Laser speckle contrast imaging (LSCI) is awidefield, non-invasive optical imaging method for measuring two-dimensional blood flow changes with high temporal-spatial resolution, and has been widely used in clinical disease diagnosis and treatment,brain neuroscience researchand other applications. However, due to the effect of noise, the complexity of biological tissues, and the multiple scattering of photons in the tissue, it is difficult to accurately quantify the relative changes in blood flowbyLSCI.
Under the guidance of Professor Pengcheng Li from the Biomedical Photonics Laboratory of Wuhan National Laboratory of Optoelectronics, PhD student Yang Wang and others considered the effects of static scattering and CCD noise on blood flow measurement in biological tissues. Two correction methods were proposed to improve the accuracy of blood flow detection in laser speckle contrast imaging.
(1)Aiming at the problem that the blood flow velocity is underestimated due to static components in biological tissues, such as the skull or the cuticle of the skin,we proposed a correction method that reduces the effect of static scattering by combining temporal-spatial contrast analysis, based on the differences between the statistical properties of the temporal contrast and the spatial contrast. The validity of the proposed correction method was verified through phantom experiments and animal experiments.
This research was published on the Optics Letters (Volume 42, Issue 1, Pages 57-60), a journal of the American Optical Society, entitled "Improving the estimation of flow speed for laser speckle imaging with single exposure time" on January 1, 2017. This work has been supported by the National Natural Science Foundation of China and the "863" Program.
(2)According to the temporal-spatial distribution and statistical characteristics of CCD noise,we found that shot noise and dark noise are the main factors affecting the accuracy of speckle contrast measurement. By correcting the shot noise and dark noise, the effects of exposure time and low light intensity illumination can be reduced, so that the speckle flow index under different exposure times and illumination intensities are basically the same.
This research was published on the Optics Letters (Volume 42, Issue 22, Pages 4655-4658), a journal of the American Optical Society, entitled "Improving the sensitivity of velocity measurements in laser speckle contrast imaging using a noise correction method" On November 7, 2017. This work has been supported by the National Natural Science Foundation and the National key research and development program.
Fig.1 Blood flow images obtained at mean counts of 200 (a) before and (b) after noise correction, and obtained at mean counts of 800 (c) before and (d) after noise correction. (e) Comparison of the SFIs within different ROIs before and after noise correction.
