Determination of biological tissue optical coefficients from the spatial or temporal scattered profile of a collimated pulsed light source

A method has been developed to evaluate the absorption and reduced scattering coefficients of slabs of turbid materials, biological tissues in particular, with a one step procedure. The biological tissue is transilluminated by a collimated source and the transmitted part of the signal is detected. The spatial intensity profile of the light is collected by a linear CCD. The temporal profile of an ultrashort laser pulse is measured with an ultrafast photodiode. The spatial or temporal profiles are compared to the results of Monte-Carlo simulations in order to predict the absorption and reduced scattering coefficients of the investigated tissue. The validity of our photon migration model has been carefully assessed by experiments on microspheres suspensions, where exact scattering coefficient and the associated phase function have been derived from Mie theory. These results have allowed us to determine the accuracy of the method. The method has been applied to determine locally the optical coefficients of several selected slabs of biological tissues, and the validity of this approach has been verified.