Mixed scattering as a problem in laser speckle contrast analysis.

Area of Science:

• Biomedical Optics
• Medical Imaging
• Laser Physics

Background:

• Laser Speckle Contrast Analysis (LASCA) is used for skin perfusion measurement.
• Static scattering significantly impacts the accuracy of LASCA, especially for absolute perfusion values needed in tissue injury assessment.
• Existing models often overlook mixed scattering contributions.

Purpose of the Study:

• To investigate the detrimental effect of static scattering on LASCA measurements.
• To evaluate the influence of varying dynamic/static scattering ratios on perfusion calculations.
• To explore methods for correcting perfusion data affected by static scattering.

Main Methods:

• Calculated perfusion values using two evaluation models on skin and tissue phantoms.
• Manipulated the dynamic/static scattering ratio of the phantoms.
• Utilized multi-exposure LASCA to obtain dynamic ratio values.

Main Results:

• Perfusion measurements were significantly affected by increased static scattering contributions.
• Mixed scattering, often omitted in models, was identified as a major cause of perfusion value changes.
• A modified tissue phantom experiment confirmed the impact of mixed scattering.

Conclusions:

• Static scattering poses a significant challenge to accurate absolute perfusion measurements using LASCA.
• Current evaluation models are insufficient when mixed scattering is present.
• Multi-exposure LASCA's dynamic ratio offers a potential solution for correcting perfusion data affected by static scattering.