High-flow-velocity and shear-rate imaging by use of color Doppler optical coherence tomography

Color Doppler optical coherence tomography (CDOCT) is capable of precise ve locity mapping in turbid media. Previous CDOCT systems based on the short-t ime Fourier transform have been limited to maximum flow velocities of the o rder of tens of millimeters per second. We describe a technique, based on i nterference signal demodulation at multiple frequencies, to extend the phys iological relevance of CDOCT by increasing the dynamic range of measurable velocities to hundreds of millimeters per second. The physiologically impor tant parameter of shear rate is also derived from CDOCT measurements. The m easured flow-velocity profiles and shear-rate distributions correlate very well with theoretical predictions. The multiple demodulation technique, the refore, may be useful to monitor blood flow in vivo and to identify regions with high and low shear rates. (C) 1999 Optical Society of America.