Systematic diffuse optical image errors resulting from uncertainty in the background optical properties

We investigated the diffuse optical image errors resulting from systematic errors in the background scattering and absorption coefficients, Gaussian n oise in the measurements, and the depth at which the image is reconstructed when using a 2D linear reconstruction algorithm for a 3D object. The fourt h Born perturbation approach was used to generate reflectance measurements and k-space tomography was used for the reconstruction. Our simulations usi ng both single and dual wavelengths show large systematic errors in the abs olute reconstructed absorption coefficients and corresponding hemoglobin co ncentrations, while the errors in the relative oxy- and deoxy- hemoglobin c oncentrations are acceptable. The greatest difference arises from a systema tic error in the depth at which an image is reconstructed. While an absolut e reconstruction of the hemoglobin concentrations can deviate by 100% for a depth error of +/-1 mm, the error in the relative concentrations is less t han 5%. These results demonstrate that while quantitative diffuse optical t omography is difficult, images of the relative concentrations of oxy- and d eoxy- hemoglobin are accurate and robust. Other results, not presented, con firm that these findings hold for other linear reconstruction techniques (i . e. SVD and SIRT) as well as for transmission through slab geometries. (C) 1999 Optical Society of America.