Observing under the microscope the movement of red blood cells in the capillary, one can measure
the velocity of blood flow (v= 0.5 mm/s). the average velocity of blood flow in the aorta is = 40 cm/s. based on these data, determine how many times the sum of the cross sections of all
functioning capillaries is greater than the aortic section. (s1v1 =s2v2).

As capillaries exhibit heterogeneous and fluctuating dynamics even during baseline, a technique measuring red blood cell (RBC) speed and flux over many capillaries at the same time is needed. Here, we report that optical coherence tomography can capture individual RBC passage simultaneously over many capillaries located at different depths. Further, we demonstrate the ability to quantify RBC speed, flux, and linear density. This technique will provide a means to monitor microvascular flow dynamics over many capillaries at different depths at the same time.

Keywords: capillaries, cerebral blood flow measurement, cranial windows, microscopy, optical imaging