Experimental determination of optical and mechanical properties of an optical elastography phantom

摘要

We report the results of experiments conducted to determine optical and mechanical properties of tissue mimicking phantoms that are designed for optical elastography. In optical elastography the readout mechanism for displacement is optical, and the mechanical and optical properties of the phantom are to be tailored to match those of the tissue being imaged. The optical characterization is based on diffusive nature of light propagation including scattering anisotropy and boundary reflection. The anisotropy factor (g) is measured using a relatively thin sample (where single scattering assumption is valid) through experimentally measuring the angular intensity transmittance. The measured intensity distributions are fitted to, known theoretically available intensity distributions, which have scattering anisotropy (g) as one of the parameters, to extract g . The scattering coefficient (μ_s) and refractive index (n) are obtained using a thicker slab (multiple scattering regime) from where angle-resolved intensity transmittance is measured. Computed intensity distributions using Monte-Carlo(MC) simulations are curve fitted to extract ' μ_s' and ' n' which are used in the Monte-Carlo simulation. The visco-elastic properties such as frequency dependent elastic and loss moduli of the phantom are determined by measuring the complex modulus using a dynamic mechanical analyzing system.