Automated method for tracking individual red blood cells within capillaries to compute velocity and oxygen saturation

OBJECTIVE: The authors present a new method to track individual red blood cells (RBCs) as they move through capillaries. This method uses a recently developed Measurement and Analysis System for Capillary Oxygen Transport (MASCOT) and the concept of space-time images to track RBCs between consecutive frames of video recordings of the microcirculation. METHODS: A space-time image displays in a single static image for a single capillary the location of all RBCs as a function of time. Analysis is performed on video tapes of RBC flow through capillaries to obtain velocity of individual cells as they traverse the capillary of interest. A space-time image is generated to track RBCs from one frame to the next and their velocities are computed. Based on the optical density values of each cell obtained from synchronized videotapes at two wavelengths, the oxygen saturation of a cell can be determined. In this manner, oxygen saturation can be tracked for the same cells as they move through the capillary. RESULTS AND CONCLUSIONS: These measurements, taken together, allow one to determine how much and how fast oxygen is being delivered to the surrounding tissue. This method provides, for the first time, a way to track individual RBCs flowing through capillary networks and study their RBC dynamics and oxygenation.