Time-domain diffuse correlation spectroscopy (TD-DCS) is a non-invasive optical technique, which measures tissue blood flow with path-length resolution. Ideally, this technique requires a pulsed laser with an adequate illumination power, a long coherence length, and a narrow instrument response function (IRF), while available laser modules cannot satisfy all these conditions. We systematically characterized three pulsed laser sources and compared their performances using phantom and in vivo measurements. We found that each laser has the potential to be used in TD-DCS applications. Also, the effects caused by the IRF are more significant than the effect of the limited coherence length.
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