Abstract
.Blood flow is a parameter used to diagnose vascular diseases based on flow speed, blood pressure, and vessel size. Different techniques have been developed to estimate the relative blood flow speed and to improve the visualization of deep blood vessels; one such technique is laser speckle contrast imaging (LSCI). LSCI images contain a high level of noise mainly when deep blood vessels are imaged. To improve their visualization, several approaches for contrast computation have been developed. However, there is a compromise between noise attenuation and temporal resolution. On the one hand, spatial approaches have low spatial resolution, high temporal resolution, and significant noise attenuation, while temporal approaches have the opposite. A recent approach combines a temporal base with a directional process that allows improving the visualization of blood vessels. Nevertheless, it still contains a high level of noise and requires a high number of raw frames for its base. We propose, a space-directional approach focused on improving noise attenuation and temporal resolution for contrast computation. The results of reference approaches and the proposed one are compared quantitatively. Moreover, it is shown that the visualization of blood vessels in LSCI images can be improved by a general morphological process when the noise level is reduced.
Highlights
Blood flow carries oxygen and nutrients through the blood cells to keep tissues healthy.[1]
Laser speckle contrast imaging (LSCI) is a noninvasive technique developed in the 1980s for blood perfusion assessment.[3]. This method is based on obtaining a set of raw speckle images (RSIs) and computing a contrast representation of them, which allows the visualization of blood vessels and an estimation of a relative flow index in tissues, such as skin,[2] brain,[4] and retina.[5]
The RSIs were processed under the same conditions, i.e., by considering the same number of pixels, in order to provide a fair comparison among the different approaches (Table 1)
Summary
Blood flow carries oxygen and nutrients through the blood cells to keep tissues healthy.[1]. Laser speckle contrast imaging (LSCI) is a noninvasive technique developed in the 1980s for blood perfusion assessment.[3] This method is based on obtaining a set of raw speckle images (RSIs) and computing a contrast representation of them, which allows the visualization of blood vessels and an estimation of a relative flow index in tissues, such as skin,[2] brain,[4] and retina.[5] To obtain the contrast representation, the LSCI method is used, for which several approaches have been reported in the literature Spatial approaches, such as spatial LSCI (sK)[1] and spatial-average LSCI (savgK),[6] use a sliding analysis window, where the contrast is computed from the pixels inside the window until a single contrast image is generated or the average contrast is computed
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