Laser speckle imaging with an active noise reduction scheme

Völker, Andreas Charles; Zakharov, Pavel; Weber, Bruno; Buck, Florian M.; Scheffold, Frank

doi:10.1364/opex.13.009782

Cited by 83 publications

(44 citation statements)

References 20 publications

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“…6 and the values of * obtained in this way lead to a mean value * = 250 ± 10μm, which is in fairly good agreement with the value obtained from the analysis of the asymptotic decay rate. Moreover, our estimates of the transport mean free path and absorption length are consistent with previous results reported in literature [24].…”

Section: Resultssupporting

confidence: 92%

“…The photon path length distributions recovered for each L were accurately fitted with theoretical curves predicted according to the photon diffusion approximation theory, which allowed us to estimate the Teflon transport mean free path * ≈ 250 μm and the absorption length s a ≈ 685 mm. These figures were consistent with previous results available in literature, but obtained with different methods [24], and provided an a posteriori confirmation that the weak scattering ( * > λ) and diffusive regime ( * s a , * L) requirements for the applicability of the photon diffusion approximation were both fulfilled by our samples.…”

Section: Discussionsupporting

confidence: 93%

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Photon path length distribution in random media from spectral speckle intensity correlations

Rojas

Bina

Cerchiari

et al. 2011

Eur. Phys. J. Spec. Top.

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Abstract. We show that the spectral speckle intensity correlation (SSIC) technique can be profitably exploited to recover the path length distribution of photons scattered in a random turbid medium. We applied SSIC to the study of Teflon slabs of different thicknesses and were able to recover, via the use of the photon diffusion approximation theory, the characteristic transport mean free path * and absorption length s a of the medium. These results were compared and validated by means of complementary measurements performed on the same samples with standard pulsed laser time of flight techniques.

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Section: Resultssupporting

confidence: 92%

Section: Discussionsupporting

confidence: 93%

Photon path length distribution in random media from spectral speckle intensity correlations

Rojas

Bina

Cerchiari

et al. 2011

Eur. Phys. J. Spec. Top.

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“…Numerous modifications, simplifications and optimizations appeared recently, some more focused on practical improvements of the image formation process [10][11][12] while others were addressing more fundamental questions related to the speckle statistical properties and the underlying temporal fluctuations [8,9,[13][14][15] with the final goal to turn LSI into a "quantitative tool". One of the major pitfalls in LASCA is the fact that one needs to assume a particular shape of intensity correlation function in order to quantify the underlying dynamic processes.…”

Section: Optical Signal and Processingmentioning

confidence: 99%

Dynamic laser speckle imaging of cerebral blood flow

Zakharov¹,

Völker²,

Wyss³

et al. 2009

Opt. Express

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150

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Laser speckle imaging (LSI) based on the speckle contrast analysis is a simple and robust technique for imaging of heterogeneous dynamics. LSI finds frequent application for dynamical mapping of cerebral blood flow, as it features high spatial and temporal resolution. However, the quantitative interpretation of the acquired data is not straightforward for the common case of a speckle field formed by both by moving and localized scatterers such as blood cells and bone or tissue. Here we present a novel processing scheme, we call dynamic laser speckle imaging (dLSI), that can be used to correctly extract the temporal correlation parameters from the speckle contrast measured in the presence of a static or slow-evolving background. The static light contribution is derived from the measurements by cross-correlating sequential speckle images. In-vivo speckle imaging experiments performed in the rodent brain demonstrate that dLSI leads to improved results. The cerebral hemodynamic response observed through the thinned and intact skull are more pronounced in the dLSI images as compared to the standard speckle contrast analysis. The proposed method also yields benefits with respect to the quality of the speckle images by suppressing contributions of non-uniformly distributed specular reflections.Dynamic laser speckle imaging of cerebral blood flow Abstract: Laser speckle imaging (LSI) based on the speckle contrast analysis is a simple and robust technique for imaging of heterogeneous dynamics. LSI finds frequent application for dynamical mapping of cerebral blood flow, as it features high spatial and temporal resolution. However, the quantitative interpretation of the acquired data is not straightforward for the common case of a speckle field formed by both by moving and localized scatterers such as blood cells and bone or tissue. Here we present a novel processing scheme, we call dynamic laser speckle imaging (dLSI), that can be used to correctly extract the temporal correlation parameters from the speckle contrast measured in the presence of a static or slow-evolving background. The static light contribution is derived from the measurements by cross-correlating sequential speckle images. In-vivo speckle imaging experiments performed in the rodent brain demonstrate that dLSI leads to improved results. The cerebral hemodynamic response observed through the thinned and intact skull are more pronounced in the dLSI images as compared to the standard speckle contrast analysis. The proposed method also yields benefits with respect to the quality of the speckle images by suppressing contributions of non-uniformly distributed specular reflections. ©2009 Optical Society of America

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“…To convert the variations of speckle contrast to the intensity variations, a small area on the raw speckle image was chosen in which a sufficient number of speckles were expected. For our settings (25 ms exposure time plus 475 ms delay time), it is reasonable to believe that speckles in sequential images are not correlated (as there is significant movement of the scatters in that time) and hence a 3 Â 3 template was used so that spatial resolution was not compromised (Vö lker et al, 2005). The numerical integrations and other data processing in this study were performed using MATLAB (The MathWorks, Natick, MA, USA).…”

Section: Data Acquisition and Analysismentioning

confidence: 99%

Theoretical and Experimental Optimization of Laser Speckle Contrast Imaging for High Specificity to Brain Microcirculation

Wang

Hughes

Dayasundara

et al. 2007

J Cereb Blood Flow Metab

105

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The functional spatial resolution in most of hemodynamics-based functional neuroimaging techniques is limited by the fineness of hemodynamic control with the active vascular beds likely at submillimeter resolution. This study was designed to visualize changes of cerebral blood flow (CBF) at submillimeter spatial scale on the prolonged isoflurane-anesthetized rats model by using laser speckle contrast imaging (LSCI) technique. Recently, this old method has attracted an increasing interest in studies of brain activities under normal and pathophysiologic conditions. However, some paramount assumptions behind this imaging technique have been kept ignored in this field since 1981 firstly proposed by Fercher and Briers. Most recently, these assumptions are claimed as serious mistakes that made LSCI fail to reproducibly and correctly measure blood flow speed. In our study, these issues are also re-examined theoretically and re-evaluated experimentally based on the results from the classical carbon dioxide challenge model. The detailed distribution of CBF responses to the stimulation induced by different levels of carbon dioxide pressure was obtained with tens of micron spatial resolution. The relative CBF images over the exposed cortical area acquired by LSCI were also compared with laser-Doppler measurements. Our results show that these assumptions would not produce any significant errors on investigating changes of blood flow and also achieve high specificity to assess cerebral microcirculation, as would facilitate its broad application in functional imaging field.

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Laser speckle imaging with an active noise reduction scheme

Cited by 83 publications

References 20 publications

Photon path length distribution in random media from spectral speckle intensity correlations

Photon path length distribution in random media from spectral speckle intensity correlations

Dynamic laser speckle imaging of cerebral blood flow

Theoretical and Experimental Optimization of Laser Speckle Contrast Imaging for High Specificity to Brain Microcirculation

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