Last year we introduced a new Full Field Optical Transmission Tomography (FFOTT) technique that we applied to CELL studies. This interferometric technique is based on the use of the Gouy phase shift that takes place close to a microscope objective focus. We will now show results obtained in biological tissues using both a static mode (morphology) and dynamic one (metabolic contrast). In particular we have been able with our 400 $ microscope to section in tissues. We will discuss the importance of the spatial coherence of the illumination and compare the results with those obtained with Full Field OCT.
This work focuses on making a novel ophthalmic Optical transmission tomography (OTT) device at the lowest possible cost and size. OTT prototype demonstrates images from all the layers in anterior human eye, while also benefiting from the cost-efficient design solutions: common-path architecture, mass-market CMOS cameras, latest USB data transfer standards, Arduino electronic control, etc. Notably, we show that the large degree of noise degradation (due to the use of low-cost optics/cameras) can be corrected with denoised neural networks. Moreover, the model trained on one type of camera (global shutter) can be used to improve signal in another camera (rolling shutter).
Our past contribution was to introduce a Gouy phase Full Field Optical Transmission technique applied to detect and characterise nanoparticles such as virus, vesicles and nano plastics in terms of size and refractive index. More recently we have adapted this interferometric approach to achieve optical tomography in cells and tissues. We will show improvements in sensitivity and resolution obtained with 20 nm virus as well as with biological tissues using both a static mode (morphology) and dynamic one (metabolic contrast). We discuss the importance of the illumination spatial coherence and compare the results with those obtained with Full Field OCT.
We have used Full Field OCT (FFOCT) in its static (morphology contrast) and dynamic (metabolic contrast) modes mostly for tissue diagnosis. Last year we introduced a new way of optical sectioning 3D structures. For this purpose, we use Full Field Optical Transmission Tomography (FFOTT) a Gouy phase shift interference approach that takes place close to the focus of a microscope objective. We will show striking differences between FFOCT and FFOTT associated to the scattering anisotropy of tissue structures. Moreover, we will pay a particular attention to the requirements of FFOTT in term of spatial coherence and to the speckle appearance for both techniques.
In this conference proceeding we illustrate an early concept of a new anterior eye imaging method—optical transmission tomography (OTT). Thanks to the 20× larger viewing area, OTT can enhance the precision of corneal cell/nerve density biomarkers compared to clinical specular and confocal microscopies. This holds promise for improving the selection of candidates for refractive surgery and for reducing the incidence rates of post-surgical dry eye, endothelial decompensation as well as other common complications.
We propose a robust deep learning algorithm for denoising TD FF-OCT in vivo images. This algorithm does not require any clean images in its training. It specifically detects and removes residual fringes as well as other types of noise present in in vivo eye images. It can also be trained using ex vivo images as well as simulated patterns for fringe removal. Testing is performed on in vivo corneal images, but can be expanded to any TD FF-OCT images. The obtained outputs are thus easier to interpret and exploit in clinical practice as well as other image processing tasks.
In this work, we implement a pupil conjugated DM-based wavefront sensorless approach in our FFOCT setup. Given the high DM stroke and precision, as well as the Zernike mode-based wavefront optimization using the high-speed DONE algorithm, we showed that higher resolution can be achieved in foveal imaging, as well as obtaining an improved SNR when imaging photoreceptors and NFL when compared to our previous work. Thanks to this SNR improvement, we were able to visualize inner retinal features not previously observed in FFOCT.
Recently, time-domain full-field OCT (TD-FF-OCT) evolved into the tool for in vivo eye exploration. Particular benefits of TD-FF-OCT include cellular resolution, rapid en face imaging without scanning artifacts, reduced sensitivity to optical aberrations, and non-contact performance. One limitation of TD-FF-OCT is related to its ’time-domain’ nature – tomographic image is reconstructed from several consecutive (in time) camera frames. The sample should stay static, otherwise the signal is reduced. In this work we present TD-FF-OCT that can capture in vivo human corneal images in a single camera shot. This became possible by using a combination of optical/image processing and deep learning techniques.
We have recently (BOE July 2022) proposed an interferometric approach called full-field transmission tomography (FFOTT) based on the use of the Gouy phase shift that manifests at the focus of microscope objectives. Forward scattering of cellular structures larger than 100 nm being much greater than backscattering (used in OCT) performances constraints of the imaging system are strongly relaxed and setups using cheap microscopes and a smartphones become possible. Note that good quality 100X, NA+1.25 objectives are available for less than $100.
We show cells and tissues images through their morphological or metabolic contrasts modified by a chemical or biological environments.
We developed a novel combined SD-OCT + TD-FF-OCT device that provides cell-resolution view of TD-FF-OCT without compromising SD-OCT performance. SD-OCT gives global view for eye exploration and FF-OCT shows cell-detail in the central region of the OCT scan. Eye imaging is fast enough to be part of the routine clinical exam (10 min/patient). Four patients with different eye pathologies were imaged. FF-OCT resolved: striae (stromal mechanical folds), guttata, loss of endothelial cells and stromal cuts following the surgery. Additionally, we could access the trabecular meshwork region of the eye and obtain the first images of meshwork fibers at micron resolution.
We present the first clinical uses of time-domain FF-OCT in Anterior eye. Four patients with different eye pathologies (keratoconus, Fuch's endothelial dystrophy, age-related changes, post-PRK surgery) were imaged as part of the routine clinical examination (10 min per patient). FF-OCT resolved micron–size pathologies: striae (mechanical folds of corneal stroma), guttata (excrescences in Descemet's membrane), loss of endothelial cells and stromal cuts following the surgery. High resolution (1.7 µm) makes FF-OCT a promising tool for diagnosis of diseases at earlier stages than was possible before and their effective treatment with medication instead of surgery.
Eye movements are commonly seen as an obstacle to high-resolution ophthalmic imaging. In this context we study the natural axial movements of 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 different image retrieval schemes (2-phase and 4-phase) and different exposure times (3.5 ms, 10 ms, 20 ms).
KEYWORDS: Optical coherence tomography, In vivo imaging, Real time imaging, Angiography, Eye, Cornea, Confocal microscopy, Microscopes, Imaging systems, Blood circulation
We present a filtering procedure based on singular value decomposition to remove artifacts arising from sample motion during dynamic full field OCT acquisitions. The presented method succeeded in removing artifacts created by environmental noise from data acquired in a clinical setting, including in vivo data. Moreover, we report on a new method based on using the cumulative sum to compute dynamic images from raw signals, leading to a higher signal to noise ratio, and thus enabling dynamic imaging deeper in tissues.
KEYWORDS: In vivo imaging, Retinal scanning, Optical coherence tomography, Wavefronts, 3D image processing, Adaptive optics, Stereoscopy, 3D metrology, Sensors, Eyeglasses
Full-Field Optical Coherence Tomography (FF-OCT) offers aberration independent resolution. This inherent property makes FF-OCT a promising imaging modality for 3D high-resolution retinal imaging. Nevertheless, ocular aberrations affect signal reduction, imposing Adaptive Optics. Here we investigate the best strategy to compensate for ocular aberrations in our FF-OCT setup, in terms of wavefront measurement and correction. The use of wavefront sensorless approach based on the FF-OCT signal level is investigated. Moreover, a strategy of static wavefront correction in a non-conjugated pupil plane and next to the eye’s pupil, just like spectacles, favoring a compact and non-complex AO design, is also investigated. Additionally, the use of wavefront corrector devices such as an adaptive liquid lens (correcting to defocus and astigmatism) and multi-actuator adaptive lenses (correcting up to the 4th order Zernike polynomial) are evaluated. Finally, we expect the implementation of one or a combination of the studied strategies into our FF-OCT setup to lead to the first in-vivo retinal images obtained using AO-assisted FF-OCT, for different retinal layers with enhanced SNR and a 3D high-resolution.
Despite obvious improvements in visualization of the in vivo cornea through the faster imaging speeds and higher axial resolutions, cellular imaging stays unresolvable task for OCT, as en face viewing with a high lateral resolution is required. The latter is possible with FFOCT, a method that relies on a camera, moderate numerical aperture (NA) objectives and an incoherent light source to provide en face images with a micrometer-level resolution. Recently, we for the first time demonstrated the ability of FFOCT to capture images from the in vivo human cornea1. In the current paper we present an extensive study of appearance of healthy in vivo human corneas under FFOCT examination. En face corneal images with a micrometer-level resolution were obtained from the three healthy subjects. For each subject it was possible to acquire images through the entire corneal depth and visualize the epithelium structures, Bowman’s layer, sub-basal nerve plexus (SNP) fibers, anterior, middle and posterior stroma, endothelial cells with nuclei. Dimensions and densities of the structures visible with FFOCT, are in agreement with those seen by other cornea imaging methods. Cellular-level details in the images obtained together with the relatively large field-of-view (FOV) and contactless way of imaging make this device a promising candidate for becoming a new tool in ophthalmological diagnostics.
According to the World Health Organization (WHO), corneal diseases alongside with cataract and retinal diseases are major causes of blindness worldwide. For the 95.5% of corneal blindness cases, prevention or rehabilitation could have been possible without negative consequences for vision, provided that disease is diagnosed early. However, diagnostics at the early stage requires cellular-level resolution, which is not achieved with routinely used Slit-lamp and OCT instruments. Confocal microscopy allows examination of the cornea at a resolution approaching histological detail, however requires contact with a patient’s eye. The recently developed full-field OCT technique, in which 2D en face tangential optical slices are directly recorded on a camera, was successfully applied for ex vivo eye imaging. However, in vivo human eye imaging has not been demonstrated yet. Here we present a novel non-contact full-field OCT system, which is capable of imaging in air and, therefore, shows potential for in vivo cornea imaging in patients. The first cellular-level resolution ex vivo images of cornea, obtained in a completely non-contact way, were demonstrated. We were able to scan through the entire cornea (400 µm) and resolve epithelium, Bowman’s layer, stroma and endothelium. FFOCT images of the human cornea in vivo were obtained for the first time. The epithelium structures and stromal keratocyte cells were distinguishable. Both ex vivo and in vivo images were acquired with a large (1.26 mm x 1.26 mm) field of view. Cellular details in obtained images make this device a promising candidate for realization of high-resolution in vivo cornea imaging.
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