Archival Legacy Investigations of Circumstellar Environments: Overview and First Results

We are currently conducting a comprehensive and consistent re-processing of archival HST-NICMOS coronagraphic surveys using advanced PSF subtraction methods, entitled the Archival Legacy Investigations of Circumstellar Environments program (ALICE, HST/AR 12652). This virtual campaign of about 400 targets has already produced numerous new detections of previously unidentified point sources and circumstellar structures. We present five newly spatially resolved debris disks revealed in scattered light by our analysis of the archival data. These images provide new views of material around young solar-type stars at ages corresponding to the period of terrestrial planet formation in our solar system. We have also detected several new candidate substellar companions, for which there are ongoing followup campaigns (HST/WFC3 and VLT/SINFONI in ADI mode). Since the methods developed as part of ALICE are directly applicable to future missions (JWST, AFTA coronagraph) we emphasize the importance of devising optimal PSF subtraction methods for upcoming coronagraphic imaging missions. We describe efforts in defining direct imaging high-level science products (HLSP) standards that can be applicable to other coronagraphic campaigns, including ground-based (e.g., Gemini Planet Imager), and future space instruments (e.g., JWST). ALICE will deliver a first release of HLSPs to the community through the MAST archive at STScI in 2014.Comment: Proceedings of the SPIE, 9143-199. 17 pages, 11 figure

Malacofauna del Banco Chella y alrededores (Mediterráneo occidental)

Molluscs of Chella Bank and its surroundings were studied from 21 samples collected with a van Veen grab in the depth range 95-729 m. A total of 299 taxa were identified (77 live-taken), thus increasing by more than 95% the species of molluscs reported in the recently declared site of community importance “Sur de Almería-Seco de los Olivos”. Two of the species are new records to Spanish waters and one to the Alboran Sea. The high species richness observed could be related to the location, the hydrological characteristics and the topographical heterogeneity of the area within the Alboran Sea. Four significant groups of samples were discriminated through multivariate analysis of quantitative data of live-taken molluscs: (I) bathyal muddy bottoms with buried rhodoliths; (II) bathyal muddy bottoms with coral rubble; (III) bathyal hemipelagic muddy bottoms and (IV) bathyal sandy bottoms. Molluscs were more diverse on coral framework bottoms than on sedimentary bottoms around Chella Bank. Most of the live-taken species are widely distributed along the Atlantic and Mediterranean Sea, and a few are strictly Mediterranean. The most striking feature was the occurrence of two species with planktotrophic larval development for which Chella Bank is the sole recorded locality in the Mediterranean (Episcomitra angelesae and Mitrella templadoi) and which elsewhere extremely rare (Mathilda spp.).Se estudiaron los moluscos del banco Chella y sus fondos adyacentes a partir de veintiuna muestras cogidas con draga Van Veen entre 95 y 729 m de profundidad. Un total de 299 taxones fueron identificados (77 vivos), incrementando en un 95% el total de moluscos citados en el reciente Lugar de Importancia Comunitaria “Sur de Almería-Seco de los Olivos”. Dos especies son nuevas citas para aguas españolas y una para el mar de Alborán. La elevada riqueza específica puede estar relacionada con la localización, las características hidrológicas y la heterogeneidad topográfica de esta zona situada dentro del mar de Alborán. Mediante análisis multivariantes usando datos cuantitativos de la taxocenosis se han diferenciado cuatro grupos de muestras: (I) fangos del batiales con rodolitos enterrados, (II) fangos batiales con restos de corales, (III) fangos hemipelágicos batiales, y (IV) arenas batiales. La mayor diversidad se encontró en los fondos con restos de corales, a diferencia de los fondos sedimentarios situados alrededor del banco Chella. La mayoría de las especies vivas están ampliamente distribuidas por el Atlántico y el Mediterráneo, y muy pocas son estrictamente mediterráneas. Cabe destacar la ocurrencia de algunas especies con desarrollo planctotrófico (Episcomitra angelesae, Mitrella templadoi) en el banco Chella como única localidad registrada en el Mediterráneo o especies extremadamente raras en otros lugares (Mathilda spp.)

Manipulation de la géométrie de l’illumination pour l’imagerie fonctionnelle de la rétine par ophtalmoscope plein champ corrigé par optique adaptative

As the only transparent optical window of our body, the eye gives a unique access to the observation of neural and vascular networks. Today however, a new era is opening up for high-resolution imaging, which should no longer be limited to giving access to tissue structures, but may also tackle their functions. In fact, biomarkers for the functioning of the whole human body can be found in retinal imaging. Neurodegenerative diseases (Parkinson's, Alzheimer's) or arterial hypertension could thus be diagnosed early by high precision imaging of the retina. In my thesis work, I intended to show how the full-field ophthalmoscope, associated to imaging modalities adjusting geometrical settings of the illumination, could contribute to research on the retina. To achieve this ambitious goal, we modified the full-field ophthalmoscope built at the National Hospital Center of Quinze-Vingts with a specific image processing and two new instruments inspired by full-field microscopy. We have integrated these instruments into the illumination path of the ophthalmoscope to manipulate the geometry of the retinal illumination. These new implementations allow us to make use of more advanced imaging techniques, such as dark field imaging or noninvasive near infrared angiography. These imaging modalities have been exploited to image the retina functionally. We focused mainly on the light coupling function of photoreceptors and on blood perfusion.L’œil étant la seule fenêtre optique transparente de notre corps, il donne un accès unique à l’observation de réseaux neuronaux et vasculaires. Mais aujourd’hui une nouvelle ère s’ouvre pour l’imagerie haute résolution, qui ne doit plus se contenter de donner accès aux structures des tissus, mais aussi d’en apprécier les fonctions. En effet, on peut trouver dans l’imagerie rétinienne des biomarqueurs du fonctionnement de l’ensemble du corps humain. Des maladies neurodégénératives (Parkinson,Alzheimer) ou l’hypertension artérielle pourraient être ainsi précocement diagnostiquées par une imagerie de haute précision de la rétine. L’optique adaptative, adaptée à l’imagerie rétinienne dès 1997, a amélioré nettement la résolution spatiale des images rétiniennes entraînant la multiplication des études de rétine par ophtalmoscope. Elle a notamment été couplée avec l’ophtalmoscope à balayage, qui devint le choix le plus populaire par sa supériorité en résolution spatiale et sectionnement optique par rapport au plein champ. Cependant, contrairement aux systèmes à balayage, l’ophtalmoscope plein champ produit des images grand champ à forte cadence d’acquisition et sans distorsion. Dans mon travail de thèse, j’ai cherché à montrer qu’un tel système, associé à des modalités d’imagerie jouant sur la géométrie d’éclairement, pourrait apporter à la recherche sur la rétine. Pour atteindre cet objectif ambitieux, nous avons modifié l’ophtalmoscope plein champ construit au Centre Hospitalier National des Quinze-Vingts avec un traitement d’image spécifique et deux nouveaux instruments inspirés de la microscopie plein champ. Nous avons intégré ces instruments dans le trajet d’illumination de l’ophtalmoscope afin de manipuler la géométrie de l’éclairage de la rétine. Ces nouvelles implémentations nous permettent de mettre en œuvre des techniques d’imagerie plus avancées, comme par exemple l’imagerie en champ sombre ou l’angiographie non invasive en proche infrarouge. Ces modalités d’imagerie ont été exploitées pour imager la rétine de façon fonctionnelle. Nous nous sommes intéressés principalement à la fonction de couplage de lumière des photorécepteurs et à la perfusion sanguine

Optical Incoherence Tomography: a method to generate tomographic retinal cross-sections with non-interferometric adaptive optics ophthalmoscopes

International audienceWe present Optical Incoherence Tomography (OIT): a completely digital method to generate tomographic retinal cross-sections from en-face through-focus image stacks acquired by non-interferometric imaging systems, such as en-face adaptive optics (AO)-ophthalmoscopes. We demonstrate that OIT can be applied to different imaging modalities using back-scattered light, including systems without inherent optical sectioning and, for the first time, multiply-scattered light, revealing a distinctive cross-sectional view of the retina. The axial dimension of OIT cross-sections is given in terms of focus position rather than optical path, as in OCT. We explore this property to guide focus position in cases where the user is "blind" focusing, allowing precise plane selection for en-face imaging of retinal pigment epithelium, the vascular plexuses and translucent retinal neurons, such as photoreceptor inner segments and retinal ganglion cells, using respectively autofluorescence, motion contrast and split detection techniques

Tomographie par incohérence optique : une méthode pour générer des coupes tomographiques de la rétine avec des ophtalmoscopes à optique adaptative non interférométrique

International audienceWe present Optical Incoherence Tomography (OIT): a completely digital method to generate tomographic retinal cross-sections from en-face through-focus image stacks acquired by non-interferometric imaging systems, such as en-face adaptive optics (AO)-ophthalmoscopes. We show how to use OIT to guide focus position in cases where the user is “blind" focusing, such as auto fluorescence imaging of the Retinal Pigment Epithelium (RPE). We also demonstrate that OIT can produce distinctive cross-sectional views of the retina using back-scattered, multiply-scattered or even fluorescent light, making it a complementary technique to OCT.Nous présentons la Tomographie par Incohérence Optique (OIT) : une méthode entièrement numérique pour générer des coupes transversales de la rétine tomographique à partir de piles d'images en face acquises pour différents plans focales par des systèmes d'imagerie non interférométriques, tels que les ophtalmoscopes à optique adaptative. Nous montrons comment utiliser l'OIT pour guider la position du plan focal dans les cas où l'utilisateur effectue une mise au point "en aveugle", comme l'imagerie par autofluorescence de l'épithélium pigmentaire de la rétine. Nous démontrons également que l'OIT peut produire des vues en coupe transversale distinctes de la rétine en utilisant une lumière rétrodiffusée, multidiffusée ou même fluorescente, ce qui en fait une technique complémentaire à l'OCT

In vivo near-infrared autofluorescence imaging of retinal pigment epithelial cells with 757 nm excitation

International audienceWe demonstrate near-infrared autofluorescence (NIRAF) imaging of retinal pigment epithelial (RPE) cells in vivo in healthy volunteers and patients using a 757 nm excitation source in adaptive optics scanning laser ophthalmoscopy (AOSLO). NIRAF excited at 757 nm and collected in an emission band from 778 to 810 nm produced a robust NIRAF signal, presumably arising from melanin, and revealed the typical hexagonal mosaic of RPE cells at most eccentricities imaged within the macula of normal eyes. Several patterns of altered NIRAF structure were seen in patients, including disruption of the NIRAF over a drusen, diffuse hyper NIRAF signal with loss of individual cell delineation in a case of non-neovascular age-related macular degeneration (AMD), and increased visibility of the RPE mosaic under an area showing loss of photoreceptors. In some participants, a superposed cone mosaic was clearly visible in the fluorescence channel at eccentricities between 2 and 6° from the fovea. This was reproducible in these participants and existed despite the use of emission filters with an optical attenuation density of 12 at the excitation wavelength, minimizing the possibility that this was due to bleed through of the excitation light. This cone signal may be a consequence of cone waveguiding on either the ingoing excitation light and/or the outgoing NIRAF emitted by fluorophores within the RPE and/or choroid and warrants further investigation. NIRAF imaging at 757 nm offers efficient signal excitation and detection, revealing structural alterations in retinal disease with good contrast and shows promise as a tool for monitoring future therapies at the level of single RPE cells

Phase contrast imaging to detect transparent cells in the retinal ganglion cells layer

The eye is an optical window giving access to neural networks in a non-invasive way. It is possible to find in the retina biomarkers informing about the pathological state of other parts of the human body, and in particular of the brain. Neurodegenerative diseases could thus be diagnosed early and monitored by high-resolution imaging of the retina. However, a large part of the neurons in the retina are too transparent to be detected by existing techniques. At the Quinze-Vingts hospital, we have a unique retinal imaging platform in which ophthalmologists, neurologists and engineers participate. We implemented a technique based on scanning laser ophthalmoscopy (SLO) to capture the fine variations in refractive index between retinal cells. In this project we aimed at imaging and monitor cellular changes on transparent cells in the retinal ganglion cells layer in vivo on healthy participants and patients with neurodegenerative diseases

Higher adaptive optics loop rate enhances axial resolution in nonconfocal ophthalmoscopes

International audienceIn this Letter, we propose a way to better understand the impact of dynamic ocular aberrations in the axial resolution of nonconfocal adaptive optics (AO) ophthalmoscopes via a simulation of the 3D PSF in the retina for various AO-loop rates. We then use optical incoherence tomography, a method enabling the generation of tomographic retinal cross sections in incoherent imaging systems, to evaluate the benefits of a fast AO-loop rate on axial resolution and, consequently, on AO-corrected retinal image quality. We used the PARIS AO flood-illumination ophthalmoscope for this study, where retinal images from different focal planes at an AO-loop rate of 10 and 50 Hz were acquired

Near infrared adaptive optics flood illumination retinal angiography

International audienceImage-based angiography is a well-adapted technique to characterize vasculature, and has been used in retinal neurovascular studies. Because the microvasculature is of particular interest, being the site of exchange between blood and tissue, a high spatio-temporal resolution is required, implying the use of adaptive optics ophthalmoscopes with a high frame rate. Creating the opportunity for decoupled stimulation and imaging of the retina makes the use of near infrared (NIR) imaging light desirable, while the need for a large field of view and a lack of distortion implies the use of a flood illumination-based setup. However, flood-illumination NIR video sequences of erythrocytes, or red blood cells (RBC), have a limited contrast compared to scanning systems and visible light. As a result, they cannot be processed via existing image-based angiography methods. We have therefore developed a new computational method relying on a spatio-temporal filtering of the sequence to isolate blood flow from noise in low-contrast sequences. Applying this computational approach enabled us to perform angiography with an adaptive optics flood illumination ophthalmoscope (AO-FIO) using NIR light, both in bright-field and dark-field modalities. Finally, we demonstrate the capabilities of our system to differentiate blood flow velocity on a retinal capillary network in vivo