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Alvarez N, Vadnjal AL, Etchepareborda P, Bianchetti A, Federico A. Assessment of multifractal analysis in dynamic laser speckle signals using a spatial light modulator. APPLIED OPTICS 2019; 58:1587-1595. [PMID: 30874049 DOI: 10.1364/ao.58.001587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 01/23/2019] [Indexed: 06/09/2023]
Abstract
We assess and discuss several technical aspects of the multifractal statistical analysis applied to time series of dynamic speckle intensity signals. Due to the complexity of this goal, we implemented an optical setup that mimics the light scattering effect from the illuminated object using a spatial light modulator. The multifractal spectrum of the obtained dynamic speckle intensity signals is quantified by utilizing a mathematical framework based on the decomposition of wavelet leaders' functions. The propagated light that is scattered utilizing the spatial light modulator verifies the well-known first- and second-order statistics of the obtained speckle images and also a given temporal correlation function determined by a copula algorithm adding several classes of fractional Gaussian noises. To experimentally implement these issues, we load appropriate dynamic temporal phase screens in the spatial light modulator working on phase-only mode and guide the light propagation through an optical setup composed of a 4f correlator. Different types of statistical trends in the scaling properties as a function of frequency sampling, intensity signal discretization, mean size of speckle, temporal correlation length, and vanishing moments of the elected mother wavelet analysis are theoretically and experimentally tested and compared.
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Vaz PG, Humeau-Heurtier A, Figueiras E, Correia C, Cardoso J. Effect of static scatterers in laser speckle contrast imaging: an experimental study on correlation and contrast. ACTA ACUST UNITED AC 2017; 63:015024. [DOI: 10.1088/1361-6560/aa9f3a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Kirby MA, Pelivanov I, Song S, Ambrozinski Ł, Yoon SJ, Gao L, Li D, Shen TT, Wang RK, O’Donnell M. Optical coherence elastography in ophthalmology. JOURNAL OF BIOMEDICAL OPTICS 2017; 22:1-28. [PMID: 29275544 PMCID: PMC5745712 DOI: 10.1117/1.jbo.22.12.121720] [Citation(s) in RCA: 120] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 12/14/2017] [Indexed: 05/03/2023]
Abstract
Optical coherence elastography (OCE) can provide clinically valuable information based on local measurements of tissue stiffness. Improved light sources and scanning methods in optical coherence tomography (OCT) have led to rapid growth in systems for high-resolution, quantitative elastography using imaged displacements and strains within soft tissue to infer local mechanical properties. We describe in some detail the physical processes underlying tissue mechanical response based on static and dynamic displacement methods. Namely, the assumptions commonly used to interpret displacement and strain measurements in terms of tissue elasticity for static OCE and propagating wave modes in dynamic OCE are discussed with the ultimate focus on OCT system design for ophthalmic applications. Practical OCT motion-tracking methods used to map tissue elasticity are also presented to fully describe technical developments in OCE, particularly noting those focused on the anterior segment of the eye. Clinical issues and future directions are discussed in the hope that OCE techniques will rapidly move forward to translational studies and clinical applications.
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Affiliation(s)
- Mitchell A. Kirby
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - Ivan Pelivanov
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - Shaozhen Song
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - Łukasz Ambrozinski
- Akademia Górniczo-Hutnicza University of Science and Technology, Krakow, Poland
| | - Soon Joon Yoon
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - Liang Gao
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - David Li
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
- University of Washington, Department of Chemical Engineering, Seattle, Washington, United States
| | - Tueng T. Shen
- University of Washington, Department of Ophthalmology, Seattle, Washington, United States
| | - Ruikang K. Wang
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
- University of Washington, Department of Ophthalmology, Seattle, Washington, United States
| | - Matthew O’Donnell
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
- Address all correspondence to: Matthew O’Donnell, E-mail:
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Wang Y, Lv W, Chen X, Lu J, Li P. Improving the sensitivity of velocity measurements in laser speckle contrast imaging using a noise correction method. OPTICS LETTERS 2017; 42:4655-4658. [PMID: 29140335 DOI: 10.1364/ol.42.004655] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 10/10/2017] [Indexed: 06/07/2023]
Abstract
We demonstrate that noise is an important factor contributing to the decline of sensitivity and linear response range of velocity measurements for laser speckle contrast imaging. We propose to use a noise correction method to improve the sensitivity of velocity measurements. For a kind of camera in which the mean values of the dark noise have been subtracted and negative counts have been set to zero, we propose a method to estimate the true dark noise based on the maximum likelihood estimation, which expands the application scope of the noise correction method.
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Khaksari K, Kirkpatrick SJ. Combined effects of scattering and absorption on laser speckle contrast imaging. JOURNAL OF BIOMEDICAL OPTICS 2016; 21:76002. [PMID: 27380448 DOI: 10.1117/1.jbo.21.7.076002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 05/18/2016] [Indexed: 05/20/2023]
Abstract
Several variables may affect the local contrast values in laser speckle contrast imaging (LSCI), irrespective of relative motion. It has been suggested that the optical properties of the moving fluid and surrounding tissues can affect LSCI values. However, a detailed study of this has yet to be presented. In this work, we examined the combined effects of the reduced scattering and absorption coefficients on LSCI. This study employs fluid phantoms with different optical properties that were developed to mimic whole blood with varying hematocrit levels. These flow phantoms were imaged with an LSCI system developed for this study. The only variable parameter was the optical properties of the flowing fluid. A negative linear relationship was seen between the changes in contrast and changes in reduced scattering coefficient, absorption coefficient, and total attenuation coefficient. The change in contrast observed due to an increase in the scattering coefficient was greater than what was observed with an increase in the absorption coefficient. The results indicate that optical properties affect contrast values and that they should be considered in the interpretation of LSCI data.
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