In vivo Photoacoustic Spectroscopic Imaging of Hemoglobin Derivatives in Thermally Damaged Tissue

Photoacoustic (PA) spectroscopic measurement was performed for thermally damaged skin in a rat in vivo to analyze hemoglobin derivatives in the tissue. We observed PA signals at around 500 and 633 nm, which are center wavelengths of methemoglobin (MetHb) absorption peaks, at depths corresponding the uppermost dermis (similar to 0.16 mm) and hair follicles (similar to 0.62 mm), indicating formation of MetHb in these tissue regions. By scanning a PA detector on the tissue, two-dimensional PA images (tomograms) were produced. Subtraction imaging technique was used for multispectral PA tomograms to analyze specific components of hemoglobin derivatives in the tissue, by which the contrast of oxyhemogobin (HbO(2))-associated PA signal has been improved and the distribution of PA signal that seems to reflect the concentration of MetHb has been visualized. (C) 2009 The Japan Society of Applied Physics