Dynamic Light Scattering and Laser Speckle Contrast Imaging

Laser speckle is a random interference pattern arising from interaction of the coherent light with rough scattering surface and/or with turbid randomly inhomogeneous media. Changes in local dynamics in observed media (moving of scattering particles) leads to fluctuations of speckle pattern and, thus,results in its blurring on captured frame due to the finite camera exposure time. The higher movement in observed object the more blurred speckle pattern will be captured by camera. This blurring consequently decreases the speckle contrast value, which, in fact, allows the quantification of the flow rate.

Our research group aims at investigation of the applicability boundaries of the LSCI in the case when the ergodicity condition is not fulfilled, as well as at estimating optimal parameters for conducting measurements with live objects.

Selected results

Coefficient of speckle dynamics

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.

Analysis of spatial and temporal speckle contrasts, the values of the coefficient of speckle dynamics, along with the results of Monte-Carlo simulation of the sampling volume, revealed that the presence of a relatively thin, up to 30% of entire volume, static layer does not introduce considerable changes into the results of measurements by the method of laser speckle-contrast imaging. The exposure time of the camera,
along with the number of frames used for image processing, can be varied and chosen individually for each experiment. The developed algorithms of spatial and temporal processing of images obtained by the method of laser speckle-contrast imaging were tested in the experiments on transcranial visualization of the cerebral blood flow of a mouse.

Combined use of speckle contrast and fluorescent intravital microscopy

Utilizing a combined use of speckle contrast and fluorescent intravital microscopy , we present a simple and robust method to overcome the limitations mentioned above for the speckle contrast approach. The proposed technique provides more relevant, abundant, and valuable information regarding perfusion rate ration between different types of vessels that makes this method highly useful for in vivo brain surgical operations.

Media appearance:

(ENG) https://sputniknews.com/20191121/handwriting-as-detector-scientists-lea…

(ENG) https://www.sott.net/article/424346-Handwriting-as-detector-Scientists

(ENG) https://phys.org/news/2019-12-scientists-lasers-mental-states.html

(RU) https://iz.ru/950504/olga-kolentcova/risui-pro-zdorove-pocherk-liudei-r…

(RU) https://ria.ru/20191107/1560639301.html

References

  1. Piavchenko, G., Kozlov, I., Dremin, V., Stavtsev, D., Seryogina, E., Kandurova, K., ... & Meglinski, I. (2021). Impairments of cerebral blood flow microcirculation in rats brought on by cardiac cessation and respiratory arrest. Journal of Biophotonics, e202100216. DOI: 10.1002/jbio.202100216.
  2. Sdobnov, A. Y., Kalchenko, V. V., Bykov, A. V., Popov, A. P., Molodij, G., & Meglinski, I. V. (2020). Blood Flow Visualization by Means of Laser Speckle-Contrast Measurements under the Conditions of Nonergodicity. Opt Spectrosc, 128(6), 778-786. DOI: 10.1134/S0030400X2006020X.
  3. Molodij, G., Sdobnov, A., Kuznetsov, Y., Harmelin, A., Meglinski, I., & Kalchenko, V. (2020). Time-space Fourier κω′ filter for motion artifacts compensation during transcranial fluorescence brain imaging. Phys Med Biol, 65(7), 075007. DOI: 10.1088/1361-6560/ab7631.
  4. Kalchenko, V., Sdobnov, A., Meglinski, I., Kuznetsov, Y., Molodij, G., & Harmelin, A. (2019). A robust method for adjustment of laser speckle contrast imaging during transcranial mouse brain visualization. Photonics, 6(3), 80. DOI:10.3390/photonics6030080.
  5. Kalchenko, V., Meglinski, I., Sdobnov, A., Kuznetsov, Y., & Harmelin, A. (2019). Combined laser speckle imaging and fluorescent intravital microscopy for monitoring acute vascular permeability reaction. J Biomed Opt, 24(6), 060501. DOI: 10.1117/1.JBO.24.6.060501.
  6. Sdobnov, A., Bykov, A., Popov, A., Lihacova, I., Lihachev, A., Spigulis, J., & Meglinski, I. (2019). Combined multi-wavelength laser speckle contrast imaging and diffuse reflectance imaging for skin perfusion assessment. Proc SPIE 11075: 11075F-1-6. DOI: 10.1117/12.2526921.
  7. Kuznetsov, Y., Sdobnov, A., Meglinski, I., Harmelin, A., & Kalchenko, V. (2019). Evaluation of handwriting peculiarities utilizing laser speckle contrast imaging. Las Phys Lett, 16(11), 115601. DOI: 10.1088/1612-202X/ab43d7.
  8. Sdobnov, A., Bykov, A., Popov, A., Zherebtsov, E., & Meglinski, I. (2018). Investigation of speckle pattern dynamics by laser speckle contrast imaging. Proc SPIE 10685: 1068509-1-5. DOI: 10.1117/12.2306631.
  9. Sdobnov, A., Bykov, A., Molodij, G., Kalchenko, V., Jarvinen, T., Popov, A., Kprdas, K. & Meglinski, I. (2018). Speckle dynamics under ergodicity breaking. J Phys D: Appl Phys, 51(15), 155401. DOI: 10.1088/1361-6463/aab404.