Abstract
Single-frame blood flow maps from laser speckle contrast imaging (LSCI) contain high spatiotemporal variation that obscures high spatial-frequency vascular features, making precise image registration for signal amplification challenging. In this work, novel bivariate standardized moment filters (BSMFs) were used to provide stable measures of vessel edge location, permitting more robust LSCI registration. Relatedly, BSMFs enabled the stable reconstruction of vessel edges from sparsely distributed blood flow map outliers, which were found to retain most of the temporal dynamics. Consequently, data discarding and BSMF-based reconstruction enable efficient real-time quantitative LSCI data compression. Smaller LSCI-kernels produced log-normal blood flow distributions, enhancing sparse-to-dense inference.
Highlights
A technique for full-field blood flow imaging, laser speckle contrast imaging (LSCI), provides rapid snapshots of blood flow values
We have previously demonstrated a sub-depth of field (DOF) active misfocus correction scheme for LSCI based on the fourth standardized moment of vessel cross-sections [11]
We found that when applied to LSCI blood flow maps, bivariate standardized moment filters (BSMFs) produced sharp stable features associated with vessel edges
Summary
A technique for full-field blood flow imaging, laser speckle contrast imaging (LSCI), provides rapid snapshots of blood flow values. Pseudo-random high-frequency spatial and temporal measurement variation burdens LSCI with a low SNR at small spatial and short temporal scales (as with all laser speckle correlation techniques [3]). The aforementioned variation in the LSCI blood flow maps (or unprocessed speckle images) is highly problematic for accurate sequential image registration as high contrast features are obscured. It has been shown that the perceived vessel visibility associated with macroscopic temporal speckle contrast maps are improved by prior speckle image registration based on persistent pixel-scale structural features [6]. Microscopy-based LSCI permits accuracy optimized (pixel-wise speckle contrast Nyquist criteria [7]) micro-vascular flowmetry with high optical collection efficiency and minimum speckle size relative to vessel size (higher resolution). The increased accuracy and resolution are associated with higher spatiotemporal signal variation and, as such, persistent pixel-scale structural features are absent. Pixel-scale speckle-driven features are assuredly changed for large displacements
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