Determination of optical properties in situ from radial backscattering profile using a CCD camera

Local tissue optical parameters are of principal importance in determining the ideal dosage of laser energy and choosing the most suitable therapeutic wavelength for a specific organ. We have developed a non-invasive method for the determination of optical parameters of whole tissue in-situ. Backscattered laser light from a pencil beam incident on the tissue surface was measured using a CCD camera interfaced with a personal computer. Backscatter measurements were performed on in-vitro canine myocardium and on phantoms, with optical properties predetermined by the integrating sphere method. Backscattering radiance proved to be a function of the distance to the incident beam. Regression analysis of the backscatter showed that the backscatter can be expressed as an exponential function of the distance to the beam with a regression coefficient ((mu) r) resembling the tissue diffusion coefficient ((mu) eff), for tissue thickness much greater than optical free path. The CCD derived backscatter radiance exponent showed excellent agreement with the diffusion coefficient, with a correlation coefficient of 0.91. The backscattering technique might prove to be a simple, non-invasive, accurate new technique in the determination of in-vivo optical properties.