Multi-spectral laser speckle contrast imaging for depth-resolved blood perfusion assessment.

Significance: Laser speckle contrast imaging (LSCI) is a widely used tool in biomedical imaging that leverages the interactions between coherent laser light and tissue to assess blood perfusion. Although effective for 2D imaging applications such as skin burn assessment and wound healing, conventional LSCI lacks depth-resolved capabilities, limiting its potential for deeper perfusion analysis. Enhancing LSCI for depth profiling would significantly expand its utility in applications such as vascular imaging and burn diagnostics.

Aim: We investigate the use of multi-spectral laser speckle contrast imaging (MS-LSCI) for assessing blood perfusion at multiple depths, utilizing multiple laser wavelengths and advanced correlation techniques to improve depth localization.

Approach: Two tissue phantom molds were fabricated to simulate blood vessels at varying depths. Laser wavelengths from blue to near-infrared (NIR) were used to perform controlled experiments. The visibility parameter, $V_r$ , was employed to correlate and estimate the depth between the phantoms. In addition, a spectral wavelength mapping technique was implemented to enhance signal quality. Validation was conducted by imaging a human hand using the MS-LSCI setup.

Results: MS-LSCI demonstrated improved depth profiling accuracy across varying laser wavelengths. The spectral wavelength mapping technique enhanced signal quality for wavelengths with limited penetration. The visibility parameter, $V_r$ , provided consistent depth correlations across phantom models, with results validated through successful imaging of blood perfusion in a human hand.

Conclusions: We highlight the potential of MS-LSCI for depth-resolved blood perfusion imaging using multi-wavelength approaches. The findings emphasize the technique's feasibility for non-invasive biomedical applications, including burn wound assessment and vascular imaging.