Laser Speckle Contrast Imaging for the Quantitative Assessment of Flow

The ultimate objective of laser speckle flowmetry is to infer flow velocity from observed speckle contrast. Since introduction of this concept over 25 years ago, a variety of researchers have demonstrated such a qualitative relationship (between speckle contrast and flow velocity), but a quantitative relationship has proven elusive. A fundamental reason for this failure to demonstrate a convincing quantitative relationship is that the underlying mathematics describing LSCA is identical to that of quasi-elastic light scatter (QLS). As a result, it is commonly (and erroneously) assumed that the requirements for the data acquisition, the model linking the scatter dynamics to the speckle fluctuation, and the data processing are the same as well. Here we discuss some of our recent advances towards achieving quantitative velocity estimates from laser speckle contrast measurements. This concept is free of any assumptions relating scatterer dynamics to light fluctuations and is compatible with accepted data acquisition methods, but uses an entirely new data processing scheme. Results are demonstrated with a murine model.