An apparatus, including: a probe to interface with a surface of a tissue; a light source optically coupled to the probe, the light source directing light of at least 1000 nm into the tissue; a detector optically coupled to the probe, the detector to detect light based on scattering of light from the light source in the tissue, and the detector having a light sensitivity in a range of at least 1000 nm; a processor coupled to the detector, the processor to: receive a signal from the detector corresponding to the detected light from the light source, and determine a blood flow measurement from the region of interest using diffuse correlation spectroscopy based on the signal.