scholarly journals Shot-noise limited, supercontinuum-based optical coherence tomography

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Shreesha Rao D. S. ◽  
Mikkel Jensen ◽  
Lars Grüner-Nielsen ◽  
Jesper Toft Olsen ◽  
Peter Heiduschka ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Shot Noise ◽  
Low Noise ◽  
Optical Coherence ◽  
Center Wavelength ◽  
Normal Dispersion ◽  
Oct Imaging ◽  
Commercial Sources ◽  
Multilayer Stacks ◽  
Sd Oct

AbstractWe present the first demonstration of shot-noise limited supercontinuum-based spectral domain optical coherence tomography (SD-OCT) with an axial resolution of 5.9 μm at a center wavelength of 1370 nm. Current supercontinuum-based SD-OCT systems cannot be operated in the shot-noise limited detection regime because of severe pulse-to-pulse relative intensity noise of the supercontinuum source. To overcome this disadvantage, we have developed a low-noise supercontinuum source based on an all-normal dispersion (ANDi) fiber, pumped by a femtosecond laser. The noise performance of our 90 MHz ANDi fiber-based supercontinuum source is compared to that of two commercial sources operating at 80 and 320 MHz repetition rate. We show that the low-noise of the ANDi fiber-based supercontinuum source improves the OCT images significantly in terms of both higher contrast, better sensitivity, and improved penetration. From SD-OCT imaging of skin, retina, and multilayer stacks we conclude that supercontinuum-based SD-OCT can enter the domain of shot-noise limited detection.

scholarly journals Virtual-OCT: A simulated optical coherence tomography instrument

2014 ◽  
Vol 07 (05) ◽  
pp. 1450030 ◽  
Author(s):  
Ning Liu ◽  
Cuixia Dai ◽  
Yuanhe Tang ◽  
Peng Xi
Keyword(s):  
Optical Coherence Tomography ◽  
Dynamic Range ◽  
Partial Coherence ◽  
Spectral Domain ◽  
Optical Coherence ◽  
Algorithm Optimization ◽  
Virtual Instrumentation ◽  
Parameter Evaluation ◽  
Oct Imaging ◽  
Sd Oct

We report the virtual instrumentation of both time-domain (TD) and spectral-domain (SD) optical coherence tomography (OCT) systems. With a virtual partial coherence source from either a simulated or measured spectrum, the OCT signals of both A-scan and B-scan were demonstrated. The spectrometric detector's pixel number, dynamic range, noise, as well as spectral resolution can be simulated in the virtual spectral domain (SD-OCT). The virtual-OCT system provides an environment for parameter evaluation and algorithm optimization for experimental OCT instrumentation, and promotes the understanding of OCT imaging and signal post-processing processes.

Novel method using 3-dimensional segmentation in spectral domain-optical coherence tomography imaging in the chick reveals defocus-induced regional and time-sensitive asymmetries in the choroidal thickness

2016 ◽  
Vol 33 ◽  
Author(s):  
DIANE R. NAVA ◽  
BHAVNA ANTONY ◽  
LI ZHANG ◽  
MICHAEL D. ABRÀMOFF ◽  
CHRISTINE F. WILDSOET
Keyword(s):  
Optical Coherence Tomography ◽  
High Resolution ◽  
Choroidal Thickness ◽  
Optical Coherence ◽  
3 Dimensional ◽  
Choroidal Thickening ◽  
Area Centralis ◽  
Oct Imaging ◽  
Sd Oct

AbstractStudies into the mechanisms underlying the active emmetropization process by which neonatal refractive errors are corrected, have described rapid, compensatory changes in the thickness of the choroidal layer in response to imposed optical defocus. While high frequency A-scan ultrasonography, as traditionally used to characterize such changes, offers good resolution of central (on-axis) changes, evidence of local retinal control mechanisms make it imperative that more peripheral, off-axis changes also be tracked. In this study, we used in vivo high resolution spectral domain-optical coherence tomography (SD-OCT) imaging in combination with the Iowa Reference Algorithms for 3-dimensional segmentation, to more fully characterize these changes, both spatially and temporally, in young, 7-day old chicks (n = 15), which were fitted with monocular +15 D defocusing lenses to induce choroidal thickening. With these tools, we were also able to localize the retinal area centralis, which was used as a landmark along with the ocular pectin in standardizing the location of scans and aligning them for subsequent analyses of choroidal thickness (CT) changes across time and between eyes. Values were derived for each of four quadrants, centered on the area centralis, and global CT values were also derived for all eyes. Data were compared with on-axis changes measured using ultrasonography. There were significant on-axis choroidal thickening that was detected after just one day of lens wear (∼190 µm), and regional (quadrant-related) differences in choroidal responses were also found, as well as global thickness changes 1 day after treatment. The ratio of global to on-axis choroidal thicknesses, used as an index of regional variability in responses, was also found to change significantly, reflecting the significant central changes. In summary, we demonstrated in vivo high resolution SD-OCT imaging, used in combination with segmentation algorithms, to be a viable and informative approach for characterizing regional (spatial), time-sensitive changes in CT in small animals such as the chick.

scholarly journals Total venous nature of retinal deep capillary plexus inferred by continuity of prominent middle limiting membrane sign in optical coherence tomography

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0257698
Author(s):  
Jialiang Duan ◽  
Minhao Li ◽  
Zhifeng Wu ◽  
Zhengwei Zhang
Keyword(s):  
Optical Coherence Tomography ◽  
Retinal Artery Occlusion ◽  
Artery Occlusion ◽  
Optical Coherence ◽  
Medical Centers ◽  
Vein Occlusion ◽  
Capillary Plexus ◽  
Retinal Artery ◽  
Oct Imaging ◽  
Sd Oct

This study aimed to theoretically identify the vascular nature of the deep capillary plexus (DCP) by examining patients presenting with both paracentral acute middle maculopathy (PAMM) and prominent middle limiting membrane (p-MLM) sign and p-MLM sign alone in spectral-domain optical coherence tomography (SD-OCT). A retrospective review of the medical records of patients with retinal vein or artery occlusion from two tertiary medical centers was performed. Consecutive patients with a clinical diagnosis of all categories of retinal artery occlusion (RAO) and retinal vein occlusion (RVO) (branch or central and ischemic or non-ischemic) who had undergone SD-OCT imaging from January 2015 to May 2020 were recruited and their p-MLM signs and PAMM lesions were assessed. We included 118 patients who presented with p-MLM sign with or without PAMM lesions. Amon them, 40 were female and 78 were male, with a mean age of 61.1 years. Of the 109 patients with both p-MLM sign and PAMM lesions, 23 had branch RAO, two had branch RVO, 67 had central RAO, 13 had central RVO, and four had a combination of central RAO and central RVO. All nine patients with the p-MLM sign alone had central RVO accompanied by cystoid macular edema. In all the enrolled patients, the hyperreflective lines of the p-MLM sign were continuous, regardless of the type of PAMM lesions. In conclusion, when PAMM and p-MLM sign are examined together, further proof regarding the possible complete venous nature of the vasculature of the retinal DCP might be speculated.

scholarly journals Fundus Autofluorescence and Optical Coherence Tomography Characteristics in Different Stages of Central Serous Chorioretinopathy

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Mary Ho ◽  
Stephanie H. W. Kwok ◽  
Andrew C. Y. Mak ◽  
Frank H. P. Lai ◽  
Danny S. C. Ng ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Central Serous Chorioretinopathy ◽  
Morphological Changes ◽  
Fundus Autofluorescence ◽  
Serous Retinal Detachment ◽  
Dependent Manner ◽  
Optical Coherence ◽  
Photoreceptor Layer ◽  
Oct Imaging ◽  
Sd Oct

Objective. To describe the morphological changes on fundus autofluorescence (FAF) and spectral-domain optical coherence tomography (SD-OCT) imaging at different chronicity of central serous chorioretinopathy (CSC). Methods. This cross-sectional study included patients with CSC of different chronicity. Changes in FAF scans and morphological changes on SD-OCT were evaluated and compared at different stages of CSC. Results. Sixty-nine patients were enrolled in the study, with a mean age of 52.1 ± 11.8 years. A distinct hypoautofluorescence (AF) pattern was observed at the leakage point in acute CSC (100%). The leakage site was indistinguishable in 48% of the patients with late-chronic CSC. The majority of acute CSC patients showed hyper-AF in the area of serous retinal detachment (SRD), which persisted in the early-chronic stage of CSC. In late-chronic CSC, many cases of hypo-AF (22.2%) and mixed-pattern AF (14.8%) were observed. SD-OCT revealed evolving features of retinal pigment epithelium (RPE) abnormalities in a time-dependent manner: from peaked PEDs in acute CSC to low-lying PEDs in early-chronic CSC and, eventually, flat, irregular PEDs in late-chronic CSC. The average thickness of the photoreceptor layer (inner and outer segment; IS/OS) was 79 μm in the acute group and 55.2 μm in the chronic group. The photoreceptor layer (IS/OS) height was positively associated with visual acuity ( p = 0.002 ). Conclusion. Different stages of CSC present different patterns on FAF and SD-OCT imaging. Chronicity of CSC can be estimated using specific features in these images. Photoreceptor layer (IS/OS) height acts as a good and objective predictor of visual outcomes in CSC patients.

scholarly journals Spectral Domain Optical Coherence Tomography Imaging Performance Improvement Based on Field Curvature Aberration-Corrected Spectrometer

2020 ◽  
Vol 10 (10) ◽  
pp. 3657
Author(s):  
Seung Seok Lee ◽  
Woosub Song ◽  
Eun Seo Choi
Keyword(s):  
Optical Coherence Tomography ◽  
Spectral Domain ◽  
Optical Coherence ◽  
Modulation Transfer ◽  
Field Curvature ◽  
Spatial Frequencies ◽  
Oct Imaging ◽  
Imaging Depth ◽  
Imaging Performance ◽  
Sd Oct

We designed and fabricated a telecentric f-theta imaging lens (TFL) to improve the imaging performance of spectral domain optical coherence tomography (SD-OCT). By tailoring the field curvature aberration of the TFL, the flattened focal surface was well matched to the detector plane. Simulation results showed that the spot in the focal plane fitted well within a single pixel and the modulation transfer function at high spatial frequencies showed higher values compared with those of an achromatic doublet imaging lens, which are commonly used in SD-OCT spectrometers. The spectrometer using the TFL had an axial resolution of 7.8 μm, which was similar to the theoretical value of 6.2 μm. The spectrometer was constructed so that the achromatic doublet lens was replaced by the TFL. As a result, the SD-OCT imaging depth was improved by 13% (1.85 mm) on a 10 dB basis in the roll-off curve and showed better sensitivity at the same depth. The SD-OCT images of a multi-layered tape and a human palm proved that the TFL was able to achieve deeper imaging depth and better contrast. This feature was seen very clearly in the depth profile of the image. SD-OCT imaging performance can be improved simply by changing the spectrometer’s imaging lens. By optimizing the imaging lens, deeper SD-OCT imaging can be achieved with improved sensitivity.

scholarly journals Comparison of Physiologic versus Pharmacologic Mydriasis on Anterior Chamber Angle Measurements Using Spectral Domain Optical Coherence Tomography

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Anna I. Dastiridou ◽  
Xiaojing Pan ◽  
ZhouYuan Zhang ◽  
Kenneth M. Marion ◽  
Brian A. Francis ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Anterior Chamber ◽  
Spectral Domain ◽  
Optical Coherence ◽  
Anterior Chamber Angle ◽  
Lighting Condition ◽  
Inferior Angle ◽  
Oct Imaging ◽  
Chamber Angle ◽  
Sd Oct

Purpose. To compare the effects of physiologic versus pharmacologic pupil dilation on anterior chamber angle (ACA) measurements obtained with spectral domain optical coherence tomography (SD-OCT).Methods. Forty eyes from 20 healthy, phakic individuals with open angles underwent anterior segment OCT imaging under 3 pupillary states: (1) pupil constricted under standard room lighting, (2) physiologic mydriasis in a darkened room, and (3) postpharmacologic mydriasis. Inferior angle Schwalbe’s line-angle opening distance (SL-AOD) and SL-trabecular-iris-space area (SL-TISA) were computed for each eye and pupillary condition by masked, certified Reading Center graders using customized grading software.Results. SL-AOD and SL-TISA under pupillary constriction to room light were0.87±0.31 mm and0.33±0.14 mm2, respectively; decreased to0.75±0.29 mmP<0.01and0.29±0.13 mm2  P<0.01, respectively, under physiologic mydriasis; and increased to0.90±0.38 mmP<0.01and0.34±0.17 mm2  P=0.06under pharmacologic mydriasis compared to baseline.Conclusions. Using SD-OCT imaging, pharmacologic mydriasis yielded the widest angle opening, whereas physiologic mydriasis yielded the most angle narrowing in normal individuals with open iridocorneal angles. Accounting for the state of the pupil and standardizing the lighting condition would appear to be of importance for future studies of the angle.

Blood Vessel Density Measured Using Dynamic Optical Coherence Tomography is a Tool for Wound Healers

2021 ◽  
pp. 153473462110173
Author(s):  
Rajgopal Mani ◽  
Jon Holmes ◽  
Kittipan Rerkasem ◽  
Nikolaos Papanas
Keyword(s):  
Blood Flow ◽  
Optical Coherence Tomography ◽  
Blood Vessel ◽  
Chronic Wounds ◽  
Vessel Density ◽  
Optical Coherence ◽  
Skin Microcirculation ◽  
Wound Edge ◽  
Venous Ulcers ◽  
Oct Imaging

Dynamic optical coherence tomography (D-OCT) is a relatively new technique that may be used to study the substructures in the retina, in the skin and its microcirculation. Furthermore, D-OCT is a validated method of imaging blood flow in skin microcirculation. The skin around venous and mixed arterio-venous ulcers was imaged and found to have tortuous vessels assumed to be angiogenic sprouts, and classified as dots, blobs, coils, clumps, lines, and curves. When these images were analyzed and measurements of vessel density were made, it was observed that the prevalence of coils and clumps in wound borders was significantly greater compared with those at wound centers. This reinforced the belief of inward growth of vessels from wound edge toward wound center which, in turn, reposed confidence in following the wound edge to study healing. D-OCT imaging permits the structure and the function of the microcirculation to be imaged, and vessel density measured. This offers a new vista of skin microcirculation and using it, to better understand angiogenesis in chronic wounds.

Feasibility and Clinical Utility of Ultra-Widefield–Navigated Swept-Source Optical Coherence Tomography Imaging

2021 ◽  
pp. 247412642199733
Author(s):  
Kyle D. Kovacs ◽  
M. Abdallah Mahrous ◽  
Luis Gonzalez ◽  
Benjamin E. Botsford ◽  
Tamara L. Lenis ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Clinical Utility ◽  
Clinical Decision Making ◽  
Imaging System ◽  
Imaging Modality ◽  
Case Series ◽  
Subretinal Fluid ◽  
Optical Coherence ◽  
Swept Source ◽  
Oct Imaging

Purpose: This work aims to evaluate the clinical utility and feasibility of a novel scanning laser ophthalmoscope-based navigated ultra-widefield swept-source optical coherence tomography (UWF SS-OCT) imaging system. Methods: A retrospective, single-center, consecutive case series evaluated patients between September 2019 and October 2020 with UWF SS-OCT (modified Optos P200TxE, Optos PLC) as part of routine retinal care. The logistics of image acquisition, interpretability of images captured, nature of the peripheral abnormality, and clinical utility in management decisions were recorded. Results: Eighty-two eyes from 72 patients were included. Patients were aged 59.4 ± 17.1 years (range, 8-87 years). During imaging, 4.4 series of images were obtained in 4.1 minutes, with 86.4% of the image series deemed to be diagnostic of the peripheral pathology on blinded image review. The most common pathologic findings were chorioretinal scars (18 eyes). In 31 (38%) eyes, these images were meaningful in supporting clinical decision-making with definitive findings. Diagnoses imaged included retinal detachment combined with retinoschisis, retinal hole with overlying vitreous traction and subretinal fluid, vitreous inflammation overlying a peripheral scar, Coats disease, and peripheral retinal traction in sickle cell retinopathy. Conclusions: Navigated UWF SS-OCT imaging was clinically practical and provided high-quality characterization of peripheral retinal lesions for all eyes. Images directly contributed to management plans, including laser, injection or surgical treatment, for a clinically meaningful set of patients (38%). Future studies are needed to further assess the value of this imaging modality and its role in diagnosing, monitoring, and treating peripheral lesions.

scholarly journals Optical Coherence Tomography of Peri-Ocular Skin Cancers: An Optical Biopsy

2020 ◽  
pp. 1-9
Author(s):  
Sabrina Bergeron ◽  
Bryan Arthurs ◽  
Debra-Meghan Sanft ◽  
Christina Mastromonaco ◽  
Miguel N. Burnier Jr.
Keyword(s):  
Squamous Cell Carcinoma ◽  
Optical Coherence Tomography ◽  
Basal Cell Carcinoma ◽  
Cell Carcinoma ◽  
Squamous Cell ◽  
Basal Cell ◽  
Skin Lesions ◽  
Sebaceous Carcinoma ◽  
Optical Coherence ◽  
Oct Imaging

<b><i>Introduction:</i></b> Optical coherence tomography (OCT) imaging has been used as a diagnostic tool for retinal disease for several years, and OCT apparatuses are becoming increasingly powerful. However, OCT has yet to reach its full potential in ophthalmology clinics. Alike retinal layers, it has been shown that OCT is able to generate cross-sectional images of the skin and allows visualization of skin lesions in a histopathology-like manner. <b><i>Objective:</i></b> We aim to validate OCT as an imaging modality for peri-ocular skin cancer. Through a series of cases, we highlight findings for 3 common eyelid malignancies: basal cell carcinoma, squamous cell carcinoma and sebaceous carcinoma. We propose an OCT image-based signature for basal cell carcinoma. <b><i>Methods:</i></b> This is a prospective study. Fifty-eight lesions suspicious of malignancy from 57 patients were subjected to OCT imaging prior to the surgical excision of the lesion. OCT images were analysed and scored according to previously identified OCT features. Eight representative examples are presented, highlighting the OCT patterns for each malignancy side by side to its corresponding histopathological sections. <b><i>Results:</i></b> Out of the 58 lesions analysed, 53 were malignant. A loss of the dermal-epidermal junction is observed in all malignant lesions. A strong link is observed between the presence of subepithelial hyporeflective nests on OCT and the diagnosis of basal cell carcinoma (present in 83% of cases). Conversely, lesions of epithelial origin such as squamous cell carcinoma are most often represented on OCT by acanthosis. Two supplementary cases, one basal cell carcinoma and one sebaceous carcinoma, are provided to illustrate how OCT imaging is a valuable tool in cases where clinical observations may be unusual. <b><i>Conclusions:</i></b> We provide evidence supporting the use of OCT for the evaluation of peri-ocular cancers. OCT enables visualization of the skin layers in vivo, before biopsy. Our results show that certain OCT features can contribute to include or exclude a diagnosis of basal cell carcinoma. By integrating this non-invasive imaging methodology into the routine assessment of peri-ocular skin lesions, especially in health care centres where access to specialists is limited, OCT imaging can increase clinical precision, reduce delays in patient referral and enhance patient care.

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