10 research outputs found

    Comparative analysis of full-field OCT and optical transmission tomography

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    This work compares two tomographic imaging technologies, time-domain full-field optical coherence tomography (FFOCT) working in reflection and optical transmission tomography (OTT), using a new optical setup that combines both. We show that, due to forward-scattering properties, the axial sectioning and contrast in OTT can be optimized by tuning illumination. The influence of sample scattering and thickness are discussed. We illustrate the comparison of the two methods in static (morphology) and dynamic (metabolic contrast) regimes using cell cultures, tissues and entire organisms emphasizing the advantages of both approaches

    Full-field optical coherence tomography for non-contact cellular-level resolution in vivo human cornea imaging

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    Ce projet de thèse vise à créer un système optique pour l'imagerie à haute résolution sans contact de la cornée humaine in vivo. Pour y parvenir, le système de tomographie par cohérence optique plein champ travaillant dans le domaine temporel ex vivo par contact (FFOCT) a été transformé en un dispositif d'imagerie in vivo sans contact et a été appliqué pour la première fois à l'œil humain. La FFOCT a permis d’acquérir des images de la cornée, du limbe, de la sclère et du film lacrymal sur des yeux humains, révélant des cellules et des nerfs, pouvant être quantifiés sur un champ de vision millimétrique, bien au-delà des capacités de la microscopie confocale et de la tomographie par cohérence optique (OCT) conventionnelle. Le flux sanguin et la dynamique du film lacrymal ont pu être suivis directement et quantifiés. De plus, la FFOCT a été combinée à un OCT spectral pour effectuer un suivi des mouvements axiaux de l'œil en temps réel et une correction de la défocalisation. Ce dernier ajout a permis l’imagerie et l’affichage FFOCT en temps réel, ce qui ouvre la voie à la mise en œuvre future de dispositifs dans pour la recherche que pour la pratique clinique. Le transfert de FFOCT du laboratoire à l’hôpital est en outre stimulé par plusieurs solutions qui sont proposées dans le manuscrit, dans le but de réduire la complexité instrumentale. Enfin, un dispositif FFOCT apparenté a été appliqué à l’imagerie rétinienne humaine in vivo, révélant des photorécepteurs.This PhD project aimed to create an optical system for non-contact cellular resolution imaging of the human cornea in vivo. To achieve that, the contact ex vivo time-domain full-field optical coherence tomography (FFOCT) system was transformed into a non-contact in vivo imaging device and was for the first time applied to the human eye. FFOCT acquired images from the entire human cornea, limbus, sclera and tear film, revealing cells and nerves, which could be quantified over a millimetric field-of-view, beyond the capability of confocal microscopy and conventional optical coherence tomography (OCT). Blood flow and tear film dynamics could be directly followed and quantified. Furthermore, FFOCT was combined with a conventional OCT to perform real-time axial eye tracking and defocusing correction. The latter enabled real-time FFOCT imaging and display, which opens a path for future device implementation in clinical research and practice. Bench to bedside transfer of FFOCT is further stimulated by several solutions proposed in the manuscript, aiming to reduce the instrumentational complexity. Finally, a related FFOCT device was applied to imaging in vivo human retina, revealing the photoreceptors

    Tomographie optique cohérente pour l’imagerie in vivo de la cornée

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    This PhD project aimed to create an optical system for non-contact cellular resolution imaging of the human cornea in vivo. To achieve that, the contact ex vivo time-domain full-field optical coherence tomography (FFOCT) system was transformed into a non-contact in vivo imaging device and was for the first time applied to the human eye. FFOCT acquired images from the entire human cornea, limbus, sclera and tear film, revealing cells and nerves, which could be quantified over a millimetric field-of-view, beyond the capability of confocal microscopy and conventional optical coherence tomography (OCT). Blood flow and tear film dynamics could be directly followed and quantified. Furthermore, FFOCT was combined with a conventional OCT to perform real-time axial eye tracking and defocusing correction. The latter enabled real-time FFOCT imaging and display, which opens a path for future device implementation in clinical research and practice. Bench to bedside transfer of FFOCT is further stimulated by several solutions proposed in the manuscript, aiming to reduce the instrumentational complexity. Finally, a related FFOCT device was applied to imaging in vivo human retina, revealing the photoreceptors.Ce projet de thèse vise à créer un système optique pour l'imagerie à haute résolution sans contact de la cornée humaine in vivo. Pour y parvenir, le système de tomographie par cohérence optique plein champ travaillant dans le domaine temporel ex vivo par contact (FFOCT) a été transformé en un dispositif d'imagerie in vivo sans contact et a été appliqué pour la première fois à l'œil humain. La FFOCT a permis d’acquérir des images de la cornée, du limbe, de la sclère et du film lacrymal sur des yeux humains, révélant des cellules et des nerfs, pouvant être quantifiés sur un champ de vision millimétrique, bien au-delà des capacités de la microscopie confocale et de la tomographie par cohérence optique (OCT) conventionnelle. Le flux sanguin et la dynamique du film lacrymal ont pu être suivis directement et quantifiés. De plus, la FFOCT a été combinée à un OCT spectral pour effectuer un suivi des mouvements axiaux de l'œil en temps réel et une correction de la défocalisation. Ce dernier ajout a permis l’imagerie et l’affichage FFOCT en temps réel, ce qui ouvre la voie à la mise en œuvre future de dispositifs dans pour la recherche que pour la pratique clinique. Le transfert de FFOCT du laboratoire à l’hôpital est en outre stimulé par plusieurs solutions qui sont proposées dans le manuscrit, dans le but de réduire la complexité instrumentale. Enfin, un dispositif FFOCT apparenté a été appliqué à l’imagerie rétinienne humaine in vivo, révélant des photorécepteurs

    Time-domain full-field optical coherence tomography (TD-FF-OCT) in ophthalmic imaging

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    Ocular imaging plays an irreplaceable role in the evaluation of eye diseases. Developing cellular-resolution ophthalmic imaging technique for more accurate and effective diagnosis and pathogenesis analysis of ocular diseases is a hot topic in the cross-cutting areas of ophthalmology and imaging. Currently, ocular imaging with traditional optical coherence tomography (OCT) is limited in lateral resolution and thus can hardly resolve cellular structures. Conventional OCT technology obtains ultra-high resolution at the expense of a certain imaging range and cannot achieve full field of view imaging. In the early years, Time-domain full-field OCT (TD-FF-OCT) has been mainly used for ex vivo ophthalmic tissue studies, limited by the low speed and low full-well capacity of existing two-dimensional (2D) cameras. The recent improvements in system design opened new imaging possibilities for in vivo applications thanks to its distinctive optical properties of TD-FF-OCT such as a spatial resolution almost insensitive to aberrations, and the possibility to control the curvature of the optical slice. This review also attempts to look at the future directions of TD-FF-OCT evolution, for example, the potential transfer of the functional-imaging dynamic TD-FF-OCT from the ex vivo into in vivo use and its expected benefit in basic and clinical ophthalmic research. Through non-invasive, wide-field, and cellular-resolution imaging, TD-FF-OCT has great potential to be the next-generation imaging modality to improve our understanding of human eye physiology and pathology

    In vivo high-resolution human retinal imaging with wavefront-correctionless full-field OCT

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    International audienceAs the lateral resolution of full-field optical coherence tomography (FFOCT) with spatially incoherent illumination has been shown to be insensitive to aberrations, we demonstrate high-resolution en face FFOCT retinal imaging without wavefront correction in the human eye in vivo for the first time, to our knowledge. A combination of FFOCT with spectral-domain OCT (SDOCT) is applied for real-time matching of the optical path lengths (OPLs) of FFOCT. Through the real-time cross-sectional SDOCT images, the OPL of the FFOCT reference arm is matched with different retinal layers in the FFOCT sample arm. Thus, diffraction-limited FFOCT images of multiple retinal layers are acquired at both the near periphery and the fovea. The en face FFOCT retinal images reveal information about various structures, such as the nerve fiber orientation, the blood vessel distribution, and the photoreceptor mosaic

    Real-time non-contact cellular imaging and angiography of human cornea and limbus with common-path full-field/SD OCT

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    International audienceIn today's clinics, a cell-resolution view of the cornea can be achieved only with a confocal microscope (IVCM) in contact with the eye. Here, we present a common-path full-field/spectral-domain OCT microscope (FF/SD OCT), which enables cell-detail imaging of the entire ocular surface in humans (central and peripheral cornea, limbus, sclera, tear film) without contact and in real-time. Real-time performance is achieved through rapid axial eye tracking and simultaneous defocusing correction. Images contain cells and nerves, which can be quantified over a millimetric field-of-view, beyond the capability of IVCM and conventional OCT. In the limbus, palisades of Vogt, vessels, and blood flow can be resolved with high contrast without contrast agent injection. The fast imaging speed of 275 frames/s (0.6 billion pixels/s) allows direct monitoring of blood flow dynamics, enabling creation of high-resolution velocity maps. Tear flow velocity and evaporation time can be measured without fluorescein administration

    Optical phase modulation by natural eye movements: application to time-domain FF-OCT image retrieval

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    International audienceEye movements are commonly seen as an obstacle to high-resolution ophthalmic imaging. In this context we study the natural axial movements of the in vivo human eye and show that they can be used to modulate the optical phase and retrieve tomographic images via time-domain full-field optical coherence tomography (TD-FF-OCT). This approach opens a path to a simplified ophthalmic TD-FF-OCT device, operating without the usual piezo motor-camera synchronization. The device demonstrates in vivo human corneal images under the different image retrieval schemes (2-phase and 4-phase) and different exposure times (3.5 ms, 10 ms, 20 ms). Data on eye movements, acquired with a spectral-domain OCT with axial eye tracking (180 B-scans/s), are used to study the influence of ocular motion on the probability of capturing high-signal tomographic images without phase washout. The optimal combinations of camera acquisition speed and amplitude of piezo modulation are proposed and discussed

    In vivo high resolution human corneal imaging using full-field optical coherence tomography

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    International audienceWe present the first full-field optical coherence tomography (FFOCT) device capable of in vivo imaging of the human cornea. We obtained images of the epithelial structures, Bowman's layer, sub-basal nerve plexus (SNP), anterior and posterior stromal keratocytes, stromal nerves, Descemet's membrane and endothelial cells with visible nuclei. Images were acquired with a high lateral resolution of 1.7 µm and relatively large field-of-view of 1.26 mm x 1.26 mm – a combination, which, to the best of our knowledge, has not been possible with other in vivo human eye imaging methods. The latter together with a contactless operation, make FFOCT a promising candidate for becoming a new tool in ophthalmic diagnostics

    Probing dynamic processes in the eye at multiple spatial and temporal scales with multimodal full field OCT

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    International audienceWe describe recent technological progress in multimodal en face full-field optical coherence tomography that has allowed detection of slow and fast dynamic processes in the eye. We show that by combining static, dynamic and fluorescence contrasts we can achieve label-free high-resolution imaging of the retina and anterior eye with temporal resolution from milliseconds to several hours, allowing us to probe biological activity at subcellular scales inside 3D bulk tissue. Our setups combine high lateral resolution over a large field of view with acquisition at several hundreds of frames per second which make it a promising tool for clinical applications and biomedical studies. Its contactless and non-destructive nature is shown to be effective for both following in vitro sample evolution over long periods of time and for imaging of the human eye in vivo
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