1. © CEA 2008. Tous droits réservés. Toute reproduction totale ou partielle sur quelque support que ce soit ou utilisation du contenu de ce document est interdite sans l’autorisation écrite préalable du CEA All rights reserved. Any reproduction in whole or in part on any medium or use of the information contained herein is prohibited without the prior written consent of CEA 200 7 www.leti.fr Fluorescence Reflectance Imaging (FRI)Abstract Fluorescence enhanced diffuse optical tomography is an emergent diagnosis tool for the localization and the quantification of fluorescent probes ; this technique comes as a supplement or sometimes replaces the classical ionizing radiation imaging techniques, and in particular if a simple, inexpensive, non invasive and accurate instrumentation is sought. For 5 years now, the CEA-LETI has built a base of knowledge in markers and instrumentation within the framework of small animal imaging. More recently, an instrumentation has been developed, the purpose of which is a specific approach to the examination of underlying structures, deeply embedded within the tissues, and in fine for human being screening. Cooled CCD camera lens Why fluorescence ?  Visualization techniques widely used in vitro  Non ionizing technique  Cheap Principle In vivo Fluorescence imaging limitations The excitation and emission wavelengths must be in the near infra red: higher than 650 nm and lower than 900 nm. The scattering coefficient is much higher than the absorption coefficient, therefore the outcoming photons have been highly scattered. Light propagation in biological tissues is modeled as a diffusion process. µ s >>µ a light source Strong heamoglobin attenuation Strong water attenuation Excitation light scattering ~20cm CCD Camera Emission filter Optical fibers Laser source Halogen lamp IR filter IR filtered visible light illumination Two optical fibred 690nm laser light 100mW for fluorescence excitation Scattering of the illumination source with a holographic lens Field homogeneity better than 30% Illumination: 2,6 mW/cm² 3D imaging: Trans-illumination Diffuse Optical Tomography liver Nodules in the lungs day 10 day 12day 14 Course of an experiment   Exemple of in vivo follow up [*] National funded project Prostafluo Deep Tissue Screening: endoscopy The major challenge in deep tissues fluorescence imaging initially consists in bringing the fluorescent marker in sufficient quantity on the target. The second difficulty in deep tissue screening consists in being freed from the intrinsic fluorescence of biological tissues. To get rid of this autofluorescence, the approach considered consists in using a pulsed signal and time- resolved measurements in order to achieve a temporal discrimination between the autofluorescence signal and the fluorophores emission signal. This discrimination will be all the more efficient if the fluorescence marker lifetime is significantly different from the autofluorescence lifetime. [*] A. Koenig, L. Hervé, V. Josserand, M. Berger, J. Boutet, A. Da Silva, J.-M. Dinten, P. Peltié, J.- L. Coll, P. Rizo, “In vivo mice lungs tumors follow-up with fDOT”, to be published in Journal of Biomedical Optics 2008 Edges detection 3D Visualisation 10x10 fluorescence images acquisition -> 5 minutes Reconstruction -> 5-10 min IAB 2D fluorescence reflectance image