Performance of fitting procedures in curved geometry for retrieval of the optical properties of tissue from time-resolved measurements

By use of the solution of the diffusion equation for cylindrical and spheri cal geometry, two fitting procedures for retrieval of the optical propertie s from time-resolved measurements have been implemented. The fitting proced ures are based on the Levenberg-Marquardt algorithm, in which the fitting p arameters are the absorption coefficient, the reduced scattering coefficien t, and an amplitude factor. Monte Carlo data generated for cylindrical and spherical geometry were fitted by these fitting procedures, and the retriev ed optical properties were compared with those obtained from the inversion procedure with a mismatched geometry of a semi-infinite medium. The effects of refractive-index mismatch and of different boundary conditions of the d iffusion equation were also studied, together with the effects of several s ources of error that are typically found in time-resolved measurements. The advantages and drawbacks of these fitting procedures, including many detai ls in several situations of interest in the field of tissue optics, are dis cussed. The results also offer a guideline to understanding the effects of mismatching in curved geometry as functions of source-detector distance and radii of cylinders or spheres. (C) 2001 Optical Society of America OCIS co des: 170.3660, 170.5280, 170.7050.