A catheter for imaging flow velocity profiles using optical Doppler tomography

The purpose of this dissertation is to develop a new light imaging technique for discerning velocity profiles in scattering fluids. The importance and need for such a device is apparent in studying the etiology and treatment of vascular disease. An optical Doppler tomography (ODT) interferometer is constructed with a multicore fiber in its sample arm acting as an imaging catheter. This multicore fiber has the ability to image an entire two dimensional plane at once with high spatial resolution. The catheter is introduced into a scattering flow field with either microspheres or intralipid fat particles. A photodetector is used to gather Doppler shifted light from moving scatterers in the flow field. By this method, velocity values of physiologic relevance are detected. In order to demonstrate that a two dimensional velocity map can be generated, experiments are also performed with a CCD camera. Even though frame rates are too slow for practical measurements, the CCD camera has the ability to capture images with high spatial resolution, so that the individual cores of the multicore fiber can be seen independently. Analysis of the fluid dynamics and photon transport through the fluid has been attempted. Together these two sets of experiments show that a catheter based ODT system can be a feasible method for discerning flow information with accuracy that is beyond any current method. Modifications and improvements for a future device are also discussed. A device which has the ability to generate high resolution flow velocity profiles is unprecedented and the utility of this information has implications for all who study flow phenomena in whatever field they may be.