In this novel imaging system, we have combined three non-invasive and label free imaging tech-
niques: Optoacoustic microscopy (OAM) , non-linear microscopy (NLM) and Stimulated Raman
Scattering (SRS) microscopy . OAM exhibits resolution comparable to that of optical microscopy,
but can penetrate deeper into high-scattering tissue. The increased possibilities stem from the
fundamental scattering difference between light and sound, which constitute the signal for optical
microscopy and OAM, respectively. NLM includes two photon excitation fluorescence (TPEF) and
Second Harmonic Generation (SHG) . OAM, TPEF, SHG and SRS are combined complementary and
thus reveal a wide range of discrete and non-overlapping information. TPEF presents crisp contrast
between bio-molecules that possess different excitation or emission spectra. SHG can provide
information about biological structures such as lipid depositions while OAM pinpoints photon
absorbing molecules with non-radiative relaxation. SRS imaging provides chemical information
with high specificity allowing molecular pattern recognition inside tissues and their association
with diseases and pathological conditions. Using these techniques, even sensitive and unreachable
structures like the retina and the ocular cavity can be investigated with high resolution. The nerve
fibers in the ocular cavity are essentially an extension of the central nervous system and since
several neurodegenerative disorders present symptoms in the cavity, they could be diagnosed
before the manifestation of conventional symptoms. The presence of possible bio-markers was
investigated with TPEF, SHG and OAM in retina samples from mouse models of the Alzheimer’s
disease.
(EN)
University of Crete
