HAL (Le Centre pour la Communication Scientifique Directe), May 1, 2004
ABSTRACT Scanning near-field optical microscopy (SNOM) has proven to be very powerful in terms of... more ABSTRACT Scanning near-field optical microscopy (SNOM) has proven to be very powerful in terms of both resolution and efficiency. We report on new advances of this technique using metallic tips to scatter the optical field and induce dramatic field enhancements. We also present a new technique under development using multiple nanometric beads as scattering probes dispersed in the volume of the sample, rather than using a single tip. The bead positions are determined in three dimensions (3-D) with a precision better than the diffraction limit, making possible high-resolution 3-D imaging of hollow structures in relatively transparent materials.
Eye movements are commonly seen as an obstacle to high-resolution ophthalmic imaging. In this con... more Eye 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.
The adoption of emerging imaging technologies in the medical community is often hampered if they ... more The adoption of emerging imaging technologies in the medical community is often hampered if they provide a new unfamiliar contrast that requires experience to be interpreted. Here, in order to facilitate such integration, we developed two complementary machine learning approaches, respectively based on feature engineering and on convolutional neural networks (CNN), to perform automatic diagnosis of breast biopsies using dynamic full field optical coherence tomography (D-FF-OCT) microscopy. This new technique provides fast, high resolution images of biopsies with a contrast similar to H&E histology, but without any tissue preparation and alteration. We conducted a pilot study on 51 breast biopsies, and more than 1,000 individual images, and performed standard histology to obtain each biopsy diagnosis. Using our automatic diagnosis algorithms, we obtained an accuracy above 88 % at the image level, and above 96% at the biopsy level. Finally, we proposed different strategies to narrow d...
In optical imaging, light propagation is affected by the medium inhomogeneities. Adaptive optics ... more In optical imaging, light propagation is affected by the medium inhomogeneities. Adaptive optics has been employed to compensate for sample-induced aberrations but the field-of-view is often limited to a single isoplanatic patch. Here, we propose a noninvasive approach based on the distortion matrix concept. This matrix basically connects any focusing point with the distorted part of its wave-front in reflection. Its time reversal and entropy analysis allow to correct for high-order aberrations over multiple isoplanatic areas. We demonstrate a Strehl ratio enhancement up to 2500 and a diffraction-limited resolution until a depth of ten scattering mean free paths through an opaque cornea.
Cell-resolution optical imaging methods, such as confocal microscopy and full-field optical coher... more Cell-resolution optical imaging methods, such as confocal microscopy and full-field optical coherence tomography, capture flat optical sections of the sample. If the sample is curved, the optical field sections through several sample layers, and the view of each layer is reduced. Here we present curved-field optical coherence tomography, capable of capturing optical sections of arbitrary curvature. We test the device on a challenging task of imaging the human cornea in vivo and achieve a 10 × larger viewing area comparing to the clinical state-of-the-art. This enables more precise cell and nerve counts, opening a path to improved monitoring of corneal and general health conditions (e.g., diabetes). The method is non-contact, compact, and works in a single fast shot (3.5 ms), making it readily available for use in optical research and clinical practice.
Iterative time reversal overcomes multiple scattering and breaks the imaging-depth limit in optic... more Iterative time reversal overcomes multiple scattering and breaks the imaging-depth limit in optical coherence tomography.
We developed a new endogenous approach to reveal subcellular metabolic contrast in fresh ex vivo ... more We developed a new endogenous approach to reveal subcellular metabolic contrast in fresh ex vivo tissues taking advantage of the time dependence of the full field optical coherence tomography interferometric signals. This method reveals signals linked with local activity of the endogenous scattering elements which can reveal cells where other OCT-based techniques fail or need exogenous contrast agents. We benefit from the micrometric transverse resolution of full field OCT to image intracellular features. We used this time dependence to identify different dynamics at the millisecond scale on a wide range of organs in normal or pathological conditions.
Abstract We present a full-field OCT system that measures the intensity, the spectrum, and the ph... more Abstract We present a full-field OCT system that measures the intensity, the spectrum, and the phase-retardation simultaneously. Imaging is also possible at two wavelengths. By producing multi-contrasted images with high resolution, this technology could replace ...
HAL (Le Centre pour la Communication Scientifique Directe), May 1, 2004
ABSTRACT Scanning near-field optical microscopy (SNOM) has proven to be very powerful in terms of... more ABSTRACT Scanning near-field optical microscopy (SNOM) has proven to be very powerful in terms of both resolution and efficiency. We report on new advances of this technique using metallic tips to scatter the optical field and induce dramatic field enhancements. We also present a new technique under development using multiple nanometric beads as scattering probes dispersed in the volume of the sample, rather than using a single tip. The bead positions are determined in three dimensions (3-D) with a precision better than the diffraction limit, making possible high-resolution 3-D imaging of hollow structures in relatively transparent materials.
Eye movements are commonly seen as an obstacle to high-resolution ophthalmic imaging. In this con... more Eye 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.
The adoption of emerging imaging technologies in the medical community is often hampered if they ... more The adoption of emerging imaging technologies in the medical community is often hampered if they provide a new unfamiliar contrast that requires experience to be interpreted. Here, in order to facilitate such integration, we developed two complementary machine learning approaches, respectively based on feature engineering and on convolutional neural networks (CNN), to perform automatic diagnosis of breast biopsies using dynamic full field optical coherence tomography (D-FF-OCT) microscopy. This new technique provides fast, high resolution images of biopsies with a contrast similar to H&E histology, but without any tissue preparation and alteration. We conducted a pilot study on 51 breast biopsies, and more than 1,000 individual images, and performed standard histology to obtain each biopsy diagnosis. Using our automatic diagnosis algorithms, we obtained an accuracy above 88 % at the image level, and above 96% at the biopsy level. Finally, we proposed different strategies to narrow d...
In optical imaging, light propagation is affected by the medium inhomogeneities. Adaptive optics ... more In optical imaging, light propagation is affected by the medium inhomogeneities. Adaptive optics has been employed to compensate for sample-induced aberrations but the field-of-view is often limited to a single isoplanatic patch. Here, we propose a noninvasive approach based on the distortion matrix concept. This matrix basically connects any focusing point with the distorted part of its wave-front in reflection. Its time reversal and entropy analysis allow to correct for high-order aberrations over multiple isoplanatic areas. We demonstrate a Strehl ratio enhancement up to 2500 and a diffraction-limited resolution until a depth of ten scattering mean free paths through an opaque cornea.
Cell-resolution optical imaging methods, such as confocal microscopy and full-field optical coher... more Cell-resolution optical imaging methods, such as confocal microscopy and full-field optical coherence tomography, capture flat optical sections of the sample. If the sample is curved, the optical field sections through several sample layers, and the view of each layer is reduced. Here we present curved-field optical coherence tomography, capable of capturing optical sections of arbitrary curvature. We test the device on a challenging task of imaging the human cornea in vivo and achieve a 10 × larger viewing area comparing to the clinical state-of-the-art. This enables more precise cell and nerve counts, opening a path to improved monitoring of corneal and general health conditions (e.g., diabetes). The method is non-contact, compact, and works in a single fast shot (3.5 ms), making it readily available for use in optical research and clinical practice.
Iterative time reversal overcomes multiple scattering and breaks the imaging-depth limit in optic... more Iterative time reversal overcomes multiple scattering and breaks the imaging-depth limit in optical coherence tomography.
We developed a new endogenous approach to reveal subcellular metabolic contrast in fresh ex vivo ... more We developed a new endogenous approach to reveal subcellular metabolic contrast in fresh ex vivo tissues taking advantage of the time dependence of the full field optical coherence tomography interferometric signals. This method reveals signals linked with local activity of the endogenous scattering elements which can reveal cells where other OCT-based techniques fail or need exogenous contrast agents. We benefit from the micrometric transverse resolution of full field OCT to image intracellular features. We used this time dependence to identify different dynamics at the millisecond scale on a wide range of organs in normal or pathological conditions.
Abstract We present a full-field OCT system that measures the intensity, the spectrum, and the ph... more Abstract We present a full-field OCT system that measures the intensity, the spectrum, and the phase-retardation simultaneously. Imaging is also possible at two wavelengths. By producing multi-contrasted images with high resolution, this technology could replace ...
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