A systematic study on fluorescence contrast in near-infrared diffuse transmittance imaging with indocyanine green

MACDONALD, RAINER; WAKS SERRA, MARÍA VICTORIA; POMARICO, J. A.; GROSENICK, DIRK; IRIARTE, D. I.; MACDONALD, RAINER; WAKS SERRA, MARÍA VICTORIA; POMARICO, J. A.; GROSENICK, DIRK; IRIARTE, D. I.

JOURNAL OF NEAR INFRARED SPECTROSCOPY

N I R PUBLICATIONS

Año: 2019 p. 1 - 12

0967-0335

Near infrared fluorescence imaging is a sensitive, noninvasive technique,for diagnostic applications in biomedical optics. Main purpose of thiswork is thus to explore how to improve the contrast of images obtainedby NIR light using a fluorescent extrinsic agent. Among differentfluorophores, indocyanine green (ICG) has been most studied because itis approved for use in humans. In this work, simulations andexperimental studies on phantoms (systems that optically emulatebiological tissues) are used to systematically investigate the influence ofthe increased intrinsic tissue absorption by adding ICG. The experimentsreproduce the situation of fluorescence imaging of carcinomas in thehuman breast, where the natural absorption due to neovascularization isincreased by the injection of this fluorophore. Assuming measurementsin transmission geometry, the breast is modeled by a homogeneousbackground medium containing a tumor - like inclusion (or lesion) withAbstract:two- or threefold increased absorption. Fluorescence contrast issimulated over a broad range of dye concentrations using diffusiontheory. Selected concentrations ratios are applied in experimentalstudies with laser excitation of ICG fluorescence and with a CCD camerafor fluorescence detection. Both, simulations and experiments show thatthe intrinsic absorption of the inclusion strongly reduces the number ofdetected fluorescence photons and that the fluorescence contrast can becanceled or become even negative. It was found that for typical opticalproperties and geometrical conditions in fluorescence imaging of breastcancer, a dye ratio of about 10:1 (lesion:background) is required to turnfrom negative to positive fluorescence contrast. Since such a high ratio isdifficult to attain, raw fluorescence images need to be normalized by theintrinsic lesion absorption (without ICG) to enhance the presence} of thedye in the lesion.