The optical-CT system developed for this study provides non-contact multiple-angle measurements of biopsy samples in order to calculate 3-D maps of their optical properties.46,47 The principle of the system is depicted schematically in Fig. 1. The light source was a white light lamp consisting of 80 light-emitting diode (LEDs). A diffuser was placed between the light source and the optical components directing the light onto the sample. Diffuse light was preferred rather than collimated laser beam for homogeneous illumination and for acquiring average values of the optical properties. The light was then reflected by a flat mirror, and it was guided to a linear polarizer (Hoya, Japan). After transmission through the sample, which was positioned on a rotational stage (Standa, Lithuania) covering 360 deg of rotation, the linear polarization of light was mostly lost due to scattering. Ambient light was blocked by a black, totally absorbing, paper tube. Light signals were detected by a sensitive charge coupled device camera (CCD-Camera) (Andor Corp., DV434, Belfast, Northern Ireland), which was thermoelectrically cooled down to . The CCD-Camera was equipped with a SIGMA 50 mm objective lens (SIGMA Corporation, Tokyo, Japan). A second polarizer (Hoya, Japan) was attached to the input of the lens and was adjusted either parallel or perpendicular to the polarization of the light used for illumination. The whole experimental procedure was controlled with in-house-developed software, and images were stored on a PC.