We introduced an improved iteration of a panoramic retinal (panretinal) handheld swept-source OCT angiography (OCTA) imaging system with an 800kHz VCSEL light source. The advanced system successfully achieved a remarkable 140° field of view (FOV, visual angle measured from the pupil plane), enabling comprehensive imaging coverage from the posterior pole to the peripheral retina in a single capture.
KEYWORDS: Optical coherence tomography, Imaging systems, Cornea, Signal processing, Retina, Cameras, Signal detection, Real time imaging, In vivo imaging, Sensors
A line-field optical coherence tomography (LFOCT) application is implemented for real-time in vivo corneal and retinal imaging. In contrast to other described systems of LFOCT that use single-shot high-speed cameras, we describe the first results utilizing a camera with continuous high-speed data transfer and display. The system is based on a previously published design using a center wavelength of 840nm and a bandwidth of 50nm. The system’s B-frame and en-face display speed reaches up to 5000 frames per second corresponding to 2,500,000 A-lines. A visible light camera is used to detect the interferometric signal to reduce costs and improve optomechanical integration. Balancing the sensitivity vs. acquisition speed allows continuous high data transfer and processing rates and simplifies the implementation as a bedside system. Higher frame rates are important for scan positioning on non-compliant subjects such as infants and children.
Our research investigates retinal pigmentary abnormalities in Retinitis Pigmentosa (RP) patients using ultra-wide-field high-speed Polarization Diversity Optical Coherence Tomography (PD-OCT) in a clinical setting. To account for the retinal curvature in the wide field of view, adaptive kernel-based spatial averaging is employed for Degree-of-Polarization-Uniformity (DOPU) contrast formation with two complex OCT signals from two orthogonal polarization channels. 20 patients diagnosed with RP were recruited for this study and imaged with PD-OCT. Then, the melanin distribution images from PD-OCT were compared to standard multimodal imaging techniques, including intensity-based OCT, fundus photography, and short-wavelength fundus autofluorescence images. Wide-field PD-OCT imaging technique presented in this study was capable of precisely assessing melanin-related changes in RP over a large field of view and monitoring the disease progression. As a next step, we are investigating the correlation of specific genetic mutations in RP patients with specific clinical presentations and disease progression rates as assessed by the quantitative measurements in PD-OCT. The clinical findings will be presented during the conference.
We demonstrated a contact handheld ultra-widefield (UWF) swept-source OCT (SS-OCT) imaging system with a 400 kHz VCSEL light source that achieved an unprecedented 140° field of view (FOV), which was capable to extend the imaging area from the posterior pole to peripheral retina in a single shot. The contact imaging approach provided faster and more efficient retinal imaging and improve image quality. To the best of our knowledge, this prototype achieved the widest FOV among all the retinal OCT research prototypes and commercial systems in desktop and portable format.
KEYWORDS: Signal processing, Optical coherence tomography, Beam diameter, Light sources and illumination, Imaging systems, High speed cameras, Medical device development
A real-time high-speed line-field optical coherence tomography (LFOCT) configuration at 5,000 B-frames or 2,500,000 A-lines per second for clinical applications is described. The development of the LFOCT technology has experienced increasing interest despite the challenge of achieving sufficient sensitivity and resolution due to crosstalk. Publications of research systems usually apply expensive infrared cameras to improve image quality. The costs, complexity, and lack of real-time data transfer of dedicated highspeed IR cameras make it challenging to employ LFOCT for a more comprehensive application range. We demonstrate using a comparatively low-cost, high-speed camera for real-time data transfer and image display in conjunction with a light source at a center wavelength of 840 nm and a bandwidth of 50 nm. Although the camera and available sample power limits the sensitivity (75 dB), we can demonstrate imaging on a human fingertip (in vivo) and the cornea of a rabbit eye. Further development of the system will focus on compensating for the camera's limited sensitivity and improving resolution to target clinical in vivo imaging such as ophthalmic applications.
Thinning of the outer nuclear layer (ONL) is an important pathological feature and possible biomarker of age-related macular degeneration (AMD). The demarcation of the ONL and Henle’s fiber layer (HFL) is visually unattainable with standard optical coherence tomography (OCT) imaging. In this work, we built a volumetric directional OCT prototype which constitutes two optical scanners in the sample arm that synchronously scan the imaging beam on the pupil and retina. The imaging beam’s entry positions and incident angles on the pupil and retina respectively are precisely controlled and optimally maintained to generate sufficient contrast of the HFL over the entire macular volume.
We demonstrated a handheld swept-source optical coherence tomography (OCT) imaging system with a 400 kHz vertical-cavity surface-emitting laser (VCSEL) light source, a non-contact approach, and an unprecedented 105° field of view (FOV) that was capable of obtaining images from the posterior pole to peripheral retina in a single shot. A spiral scanning pattern allowing real-time visualization was also implemented here to improve the sampling efficiency. To the best of our knowledge, this is the widest FOV for a portable non-contact OCT retinal imaging system to date. Improvements to the FOV allow detection of peripheral pathology and aid better understanding of the role of peripheral pathology in retinal diseases.
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