Abstract
Laser speckle contrast imaging (LSCI) has emerged as a valuable tool for cerebral blood flow (CBF) imaging. We present a multi-exposure laser speckle imaging (MESI) method which uses a high-frame rate acquisition with a negligible inter-frame dead time to mimic multiple exposures in a single-shot acquisition series. Our approach takes advantage of the noise-free readout and high-sensitivity of a complementary metal-oxide-semiconductor (CMOS) single-photon avalanche diode (SPAD) array to provide real-time speckle contrast measurement with high temporal resolution and accuracy. To demonstrate its feasibility, we provide comparisons between in vivo measurements with both the standard and the new approach performed on a mouse brain, in identical conditions.
Highlights
Non-invasive, optical imaging of blood flow in general, and in particular cerebral blood flow (CBF) has many applications in studying both the normal and pathopshysiological brain [1]
Diffuse correlation spectroscopy (DCS) [2], laser Doppler flowmetry [3], laser speckle contrast imaging (LSCI) [4] are some of the optical methods based on the spatio-temporal statistics of the laser speckles that are used to measure blood flow in the microvasculature
The bulk of LSCI work relied on the use of a single-exposure time, which allowed fairly simple and inexpensive experimental set-up that can measure the relative changes in CBF with high spatio-temporal resolution
Summary
Non-invasive, optical imaging of blood flow in general, and in particular cerebral blood flow (CBF) has many applications in studying both the normal and pathopshysiological brain [1]. Diffuse correlation spectroscopy (DCS) [2], laser Doppler flowmetry [3], laser speckle contrast imaging (LSCI) [4] are some of the optical methods based on the spatio-temporal statistics of the laser speckles that are used to measure blood flow in the microvasculature. The bulk of LSCI work relied on the use of a single-exposure time, which allowed fairly simple and inexpensive experimental set-up that can measure the relative changes in CBF with high spatio-temporal resolution. The main drawback of MESI is due to the additional time necessary for acquiring different exposure time sequences. It lacks the temporal resolution necessary for imaging rapid changes in blood flow, preventing realtime in vivo measurements to be performed and leading to a trade-off between accuracy, resolution and speed
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