We demonstrate a single multi-mode fiber-based micro-endoscope for measuring blood flow speeds. We use the transmission-matrix wavefront shaping approach to calibrate the multi-mode fiber and raster-scan a focal spot across the distal fiber facet, imaging the cross-polarized back-reflected light at the proximal facet using a camera. This setup allows assessment of the backscattered photon statistics: by computing the mean speckle contrast values across the proximal fiber facet we show that spatially-resolved flow speed maps can be inferred by selecting an appropriate camera integration time. The proposed system is promising for minimally-invasive studies of neurovascular coupling in deep brain structures.
Iliya Sigal, Antonio M. Caravaca Aguirre, Raanan Gad, Rafael Piestun, and Ofer Levi, "Label free imaging system for measuring blood flow speeds using a single multi-mode optical fiber (Conference Presentation)," Proc. SPIE 9717, Adaptive Optics and Wavefront Control for Biological Systems II, 97171G (Presented at SPIE BiOS: February 15, 2016; Published: 26 May 2016); https://doi.org/10.1117/12.2213173.4848767696001.
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