Laser speckle contrast imaging in biomedical optics
01 Jan 2010-Journal of Biomedical Optics (International Society for Optics and Photonics)-Vol. 15, Iss: 1, pp 011109-011109
TL;DR: The underlying physics of speckle contrast imaging is reviewed, recent developments to improve the quantitative accuracy of blood flow measures are discussed and applications in neuroscience, dermatology and ophthalmology are reviewed.
Abstract: First introduced in the 1980s, laser speckle contrast imaging is a powerful tool for full-field imaging of blood flow. Recently laser speckle contrast imaging has gained increased attention, in part due to its rapid adoption for blood flow studies in the brain. We review the underlying physics of speckle contrast imaging and discuss recent developments to improve the quantitative accuracy of blood flow measures. We also review applications of laser speckle contrast imaging in neuroscience, dermatology and ophthalmology.
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TL;DR: Through-scalp and through-skull fluorescence imaging of mouse cerebral vasculature without craniotomy is reported utilizing the intrinsic photoluminescence of single-walled carbon nanotubes in the 1.3–1.4 micrometre near-infrared window, providing real-time assessment of blood flow anomaly in a mouse middle cerebral artery occlusion stroke model.
Abstract: To date, brain imaging has largely relied on X-ray computed tomography and magnetic resonance angiography with limited spatial resolution and long scanning times. Fluorescence-based brain imaging in the visible and traditional near-infrared regions (400-900 nm) is an alternative but currently requires craniotomy, cranial windows and skull thinning techniques, and the penetration depth is limited to 1-2 mm due to light scattering. Here, we report through-scalp and through-skull fluorescence imaging of mouse cerebral vasculature without craniotomy utilizing the intrinsic photoluminescence of single-walled carbon nanotubes in the 1.3-1.4 micrometre near-infrared window. Reduced photon scattering in this spectral region allows fluorescence imaging reaching a depth of >2 mm in mouse brain with sub-10 micrometre resolution. An imaging rate of ~5.3 frames/s allows for dynamic recording of blood perfusion in the cerebral vessels with sufficient temporal resolution, providing real-time assessment of blood flow anomaly in a mouse middle cerebral artery occlusion stroke model.
781 citations
TL;DR: Recent clinical research that employs DCS-measured CBF as a biomarker of patient well-being, and as an indicator of hemodynamic and metabolic responses to functional stimuli, is described.
410 citations
Cites background from "Laser speckle contrast imaging in b..."
...…of local, microvascular CBF is desirable, and it should be apparent to the reader that a potential niche exits for near-infrared optics and, particularly, diffuse correlation spectroscopy (DCS) in the clinic (Boas and Dunn, 2010; Daly and Leahy, 2012; Devor et al., 2012; Durduran et al., 2010a)....
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...Clearly, an independent, versatile and non-invasive bedside monitor of local, microvascular CBF is desirable, and it should be apparent to the reader that a potential niche exits for near-infrared optics and, particularly, diffuse correlation spectroscopy (DCS) in the clinic (Boas and Dunn, 2010; Daly and Leahy, 2012; Devor et al., 2012; Durduran et al., 2010a)....
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TL;DR: LSCI is used primarily to map flow systems, especially blood flow, and its limitations and problems are investigated.
Abstract: When laser light illuminates a diffuse object, it produces a random interference effect known as a speckle pattern. If there is movement in the object, the speckles fluctuate in intensity. These fluctuations can provide infor- mation about the movement. A simple way of accessing this information is to image the speckle pattern with an exposure time longer than the shortest speckle fluctuation time scale—the fluctuations cause a blurring of the speckle, leading to a reduction in the local speckle contrast. Thus, velocity distributions are coded as speckle con- trast variations. The same information can be obtained by using the Doppler effect, but producing a two-dimen- sional Doppler map requires either scanning of the laser beam or imaging with a high-speed camera: laser speckle contrast imaging (LSCI) avoids the need to scan and can be performed with a normal CCD- or CMOS-camera. LSCI is used primarily to map flow systems, especially blood flow. The development of LSCI is reviewed and its lim- itations and problems are investigated. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.
399 citations
TL;DR: Using the tissue optical clearing technique with advanced microscopy image or labeling technique, applications for 3D microstructure of whole tissues such as brain and central nervous system with unprecedented resolution are demonstrated.
Abstract: Tissue optical clearing technique provides a prospective solution for the application of advanced optical methods in life sciences. This paper gives a review of recent developments in tissue optical clearing techniques. The physical, molecular and physiological mechanisms of tissue optical clearing are overviewed and discussed. Various methods for enhancing penetration of optical-clearing agents into tissue, such as physical methods, chemical-penetration enhancers and combination of physical and chemical methods are introduced. Combining the tissue optical clearing technique with advanced microscopy image or labeling technique, applications for 3D microstructure of whole tissues such as brain and central nervous system with unprecedented resolution are demonstrated. Moreover, the difference in diffusion and/or clearing ability of selected agents in healthy versus pathological tissues can provide a highly sensitive indicator of the tissue health/pathology condition. Finally, recent advances in optical clearing of soft or hard tissue for in vivo imaging and phototherapy are introduced.
363 citations
TL;DR: The purpose of this review is to help readers understand and select appropriate OCT angiography algorithm for use in specific applications and it is found that the method that utilizes complex OCT signal to contrast retinal blood flow delivers the best performance among all the algorithms in terms of image contrast and vessel connectivity.
Abstract: Optical coherence tomography (OCT)-based angiography is increasingly becoming a clinically useful and important imaging technique due to its ability to provide volumetric microvascular networks innervating tissue beds in vivo without a need for exogenous contrast agent. Numerous OCT angiography algorithms have recently been proposed for the purpose of contrasting microvascular networks. A general literature review is provided on the recent progress of OCT angiography methods and algorithms. The basic physics and mathematics behind each method together with its contrast mechanism are described. Potential directions for future technical development of OCT based angiography is then briefly discussed. Finally, by the use of clinical data captured from normal and pathological subjects, the imaging performance of vascular networks delivered by the most recently reported algorithms is evaluated and compared, including optical microangiography, speckle variance,phase variance, split-spectrum amplitude decorrelation angiography, and correlation mapping. It is found that the method that utilizes complex OCT signal to contrast retinal blood flow delivers the best performance among all the algorithms in terms of image contrast and vessel connectivity. The purpose of this review is to help readers understand and select appropriate OCT angiography algorithm for use in specific applications.
312 citations
Cites background from "Laser speckle contrast imaging in b..."
...The speckle pattern is associated with the movement of scattering particles in random medium since such movement would cause phase shift in the backscattered light that consequently would lead to a change in random interference pattern.(41,42) Hence, the temporal and spatial statistics of the speckle pattern contain the information of the motion of the scattering particles....
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TL;DR: This article provides a framework that can be used to generate testable hypotheses and treatment strategies that are linked to the appearance of specific pathophysiological events within the ischaemic brain.
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TL;DR: In this article, an interesting response elicited by electrical stimulation was noticed in the cortex of rabbits, and the distinctive feature of this response was a marked, enduring reduction of the "spontaneous" electrical activity of the cortex.
Abstract: THIS STUDY originated in an attempt to secure more data for the understanding of the cortical electrogram which occurs in “experimental epilepsy,” and of the conditions in which it is brought forth by electrical stimulation. Early in the development of the study an interesting response, elicited by electrical stimulation, was noticed in the cortex of rabbits. The distinctive feature of this response was a marked, enduring reduction of the “spontaneous” electrical activity of the cortex. We have endeavored to define experimentally some of the characteristics of this response.
2,485 citations
"Laser speckle contrast imaging in b..." refers background in this paper
...One of the mechanisms that may lead to cell death in the penumbra is the presence of periinfarct depolarizations PIDs , which resemble the spreading depressions of Leao.60 PIDs are spontaneously generated following an ischemic insult....
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...penumbra is the presence of periinfarct depolarizations PIDs , which resemble the spreading depressions of Leao.(60)...
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...3.3.2 Cortical spreading depression and migraine headache Cortical spreading depression or spreading depolarization SD is a wave of negative potential shift that slowly propagates across the cortex at a rate of 2 to 5-mm /min, and was first identified in rabbits in 1944 by Leao.60 SD is associated with large ionic shifts, increased metabolism, and hemodynamic changes....
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...gates across the cortex at a rate of 2 to 5-mm /min, and was first identified in rabbits in 1944 by Leao.(60) SD is associated with large ionic shifts, increased metabolism, and hemodynamic changes....
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01 Dec 1963
TL;DR: In this article, the first order statistics of the observed electric-field strength, the observed light intensity, and observed light phase are examined, and the autocorrelation functions of the complex field and intensity processes are investigated, and that of the electric field is found to be proportional to the Fourier transform of the light intensity distribution incident on the scattering surface.
Abstract: : When laser light strikes a diffuse object, such as paper, the scattered light has been observed to possess a granular spatial structure. The statistical properties of these so-called 'sparkle patterns,' as seen by an observer in the far field of the scattering spot, are investigated. The first order statistics of the observed electric-field strength, the observed light intensity, and the observed light phase are examined. The electric field is reasoned to be a complex normal random variable; the intensity a real, exponentially distributed random variable; and the phase a uniformly distributed random variable. Higher order statistics of these random processes are also discussed. The autocorrelation functions of the complex field and the intensity processes are investigated, and that of the electric field is found to be proportional to the Fourier transform of the light-intensity distribution incident on the scattering surface. Spatial averages of the light intensity are considered and are found to converge to corresponding ensemble averages when either the area of the scattering spot or the average area grows large.
1,526 citations