Application of time-gated, intensified CCD camera for imaging of absorption changes in non-homogenous medium

Abstract

The paper presents application of time-gated, intensified CCD camera for imaging of local changes of absorption in the non-homogenous liquid phantom. The surface of the phantom was illuminated sequentially at 25 points (forming 5 × 5 array) by laser beam at wavelength of 780 nm generated by picosecond, near-infrared diode laser. The spatial distribution of diffusely reflected photons was measured in reflectance geometry at null source-detector separation. For each position of the laser beam the reflectance was measured for two different time windows, distinctly delayed in respect to the laser pulse. The observation of late photons, which penetrated deeply in the optically turbid medium allowed to image the absorbing inclusion (10 mm diameter black ball) located at depth of 15 mm. For each of two time windows the single images for all scanned points were summed. Obtained final images allowed to localize the non-homogeneity in the phantom. The study shows, that the presented method based on imaging at null source-detector separation distance for late time windows may be applied in the evaluation of the tissue absorption measurements, especially in the brain oxygenation imaging.