Abstract
Indocyanine green (ICG) is used in non-invasive liver function testing. It is known that ICG binds plasma protein especially. These methods use ICG as a visible light marker for special protein. However, ICG has sharp and large absorption peaks not only in visible legion but also in IR region. ICG has an IR absorption peak of -13000 cm-1 at 7.1 μm. In this study, ICG was exposed to free-electron lasers (FELs) with wavelength of 7.1 μm and usefulness of ICG as an IR-marker was discussed. The results from FT-IR and sample thickness measurements showed that ICG ablated with the power density of more than 5 W/cm2 (=Pt), and that the molecular structure of ICG was stable at 7.1 μm -FELs of less than Pt, 3.0 W/cm2. Therefore ICG can be considered as a novel infrared marker (IR-marker) to the living tissue.
