Abstract: The present invention relates to a non-invasive optical system equipped with optical tomographic scanning method and algorithm for quantifying scattering and absorption properties and chromophore concentrations of highly scattering medium such as biological tissues, for 3D mapping and imaging reconstruction of the spatial and temporal variations in such properties. The invention further relates to a method and an apparatus for simultaneous measurement of concentrations of biochemical substances and blood oxygen saturation inside a biological tissue and arterial blood.