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Much insight into metabolic interactions, tissue growth, and tissue organization can be gained by analyzing differently stained histological serial sections. One opportunity unavailable to classic histology is three-dimensional (3D) examination and computer aided analysis of tissue samples. In this case, registration is needed to reestablish spatial correspondence between adjacent slides that is lost during the sectioning process. Furthermore, the sectioning introduces various distortions like cuts, folding, tearing, and local deformations to the tissue, which need to be corrected in order to exploit the additional information arising from the analysis of neighboring slide images. In this paper we present a novel image registration based method for reconstructing a 3D tissue block implementing a zooming strategy around a user-defined point of interest. We efficiently align consecutive slides at increasingly fine resolution up to cell level. We use a two-step approach, where after a macroscopic, coarse alignment of the slides as preprocessing, a nonlinear, elastic registration is performed to correct local, non-uniform deformations. Being driven by the optimization of the normalized gradient field (NGF) distance measure, our method is suitable for differently stained and thus multi-modal slides. We applied our method to ultra thin serial sections (2 μm) of a human lung tumor. In total 170 slides, stained alternately with four different stains, have been registered. Thorough visual inspection of virtual cuts through the reconstructed block perpendicular to the cutting plane shows accurate alignment of vessels and other tissue structures. This observation is confirmed by a quantitative analysis. Using nonlinear image registration, our method is able to correct locally varying deformations in tissue structures and exceeds the limitations of globally linear transformations.

This poster advertizes the Jean-Marie Mariotti Center software tools, databases and services aimed at facilitating the use of optical interferometry worldwide such as preparation of observations, data reduction and data analysis. Its mission and organization are presented before listing the current software suite. Finally some facts and perspectives are mentioned.

Lithium Niobate (LN) based electro-optic modulators are well known in the optical communications field, due to their high bandwidth and deep rejection ratio [1]. These performances could be used in the field of astronomy for stellar interferometry in the mid-infrared domain [2]. With our partners from Photline Technologies, we have conceived, developed and characterized a 2T ABCD [3] beam combiner in the near-infrared (1.5μm, the H-band in astrophysics). The modulation scheme, presented below in Figure 1, allows to determine the fringe characteristics in a single shot measurement, without the need to externally scan the optical phase delay. Fine adjustment of the relative phase can be achieved using the electro-optic properties of the lithium niobate waveguides. In particular, the phase on each output can be electrically controlled and locked by using appropriate electrodes. These devices have to ensure modal filtering to reject optical aberrations of the wavefront and thus optimize the fringes contrast, which means that they have to be single mode through all the spectral range of interest. This also means that the couplers should be achromatic and balanced in order to optimize the fringe contrast. We will present results on global transmission, performance of the couplers and the electro-optic behavior of the device using monochromatic as well as wide spectral sources in the H-band.

In this paper, we study the feasibility of obtaining near-infrared spectra of bright extrasolar planets with the 2nd generation VLTI Spectro-Imager instrument (VSI), which has the required angular resolution to resolve nearby hot Extrasolar Giant Planets (EGPs) from their host stars. Taking into account fundamental noises, we simulate closure phase measurements of several extrasolar systems using four 8-m telescopes at the VLT and a low spectral resolution (R = 100). Synthetic planetary spectra from T. Barman are used as an input. Standard chi2-fitting methods are then used to reconstruct planetary spectra from the simulated data. These simulations show that low-resolution spectra in the H and K bands can be retrieved with a good fidelity for half a dozen targets in a reasonable observing time (about 10 hours, spread over a few nights). Such observations would strongly constrain the planetary temperature and albedo, the energy redistribution mechanisms, as well as the chemical composition of their atmospheres. Systematic errors, not included in our simulations, could be a serious limitation to these performance estimations. The use of integrated optics is however expected to provide the required instrumental stability (around 10^-4 on the closure phase) to enable the first thorough characterisation of extrasolar planetary emission spectra in the near-infrared.

This paper presents the experimental laboratory interferometer simulator implemented to prepare the VSI-Vitruv instrument. In its final phase, VSI-Vitruv will recombine up to 6 beams of the VLTI thanks to a set of planar Integrated Optics (IO) combiners. This simulator will be used to characterize the IO combiner concepts developed for VSI-Vitruv and will allow to optimize the system up to the data reduction and image reconstruction issues. The simulator consists of three sub-systems: a binary object simulator, a VLTI simulator presenting an array of 8 telescopes, the IO beam combiner and a low resolution spectro-imager. After a detailled presentation of the bench, we will present the first validation tests and the performances of the experiment. The characterizations of the combiners developped for VSI-Vitruv are presented in the accompanying paper (Benisty et al.,6268-89).