Simultaneous in vivo measurements of the total hemoglobin, oxygen saturation, and tissue blood flow via hybrid near-infrared diffuse optical techniques

Diagnosing a stroke at an emergency site is an important potential clinical application for near-infrared light techniques. We have fabricated a hybrid diffuse optical device that combines diffuse optical spectroscopy and diffuse correlation spectroscopy (DCS) to monitor the total hemoglobin concentration (HbT), tissue oxygen saturation (StO2), and blood flow index (BFI) of a patient. The device used hybrid light sources consisting of three incoherent laser diodes (LDs) and one long coherent LD. Single-photon-counting avalanche photodiodes detected light reemitted from the tissue. Arm cuff experiments were performed using a healthy subject to validate device capabilities. Changes in hemodynamic parameters including the HbT, StO2, and BFI were measured continuously during the arm cuff experiments. The StO2 decreased linearly from 63% to 51% during the 3 min occlusion period. The blood flow decreased immediately by 16% when the occlusion was placed on the forearm. Overshot increases in the HbT, StO2, and BFI were all observed after occlusion release. Stroke is related to abnormal hemodynamic changes in cerebral vasculature and our device is sensitive to such changes. Thus, we believe that the hybrid device developed here may have potential clinical applications for stroke diagnosis at emergency sites.