Abstract
.We present a technique to reduce speckle in visible-light optical coherence tomography (vis-OCT) that preserves fine structural details and is robust against sample motion. Specifically, we locally modulate B-scans orthogonally to their axis of acquisition. Such modulation enables acquisition of uncorrelated speckle patterns from similar anatomical locations, which can be averaged to reduce speckle. To verify the effectiveness of speckle reduction, we performed in-vivo retinal imaging using modulated raster and circular scans in both mice and humans. We compared speckle-reduced vis-OCT images with the images acquired with unmodulated B-scans from the same anatomical locations. We compared contrast-to-noise ratio (CNR) and equivalent number of looks (ENL) to quantify the image quality enhancement. Speckle-reduced images showed up to a 2.35-dB improvement in CNR and up to a 3.1-fold improvement in ENL with more discernable anatomical features using eight modulated A-line averages at a 25-kHz A-line rate.
Highlights
Optical coherence tomography (OCT) is a scattering-based imaging technology that acquires high-resolution threedimensional images of biological samples in vivo.[1]
We showed that our orthogonal modulation protocol significantly reduced the speckle for both raster and circular scans in visible-light optical coherence tomography (vis-OCT) without additional hardware
We showed that speckle-reduced vis-OCT imaging does not require additional training for a clinical photographer to operate, allowing smooth clinical translation
Summary
Optical coherence tomography (OCT) is a scattering-based imaging technology that acquires high-resolution threedimensional images of biological samples in vivo.[1] Following its initial report in 1991, OCT has become the “gold standard” for noninvasive retinal imaging Today, it is an essential technology in labs and clinics for studying and managing a wide variety of retinal diseases.[2] Advances in optoelectronics in the past 25 years has led to improved resolution, signal-to-noise ratio (SNR), and imaging field of view (FOV) in OCT.[3] speckle, an image artifact caused by the self-interference of coherent light at random phases, remains a significant source of reduced image quality.[4] This is of particular salience in retinal imaging, where speckle noise can obscure fine structures in the outer retina, such as the retinal pigment epithelium (RPE) and Bruch’s membrane (BM). Minute pathological changes in these structures may be strongly associated with the progressions of several retinal diseases, including macular degeneration[5] and central serous retinopathy (CSR).[6]
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