Feasibility of NIR tomographic reconstruction with multispectral continuous wave data by mapping into frequency domain data

Diffuse near-infrared tomography of tissue can provide intrinsically useful information about total hemoglobin, oxygen saturation, water and cytochromes within tissue, yet to extract this information spectral data is required at many wavelengths. In this study, we examine a new approach to using multispectral continuous wave measurements through tissue along with second-derivative data analysis methods to estimate the pathlength in tissues over multiple tomographic paths. The goal of this work has been to demonstrate that the optical differential pathlength that is estimated by spectroscopy methods is directly related to the optical pathlength as measured by frequency-domain signals. This direct relation then allows the use of tomographic algorithms which have been developed for frequency-domain optical tomography to be applied to multispectral continuous wave data. The theoretical development is presented here, along with numerical validation in homogeneous and heterogeneous tissue-simulating regions. These results indicate that the approach outlined is valid and provides the theoretical basis for developing multispectral near-infrared tomography of tissues.