Laser speckle micro-rheology in characterization of biomechanical properties of tissues

A method for determining a mechanical property of biological tissue using laser speckle microrheology, the method comprising:

• receiving speckle frames acquired by illuminating a coherent light and capturing back-scattered rays in parallel and cross-polarized states with respect to illumination;
• analyzing the speckle frames temporally to obtain diffuse reflectance profiles (DRPs) for the parallel-polarized and cross-polarized states;
• determining a scattering characteristic or an absorption characteristic of particles in the biological tissue based on the DRPs;
• determining a displacement characteristic based at least in part on a speckle intensity autocorrelation function and at least one of the scattering characteristic and the absorption characteristic;
• determining a size characteristic of scattering particles based on the DRP for the parallel polarization state;
• and
• calculating the mechanical property using the displacement characteristic and the size characteristic.

A system for determining a mechanical property of biological tissue using laser speckle microrheology, the system comprising a processor and memory with instructions thereon, the processor being configured to:

• receive speckle frames acquired by illuminating a coherent light and capturing back-scattered rays in parallel and cross-polarized states with respect to illumination;
• analyze the speckle frames temporally to obtain diffuse reflectance profiles (DRPs) for the parallel-polarized and cross-polarized states;
• determine a scattering characteristic or an absorption characteristic of particles in the biological tissue based on the DRPs;
• determine a displacement characteristic based at least in part on a speckle intensity autocorrelation function and at least one of the scattering characteristic and the absorption characteristic;
• determine a size characteristic of scattering particles based on the DRP for the parallel polarization state;
• and
• calculate the mechanical property using the displacement characteristic and the size characteristic.

A method for determining a mechanical property of biological tissue using laser speckle microrheology, the method comprising:

• acquiring speckle frame series by illuminating a laser light and capturing back-scattered rays for parallel and cross-polarized states;
• calculating a speckle intensity autocorrelation curve;
• temporally averaging speckle intensity, and calculating radial diffuse reflectance profiles (DRPs) for the parallel and cross-polarized speckle frame series;
• fitting the radial DRP to a steady-state diffusion model to extract a scattering coefficient;
• deducing mean square displacement (MSD) of light-scattering particles based on the speckle intensity autocorrelation curve and the scattering coefficient;
• calculating a ratio of parallel-polarized DRP along short and long axes, and comparing the ratio with a calibration curve to determine average radius of scattering particles;
• and
• calculating a viscoelastic modulus for the biological tissue using the MSD and the average radius of scattering particles.