In the last decade, Laser Speckle Contrast Imaging (LSCI) has been proposed and validated for imaging cerebral blood
flow at the rodent brain surface in vivo. The technique relies on the calculation of the spatial speckle contrast, which is
related to the velocity of scatterers (red blood cells). The implementation of the technique requires a partial craniotomy
so that the brain tissues of interest can be illuminated with a laser diode. However, the studies of changes in the
microcirculation during disease progression or treatment require longitudinal studies (i.e. imaging is done repeatedly
over weeks or even months). Practically, the less invasive way to obtain such data is to image through the thinned skull
without a craniotomy. However the presence of static scatterers (skull) will affect the speckle calculation and produce a
bias in the estimation of the microcirculation changes. An extension to LSCI, termed Multi-Exposure Speckle Imaging
(MESI) was proposed and validated a few years ago that address these limitations. It relies on a model of the speckle
contrast as a function of the exposure time and the proportion of static scatterers. Here, we used MESI with the aim of
repeatedly imaging the olfactory bulb of mice models of obesity. First, we have developed a MESI set up which was
characterized on microfluidic flow phantoms with different flow-rates and channel diameters to simulate blood flow in
animal model characteristics. Second, we show that MESI can discriminate flows in the presence of static scatterers and
it can measure flow changes consistently. Finally we provide an in vivo validation of the technique in mice with and
without a craniotomy.
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