In vivo Doppler shift measurements using multimode fiber-optic catheters

Area of Science:

• Biomedical Engineering
• Optical Physics
• Fluid Dynamics

Background:

• Accurate in vivo blood flow measurement is crucial for diagnosing and managing various cardiovascular conditions.
• Existing methods may have limitations in directional sensitivity or calibration linearity.

Purpose of the Study:

• To develop and validate a new fiber-optic catheter system for precise in vivo blood flow velocity measurements.
• To assess the catheter's capability in measuring both forward and reverse blood flow.
• To establish a linear calibration method for accurate free stream velocity prediction.

Main Methods:

• Development of a dual-fiber optic catheter utilizing laser Doppler principles.
• Transmission of a laser beam into blood and reception of backscattered light from erythrocytes.
• Experimental flow studies and numerical simulations to analyze Doppler shift frequencies and flow velocities.
• Comparison of maximum shift frequency and dominant shift frequency linearity against flow velocities.

Main Results:

• The developed fiber-optic catheter successfully measured blood flow in both forward and reverse directions.
• Experimental and simulation data confirmed laminar flow within the boundary layer, supporting a linear relationship between Doppler shift and velocity.
• The maximum shift frequency demonstrated a more linear correlation with flow velocities compared to the dominant shift frequency.
• Linear calibration was achievable for predicting free stream flow velocity.

Conclusions:

• The new fiber-optic catheter provides a reliable tool for in vivo blood flow assessment.
• The system's ability to measure bidirectional flow and its linear calibration potential offer significant advantages for clinical and research applications.
• The findings support the use of this technology for accurate hemodynamic monitoring.