show that a better speckle characterization is achieved when using GG and GGMM rather than other state-of-the-art distributions and mixture models. Results showed the better performance of the GG distribution in characterizing the speckle of blood and myocardial tissue in ultrasonic images.

A Generalized Gamma Mixture Model for Ultrasonic Tissue Characterization

PubMed Central

Palencia, Cesar; Martin-Fernandez, Marcos

2012-01-01

Several statistical models have been proposed in the literature to describe the behavior of speckles. Among them, the Nakagami distribution has proven to very accurately characterize the speckle behavior in tissues. However, it fails when describing the heavier tails caused by the impulsive response of a speckle. The Generalized Gamma (GG) distribution (which also generalizes the Nakagami distribution) was proposed to overcome these limitations. Despite the advantages of the distribution in terms of goodness of fitting, its main drawback is the lack of a closed-form maximum likelihood (ML) estimates. Thus, the calculation of its parameters becomes difficult and not attractive. In this work, we propose (1) a simple but robust methodology to estimate the ML parameters of GG distributions and (2) a Generalized Gama Mixture Model (GGMM). These mixture models are of great value in ultrasound imaging when the received signal is characterized by a different nature of tissues. We show that a better speckle characterization is achieved when using GG and GGMM rather than other state-of-the-art distributions and mixture models. Results showed the better performance of the GG distribution in characterizing the speckle of blood and myocardial tissue in ultrasonic images. PMID:23424602

Amplitude and intensity spatial interferometry; Proceedings of the Meeting, Tucson, AZ, Feb. 14-16, 1990

NASA Technical Reports Server (NTRS)

Breckinridge, Jim B. (Editor)

1990-01-01

Attention is given to such topics as ground interferometers, space interferometers, speckle-based and interferometry-based astronomical observations, adaptive and atmospheric optics, speckle techniques, and instrumentation. Particular papers are presented concerning recent progress on the IR Michelson array; the IOTA interferometer project; a space interferometer concept for the detection of extrasolar earth-like planets; IR speckle imaging at Palomar; optical diameters of stars measured with the Mt. Wilson Mark III interferometer; the IR array camera for interferometry with the cophased Multiple Mirror Telescope; optimization techniques appliesd to the bispectrum of one-dimensional IR astronomical speckle data; and adaptive optical iamging for extended objects.

Combined optical coherence tomography and optical coherence elastography for glomerulonephritis classification

NASA Astrophysics Data System (ADS)

Liu, Chih-Hao; Du, Yong; Singh, Manmohan; Wu, Chen; Han, Zhaolong; Li, Jiasong; Mohammadzai, Qais; Raghunathan, Raksha; Hsu, Thomas; Noorani, Shezaan; Chang, Anthony; Mohan, Chandra; Larin, Kirill V.

2016-03-01

Acute Glomerulonephritis caused by anti-glomerular basement membrane disease has a high mortality due to delayed diagnosis. Thus, an accurate and early diagnosis is critical for preserving renal function. Currently, blood, urine, and tissue-based diagnoses can be time consuming, while ultrasound and CT imaging have relatively low spatial resolution. Optical coherence tomography (OCT) is a noninvasive imaging technique that provides superior spatial resolution (micron scale) as compared to ultrasound and CT. Pathological changes in tissue properties can be detected based on the optical metrics analyzed from the OCT signal, such as optical attenuation and speckle variance. Moreover, OCT does not rely on ionizing radiation as with CT imaging. In addition to structural changes, the elasticity of the kidney can significantly change due to nephritis. In this work, we utilized OCT to detect the difference in tissue properties between healthy and nephritic murine kidneys. Although OCT imaging could identify the diseased tissue, classification accuracy using only optical metrics was clinically inadequate. By combining optical metrics with elasticity, the classification accuracy improved from 76% to 95%. These results show that OCT combined with OCE can be potentially useful for nephritis detection.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Speckle suppression using a liquid-crystal cell

NASA Astrophysics Data System (ADS)

Andreev, A. L.; Kompanets, I. N.; Minchenko, M. V.; Pozhidaev, E. P.; Andreeva, T. B.

2008-12-01

A simple method for suppressing speckles in images produced by laser projectors is proposed. The coherence of the laser beam and, therefore, speckles can be destroyed when the beam passes through an electrooptical cell in which a special ferroelectric liquid crystal is used as a modulating medium. The effect is achieved due to the spatially inhomogeneous phase modulation of light when specially shaped bipolar electric pulses are applied to the cell.

Robust motion tracking based on adaptive speckle decorrelation analysis of OCT signal.

PubMed

Wang, Yuewen; Wang, Yahui; Akansu, Ali; Belfield, Kevin D; Hubbi, Basil; Liu, Xuan

2015-11-01

Speckle decorrelation analysis of optical coherence tomography (OCT) signal has been used in motion tracking. In our previous study, we demonstrated that cross-correlation coefficient (XCC) between Ascans had an explicit functional dependency on the magnitude of lateral displacement (δx). In this study, we evaluated the sensitivity of speckle motion tracking using the derivative of function XCC(δx) on variable δx. We demonstrated the magnitude of the derivative can be maximized. In other words, the sensitivity of OCT speckle tracking can be optimized by using signals with appropriate amount of decorrelation for XCC calculation. Based on this finding, we developed an adaptive speckle decorrelation analysis strategy to achieve motion tracking with optimized sensitivity. Briefly, we used subsequently acquired Ascans and Ascans obtained with larger time intervals to obtain multiple values of XCC and chose the XCC value that maximized motion tracking sensitivity for displacement calculation. Instantaneous motion speed can be calculated by dividing the obtained displacement with time interval between Ascans involved in XCC calculation. We implemented the above-described algorithm in real-time using graphic processing unit (GPU) and demonstrated its effectiveness in reconstructing distortion-free OCT images using data obtained from a manually scanned OCT probe. The adaptive speckle tracking method was validated in manually scanned OCT imaging, on phantom as well as in vivo skin tissue.

Robust motion tracking based on adaptive speckle decorrelation analysis of OCT signal

PubMed Central

Wang, Yuewen; Wang, Yahui; Akansu, Ali; Belfield, Kevin D.; Hubbi, Basil; Liu, Xuan

2015-01-01

Speckle decorrelation analysis of optical coherence tomography (OCT) signal has been used in motion tracking. In our previous study, we demonstrated that cross-correlation coefficient (XCC) between Ascans had an explicit functional dependency on the magnitude of lateral displacement (δx). In this study, we evaluated the sensitivity of speckle motion tracking using the derivative of function XCC(δx) on variable δx. We demonstrated the magnitude of the derivative can be maximized. In other words, the sensitivity of OCT speckle tracking can be optimized by using signals with appropriate amount of decorrelation for XCC calculation. Based on this finding, we developed an adaptive speckle decorrelation analysis strategy to achieve motion tracking with optimized sensitivity. Briefly, we used subsequently acquired Ascans and Ascans obtained with larger time intervals to obtain multiple values of XCC and chose the XCC value that maximized motion tracking sensitivity for displacement calculation. Instantaneous motion speed can be calculated by dividing the obtained displacement with time interval between Ascans involved in XCC calculation. We implemented the above-described algorithm in real-time using graphic processing unit (GPU) and demonstrated its effectiveness in reconstructing distortion-free OCT images using data obtained from a manually scanned OCT probe. The adaptive speckle tracking method was validated in manually scanned OCT imaging, on phantom as well as in vivo skin tissue. PMID:26600996

OBSERVATIONS OF BINARY STARS WITH THE DIFFERENTIAL SPECKLE SURVEY INSTRUMENT. III. MEASURES BELOW THE DIFFRACTION LIMIT OF THE WIYN TELESCOPE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Horch, Elliott P.; Van Altena, William F.; Howell, Steve B.

2011-06-15

In this paper, we study the ability of CCD- and electron-multiplying-CCD-based speckle imaging to obtain reliable astrometry and photometry of binary stars below the diffraction limit of the WIYN 3.5 m Telescope. We present a total of 120 measures of binary stars, 75 of which are below the diffraction limit. The measures are divided into two groups that have different measurement accuracy and precision. The first group is composed of standard speckle observations, that is, a sequence of speckle images taken in a single filter, while the second group consists of paired observations where the two observations are taken onmore » the same observing run and in different filters. The more recent paired observations were taken simultaneously with the Differential Speckle Survey Instrument, which is a two-channel speckle imaging system. In comparing our results to the ephemeris positions of binaries with known orbits, we find that paired observations provide the opportunity to identify cases of systematic error in separation below the diffraction limit and after removing these from consideration, we obtain a linear measurement uncertainty of 3-4 mas. However, if observations are unpaired or if two observations taken in the same filter are paired, it becomes harder to identify cases of systematic error, presumably because the largest source of this error is residual atmospheric dispersion, which is color dependent. When observations are unpaired, we find that it is unwise to report separations below approximately 20 mas, as these are most susceptible to this effect. Using the final results obtained, we are able to update two older orbits in the literature and present preliminary orbits for three systems that were discovered by Hipparcos.« less

Filtering and left ventricle segmentation of the fetal heart in ultrasound images

NASA Astrophysics Data System (ADS)

Vargas-Quintero, Lorena; Escalante-Ramírez, Boris

2013-11-01

In this paper, we propose to use filtering methods and a segmentation algorithm for the analysis of fetal heart in ultrasound images. Since noise speckle makes difficult the analysis of ultrasound images, the filtering process becomes a useful task in these types of applications. The filtering techniques consider in this work assume that the speckle noise is a random variable with a Rayleigh distribution. We use two multiresolution methods: one based on wavelet decomposition and the another based on the Hermite transform. The filtering process is used as way to strengthen the performance of the segmentation tasks. For the wavelet-based approach, a Bayesian estimator at subband level for pixel classification is employed. The Hermite method computes a mask to find those pixels that are corrupted by speckle. On the other hand, we picked out a method based on a deformable model or "snake" to evaluate the influence of the filtering techniques in the segmentation task of left ventricle in fetal echocardiographic images.

Measurement of concentration of sugar in solutions with laser speckle decorrelation

NASA Astrophysics Data System (ADS)

Mahajan, Swapnil; Trivedi, Vismay; Chhaniwal, Vani; Prajapati, Mahendra; Zalevsky, Zeev; Javidi, Bahram; Anand, Arun

2015-05-01

Measurement of rotation of plane of polarization of linearly polarized light can provide information about the concentration of the optically active system with which it interacts. For substances containing sugar, accurate measurement of rotation of linearly polarized light can provide quantitative information about concentration of sugar in the material. Measurement of sugar concentration is important in areas ranging from blood sugar level measurement in body fluids to measurement of sugar concentrations in juices and other beverages. But in many of these cases, the changes introduced to the state of polarization considering a sample of practical proportion is low and the measurement of low optical rotations becomes necessary. So methods with higher sensitivity, accuracy and resolution need to be developed for the measurement of low optical rotations. Here we describe the development of a compact, low cost, field portable, device for rotation sensing leading to sugar concentration measurements, using speckle de-correlation technique. The developed device measures rotations by determining the changes occurring to a speckle pattern generated by a laser beam passing through the medium under investigation. The device consists of a sample chamber, a diode laser module, a ground glass diffuser and a digital sensor for recording of laser speckle patterns. The device was found to have high resolution and sensitivity.

Handheld, point-of-care laser speckle imaging

PubMed Central

Farraro, Ryan; Fathi, Omid; Choi, Bernard

2016-01-01

Abstract. Laser speckle imaging (LSI) enables measurement of relative changes in blood flow in biological tissues. We postulate that a point-of-care form factor will lower barriers to routine clinical use of LSI. Here, we describe a first-generation handheld LSI device based on a tablet computer. The coefficient of variation of speckle contrast was <2% after averaging imaging data collected over an acquisition period of 5.3 s. With a single, experienced user, handheld motion artifacts had a negligible effect on data collection. With operation by multiple users, we did not identify any significant difference (p>0.05) between the measured speckle contrast values using either a handheld or mounted configuration. In vivo data collected during occlusion experiments demonstrate that a handheld LSI is capable of both quantitative and qualitative assessment of changes in blood flow. Finally, as a practical application of handheld LSI, we collected data from a 53-day-old neonate with confirmed compromised blood flow in the hand. We readily identified with LSI a region of diminished blood flow in the thumb of the affected hand. Our data collectively suggest that handheld LSI is a promising technique to enable clinicians to obtain point-of-care measurements of blood flow. PMID:27579578

Speckle Noise Reduction in Optical Coherence Tomography Using Two-dimensional Curvelet-based Dictionary Learning.

PubMed

Esmaeili, Mahdad; Dehnavi, Alireza Mehri; Rabbani, Hossein; Hajizadeh, Fedra

2017-01-01

The process of interpretation of high-speed optical coherence tomography (OCT) images is restricted due to the large speckle noise. To address this problem, this paper proposes a new method using two-dimensional (2D) curvelet-based K-SVD algorithm for speckle noise reduction and contrast enhancement of intra-retinal layers of 2D spectral-domain OCT images. For this purpose, we take curvelet transform of the noisy image. In the next step, noisy sub-bands of different scales and rotations are separately thresholded with an adaptive data-driven thresholding method, then, each thresholded sub-band is denoised based on K-SVD dictionary learning with a variable size initial dictionary dependent on the size of curvelet coefficients' matrix in each sub-band. We also modify each coefficient matrix to enhance intra-retinal layers, with noise suppression at the same time. We demonstrate the ability of the proposed algorithm in speckle noise reduction of 100 publically available OCT B-scans with and without non-neovascular age-related macular degeneration (AMD), and improvement of contrast-to-noise ratio from 1.27 to 5.12 and mean-to-standard deviation ratio from 3.20 to 14.41 are obtained.

Single shot laser speckle based 3D acquisition system for medical applications

NASA Astrophysics Data System (ADS)

Khan, Danish; Shirazi, Muhammad Ayaz; Kim, Min Young

2018-06-01

The state of the art techniques used by medical practitioners to extract the three-dimensional (3D) geometry of different body parts requires a series of images/frames such as laser line profiling or structured light scanning. Movement of the patients during scanning process often leads to inaccurate measurements due to sequential image acquisition. Single shot structured techniques are robust to motion but the prevalent challenges in single shot structured light methods are the low density and algorithm complexity. In this research, a single shot 3D measurement system is presented that extracts the 3D point cloud of human skin by projecting a laser speckle pattern using a single pair of images captured by two synchronized cameras. In contrast to conventional laser speckle 3D measurement systems that realize stereo correspondence by digital correlation of projected speckle patterns, the proposed system employs KLT tracking method to locate the corresponding points. The 3D point cloud contains no outliers and sufficient quality of 3D reconstruction is achieved. The 3D shape acquisition of human body parts validates the potential application of the proposed system in the medical industry.

Texture-based characterization of subskin features by specified laser speckle effects at λ = 650 nm region for more accurate parametric 'skin age' modelling.

PubMed

Orun, A B; Seker, H; Uslan, V; Goodyer, E; Smith, G

2017-06-01

The textural structure of 'skin age'-related subskin components enables us to identify and analyse their unique characteristics, thus making substantial progress towards establishing an accurate skin age model. This is achieved by a two-stage process. First by the application of textural analysis using laser speckle imaging, which is sensitive to textural effects within the λ = 650 nm spectral band region. In the second stage, a Bayesian inference method is used to select attributes from which a predictive model is built. This technique enables us to contrast different skin age models, such as the laser speckle effect against the more widely used normal light (LED) imaging method, whereby it is shown that our laser speckle-based technique yields better results. The method introduced here is non-invasive, low cost and capable of operating in real time; having the potential to compete against high-cost instrumentation such as confocal microscopy or similar imaging devices used for skin age identification purposes. © 2016 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

Handheld, point-of-care laser speckle imaging

NASA Astrophysics Data System (ADS)

Farraro, Ryan; Fathi, Omid; Choi, Bernard

2016-09-01

Laser speckle imaging (LSI) enables measurement of relative changes in blood flow in biological tissues. We postulate that a point-of-care form factor will lower barriers to routine clinical use of LSI. Here, we describe a first-generation handheld LSI device based on a tablet computer. The coefficient of variation of speckle contrast was <2% after averaging imaging data collected over an acquisition period of 5.3 s. With a single, experienced user, handheld motion artifacts had a negligible effect on data collection. With operation by multiple users, we did not identify any significant difference (p>0.05) between the measured speckle contrast values using either a handheld or mounted configuration. In vivo data collected during occlusion experiments demonstrate that a handheld LSI is capable of both quantitative and qualitative assessment of changes in blood flow. Finally, as a practical application of handheld LSI, we collected data from a 53-day-old neonate with confirmed compromised blood flow in the hand. We readily identified with LSI a region of diminished blood flow in the thumb of the affected hand. Our data collectively suggest that handheld LSI is a promising technique to enable clinicians to obtain point-of-care measurements of blood flow.

Monitoring of the microhemodynamic in an aggressive clinical behavior of cerebral hemorrhage using dynamic light scattering techniques

NASA Astrophysics Data System (ADS)

Vilensky, M. A.; Semyachkina-Glushkovskaya, O. V.; Timoshina, P. A.; Berdnikova, V. A.; Kuznetsova, Y. V.; Semyachkin-Glushkovsky, I. A.; Agafonov, D. N.; Tuchin, V. V.

2012-06-01

This paper presents the results of experimental study of full field laser speckle imaging due to cortex microcirculation state monitoring for laboratory rats under conditions of stroke and the introduction of agents. Three groups of experimental animals from five animals in each group were studied. The behavior of blood flow, studied by speckle imaging technique, matched the expected physiological response to an impact.

Speckle imaging with the PAPA detector. [Precision Analog Photon Address

NASA Technical Reports Server (NTRS)

Papaliolios, C.; Nisenson, P.; Ebstein, S.

1985-01-01

A new 2-D photon-counting camera, the PAPA (precision analog photon address) detector has been built, tested, and used successfully for the acquisition of speckle imaging data. The camera has 512 x 512 pixels and operates at count rates of at least 200,000/sec. In this paper, technical details on the camera are presented and some of the laboratory and astronomical results are included which demonstrate the detector's capabilities.

Application of laser speckle contrast image in the evaluation of arthritis animal model

NASA Astrophysics Data System (ADS)

Son, Taeyoon; Jang, Won Hyuk; Park, Jihoon; Yoon, Hyung-Ju; Lee, Jeon; Kim, Wan-Uk; Jung, Byungjo

2013-03-01

Arthritis is a chronic inflammatory disease that induces potentially damaging and commonly disabling. Various imaging modalities have been used for the evaluation of arthritis. This study aimed to investigate the feasibility of laser speckle contrast image (LSCI) in the evaluation of the severity and early stage of arthritis in animal model. Arthritis was induced on mouse foot and evaluated by a trained expert and the LSCI. The arthritis severity was quantitatively evaluated by speckle index (SI) computed from LSCI. In visual inspection by an expert, it was difficult to evaluate the arthritis because there was no noticeable different between control mouse group (CMG) and arthritis mouse group (AMG) in erythema. However, arthritis was easily evaluated by significant SI different between the CMG and AMG. In addition, the LSCI also successfully evaluated the early stage of arthritis, presenting different SI distribution depending on lesion.

Fast image processing with a microcomputer applied to speckle photography

NASA Astrophysics Data System (ADS)

Erbeck, R.

1985-11-01

An automated image recognition system is described for speckle photography investigations in fluid dynamics. The system is employed for characterizing the pattern of interference fringes obtained using speckle interferometry. A rotating ground glass serves as a screen on which laser light passing through a specklegraph plate, the flow and a compensation plate (CP) is shone to produce a compensated Young's pattern. The image produced on the ground glass is photographed by a video camera whose signal is digitized and processed through a microcomputer using a 6502 CPU chip. The normalized correlation function of the intensity is calculated in two directions of the recorded pattern to obtain the wavelength and the light deflection angle. The system has a capability of one picture every two seconds. Sample data are provided for a free jet of CO2 issuing into air in both laminar and turbulent form.

SIR-B ocean-wave enhancement with fast Fourier transform techniques

NASA Technical Reports Server (NTRS)

Tilley, David G.

1987-01-01

Shuttle Imaging Radar (SIR-B) imagery is Fourier filtered to remove the estimated system-transfer function, reduce speckle noise, and produce ocean scenes with a gray scale that is proportional to wave height. The SIR-B system response to speckled scenes of uniform surfaces yields an estimate of the stationary wavenumber response of the imaging radar, modeled by the 15 even terms of an eighth-order two-dimensional polynomial. Speckle can also be used to estimate the dynamic wavenumber response of the system due to surface motion during the aperture synthesis period, modeled with a single adaptive parameter describing an exponential correlation along track. A Fourier filter can then be devised to correct for the wavenumber response of the remote sensor and scene correlation, with subsequent subtraction of an estimate of the speckle noise component. A linearized velocity bunching model, combined with a surface tilt and hydrodynamic model, is incorporated in the Fourier filter to derive estimates of wave height from the radar intensities corresponding to individual picture elements.

New techniques for fluorescence background rejection in microscopy and endoscopy

NASA Astrophysics Data System (ADS)

Ventalon, Cathie

2009-03-01

Confocal microscopy is a popular technique in the bioimaging community, mainly because it provides optical sectioning. However, its standard implementation requires 3-dimensional scanning of focused illumination throughout the sample. Efficient non-scanning alternatives have been implemented, among which the simple and well-established incoherent structured illumination microscopy (SIM) [1]. We recently proposed a similar technique, called Dynamic Speckle Illumination (DSI) microscopy, wherein the incoherent grid illumination pattern is replaced with a coherent speckle illumination pattern from a laser, taking advantage of the fact that speckle contrast is highly maintained in a scattering media, making the technique well adapted to tissue imaging [2]. DSI microscopy relies on the illumination of a sample with a sequence of dynamic speckle patterns and an image processing algorithm based only on an a priori knowledge of speckle statistics. The choice of this post-processing algorithm is crucial to obtain a good sectioning strength: in particular, we developed a novel post-processing algorithm based one wavelet pre-filtering of the raw images and obtained near-confocal fluorescence sectioning in a mouse brain labeled with GFP, with a good image quality maintained throughout a depth of ˜100 μm [3]. In the purpose of imaging fluorescent tissue at higher depth, we recently applied structured illumination to endoscopy. We used a similar set-up wherein the illumination pattern (a one-dimensional grid) is transported to the sample with an imaging fiber bundle with miniaturized objective and the fluorescence image is collected through the same bundle. Using a post-processing algorithm similar to the one previously described [3], we obtained high-quality images of a fluorescein-labeled rat colonic mucosa [4], establishing the potential of our endomicroscope for bioimaging applications. [4pt] Ref: [0pt] [1] M. A. A. Neil et al, Opt. Lett. 22, 1905 (1997) [0pt] [2] C. Ventalon et al, Opt. Lett. 30, 3350 (2005) [0pt] [3] C. Ventalon et al, Opt. Lett. 32, 1417 (2007) [0pt] [4] N. Bozinovic et al, Opt. Express 16, 8016 (2008)

Measurement of the surface morphology of plasma facing components on the EAST tokamak by a laser speckle interferometry approach

NASA Astrophysics Data System (ADS)

Hongbei, WANG; Xiaoqian, CUI; Yuanbo, LI; Mengge, ZHAO; Shuhua, LI; Guangnan, LUO; Hongbin, DING

2018-03-01

The laser speckle interferometry approach provides the possibility of an in situ optical non-contacted measurement for the surface morphology of plasma facing components (PFCs), and the reconstruction image of the PFC surface morphology is computed by a numerical model based on a phase unwrapping algorithm. A remote speckle interferometry measurement at a distance of three meters for real divertor tiles retired from EAST was carried out in the laboratory to simulate a real detection condition on EAST. The preliminary surface morphology of the divertor tiles was well reproduced by the reconstructed geometric image. The feasibility and reliability of this approach for the real-time measurement of PFCs have been demonstrated.

Laser speckle imaging for lesion detection on tooth

NASA Astrophysics Data System (ADS)

Gavinho, Luciano G.; Silva, João. V. P.; Damazio, João. H.; Sfalcin, Ravana A.; Araujo, Sidnei A.; Pinto, Marcelo M.; Olivan, Silvia R. G.; Prates, Renato A.; Bussadori, Sandra K.; Deana, Alessandro M.

2018-02-01

Computer vision technologies for diagnostic imaging applied to oral lesions, specifically, carious lesions of the teeth, are in their early years of development. The relevance of this public problem, dental caries, worries countries around the world, as it affects almost the entire population, at least once in the life of each individual. The present work demonstrates current techniques for obtaining information about lesions on teeth by segmentation laser speckle imagens (LSI). Laser speckle image results from laser light reflection on a rough surface, and it was considered a noise but has important features that carry information about the illuminated surface. Even though these are basic images, only a few works have analyzed it by application of computer vision methods. In this article, we present the latest results of our group, in which Computer vision techniques were adapted to segment laser speckle images for diagnostic purposes. These methods are applied to the segmentation of images between healthy and lesioned regions of the tooth. These methods have proven to be effective in the diagnosis of early-stage lesions, often imperceptible in traditional diagnostic methods in the clinical practice. The first method uses first-order statistical models, segmenting the image by comparing the mean and standard deviation of the intensity of the pixels. The second method is based on the distance of the chi-square (χ2 ) between the histograms of the image, bringing a significant improvement in the precision of the diagnosis, while a third method introduces the use of fractal geometry, exposing, through of the fractal dimension, more precisely the difference between lesioned areas and healthy areas of a tooth compared to other methods of segmentation. So far, we can observe efficiency in the segmentation of the carious regions. A software was developed for the execution and demonstration of the applicability of the models

Feasibility study of hidden flow imaging based on laser speckle technique using multiperspectives contrast images

NASA Astrophysics Data System (ADS)

Abookasis, David; Moshe, Tomer

2014-11-01

This paper demonstrates the insertion of lens array in the front of a CCD camera in a laser speckle imaging (LSI) like-technique to acquire multiple speckle reflectance projections for imaging blood flow in an intact biological tissue. In some of LSI applications, flow imaging is obtained by thinning or removing of the upper tissue layers to access blood vessels. In contrast, with the proposed approach flow imaging can be achieved while the tissue is intact. In the system, each lens from an hexagonal lens array observed the sample from slightly different perspectives and captured with a CCD camera. In the computer, these multiview raw images are converted to speckled contrast maps. Then, a self-deconvolution shift-and-add algorithm is employed for processing yields high contrast flow information. The method is experimentally validated first with a plastic tube filled with scattering liquid running at different controlled flow rates hidden in a biological tissue and then extensively tested for imaging of cerebral blood flow in an intact rodent head experience different conditions. A total of fifteen mice were used in the experiments divided randomly into three groups as follows: Group 1 (n=5) consisted of injured mice experience hypoxic ischemic brain injury monitored for ~40 min. Group 2 (n=5) injured mice experience anoxic brain injury monitored up to 20 min. Group 3 (n=5) experience functional activation monitored up to ~35 min. To increase tissue transparency and the penetration depth of photons through head tissue layers, an optical clearing method was employed. To our knowledge, this work presents for the first time the use of lens array in LSI scheme.

VizieR Online Data Catalog: KOIs companions from high-resolution imaging (Hirsch+, 2017)

NASA Astrophysics Data System (ADS)

Hirsch, L. A.; Ciardi, D. R.; Howard, A. W.; Everett, M. E.; Furlan, E.; Saylors, M.; Horch, E. P.; Howell, S. B.; Teske, J.; Marcy, G. W.

2017-07-01

We report on 176 close (<2'') stellar companions detected with high-resolution imaging near 170 hosts of Kepler Objects of Interest (KOIs). Our sample consists of 170 stellar hosts of Kepler Objects of Interest (KOIs) observed with various high-resolution imaging campaigns. This sample was drawn from the overall sample of KOI stars observed with high-resolution imaging, described in the imaging compilation paper by Furlan et al. 2017 (Cat. J/AJ/153/71). We choose targets for this study by requiring that at least one companion was detected within 2'', and that the companion was detected in two or more filters, providing color information. We choose the 2'' separation limit to include all companions falling on the same Kepler pixel as the primary KOI host star. Furlan et al. 2017 (Cat. J/AJ/153/71) details the observations and measured differential magnitudes (Δm=m2-m1) for stars with high-resolution imaging, including our target systems. Each companion within 2'' must have at least two measured Δm values from the full set of filters used for follow-up observations, in order to be included in our sample. These filters include J-band, H-band, and K-band from adaptive optics imaging from the Keck/NIRC2, Palomar/PHARO, Lick/IRCAL, and MMT/Aries instruments; 562, 692 and 880nm filters from the Differential Speckle Survey Instrument (DSSI) at the Gemini North and WIYN telescopes; i and z bands from the AstraLux lucky imaging campaign at the Calar Alto 2.2m telescope; and LP600 and i bands from Palomar/RoboAO. We also include seeing-limited observations in the U-, B-, and V-bands from the UBV survey (Everett et al.) and "secure" detections (noise probability <10%) in the J-band from the UKIRT Kepler field survey. (3 data files).

Optical coherence tomography noise modeling and fundamental bounds on human retinal layer segmentation accuracy (Conference Presentation)

NASA Astrophysics Data System (ADS)

DuBose, Theodore B.; Milanfar, Peyman; Izatt, Joseph A.; Farsiu, Sina

2016-03-01

The human retina is composed of several layers, visible by in vivo optical coherence tomography (OCT) imaging. To enhance diagnostics of retinal diseases, several algorithms have been developed to automatically segment one or more of the boundaries of these layers. OCT images are corrupted by noise, which is frequently the result of the detector noise and speckle, a type of coherent noise resulting from the presence of several scatterers in each voxel. However, it is unknown what the empirical distribution of noise in each layer of the retina is, and how the magnitude and distribution of the noise affects the lower bounds of segmentation accuracy. Five healthy volunteers were imaged using a spectral domain OCT probe from Bioptigen, Inc, centered at 850nm with 4.6µm full width at half maximum axial resolution. Each volume was segmented by expert manual graders into nine layers. The histograms of intensities in each layer were then fit to seven possible noise distributions from the literature on speckle and image processing. Using these empirical noise distributions and empirical estimates of the intensity of each layer, the Cramer-Rao lower bound (CRLB), a measure of the variance of an estimator, was calculated for each boundary layer. Additionally, the optimum bias of a segmentation algorithm was calculated, and a corresponding biased CRLB was calculated, which represents the improved performance an algorithm can achieve by using prior knowledge, such as the smoothness and continuity of layer boundaries. Our general mathematical model can be easily adapted for virtually any OCT modality.

Differential standard deviation of log-scale intensity based optical coherence tomography angiography.

PubMed

Shi, Weisong; Gao, Wanrong; Chen, Chaoliang; Yang, Victor X D

2017-12-01

In this paper, a differential standard deviation of log-scale intensity (DSDLI) based optical coherence tomography angiography (OCTA) is presented for calculating microvascular images of human skin. The DSDLI algorithm calculates the variance in difference images of two consecutive log-scale intensity based structural images from the same position along depth direction to contrast blood flow. The en face microvascular images were then generated by calculating the standard deviation of the differential log-scale intensities within the specific depth range, resulting in an improvement in spatial resolution and SNR in microvascular images compared to speckle variance OCT and power intensity differential method. The performance of DSDLI was testified by both phantom and in vivo experiments. In in vivo experiments, a self-adaptive sub-pixel image registration algorithm was performed to remove the bulk motion noise, where 2D Fourier transform was utilized to generate new images with spatial interval equal to half of the distance between two pixels in both fast-scanning and depth directions. The SNRs of signals of flowing particles are improved by 7.3 dB and 6.8 dB on average in phantom and in vivo experiments, respectively, while the average spatial resolution of images of in vivo blood vessels is increased by 21%. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Evaluation of Defects inside Beryllium Foils using X-ray Computed Tomography and Shearing Interferometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sakurai, Tatsuyuki; Kohmura, Yoshiki; Takeuchi, Akihisa

2007-01-19

When beryllium is used in transmission X-ray optical elements for spatially coherent beams, speckles are usually observed in the transmission images. These speckles seem to be caused by defects either inside or on the surface of beryllium foil. We measured highly polished beryllium foil using two methods, X-ray computed tomography and X-ray shearing interferometry. The results indicate that observed speckle pattern is caused by many voids inside beryllium or inner low-density regions.

Laser speckle reduction due to spatial and angular diversity introduced by fast scanning micromirror.

PubMed

Akram, M Nadeem; Tong, Zhaomin; Ouyang, Guangmin; Chen, Xuyuan; Kartashov, Vladimir

2010-06-10

We utilize spatial and angular diversity to achieve speckle reduction in laser illumination. Both free-space and imaging geometry configurations are considered. A fast two-dimensional scanning micromirror is employed to steer the laser beam. A simple experimental setup is built to demonstrate the application of our technique in a two-dimensional laser picture projection. Experimental results show that the speckle contrast factor can be reduced down to 5% within the integration time of the detector.

Acousto-optical imaging using a powerful long pulse laser

NASA Astrophysics Data System (ADS)

Rousseau, Guy; Blouin, Alain; Monchalin, Jean-Pierre

2008-06-01

Acousto-optical imaging is an emerging biodiagnostic technique which provides an optical spectroscopic signature and a spatial localization of an optically absorbing target embedded in a strongly scattering medium. The transverse resolution of the technique is determined by the lateral extent of ultrasound beam focal zone while the axial resolution is obtained by using short ultrasound pulses. Although very promising for medical diagnostic, the practical application of this technique is presently limited by its poor sensitivity. Moreover, any method to enhance the signal-to-noise ratio must obviously satisfy the in vivo safety limits regarding the acceptable power level of both the ultrasonic pressure wave and the laser beam. In this paper, we propose to improve the sensitivity by using a pulsed single-frequency laser source to raise the optical peak power applied to the scattering medium and to collect more ultrasonically tagged photons. Such a laser source also allows illuminating the tissues mainly during the transit time of the ultrasonic wave to maintain the average optical power below the maximum permissible exposure. In our experiment, a single-frequency Nd:YAG laser emitting 500-μs pulses with a peak power superior to 100 W was used. Photons were tagged in few-cm thick optical phantoms with tone bursts generated by an ultrasonic transducer. Tagged photons were detected with a GaAs photorefractive interferometer characterized by a large optical etendue to process simultaneously a large number of speckle grains. When pumped by high intensity laser pulses, such an interferometer also provides the fast response time essential to obtain an apparatus insensitive to the speckle decorrelation due to mechanical vibrations or tissues movements. The use of a powerful long pulse laser appears promising to enhance the signal level in ultrasound modulated optical imaging. When combined with a photorefractive interferometer of large optical etendue, such a source could allow obtaining both the sensitivity and the fast response time necessary for biodiagnostic applications.

Separated Component-Based Restoration of Speckled SAR Images

DTIC Science & Technology

2013-01-01

unsupervised change detection from SAR amplitude imagery,” IEEE Trans. Geosci. Remote Sens., vol. 44, no. 10, pp. 2972–2982, Oct. 2006. [5] F. Argenti , T...Sens., vol. 40, no. 10, pp. 2196–2212, Oct. 2002. [13] F. Argenti and L. Alparone, “Speckle removal from SAR images in the undecimated wavelet domain...iterative thresh- olding algorithm for linear inverse problems with a sparsity con- straint,” Commun . Pure Appl. Math., vol. 57, no. 11, pp. 1413

Role of strain imaging in right heart disease: a comprehensive review.

PubMed

Kannan, Arun; Poongkunran, Chithra; Jayaraj, Mahendran; Janardhanan, Rajesh

2014-10-01

Advances in the imaging techniques of the heart have fueled the interest in understanding of right heart pathology. Recently, speckle tracking echocardiography has shown to aid in understanding various right heart diseases and better management. Its role is well established in diagnosing right heart failure, pulmonary artery hypertension, arrhythmogenic right ventricular dysplasia and congenital heart disease. We review the basic mechanics of speckle tracking and analyze its role in various right heart conditions.

Efficient image projection by Fourier electroholography.

PubMed

Makowski, Michał; Ducin, Izabela; Kakarenko, Karol; Kolodziejczyk, Andrzej; Siemion, Agnieszka; Siemion, Andrzej; Suszek, Jaroslaw; Sypek, Maciej; Wojnowski, Dariusz

2011-08-15

An improved efficient projection of color images is presented. It uses a phase spatial light modulator with three iteratively optimized Fourier holograms displayed simultaneously--each for one primary color. This spatial division instead of time division provides stable images. A pixelated structure of the modulator and fluctuations of liquid crystal molecules cause a zeroth-order peak, eliminated by additional wavelength-dependent phase factors shifting it before the image plane, where it is blocked with a matched filter. Speckles are suppressed by time integration of variable speckle patterns generated by additional randomizations of an initial phase and minor changes of the signal. © 2011 Optical Society of America

Blind Source Parameters for Performance Evaluation of Despeckling Filters.

PubMed

Biradar, Nagashettappa; Dewal, M L; Rohit, ManojKumar; Gowre, Sanjaykumar; Gundge, Yogesh

2016-01-01

The speckle noise is inherent to transthoracic echocardiographic images. A standard noise-free reference echocardiographic image does not exist. The evaluation of filters based on the traditional parameters such as peak signal-to-noise ratio, mean square error, and structural similarity index may not reflect the true filter performance on echocardiographic images. Therefore, the performance of despeckling can be evaluated using blind assessment metrics like the speckle suppression index, speckle suppression and mean preservation index (SMPI), and beta metric. The need for noise-free reference image is overcome using these three parameters. This paper presents a comprehensive analysis and evaluation of eleven types of despeckling filters for echocardiographic images in terms of blind and traditional performance parameters along with clinical validation. The noise is effectively suppressed using the logarithmic neighborhood shrinkage (NeighShrink) embedded with Stein's unbiased risk estimation (SURE). The SMPI is three times more effective compared to the wavelet based generalized likelihood estimation approach. The quantitative evaluation and clinical validation reveal that the filters such as the nonlocal mean, posterior sampling based Bayesian estimation, hybrid median, and probabilistic patch based filters are acceptable whereas median, anisotropic diffusion, fuzzy, and Ripplet nonlinear approximation filters have limited applications for echocardiographic images.

Blind Source Parameters for Performance Evaluation of Despeckling Filters

PubMed Central

Biradar, Nagashettappa; Dewal, M. L.; Rohit, ManojKumar; Gowre, Sanjaykumar; Gundge, Yogesh

2016-01-01

The speckle noise is inherent to transthoracic echocardiographic images. A standard noise-free reference echocardiographic image does not exist. The evaluation of filters based on the traditional parameters such as peak signal-to-noise ratio, mean square error, and structural similarity index may not reflect the true filter performance on echocardiographic images. Therefore, the performance of despeckling can be evaluated using blind assessment metrics like the speckle suppression index, speckle suppression and mean preservation index (SMPI), and beta metric. The need for noise-free reference image is overcome using these three parameters. This paper presents a comprehensive analysis and evaluation of eleven types of despeckling filters for echocardiographic images in terms of blind and traditional performance parameters along with clinical validation. The noise is effectively suppressed using the logarithmic neighborhood shrinkage (NeighShrink) embedded with Stein's unbiased risk estimation (SURE). The SMPI is three times more effective compared to the wavelet based generalized likelihood estimation approach. The quantitative evaluation and clinical validation reveal that the filters such as the nonlocal mean, posterior sampling based Bayesian estimation, hybrid median, and probabilistic patch based filters are acceptable whereas median, anisotropic diffusion, fuzzy, and Ripplet nonlinear approximation filters have limited applications for echocardiographic images. PMID:27298618

Gallium nitride light sources for optical coherence tomography

NASA Astrophysics Data System (ADS)

Goldberg, Graham R.; Ivanov, Pavlo; Ozaki, Nobuhiko; Childs, David T. D.; Groom, Kristian M.; Kennedy, Kenneth L.; Hogg, Richard A.

2017-02-01

The advent of optical coherence tomography (OCT) has permitted high-resolution, non-invasive, in vivo imaging of the eye, skin and other biological tissue. The axial resolution is limited by source bandwidth and central wavelength. With the growing demand for short wavelength imaging, super-continuum sources and non-linear fibre-based light sources have been demonstrated in tissue imaging applications exploiting the near-UV and visible spectrum. Whilst the potential has been identified of using gallium nitride devices due to relative maturity of laser technology, there have been limited reports on using such low cost, robust devices in imaging systems. A GaN super-luminescent light emitting diode (SLED) was first reported in 2009, using tilted facets to suppress lasing, with the focus since on high power, low speckle and relatively low bandwidth applications. In this paper we discuss a method of producing a GaN based broadband source, including a passive absorber to suppress lasing. The merits of this passive absorber are then discussed with regards to broad-bandwidth applications, rather than power applications. For the first time in GaN devices, the performance of the light sources developed are assessed though the point spread function (PSF) (which describes an imaging systems response to a point source), calculated from the emission spectra. We show a sub-7μm resolution is possible without the use of special epitaxial techniques, ultimately outlining the suitability of these short wavelength, broadband, GaN devices for use in OCT applications.

Computer vision elastography: speckle adaptive motion estimation for elastography using ultrasound sequences.

PubMed

Revell, James; Mirmehdi, Majid; McNally, Donal

2005-06-01

We present the development and validation of an image based speckle tracking methodology, for determining temporal two-dimensional (2-D) axial and lateral displacement and strain fields from ultrasound video streams. We refine a multiple scale region matching approach incorporating novel solutions to known speckle tracking problems. Key contributions include automatic similarity measure selection to adapt to varying speckle density, quantifying trajectory fields, and spatiotemporal elastograms. Results are validated using tissue mimicking phantoms and in vitro data, before applying them to in vivo musculoskeletal ultrasound sequences. The method presented has the potential to improve clinical knowledge of tendon pathology from carpel tunnel syndrome, inflammation from implants, sport injuries, and many others.

Measurements of 427 Double Stars With Speckle Interferometry: The Winter/Spring 2017 Observing Program at Brilliant Sky Observatory, Part 1

NASA Astrophysics Data System (ADS)

Harshaw, Richard

2018-04-01

In the winter and spring of 2017, an aggressive observing program of measuring close double stars with speckle interferometry and CCD imaging was undertaken at Brilliant Sky Observatory, my observing site in Cave Creek, Arizona. A total of 596 stars were observed, 8 of which were rejected for various reasons, leaving 588 pairs. Of these, 427 were observed and measured with speckle interferometry, while the remaining 161 were measured with a CCD. This paper reports the results of the observations of the 427 speckle cases. A separate paper in this issue will report the CCD measurements of the 161 other pairs.

Superpixel guided active contour segmentation of retinal layers in OCT volumes

NASA Astrophysics Data System (ADS)

Bai, Fangliang; Gibson, Stuart J.; Marques, Manuel J.; Podoleanu, Adrian

2018-03-01

Retinal OCT image segmentation is a precursor to subsequent medical diagnosis by a clinician or machine learning algorithm. In the last decade, many algorithms have been proposed to detect retinal layer boundaries and simplify the image representation. Inspired by the recent success of superpixel methods for pre-processing natural images, we present a novel framework for segmentation of retinal layers in OCT volume data. In our framework, the region of interest (e.g. the fovea) is located using an adaptive-curve method. The cell layer boundaries are then robustly detected firstly using 1D superpixels, applied to A-scans, and then fitting active contours in B-scan images. Thereafter the 3D cell layer surfaces are efficiently segmented from the volume data. The framework was tested on healthy eye data and we show that it is capable of segmenting up to 12 layers. The experimental results imply the effectiveness of proposed method and indicate its robustness to low image resolution and intrinsic speckle noise.

Recent progress in tissue optical clearing for spectroscopic application

NASA Astrophysics Data System (ADS)

Sdobnov, A. Yu.; Darvin, M. E.; Genina, E. A.; Bashkatov, A. N.; Lademann, J.; Tuchin, V. V.

2018-05-01

This paper aims to review recent progress in optical clearing of the skin and over naturally turbid biological tissues and blood using this technique in vivo and in vitro with multiphoton microscopy, confocal Raman microscopy, confocal microscopy, NIR spectroscopy, optical coherence tomography, and laser speckle contrast imaging. Basic principles of the technique, its safety, advantages and limitations are discussed. The application of optical clearing agent on a tissue allows for controlling the optical properties of tissue. Optical clearing-induced reduction of tissue scattering significantly facilitates the observation of deep-located tissue regions, at the same time improving the resolution and image contrast for a variety of optical imaging methods suitable for clinical applications, such as diagnostics and laser treatment of skin diseases, mucosal tumor imaging, laser disruption of pathological abnormalities, etc. Structural images of different skin layers obtained ex vivo for porcine ear skin samples at application of Omnipaque™ and glycerol solutions during 60 min. Red color corresponds to TPEAF signal channel. Green color corresponds to SHG signal channel.

An adaptive beamforming method for ultrasound imaging based on the mean-to-standard-deviation factor.

PubMed

Wang, Yuanguo; Zheng, Chichao; Peng, Hu; Chen, Qiang

2018-06-12

The beamforming performance has a large impact on image quality in ultrasound imaging. Previously, several adaptive weighting factors including coherence factor (CF) and generalized coherence factor (GCF) have been proposed to improved image resolution and contrast. In this paper, we propose a new adaptive weighting factor for ultrasound imaging, which is called signal mean-to-standard-deviation factor (SMSF). SMSF is defined as the mean-to-standard-deviation of the aperture data and is used to weight the output of delay-and-sum (DAS) beamformer before image formation. Moreover, we develop a robust SMSF (RSMSF) by extending the SMSF to the spatial frequency domain using an altered spectrum of the aperture data. In addition, a square neighborhood average is applied on the RSMSF to offer a more smoothed square neighborhood RSMSF (SN-RSMSF) value. We compared our methods with DAS, CF, and GCF using simulated and experimental synthetic aperture data sets. The quantitative results show that SMSF results in an 82% lower full width at half-maximum (FWHM) but a 12% lower contrast ratio (CR) compared with CF. Moreover, the SN-RSMSF leads to 15% and 10% improvement, on average, in FWHM and CR compared with GCF while maintaining the speckle quality. This demonstrates that the proposed methods can effectively improve the image resolution and contrast. Copyright © 2018 Elsevier B.V. All rights reserved.

Speckle contrast diffuse correlation tomography of complex turbid medium flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Chong; Irwin, Daniel; Lin, Yu

2015-07-15

Purpose: Developed herein is a three-dimensional (3D) flow contrast imaging system leveraging advancements in the extension of laser speckle contrast imaging theories to deep tissues along with our recently developed finite-element diffuse correlation tomography (DCT) reconstruction scheme. This technique, termed speckle contrast diffuse correlation tomography (scDCT), enables incorporation of complex optical property heterogeneities and sample boundaries. When combined with a reflectance-based design, this system facilitates a rapid segue into flow contrast imaging of larger, in vivo applications such as humans. Methods: A highly sensitive CCD camera was integrated into a reflectance-based optical system. Four long-coherence laser source positions were coupledmore » to an optical switch for sequencing of tomographic data acquisition providing multiple projections through the sample. This system was investigated through incorporation of liquid and solid tissue-like phantoms exhibiting optical properties and flow characteristics typical of human tissues. Computer simulations were also performed for comparisons. A uniquely encountered smear correction algorithm was employed to correct point-source illumination contributions during image capture with the frame-transfer CCD and reflectance setup. Results: Measurements with scDCT on a homogeneous liquid phantom showed that speckle contrast-based deep flow indices were within 12% of those from standard DCT. Inclusion of a solid phantom submerged below the liquid phantom surface allowed for heterogeneity detection and validation. The heterogeneity was identified successfully by reconstructed 3D flow contrast tomography with scDCT. The heterogeneity center and dimensions and averaged relative flow (within 3%) and localization were in agreement with actuality and computer simulations, respectively. Conclusions: A custom cost-effective CCD-based reflectance 3D flow imaging system demonstrated rapid acquisition of dense boundary data and, with further studies, a high potential for translatability to real tissues with arbitrary boundaries. A requisite correction was also found for measurements in the fashion of scDCT to recover accurate speckle contrast of deep tissues.« less