1. A system for determining volume-related parameters of a biological tissue, comprising: a light source for projecting light towards the biological tissue; a receiver for receiving light reflected from the biological tissue at two spectral wavelengths; an image acquisition system in communication with the receiver for forming an image from the reflected light at each wavelength; and a processor for applying a mathematical model to the image which compares the absorption of light by the biological tissue at a selected image point at each of the two spectral wavelengths to determine the volume-related parameters of the biological tissue at that location.