Abstract

Colour Doppler optical coherence tomography (CDOCT) has recently shown great promise in twodimensional, high-spatial-resolution (on the order of tens of microns) tomographic velocity mapping of blood in living tissue.¹ CDOCT is based on optical interference in a scanning Michelson interferometer under broadband illumination. When a scattering object is in motion, it generates a signal in the detection circuit, an interferogram, the envelope of which gives the spatial reflectivity, and the frequency of which is proportional to the sum of the object’s velocity and that of the reference arm scanner. Conventionally, post-processing of the entire interferogram is performed, requiring a large amount of computation, which precludes the real time operation of CDOCT necessary to provide motion-artefact-free images in vivo. Another major problem with the conventional approach concerns the bandwidth of the detection electronics.² For high dynamic range (sensitivity), the detection bandwidth should be as narrow as possible. However, the need to measure rapid and variable flows present in the vast majority of blood vessels requires a wider detection bandwidth to accommodate the variable Doppler frequency. Thus, either the dynamic range or the velocity range must be compromised.

© 2000 IEEE