En-face differential absorption optical coherence tomography with gold nanorods as the contrast agent

A new variety of nanoparticles showing unique and characteristic optical properties, appeals for its use as contrast agents in medical imaging. Gold nanospheres, nanorods and nanoshells with a silica core are new forms of promising contrast agents which can be tuned to specific absorption or scattering characteristics within the near-infrared (NIR) spectrum ranging from 650 - 1300 nm. They have the ability to be used for both image enhancement and as photosensitive markers due to their well designable scattering and absorption properties. Furthermore, their strong optical absorption permits treatment of malignant cells by photoablation processes, induced when heating them with a matched light source. Differential absorption optical coherence tomography (DA-OCT) allows for the detection and depth resolved concentration measurement of such markers. So far, reports on DA-OCT systems used A-scan based imaging systems to assess depth resolved information about the absorption properties and the concentration of a chemical compound. Enface OCT (B(T) or C(T) scan based) images allow for better depth localization and a depth resolved concentration measurement of the compound under investigation. For this aim, we evaluate the suitability of a multiscan time-domain OCT set-up, compatible with different light sources providing different wavelengths and bandwidths in the NIR, to perform differential absorption OCT measurements, using gold nanorods as the contrast agent.