|"A novel technique known as near-infrared (NIR) diffuse correlation spectroscopy (DCS) has been recently developed that enables quantifying relative changes in microvascular blood flow (rBF). DCS uses coherent near-infrared light to penetrate deep tissues and measures speckle fluctuations of the diffuse light that are sensitive
to the motions of red blood cells in tissues. DCS provides a portable, noninvasive, and inexpensive alternative for microvascular blood flow measurements and has been validated against other standards, including power spectral Doppler ultrasound, Doppler ultrasound, laser Doppler flowmetry, Xenon computed tomography, fluorescent microsphere flow measurement and ASL-MRI. The DCS technology has been extensively introduced into various tissues, including brain, tumor and skeletal muscle. The applications of DCS in brain and tumor have been previously reviewed. Interested readers are encouraged to read these publications for details. This review paper
will focus on introducing some recent progress of DCS in the study of skeletal muscles. The key components of a DCS flow-meter include a long coherence length laser at NIR range, a single-photon-counting avalanche photodiode (APD) detector and an autocorrelator board. Other components, such as source/detector fibers, computer, and
A/D board, are used to couple light in/out of tissue or control/record optical data. For tissue blood flow measurement, the laser placed on the tissue surface (e.g., skin) launches long-coherence NIR light into
the tissue via a multiple-mode source fiber, and the light transported/ scattered through the tissue was collected by a single-mode (or a fewmode) detector fiber placed millimeters to centimeters away from the source fiber. The detected light is then delivered via the detector fiber to APD detector, where the count of photons per unit time (i.e., light intensity) is recorded.
(Yu Shang, Katelyn Gurley and Guoqiang Yu- Diffuse Correlation Spectroscopy (DCS) for Assessment of Tissue Blood
Flow in Skeletal Muscle: Recent Progress)