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Histopathology and microscopic examination of infected tissue are the gold standards to prove the diagnosis of invasive fungal infection (IFI). Yet, they suffer from essential limitations that hamper rapid diagnosis and require the future development of new imaging tools dedicated to fungal diagnostics. To this end, the present work introduces the first use of dynamic full-field optical coherence tomography (D-FF-OCT) for the visualization of microscopic filamentous fungi. Data collected from the observation of three different fungal species (Nannizzia gypsea, Aspergillus fumigatus and Rhizopus arrhizus) confirm the ability of D-FF-OCT to visualize not only the main structures of all selected fungal species (hyphae, spores, conidia, sporulating structures), but also the metabolic activity of the organisms, which could provide additional help in the future to better characterize the signature of each fungal structure. These results demonstrate how D-FF-OCT could serve as potential complementary tool for rapid diagnosis of IFI in both intensive and non-intensive care units.

We report on a theoretical model for image formation in full-field optical coherence tomography (FFOCT). Because the spatial incoherence of the illumination acts as a virtual confocal pinhole in FFOCT, its imaging performance is equivalent to a scanning time-gated coherent confocal microscope. In agreement with optical experiments enabling a precise control of aberrations, FFOCT is shown to have nearly twice the resolution of standard imaging at moderate aberration level. Beyond a rigorous study on the sensitivity of FFOCT with respect to aberrations, this theoretical model paves the way towards an optimized design of adaptive optics and \rev{computational tools} for high-resolution and deep imaging of biological tissues., Comment: 23 pages, 10 figures

Dynamic FFOCT allows us to record the intrinsic motion of biological samples in 3D, over hours. We performed scratch assays on primary porcine RPE and human induced pluripotent stem cells derived RPE cell cultures. We plotted motion maps from the optical flow. For wounds

International audience; Living tissues, heterogeneous at the microscale, usually scatter light. Strong scattering is responsible for the whiteness of bones, teeth, and brain and is known to limit severely the performances of biomedical optical imaging. Transparency is also found within collagen-based extracellular tissues such as decalcified ivory, fish scales, or cornea. However, its physical origin is still poorly understood. Here, we unveil the presence of a gap of transparency in scattering fibrillar collagen matrices within a narrow range of concentration in the phase diagram. This precholesteric phase presents a three-dimensional (3D) orientational order biomimetic of that in natural tissues. By quantitatively studying the relation between the 3D fibrillar network and the optical and mechanical properties of the macroscopic matrices, we show that transparency results from structural partial order inhibiting light scattering, while preserving mechanical stability, stiffness, and nonlinearity. The striking similarities between synthetic and natural materials provide insights for better understanding the occurring transparency.

Introduction Malgre les progres de l’imagerie vasculaire, l’analyse histologique de biopsie d’artere temporale (BAT) reste l’examen de reference pour le diagnostic d’arterite a cellules geantes (ACG) [1] . Cependant, la BAT presente un certain nombre de limites - manque de sensibilite (50-85 %), caractere invasif, ou encore cout en temps et en personnel - si bien que des methodes d’imagerie des arteres temporales se developpent pour montrer des signes de vascularite (echo-Doppler, IRM, TEP scanner) [2] . Couramment utilisee en ophtalmologie clinique pour l’imagerie non invasive de coupes retiniennes, la tomographie de coherence optique (abregee OCT pour optical coherence tomography) exploite l’interference lumineuse comme principale source d’information pour l’observation des milieux biologiques. Nous rapportons pour la premiere fois son utilisation dans un montage haute resolution - l’OCT plein champ [3] - pour le diagnostic d’ACG, en comparaison de l’histologie conventionnelle. Materiels et methodes Des coupes congelees de 16 BAT ont ete analysees en OCT plein champ (Light-CTScanner, LLTech SAS, Paris, France). Apres coloration HES, les BAT etaient classees en 3 groupes: BAT negative sans hyperplasie intimale (n = 9), BAT negative avec hyperplasie intimale (n = 3) et BAT positive (n = 4). Une double analyse qualitative et quantitative des images obtenues en histologie (NDP.view2), puis OCT plein champ (ImageJ), a ensuite permis de confronter les deux techniques pour la visualisation ex vivo des modifications structurales de l’architecture de la paroi arterielle au cours de l’ACG. Enfin, l’application d’un filtre de Gabor a ete utilisee dans le but de cartographier l’orientation structurale comparee des fibres au sein de la paroi arterielle et ainsi tester l’hypothese d’une possible analyse automatisee des images acquises avec le systeme d’OCT plein champ. Resultats Les donnees acquises en OCT plein champ ont permis de visualiser les structures anatomiques presentes au sein de la paroi arterielle avec une resolution spatiale autorisant la detection d’une cellule unique: individualisation des trois tuniques (intima, media, adventice), limitante elastique interne (LEI) et vasa vasorum. La symetrie circulaire, la LEI et l’architecture de la paroi vasculaire etaient parfaitement conservees pour les 12 BAT negatives. En analyse quantitative, il existait une excellente correlation entre histologie conventionnelle et OCT plein champ pour la mesure de l’epaisseur des differentes tuniques, ce qui a permis de distinguer sans difficultes les BAT negatives avec ou sans hyperplasie intimale. Appuyee par l’application du filtre de Gabor et l’analyse d’image automatisee, l’observation des 4 BAT positives en OCT plein champ a montre une perte de la symetrie circulaire, avec homogeneisation des contrastes entre media et intima. Ce remodelage structural s’associait a une densification du tissu conjonctif qui s’etendait dans les trois directions de l’espace et finissait par effacer les contours de la LEI. Discussion Cette etude de preuve de concept rapporte la premiere utilisation de l’OCT plein champ pour le diagnostic histopathologique d’ACG. Ainsi, en quelques minutes seulement et sans traitement prealable de l’echantillon apres BAT, cette technique interferometrique hautement resolue permet l’acquisition directe de sections optiques transverses ex vivo, puis l’identification automatisee d’anomalies structurales caracteristiques d’ACG. Il devient notamment aise, meme pour des cliniciens non-inities au montage d’OCT plein champ, de retrouver des lesions elementaires d’ACG - remodelage structural de la paroi arterielle avec hyperplasie intimale et rupture de LEI - tres proches de celles observees en histologie apres colorations standards. Conclusion L’imagerie optique d’artere temporale par OCT plein champ constitue une alternative de choix pour le diagnostic rapide et automatise d’ACG. Des travaux complementaires sont en cours pour confirmer le potentiel de cette technologie et son application future.

Histopathological examination of temporal artery biopsy (TAB) remains the gold standard for the diagnosis of giant cell arteritis (GCA) but is associated with essential limitations that emphasize the need for an upgraded pathological process. This study pioneered the use of full-field optical coherence tomography (FF-OCT) for rapid and automated on-site pathological diagnosis of GCA. Sixteen TABs (12 negative and 4 positive for GCA) were selected according to major histopathological criteria of GCA following hematoxylin-eosin-saffron-staining for subsequent acquisition with FF-OCT to compare structural modifications of the artery cell wall and thickness of each tunica. Gabor filtering of FF-OCT images was then used to compute TAB orientation maps and validate a potential automated analysis of TAB sections. FF-OCT allowed both qualitative and quantitative visualization of the main structures of the temporal artery wall, from the internal elastic lamina to the vasa vasorum and red blood cells, unveiling a significant correlation with conventional histology. FF-OCT imaging of GCA TABs revealed destruction of the media with distinct remodeling of the whole arterial wall into a denser reticular fibrous neo-intima, which is distinctive of GCA pathogenesis and accessible through automated Gabor filtering. Rapid on-site FF-OCT TAB acquisition makes it possible to identify some characteristic pathological lesions of GCA within a few minutes, paving the way for potential machine intelligence-based or even non-invasive diagnosis of GCA.

Raman spectroscopy was used to study the liquid–solid water phase transition. Special attention was devoted to the OHstretching band of the Raman spectrum, which shows monotonous changes in the temperature range between 10 and − 15 °C. The interpretation of this spectral change, as well as a careful analysis of its integrated scattered intensity, led to a spectral marker that allows the determination of the water phase (liquid or solid), and the efficient identification of the liquid–solid phase transition itself. Copyright © 2011 John Wiley & Sons, Ltd.

Photoacoustic imaging can achieve high-resolution three-dimensional (3-D) visualization of optical absorbers at penetration depths of ∼1 cm in biological tissues by detecting optically induced high ultrasound frequencies. Tomographic acquisition with ultrasound linear arrays offers an easy implementation of single-side access, parallelized, and high-frequency detection, but usually comes with an image quality impaired by the directionality of the detectors. Indeed, a simple translation of the array perpendicular to its median imaging plane is often used, but results both in a poor resolution in the translation direction and strong limited-view artifacts.To improve the spatial resolution and the visibility of complex structures while retaining a planar detection geometry, we introduce, in this paper, a rotate-translate scanning scheme and investigate the performance ofa scanner implemented at 15 MHz center frequency. The developed system achieved a quasi-isotropic uniform 3-D resolution of ∼170 μm over a cubic volume of side length 8.5 mm, i.e., an improvement in the resolution in the translation direction by almost one order of magnitude. Dual-wavelength imaging was also demonstrated with ultrafast wavelength shifting. The validity of our approach was shown in vitro. We discuss the ability to enable in vivo imaging for preclinical and clinical studies.

Elasticity maps of tissue have proved to be particularly useful in providing complementary contrast to ultrasonic imaging, e.g., for cancer diagnosis at the millimeter scale. Optical coherence tomography (OCT) offers an endogenous contrast based on singly backscattered optical waves. Adding complementary contrast to OCT images by recording elasticity maps could also be valuable in improving OCT-based diagnosis at the microscopic scale. Static elastography has been successfully coupled with full-field OCT (FF-OCT) in order to realize both micrometer-scale sectioning and elasticity maps. Nevertheless, static elastography presents a number of drawbacks, mainly when stiffness quantification is required. Here, we describe the combination of two methods: transient elastography, based on speed measurements of shear waves induced by ultrasonic radiation forces, and FF-OCT, an en face OCT approach using an incoherent light source. The use of an ultrafast ultrasonic scanner and an ultrafast camera working at 10,000 to 30,000 images/s made it possible to follow shear wave propagation with both modalities. As expected, FF-OCT is found to be much more sensitive than ultrafast ultrasound to tiny shear vibrations (a few nanometers and micrometers, respectively). Stiffness assessed in gel phantoms and an ex vivo rat brain by FF-OCT is found to be in good agreement with ultrasound shear wave elastography.

We propose a new optical sensor to characterize the solid-liquid phase transition in salted solutions. The probe mainly consists of a Raman spectrometer that extracts the vibrational properties from the light scattered by the salty medium. The spectrum of the O – H stretching band was shown to be strongly affected by the introduction of NaCl and the temperature change as well. A parameter SD defined as the ratio of the integrated intensities of two parts of this band allows to study the temperature and concentration dependences of the phase transition. Then, an easy and efficient signal processing and the exploitation of a modified Boltzmann equation give information on the phase transition. Validations were done on solutions with varying concentration of NaCl.

Raman spectroscopy was used to study the NaCl aqueous solutions around the solid-liquid phase transition. Special attention was devoted to the modification induced by the salt on the OH stretching band of water. Investigations were carried out in the temperature range between-21 and 10 °C, for concentrations from 0 to 200 g/L. We demonstrated that micro-Raman spectroscopy can be used as a marker, allowing the determination of the salt concentration of an aqueous solution with an error close to ±5%.

New AlOx VCSELs are very interesting for dual-purpose applications, since the emitting aperture, which guide the current lines, may be reduced to a few microns; in parallel, the ALOx diaphragm is transparent to near IR radiations. Thus, with such devices, we can get a detective area greater than the emissive one. We present in this paper our first results for an experimental numerical optical link between two linear AlOx VCSEL arrays. We first give the characteristics of the VCSEL arrays used in our experiment and describe the associated electronics. Then we present the results obtained on our test link and the problem encountered in transmission at a data rate greater than 50 Mbits/s. Finally, we tried to explain this limitation by characterizing the bandwidths of the electronics and testing all the elements on a network analyzer.

Photoacoustic imaging is a recent and rapidly developping technique that can provide images of optical absorption at depth in soft tissue. In this work, photoacoustic imaging is applied to detect tissue lesion induced by high-intensity focused-ultrasound (HIFU).Tissue changes during HIFU therapy include changes in optical tissue properties that may be detected using photoacoustics. However, although it has been demonstrated that HIFU lession could indeed be detected using photoacoustics (Chitnis et al., JBO 15(2), 2010, Cui et al., JBO 15(2), 2010), the exact origin of the observed contrast remains unclear. In this study, lesions induced in different types of biological tissue are imaged in vitro using a photoacoustic microscope. Lesions are induced in the tissue samples with therapeutic ultrasound in the MHz frequency range, and a photoacoustic microscope with imaging frequencies from the MHz to the tens of MHz range, are used to obtain acoustic-resolution photoacoustic images of lesions located at diffe...