Transit-time analysis based on delay-encoded beam shape for velocity vector quantification by spectral-domain Doppler...

Area of Science:

• Biomedical Optics
• Medical Imaging
• Fluid Dynamics

Background:

• Accurate quantification of three-dimensional (3-D) velocity vectors is crucial in various scientific fields.
• Spectral-domain Doppler optical coherence tomography (SD-DOCT) is a powerful imaging technique for non-invasive flow assessment.
• Existing SD-DOCT methods often face challenges in precisely determining the azimuth angle of velocity vectors.

Purpose of the Study:

• To develop and validate a novel transit-time based method for determining the azimuth angle of velocity vectors using SD-DOCT.
• To enable the full quantification of 3-D velocity vectors by integrating azimuth angle measurement with existing SD-DOCT capabilities.
• To demonstrate the feasibility and accuracy of the proposed method in complex flow scenarios.

Main Methods:

• A custom-designed slit plate was employed to generate three delay-encoded sub-beams for sample probing.
• Transit-time analysis of Doppler bandwidth was utilized to evaluate the azimuth angle within a 90-degree range.
• Complex signals corresponding to three path length delays were exploited for angle estimation.
• Combined Doppler shift and Doppler bandwidth measurements were used to quantify the 3-D velocity vector.

Main Results:

• The proposed method accurately determined azimuth angles, showing good agreement with preset values.
• Feasibility was demonstrated through successful velocity vector measurements of flowing solutions in capillary tubes.
• The technique successfully quantified 3-D velocity vectors by estimating both Doppler angle and flow velocity.

Conclusions:

• The developed transit-time based method provides a robust approach for azimuth angle determination in SD-DOCT.
• This technique significantly advances the capability of SD-DOCT for comprehensive 3-D velocity vector quantification.
• The method holds potential for improved diagnostic capabilities in biomedical imaging and fluid dynamics research.