Velocity range estimation for liquid flow based on optical micro-angiography

Abstract

Optical micro-angiography (OMAG) is widely used in vivo imaging due to its non-invasive and highly sensitive measurements. It can effectively distinguish flowing and stationary particles for applications such as micro-size blood vessel. However, the detectable flow velocity of OMAG is restricted by the system parameters. Their relationship is usually unknown and thus increase the difficulty of OMAG application on liquid flow measurements. This study for the first time proposes a velocity range estimation formula to quantify the measurable velocity range of liquid flow for the OMAG and the ultrahigh-sensitivity OMAG (UHS-OMAG) methods. The velocity range not only provides rough velocity information of the measure liquid flow that is not available in original OMAG system, but also can be used as a reference for accurate velocity determination in future research. The lower limit of the proposed flow velocity range is determined through the carrier frequency of the system while the upper limit is determined by the sampling frequency based on the sampling theorem. Experiments were conducted to verify the proposed velocity range formula and liquid flows with preset velocities are measured using OMAG and UHS-OMAG system. Experimental results are in good agreement with the proposed formula. Keywords: Optical coherence tomography (OCT), Optical micro-angiography (OMAG), Flow velocity measurement, Micro flow velocity