Laser Speckle Contrast Imaging for functional visualization

Laser speckle contrast imaging is a modern technique uniquely suited for the full-field, non-invasive measurement of the motion of particles within randomly inhomogeneous highly scattering and absorbing media, including biological tissues. This technique is based on illuminating the medium with a coherent laser light, detecting the arising speckle pattern and further statistical analysis of the speckle pattern fluctuations caused by the motion of the scattering particles in the observed medium. Despite the active use of laser speckle contrast imaging for biomedical applications, this technique suffers from several issues complicating the understanding of obtained speckle contrast data.

The present work is aimed at the investigation of limitations, improving, and discovering new potentials of currently existing methods of laser speckle contrast imaging. In particular, the influence of effects of non-ergodicity on the results of speckle contrast analysis was investigated using the phantom and animal models. It was shown that the presence of a thin static layer above the dynamic layer does not introduce significant errors in speckle contrast calculation. The simple approach for the adjustment of speckle contrast values in different types of brain vasculature during transcranial visualisation was introduced. For the first time, the protocol for the monitoring of skin acute vascular permeability reaction in response to simultaneous application of tree different chemical substances has been described. Moreover, in a new approach, the optical setup combining a hyperspectral camera and multi-wavelength light source was implemented for the depth-resolved blood flow and perfusion assessment. The proposed technique was applied for skin perfusion monitoring. Finally, the unprecedented use of laser speckle contrast imaging was introduced for handwriting pressure and kinematics evaluation.