Localisation d'inclusions fluorescentes dans les milieux diffusants à l'aide de techniques laser. Application au diagnostic médical in vivo

La tomographie de fluorescence est une méthode d'imagerie préclinique et clinique permettant de localiser des traceurs fluorescents préalablement injectés ou naturellement présents dans un organisme vivant. Ce travail de thèse à consisté, dans un premier temps, à définir l'architecture et les conditions d'utilisation optimales d'un tomographe de fluorescence continu appliqué à l'observation de tissus de faible épaisseur. On s'est en particulier attaché à traiter le problème de l'observation de tissus hétérogènes et d'organes fortement absorbants. Dans un deuxième temps, pour observer des tissus de plus grande épaisseur, nous avons montré l'apport de la mesure du temps de vol moyen des photons pour améliorer la localisation d'inclusions fluorescentes. Les performances de deux types de systèmes capables de réaliser ce type de mesure ont été comparées et nous avons proposé un protocole permettant d'en optimiser les principaux paramètres. Notre procédé a été appliqué à la problématique du guidage de biopsies prostatiques. Il pourra aussi être utilisé pour visualiser d'autres pathologies moyennant une simple adaptation.Fluorescence tomography is a preclinical and clinical imaging method which aims to localize fluorescent probes injected into a living organism. In this thesis work, we defined the optimal design and parameters of a continuous wave fluorescent tomograph applied to thin tissue observation. We handled the problem of observing heterogeneous and highly absorbing organs. Secondly, we showed the advantage of time of flight measurement for inclusion detection through thicker tissues. The detection performances of two types of system capable of these measurements were compared and we proposed a protocol to optimize their main parameters. This process was applied to the problematic of prostatic biopsy guiding. It would also be used to detect and localize other pathologies by means of a simple adaptation.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Multi-confocal Fluorescence Correlation Spectroscopy : experimental demonstration and potential applications for living cell measurements

We report, for the first time, a multi-confocal Fluorescence Correlation Spectroscopy (mFCS) technique which allows parallel measurements at different locations, by combining a Spatial Light Modulator (SLM), with an Electron Multiplying-CCD camera (EM-CCD). The SLM is used to produce a series of laser spots, while the pixels of the EM-CCD play the roles of virtual pinholes. The phase map addressed to the SLM is calculated by using the spherical wave approximation and makes it possible to produce several diffraction limited laser spots, either aligned or spread over the field of view. To attain fast enough imaging rates, the camera has been used in different acquisition modes, the fastest of which leads to a time resolution of 100 $\mu$s. We qualified the experimental set-up by using solutions of sulforhodamine G in glycerol and demonstrated that the observation volumes are similar to that of a standard confocal set-up. To demonstrate that our mFCS method is suitable for intracellular studies, experiments have been conducted on two stable cell lines: mouse embryonic fibroblasts expressing eGFP-actin and H1299 cells expressing the heat shock factor fusion protein HSF1-eGFP. In the first case we could recover, by analyzing the auto-correlation curves, the diffusion constant of G-actin within the cytoplasm, although we were also sensitive to the complex network of interactions with F-actin. Concerning HSF1, we could clearly observe the modifications of the number of molecules and of the HSF1 dynamics during heat shock

Time-domain reflectance diffuse optical tomography with Mellin-Laplace transform for experimental detection and depth localization of a single absorbing inclusion.

International audienceWe show how to apply the Mellin-Laplace transform to process time-resolved reflectance measurements for diffuse optical tomography. We illustrate this method on simulated signals incorporating the main sources of experimental noise and suggest how to fine-tune the method in order to detect the deepest absorbing inclusions and optimize their localization in depth, depending on the dynamic range of the measurement. To finish, we apply this method to measurements acquired with a setup including a femtosecond laser, photomultipliers and a time-correlated single photon counting board. Simulations and experiments are illustrated for a probe featuring the interfiber distance of 1.5 cm and show the potential of time-resolved techniques for imaging absorption contrast in depth with this geometry

Quantification in time-domain diffuse optical tomography using mellin-laplace transforms

Simulations and phantom measurements are used to evaluate the ability of time-domain diffuse optical tomography using Mellin-Laplace transforms to quantify the absorption perturbation of centimetric objects immersed at depth 1-2 cm in turbid media. We find that the estimated absorption coefficient varies almost linearly with the absorption change in the range of 0-0.15 cm-1 but is underestimated by a factor that depends on the inclusion depth (~2, 3 and 6 for depths of 1.0, 1.5 and 2.0 cm respectively). For larger absorption changes, the variation is sublinear with ~20% decrease for δμa = 0.37 cm-1. By contrast, constraining the absorption change to the actual volume of the inclusion may considerably improve the accuracy and linearity of the reconstructed absorption

Effects of earthworms on soil organic matter and nutrient dynamics at a landscape scale over decades

International audienceThis chapter synthesizes information on the effects of earthworms on soil systems at scales longer than 1 year, and earthworm behavior that may affect these processes is detaile

Singlet-triplet anticrossings in 4He. III. Separation and mixing of the n=3-8 1D and 3D states

International audienceThe method of singlet-triplet anticrossing has been extended to the n1-3D levels of 4He with n=3, 4, and 5. We measure both the zero-field singlet-triplet separation with a higher accuracy than optical measurements, and the antisymmetric part of the spin-orbit coupling between singlet and triplet states. The agreement with many-body perturbation calculations for singlet-triplet intervals and with the hydrogenic approximation for spin-orbit coupling is fairly good even for low-n states. Values of singlet-triplet mixing in the n=3-8 D states, derived directly from the experimental results, are significantly more accurate than previous experimental and theoretical values

Observation of singlet-triplet anticrossings in 4He2

International audienceAnticrossings between excited singlet and triplet levels of the He2 molecule have been observed. Measurements have been made on anticrossings which take place between the f (3d) 3Δu and F (3d) 1Δu states both in the v=0, N=2,3,4 and v=1, N=2 vibrational and rotational levels. Analysis of these results yields a new and more precise value for the excitation energy, T0, from the a (2s) 3Σ to the A (2s) 1Σ state. This result, when combined with available optical data, fixes the absolute energy of all He2 excited states. The present experiment establishes that the steady state populations of the 3Δ levels are greater than the 1Δ levels under a variety of excitation conditions. Also, collisional transfer may take place before radiation giving rise to a given anticrossing signal appearing on optical emission lines of several nearby rotational levels

Time-domain diffuse optical tomography using silicon photomultipliers: feasibility study

Silicon photomultipliers (SiPMs) have been very recently introduced as the most promising detectors in the field of diffuse optics, in particular due to the inherent low cost and large active area. We also demonstrate the suitability of SiPMs for time-domain diffuse optical tomography (DOT). The study is based on both simulations and experimental measurements. Results clearly show excellent performances in terms of spatial localization of an absorbing perturbation, thus opening the way to the use of SiPMs for DOT, with the possibility to conceive a new generation of low-cost and reliable multichannel tomographic systems

Atomic Resonance and Scattering

Contains reports on six research projects.National Science Foundation (Grant PHY 83-06273)U.S. Navy - Office of Naval Research (Contract N00014-79-C-0183)Joint Services Electronics Program (Contract DAALO03-86-K-0002)National Science Foundation (Grant PHY 84-11483)National Science Foundation (Grant PHY 86-05893)National Science Foundation (Grant ECS 84-21392)U.S. Navy - Office of Naval Research (Contract N00014-83-K-0695)National Science Foundation (Grant CHE 84-21392