Noninvasive optical sensing of biological tissues, including human brain monitoring, is a major scientific challenge in diffusive optics. Thus. a number of optical methods were developed for this purpose. The primary approaches include near-infrared spectroscopy (NIRS) and diffuse correlation spectroscopy DCS). NIRS estimates optical properties from the measured photon time-of-flight (TOF) distribution, while DCS quantifies the blood flow from temporal changes of the remitted light intensity. RecenUy, there was a significant progress in combining the TOF-resolution with DCS to achieve path-length-resolved blood flow information. With TOF, we could distinguish photons that traversed superficial layers (short TOFs) from photons traveling deep into the brain (long TOFs). Thus, previous studies developed the time–domain OCS (TD-DCS). Though, TD-DCS is very powerful technique it still relies only on intensities, and thus, does not allow to sense the optical phase, which carries a significant amount of information about scatterers moving inside the sample. The optical phase is acoessible in the interferometric near-infrared spectroscopy iNIRS). Original iNIRS, however, uses single-mode fibers, making the system too slow (integration time of 1 s) to detect rapid blood flow changes in the human brain that could be linked to neural signals. Here, we demonstrate parallel interferometric near-infrared spectroscopy (nNIRS). With the unique capability of accessing complex information (amplitude and phase) about the sample with more than 1000 parallel channels, we can sense the blood flow with only 5-20 ms integration time orders of magnitude faster than other approaches), making the TTNIRS one of the fastest and most advanced diffuse optical methods. methods
About the speaker
Dawid Borycki received his MSc and PhD in theoretical physics, both with honors, from Nicolaus Copernicus University in 2007 and 2011. He combines statistical optics, physics and software engineering to develop and improve noninvasive biomedical imaging modalities based on light interferometry
