Single fiber laser-Doppler flowmetry-dependence on wavelength and tip optics.

Area of Science:

• Biomedical optics
• Laser-Doppler flowmetry
• Tissue optics

Background:

• Single fiber laser-Doppler flowmetry enables blood flow assessment in deep tissues via optical fiber insertion.
• Understanding the monitored volume geometry is crucial for accurate measurements.

Purpose of the Study:

• To estimate the geometry of the monitored volume in laser-Doppler flowmetry.
• To evaluate the impact of different wavelengths and fiber tip designs on measurement accuracy.
• To assess the potential of modified fiber tips to minimize insertion trauma effects.

Main Methods:

• Experiments utilized physical models and intramuscular measurements.
• Scattering images were analyzed in latex solutions at varying concentrations using 632.8 nm and 750 nm wavelengths.
• Fiber tip optics were evaluated in a flow-through model, comparing flat and "pear" tip designs.

Main Results:

• The near-infrared (NIR) wavelength (750 nm) demonstrated a larger scattering area at higher concentrations and increased monitoring depth compared to the He-Ne laser (632.8 nm).
• The "pear" tip fiber exhibited a sensitivity maximum 1.5 mm from the surface, unlike the flat tip which peaked near the surface.
• This suggests the "pear" tip may mitigate the impact of insertion trauma.

Conclusions:

• Wavelength selection and fiber tip design significantly influence the geometry and depth of laser-Doppler flowmetry measurements.
• Modified fiber tips, like the "pear" tip, show promise for reducing artifacts associated with tissue insertion.
• Optimized fiber optic configurations can improve the accuracy and reliability of blood flow measurements in deep tissues.