Point-scanning OCT systems often use a pair of sequential, single-axis galvanometer scanners to acquire volumetric data. This can introduce uncertainty in the beam position at the ocular pupil plane, an effect known as beam wander or pupil wobble, which can distort the resulting images. We propose a new approach to characterize and optically correct the pupil wobble with an additional scanning mirror placed anti-conjugate to the pupil plane. We evaluate this method by modeling the pattern of pupil wobble present in a research OCT system both theoretically and experimentally, and correcting for it with the proposed method.
We demonstrate in vivo imaging with a robotically aligned OCT (RAOCT) platform that incorporates interchangeable imaging modules with integrated pupil tracking cameras. Our OCT imaging platform consisted of a fixed scan head mounted to a cooperative robot and interchangeable cornea and retinal imaging modules with their own integrated pupil cameras. We validated pupil tracking in both imaging modules (<11 µm accuracy, <±4.5 µm precision). We utilized this platform for in vivo imaging of multiple target tissues of interest in a single imaging session. This flexible design enables the ability to develop new imaging modules for new robotically aligned applications.
Slit lamps are a common ophthalmic instrument used for examining the ocular anterior segment by projecting a rectangular beam of light onto the eye. Conventional slit lamp configurations require the patient to stabilize themselves using a chin rest and forehead band limiting access to patients who are mobility impaired. We developed a slit lamp module for a robotic arm to allow for autonomous imaging of a slit on the eye of individuals without physical head stabilization at a working distance of 125 mm. Here we describe the optical performance of the custom slit lamp module and present autonomous aligned imaging of a corneal phantom mounted in a mannequin head.
Real-time volumetric microscope-integrated OCT (MIOCT) visualization of ophthalmic surgeries is limited by the narrow field of view of OCT relative to the movement of the surgical instruments, requiring extensive manual repositioning by a trained operator. We developed a computer vision system for instrument tracking that utilizes a microscope video camera and a deep-learning object detector trained on synthetic data, which consisted of 3D rendered models of surgical instruments alongside an eye model. This system was then tested in a clinical MIOCT platform, providing high fidelity, video-rate (>40 Hz) object tracking of a cataract surgery instrument over a model eye phantom.
Optical coherence tomography (OCT) is a critical imaging technique for diagnosing diseases of the eye. Whole eye OCT acquires images of the cornea and retina simultaneously, which is believed to have diagnostic value for certain pathologies. However, patient motion during acquisition can corrupt spatial relationships in the final image. Additionally, OCT for the anterior and posterior segments of the eye require distinct instrumentation. Here we present a whole eye OCT system with polarization multiplexed independent channels allowing for simultaneous imaging of the anterior and posterior segments. Previously developed pupil tracking algorithms were integrated in our novel system to compensate for patient motion.
OCT angiography (OCTA) is an extension of optical coherence tomography (OCT) that identifies motion contrast from moving red blood cells to map retinal vasculature in vivo. We propose to use robotically-aligned optical coherence tomography (RAOCT) to acquire OCTA data at multiple illumination angles on the retina in order to reduce shadowing artifacts and enhance vessel visualization. Using RAOCT, retinal volumes were automatically acquired from consented subjects at various pupil entry positions and processed to generate en face OCTA images. These OCTA images were compared to identify areas of changed visualization and reduced shadowing artifact when varying illumination angle.
We present a flexible optical coherence tomography (OCT) imaging platform that allows for interchangeable imaging modules for specific target tissues of interest while meeting the requirements for robotically aligned OCT including integrated pupil tracking cameras. Our OCT imaging platform consisted of a fixed scan head (analogous to an SLR camera body) mounted to the robot and interchangeable anterior chamber (AC) and retinal imaging modules with their own integrated pupil cameras. We validated our system in both phantom and ex vivo porcine eyes. This flexible design enables the ability to develop new imaging modules for new robotically aligned applications.
Ophthalmic optical coherence tomography (OCT) has achieved remarkable clinical success but remains sequestered in ophthalmology specialty offices. Recently introduced robotic OCT systems seek to expand patient access but fall short of their full potential due to significant imaging workspace and motion planning restrictions. Here, we present a next-generation robotic OCT system capable of imaging in any configuration that is mechanically reachable. This system overcomes prior restrictions by eliminating fixed-base tracking components, extending robot reach, and planning alignment in six degrees of freedom. With this robotic system, we show repeatable subject imaging independent of posture under widely varying head orientations.
Optical coherence tomography (OCT) revolutionized diagnostics in ophthalmology.
Traditional OCT assumes static subjects and produces artifacts during motion.
Robotically-aligned OCT mitigates these artifacts via hardware motion compensation.
However, hardware imperfections result in residual motion error.
Here we present a digital motion correction approach where we utilize synchronized sensing of the pupil and scanner components to measure the state of the imaging process over time.
We subsequently map each A-scan to its corresponding location in the volume given sensor data during its acquisition.
We demonstrate our correction in human imaging and observed 68% reduction in maximum residual axial error.
Unlike conventional ophthalmic OCT, robotically aligning OCT (RAOCT) removes the requirement for close patient/operator proximity and enables remote patient imaging by autonomously aligning itself to the patient while the operator is physically elsewhere. We report kilometer-scale distance between OCT operator and patient and the first robotically aligned OCT angiography images. We acquired remote volumetric RAOCT retinal images from healthy and diseased eyes at the Duke Eye Center on both room-to-room (10m between imager and subject) and between clinic sites(>10km between imager and subject). This can serve as a foundation for socially distanced or telehealth retinal OCT without physically present technicians.
KEYWORDS: Optical coherence tomography, Visualization, Retinal scanning, Software development, Retina, In vivo imaging, Image visualization, Control systems, Clinical research
Optical coherence tomography (OCT) allows for in vivo imaging of the individual layers of the retina, but conventional methods do not differentiate the outer nuclear layer (ONL) from Henle’s fiber layer (HFL). We have developed a robotically aligned OCT (RAOCT) system capable of automatically acquiring volumes at multiple pupil entry positions to reconstruct a retinal volume that distinguishes the HFL from the ONL. We utilized the RAOCT system to acquire such volumes from consented subjects, and used mosaicking to combine them into complete retinal volumes that show enhanced contrast in the HFL on all sides of the fovea.
Optical coherence tomography (OCT) has revolutionized diagnostics in ophthalmology. Montaging of multiple OCT volumes allows for wide field retinal volumes. However, OCT requires an operator to align the scanner and requires patient cooperation to fixate on multiple targets, one for each volume in the montage. We have developed a robot-mounted OCT scanner that automatically aligns with the subjects’ eye by compensating motion and gaze error at multiple entry angles, allowing acquisition of volumes from multiple regions of interest without chin or fore rest stabilization or a fixation target. We demonstrate our system by montaging a retinal volume acquired from a free-standing subject.
Optical coherence tomography (OCT) has revolutionized diagnostics in ophthalmology. Traditionally, OCT requires an operator and patient cooperation to compensate refraction error as well as align the scanner with the subject’s eye. We have developed a robot-mounted OCT scanner that automatically focuses and aligns with the subjects’ eye by compensating motion, gaze, and refraction error. The system utilizes a combination of face and pupil tracking cameras to align while focusing through digital control of a tunable lens. We demonstrate our system by self-aligning with human eyes subject to physiological motion and gaze change as well as correcting defocus of a phantom eye.
The physical distancing requirements necessary to prevent spread of the novel coronavirus, SARS-CoV-2, requires a change in approach for clinical ophthalmic imaging. Conventional optical coherence tomography (OCT) systems require patients to position themselves in chin/forehead rests for stabilization with the system operator in close proximity. We developed a robotically aligning OCT (RAOCT) system that provides volumetric retinal images encompassing both the optic nerve head and fovea. Our RAOCT system self aligned to subjects’ eyes (seated, no contact with restraints), acquired OCT images of both normal and diseased retinas, all with allowing the operator behind a barrier >2 m from the subjects.
Optical coherence tomography (OCT) has revolutionized diagnostics in ophthalmology. However, OCT traditionally requires an operator and patient cooperation to align a scanner with the subject’s eye and image a specific location of the retina. We have developed a robot-mounted OCT scanner that automatically aligns with the subjects’ eye by compensating motion and gaze. In addition to using face and pupil tracking feedback to align the scanner, the system uses gaze feedback to track a retinal region of interest, such as the fovea. We demonstrate our system by tracking the fovea of human eyes subject to physiological motion and gaze change.
Optical coherence tomography (OCT) allows for non-contact, high resolution, volumetric imaging of biological tissue and has become an indispensable ophthalmic imaging technique. However, conventional, commercial OCT systems require a cooperative, sitting patient typically stabilized by a head and/or chin rests. Additionally, current clinical systems are designed for imaging either the anterior or posterior segment of the eye exclusively. While these limitations are not severe in the ophthalmic clinic, they do limit the use of OCT in other more challenging medical environments where novel “whole eye” imaging could provide value, such as in the military theater or emergency department (ED). One solution to eliminate the need for a patient to sit upright and be stabilized during imaging would be a hand-held probe positioned and stabilized by the photographer or physician. Here we describe a hand-held OCT probe for simultaneous imaging of the anterior chamber (13.3 mm diameter field-of-view) and posterior segment (40° as measured from the pupil nodal point) simultaneously. The use of polarization multiplexing allows for two independent imaging channels which enable a wide posterior segment field-of-view and the ability to control the posterior segment path length and focal depth independently from the anterior chamber channel. Additionally, the probe was designed for a relatively compact form factor.
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