Comparison of red and green laser doppler imaging of blood flow.

ABSTRACT

BACKGROUND AND OBJECTIVES: Laser Doppler imaging (LDI) of perfusion has been performed with a novel green wavelength (532 nm) for comparison with a HeNe laser (633 nm), the aim being validation of the green laser wavelength as a research tool. STUDY DESIGN/MATERIALS AND METHODS: The effect of wavelength and power on images was investigated and perfusion response following both finger occlusion and local heating of the dorsum were examined as reproducible stimuli for clinical studies. RESULTS: The most striking difference between red and green LDI is the absence of veins on green LDI, which are seen with red LDI. Differences have been quantified using vein LDI profiles. Differences were found between blood flow responses imaged by red and green LDI (3 and 5 mW, respectively) for occlusion and heat stimuli. Results are discussed in the context of light penetration. CONCLUSIONS: Red and green wavelengths appear to image different components of the microcirculation.