Optical Doppler methods for the measurements of flow velocities of biological liquids

Background and Objectives: In this paper the key results obtained by the authors during the years of development of Doppler optical methods for quasi-elastic light scattering and coherence gating on biomedical liquids are presented. The research is focused on the sign sensitive velocity measurement and quantitative visualization of alternating and complex geometry flows using spectral approach to digital data processing of Doppler shift of the carrier frequency. Materials and Methods: Laser Doppler microscopy allows accurate sign-sensitive measurement of the endoplasm stream velocity in the isolated strand of Physarum polycephalum. An algorithm of color Doppler mapping of multidirectional flows (vessel phantom) is developed to automatically decompose the original data into two parts corresponding to a positive and negative shift of the carrier frequency with forming up the structural image and two OSV (One Specific Velocity) ones followed by color coding and a final complexation. Results: The model based on the spectral characteristics adequately describes the change of the velocity time dependencies of the endoplasmic motility. The OSV Doppler mapping allows for the construction of structural Doppler images of biological fluids. They clearly visualize and reflect the functional state of the biological object. Conclusion: The methods of quasi-elastic light scattering, optical coherence tomography (OCT) and Doppler OCT have been developed for the direction-sensitive velocity measurements and OSV mapping of biomedical liquids, based on the automated sign-sensitive registration of the carrier and Doppler shifts. Velocity measurements and color mapping of the alternating flows of the liquids in vitro and in vivo are presented.