Simple instrument for the characterization of diffuse reflectance

An apparatus for the measurement of the radial dependence of the continuous-wave diffuse reflectance of a tissue is described. It consists in a probe, which is applied on the tissue, and a detection unit. By employing an array of incoherent semiconductor light sources (LED's) and continuous-wave detection, probe structure is considerably simpler than other devices described in literature, allowing moreover an efficient coupling of the emitted light towards the tissue. The high responsivity so obtained permits fast and accurate measurements. Measurement speed, probe compactness and accuracy are potentially sufficient for the in-vivo application of the method to surgically exposed tissue. A preliminary set of data, measured on a scattering phantom and on non-exposed in-vivo tissue, is presented. Even though available models fitted to the measured data give the correct order of magnitude for light transport coefficients, in order to extract reliable absolute values they should be corrected for probe nonidealities. The availability of extensive high-quality in-vivo data is to this regard stimulating for further theoretical investigations.