Resolution Optical Coherence Tomography Research Articles

Two Different Nuclear Mitochondrial DNA Mutations Associated with Retinal Abnormalities

Purpose: To report the posterior pole imaging characteristics of two patients with pathogenic nuclear mitochondrial mutations. Methods: Case reports Results: The first case, a 61-year-old patient, initially diagnosed with age-related macular degeneration, exhibited focal hyperpigmentation and increased autofluorescence in the parafoveal macula, along with geographic atrophy and mild optic nerve pallor. Optical coherence tomography (OCT) showed ellipsoid zone (EZ) attenuation, hyperreflective foci colocalizing to the hyperpigmentation, subretinal deposits, and hypertransmission defects. He was found to have a pathogenic mutation of MFN2, a gene defect associated with Charcot-Marie-Tooth disease. The second case, a 65-year-old patient presented with loss of central vision with pallor of the optic nerve. OCT imaging showed widespread loss of the interdigitation zone and EZ attenuation peripheral to the foveal region. There was thinning of the ganglion cell and nerve fiber layers. A pathogenic OPA1 mutation, the leading cause of autosomal dominant optic atrophy, was found. Both MFN2 and OPA1 produce proteins integral in mitochondrial fusion. Conclusions: The findings of these cases suggest ocular examinations may be helpful in evaluating patients with nuclear mitochondrial mutations using the near microscopic resolution of OCT. Retinal imaging may highlight structural abnormalities related to mitochondrial problems and allows direct imaging of the EZ, a layer dominated by mitochondria and a place where direct imaging of mitochondria is possible, in vivo.

Synthetic Fourier Domain Optical Coherence Tomography

A novel approach for image formation in optical coherence tomography (OCT) and microscopy is presented. The depth resolution of OCT, including recently developed nanosensitive OCT (nsOCT), is limited by the spectral bandwidth of the light source used for illumination. The proposed approach, synthetic OCT (synOCT), permits label‐free, depth‐resolved quantitative visualization of the subwavelength‐sized structures with nanosensitivity. Using synOCT it is possible to estimate the contribution of axial Fourier components of an object's structure in image formation at each small volume within the image. The size of such areas can be smaller than the resolution limit of the imaging system that provides potential for super‐resolution imaging. Visualization of the subwavelength periodic structures and quantitative visualization of the subwavelength internal structures of highly scattering biological samples, within voxels smaller than resolution limit of the imaging system, are demonstrated. In contrast to nsOCT, the trade‐off between spectral and spatial resolution is removed which results in dramatic improvement of both spectral and spatial resolution in synOCT relative to nsOCT.

Volume electron microscopy reveals human retinal mitochondria that align with reflective bands in optical coherence tomography [Invited

Mitochondria are candidate reflectivity signal sources in optical coherence tomography (OCT) retinal imaging. Here, we use deep-learning-assisted volume electron microscopy of human retina and in vivo imaging to map mitochondria networks in the outer plexiform layer (OPL), where photoreceptors synapse with second-order interneurons. We observed alternating layers of high and low mitochondrial abundance in the anatomical OPL and adjacent inner nuclear layer (INL). Subcellular resolution OCT imaging of human eyes revealed multiple reflective bands that matched the corresponding INL and combined OPL sublayers. Data linking specific mitochondria to defined bands in OCT may help improve clinical diagnosis and the evaluation of mitochondria-targeting therapies.

Self super-resolution of optical coherence tomography images based on deep learning.

As a medical imaging modality, many researches have been devoted to improving the resolution of optical coherence tomography (OCT). We developed a deep-learning based OCT self super-resolution (OCT-SSR) pipeline to improve the axial resolution of OCT images based on the high-resolution and low-resolution spectral data collected by the OCT system. In this pipeline, the enhanced super-resolution asymmetric generative adversarial networks were built to improve the network outputs without increasing the complexity. The feasibility and effectiveness of the approach were demonstrated by experimental results on the images of the biological samples collected by the home-made spectral-domain OCT and swept-source OCT systems. More importantly, we found the sidelobes in the original images can be obviously suppressed while improving the resolution based on the OCT-SSR method, which can help to reduce pseudo-signal in OCT imaging when non-Gaussian spectra light source is used. We believe that the OCT-SSR method has broad prospects in breaking the limitation of the source bandwidth on the axial resolution of the OCT system.

Efficacy and safety of cysteamine-isobionicamide complex in postinflammatory hyperpigmentation: A 16-week, randomized, double-blinded, vehicle-controlled trial

Abstract Background: Postinflammatory hyperpigmentation (PIH) is a prevalent acquired hyperpigmentation disorder with significant psychosocial implications. Cysteamine has demonstrated notable efficacy and safety in treating hyperpigmentation disorders. This study conducted a double-blinded, randomized clinical trial to evaluate the efficacy and safety of the cysteamine-isobionicamide complex in managing PIH. Objectives: The objective was to assess the cysteamine-isobionicamide complex’s efficacy for PIH treatment through comprehensive clinical and imaging evaluations. Methods: Forty patients with PIH were recruited at a tertiary medical center from 2021 to 2022 and randomized into the cysteamine-isobionicamide complex treatment group and placebo-vehicle control group. Dermatological assessments, investigator and patient global assessments, and quality of life scores were collected at baseline, week 4, week 8, and week 16. Quantitative evaluation of skin type and lesion pigmentation was performed with the Mexameter®, VISIA skin analyzer, and cellular resolution optical coherence tomography (OCT). Results: At week 8, the cysteamine-isobionicamide complex treatment group exhibited marked advancement in dermatological assessments, melasma area and severity index (MASI), total postacne hyperpigmentation index, and life quality score compared with the placebo-vehicle control group. Furthermore, melanin index and erythema index scores from Mexameter® and VISIA analysis exhibited significant improvement for brown spots at week 16. Cellular resolution OCT imaging revealed decreased melanosome capping and fewer hyperreflective melanophages. Conclusion: This study demonstrated the clinical effectiveness and safety of the cysteamine-isobionicamide complex through comprehensive dermatological assessments, imaging techniques, and patient-reported outcomes. The complex emerges as a promising therapeutic option for PIH, offering potential relief to individuals affected by this hyperpigmentation disorder.

Scattering angle resolved optical coherence tomography measures morphological changes in Bacillus subtilis colonies.

An unmet need is recognized for early detection and diagnosis of neurological diseases. Many psychological markers emerge years after disease onset. Mitochondrial dysfunction and corresponding neurodegeneration occur before onset of large-scale cell and tissue pathology. Early detection of subcellular morphology changes could serve as a beacon for early detection of neurological diseases. This study is on bacterial colonies, Bacillus subtilis, which are similar in size to mitochondria. This study investigates whether morphological changes can be detected in Bacillus subtilis using scattering angle resolved optical coherence tomography (SAR-OCT). The SAR-OCT was applied to detect scattering angle distribution changes in Bacillus subtilis. The rod-to-coccus shape transition of the bacteria was imaged, and the backscattering angle was analyzed by recording the distribution of the ratio of low- to medium angle scattering (L/M ratio). Bacillus orientation at different locations in colonies was analytically modeled and compared with SAR-OCT results. Significant differences in the distribution of backscattering angle were observed in Bacillus subtilis transitioning from rod-to-coccus shapes. In Bacillus subtilis, the -parameter of the Burr distribution of the SAR-OCT-derived L/M ratio was significantly smaller in coccus compared with rod-shaped bacteria. SAR-OCT-derived L/M ratio varied with bacterial position in the colony and is consistent with predicted orientations from previous studies. Study results support the potential of utilizing SAR-OCT to detect bacterial morphological changes.

SD-OCT guided analysis of retinal nerve fibre layer in ammetropes in central India

The retinal nerve fibre layer is a most crucial indicator of optic nerve damage in glaucoma as it advances visual field loss. Thickness of the RNFL can be measured using high resolution OCT. We conducted this study to evaluate the alterations in retinal nerve fibre layer thickness measured by SD- OCT in ametropes and to find various factors affecting RNFL thickness.: Study of retinal nerve fibre layer thickness (RNFL) by Optical Coherence Tomography (OCT) in ametropes in tertiary care hospital of central India.Hospital based prospective observational study included 300 eyes of 150 participants. Visiting ophthalmology outpatient department Gandhi medical college and fulfilling the inclusion and exclusion criteria.: Patients were divided into five groups of 60 eyes each on the basis of refractive status of eyes into emetropia, low hypermetropia, moderate hypermetropia, low mypopia and moderate mypopia. Subjects were subjected to OCT scan and RNFL thickness was measured. All groups were evaluated and observations were noted and results were analysed. To find the association between degree of ametropia and RNFL thickness one way ANOVA test was used. Correlation between axial length and RNFL was assesed by pearson correlation coefficient. p value <0.05 was considered as significant.: RNFL thickness in different groups followed ISNT rule with inferior quadrant showing the greatest thickness followed by the superior, nasal and temporal quadrants. The average RNFL thickness in emmetropics, Low hyperopic, Moderate hyperopic, Low myopic, Moderate myopic was 111.90μm, 110.58 μm, 114.59 μm, 103.33 μm, 93.33 μm respectively, wheras average axial length was 23.85mm, 22.36mm, 21.33mm, 24.72mm, 25.63mm.: With the help of OCT, we can differentiate the changes in RNFL thickness in various refractive errors. So, the refractive status of the eye should be kept in mind before making any ocular diagnosis in which the RNFL is a diagnostic criteria.

From Macro to Micro: Comparison of Imaging Techniques to Detect Vascular Network Formation in Left Ventricle Decellularized Extracellular Matrix Hydrogels.

Background: Angiogenesis is a crucial process in physiological maintenance and tissue regeneration. To understand the contribution of angiogenesis, it is essential to replicate this process in an environment that reproduces the biochemical and physical properties which are largely governed by the extracellular matrix (ECM). We investigated vascularization in cardiac left ventricular ECM hydrogels to mimic post-myocardial repair. We set out to assess and compare different destructive and non-destructive methods, optical as well as non-optical, to visualize angiogenesis and associated matrix remodeling in myocardial ECM hydrogels. Methods: A total of 100,000, 300,000, and 600,000 Human Pulmonary Microvascular Endothelial Cells (HPMEC) were seeded in left ventricular cardiac ECM hydrogel in 48-well plates. After 1, 7, and 14 days of culture, the HPMEC were imaged by inverted fluorescence microscopy and 3D confocal laser scanning microscopy (Zeiss Cell Discoverer 7). In addition, cell-seeded ECM hydrogels were scanned by optical coherence tomography (OCT). Fixed and paraffin-embedded gels were thin-sectioned and assessed for ECM components via H&E, picrosirius red histochemical staining, and immunostaining for collagen type I. ImageJ-based densitometry was used to quantify vascular-like networks and GraphPad was used for statistical analyses. Results: Qualitative analyses were realized through fluoromicrographs obtained by the confocal laser scanning microscope which allowed us to visualize the extensive vascular-like networks that readily appeared at all seeding densities. Quantification of networks was only possible using fluoromicrographs from inverted microscopy. These showed that, after three days, the number of master junctions was seeding density-dependent. The resolution of optical coherence tomography was too low to distinguish between signals caused by the ECM and cells or networks, yet it did show that gels, irrespective of cells, were heterogeneous. Interestingly, (immuno)histochemistry could clearly distinguish between the cast cardiac-derived matrix and newly deposited ECM in the hydrogels. The H&E staining corroborated the presence of vascular-like network structures, albeit that sectioning inevitably led to the loss of 3D structure. Conclusions: Except for OCT, all methods had complementary merit and generated qualitative and quantitative data that allowed us to understand vascular network formation in organ-derived ECM hydrogels.

Microcrystalline diamond film evaluation by spectroscopic optical coherence tomography

This study has focused on the microcrystalline diamond film (MCD) thickness evaluation. For this purpose, optical coherence tomography (OCT) enhanced by spectroscopic analysis has been used as a method of choice. The average thickness of the tested layer was about 1.5 µm, which is below the standard 2-point OCT resolution. In this case, the usefulness of the spectroscopic analysis was confirmed for the evaluation of the thickness changes in the submicrometer range. Full Text: PDF ReferencesM.D. Drory, J.W. Hutchinson, "Diamond Coating of Titanium Alloys", Science, 263 (1994). CrossRef J. Wang, J. Zhou, H.Y. Long, Y.N. Xie, X.W. Zhang, H. Luo, Z.J. Deng, Q. Wei, Z.M. Yu, J. Zhang, Z.G. Tang, "Tribological, anti-corrosive properties and biocompatibility of the micro- and nano-crystalline diamond coated Ti6Al4V", Surf. Coat. Technol., 258 (2014). CrossRef P.A. Nistor, P.W. May, F. Tamagnini, A.D. Randall, M.A. Caldwell, "Long-term culture of pluripotent stem-cell-derived human neurons on diamond – A substrate for neurodegeneration research and therapy", Biomaterials, 61 (2015). CrossRef C.A. Love, R.B. Cook, T.J. Harvey, P.A. Dearnley, R.J.K. Wood, "Diamond like carbon coatings for potential application in biological implants—a review", Tribol. Int., 63 (2013). CrossRef P. Strąkowska, R. Beutner, M. Gnyba, A. Zielinski, D. Scharnweber, "Electrochemically assisted deposition of hydroxyapatite on Ti6Al4V substrates covered by CVD diamond films — Coating characterization and first cell biological results", Materials Science and Engineering: C, 59 (2016). CrossRef T.S. Ho, P. Yeh, C.C. Tsai, K.Y. Hsu, S.L. Huang., "Spectroscopic measurement of absorptive thin films by Spectral-Domain Optical Coherence Tomography", Opt. Express 22, 5 (2014). CrossRef N. Bosschaart, T.G. van Leeuwen, M.C.G. Aalders, D.J. Faber, "Quantitative comparison of analysis methods for spectroscopic optical coherence tomography", Biomedical Opt. Express 4, 11 (2013). CrossRef F.E Robles, C. Wilson, G. Grant, A. Wax, "Molecular imaging true-colour spectroscopic optical coherence tomography", Nat. Photonics 5, 12 (2011). CrossRef A.F. Fercher, W. Drexler, C.K. Hitzenberger, T. Lasser, "Optical coherence tomography - principles and applications", Rep. Prog. Phys. 66, 239 (2003). CrossRef A.M. Kamińska, M.R. Strąkowski, J. Pluciński, "Spectroscopic Optical Coherence Tomography for Thin Layer and Foil Measurements", Sensors 20, 19, (2020). CrossRef M. Kraszewski, M. Strąkowski, J. Pluciński, B.B. Kosmowski, "Spectral measurement of birefringence using particle swarm optimization analysis", Appl. Opt. 54, 1 (2015). CrossRef

High-depth-resolution imaging of dispersive samples using quantum optical coherence tomography.

Quantum optical coherence tomography (QOCT) is a promising approach to overcome the degradation of the resolution in optical coherence tomography (OCT) due to dispersion. Here, we report on an experimental demonstration of QOCT imaging in the high-resolution regime. We achieved a depth resolution of 2.5 μm, which is the highest value for QOCT imaging, to the best of our knowledge. We show that the QOCT image of a dispersive material remains clear whereas the OCT image is drastically degraded.

Enhanced spectral-domain optical coherence tomography (SD-OCT) using in situ ultrasonic virtual tunable optical waveguides.

A conventional optical lens can enhance lateral resolution in optical coherence tomography (OCT) by focusing the input light onto the sample. However, the typical Gaussian beam profile of such a lens will impose a tradeoff between the depth of focus (DOF) and the lateral resolution. The lateral resolution is often compromised to achieve a mm-scale DOF. We have experimentally shown that using a cascade system of an ultrasonic virtual tunable optical waveguide (UVTOW) and a short focal-length lens can provide a large DOF without severely compromising the lateral resolution compared to an external lens with the same effective focal length. In addition, leveraging the reconfigurability of UVTOW, we show that the focal length of the cascade system can be tuned without the need for mechanical translation of the optical lens. We compare the performance of the cascade system with a conventional optical lens to demonstrate enhanced DOF without compromising the lateral resolution as well as reconfigurability of UVTOW for OCT imaging.

Riehl's Melanosis: A Multimodality, In Vivo, Real-Time Skin Imaging Study with Cellular Resolution Optical Coherence Tomography and Advanced Skin Diagnosis System in a Tertiary Medical Center.

Background: Riehl’s melanosis is a psychologically devastating hyperpigmentary disorder that typically occurs on the face and neck. The study of Riehl’s melanosis is limited due to its rarity, variable morphology, and lack of noninvasive diagnostic tools. Recent advances in skin imaging analysis and diagnostic systems improve diagnostic accuracy and enable the noninvasive, real-time evaluation of pigmentary disease. A comprehensive study of Riehl’s melanosis clinical morphology with multimodality and in vivo skin imaging systems has yet to be reported. Objectives: To investigate the clinical features and in vivo advanced skin imaging findings of Riehl’s melanosis. Methods: We retrospectively investigated the clinical characteristics, dermoscopic, and histopathological features of Riehl’s melanosis. We further utilized multimodality skin imaging analysis systems, including a cellular resolution optical coherence tomography (OCT) and new skin diagnosis system, to investigate the features of Riehl’s melanosis. In addition, we compared OCT findings with histopathological features and clinical assessment. Results: We evaluated 30 patients with Riehl’s melanosis at a tertiary medical center from 2010 to 2022. The average age was 47.7 ± 12.3 (mean ± SD) years, predominantly female patients (female: n = 23; male: n = 7). Cellular resolution OCT imaging from lesion skin shows increased melanocyte capping, disrupted basement membrane, telangiectatic blood vessels, and melanophages in the dermis. The advanced skin diagnosis system captured subclinical erythema of the skin, highlighting the inflammatory nature of the disease. The results correlated well with histopathological findings. Limitations: This is a single-center, cross-sectional study. Conclusions: We highlight the features of Riehl’s melanosis through a novel cellular resolution OCT and photographic skin diagnosis system. A multimodality skin diagnosis system can serve as a real-time, in vivo, noninvasive method for evaluating pigmentary disorders.

Spatial resolution in optical coherence elastography of bounded media.

Dynamic optical coherence elastography (OCE) tracks mechanical wave propagation in the subsurface region of tissue to image its shear modulus. For bulk shear waves, the lateral resolution of the reconstructed modulus map (i.e., elastographic resolution) can approach that of optical coherence tomography (OCT), typically a few tens of microns. Here we perform comprehensive numerical simulations and acoustic micro-tapping OCE experiments to show that for the typical situation of guided wave propagation in bounded media, such as cornea, the elastographic resolution cannot reach the OCT resolution and is mainly defined by the thickness of the bounded tissue layer. We considered the excitation of both broadband and quasi-harmonic guided waves in a bounded, isotropic medium. Leveraging the properties of broadband pulses, a robust method for modulus reconstruction with minimum artifacts at interfaces is demonstrated. In contrast, tissue bounding creates large instabilities in the phase of harmonic waves, leading to serious artifacts in modulus reconstructions.

Fibrotic plaques in heart transplanted patients and their association with insulin resistance syndrome and Lp(a)

BackgroundAngiographic evidence of cardiac allograft vasculopathy (CAVangio) is a major limiting factor to survival after heart transplantation (HTx). Prevention of CAVangio is therefore most relevant. Whether modifiable risk factors could be targeted for the prevention of fibrotic plaques, that are common and related to CAVangio, is not clear. Methods and resultsIn a cohort of 74 consecutive HTx patients (median post-transplant interval 9.2 [4.1–15.5] years), we used the high resolution of optical coherence tomography (OCT) to quantify angulation parameters (maximal and mean arc) and plaque load (mean arc*relative plaque length) of fibrotic plaques. Mean arc was defined as the mean value of all angulation measurements per patient. We assessed the association between cardiovascular risk factors and OCT findings. Linear regression analysis showed a significant association of TG/HDL-c with mean fibrotic arc (12.7 [3.9–21.5], p = 0.006) and fibrotic plaque load (2298 [617–3979], p = 0.009) after adjustment for recipient age and sex. We used the median value of fibrotic plaque load to define high fibrotic plaque load. In binary logistic regression analysis, TG/HDL-c (odds ratio [OR] 1.81 with 95% CI [1.09–3.03], p = 0.02) and Lp(a) (OR 1.02 [1.00–1.05], p = 0.02) were associated with high fibrotic plaque load. Multivariable logistic regression analysis confirmed Lp(a) as significant predictor of high fibrotic plaque load (OR 1.03 [1.01–1.05], p = 0.02). ConclusionTG/HDL-c ratio, a surrogate of insulin resistance syndrome, and Lp(a) were significantly associated with fibrotic plaque in HTx patients. Insulin resistance syndrome and Lp(a) might therefore represent additional targets for CAV prevention.

Dynamic microscopic optical coherence tomography to visualize the morphological and functional micro-anatomy of the airways.

In the imaging of airway tissue, optical coherence tomography (OCT) provides cross-sectional images of tissue structures, shows cilia movement and mucus secretion, but does not provide sufficient contrast to differentiate individual cells. By using fast sequences of microscopic resolution OCT (mOCT) images, OCT can use small signal fluctuations to overcome lack in contrast and speckle noise. In this way, OCT visualizes airway morphology on a cellular level and allows the tracking of the dynamic behavior of immune cells, as well as mucus transport and secretion. Here, we demonstrate that mOCT, by using temporal tissue fluctuation as contrast (dynamic mOCT), provides the possibility to study physiological and pathological tissue processes in vivo.

Assessment of sex- and age-dependency of risk factors for intimal hyperplasia in heart transplant patients using the high resolution of optical coherence tomography

BackgroundIntimal hyperplasia in cardiac allograft vasculopathy (CAVIH) is limiting survival in pediatric and adult patients after heart transplantation (HTx). Analysis of risk factors for CAVIH using the high resolution of intracoronary optical coherence tomography (OCT) is scarce, particularly in children, and recommendations for CAV prevention are largely based on data obtained in adults. Whether the predictive value of risk factors is age- or sex-dependent is unknown. Methods and resultsWe used OCT to test the age- and sex-dependency of established risk factors regarding pathological CAVIH in a cohort of 102 pediatric and adult HTx patients (35% <18 years, 69% male). Modifiable parameters such as lipid values, and the diagnoses of dyslipidemia and diabetes showed age- and sex-dependent differences. Regarding CAVIH, receiver-operating characteristic analysis showed that LDL-c was relevant only in female patients (area under the curve [AUC] 0.79, p = 0.007), and total cholesterol in female (AUC 0.81; p = 0.004) and pediatric patients (AUC 0.73, p < 0.05). The association of dyslipidemia with CAVIH was stronger in adult (odds ratio [OR] 6.33) than in pediatric patients (OR 5.00) and in women (OR 6.00) than in men (OR 4.57). Diabetes was associated with CAVIH only in women (OR 11.25). ConclusionIn our cohort, modifiable risk factors, particularly total cholesterol and dyslipidemia, had a different impact depending on age and sex. Targeting risk factors in selected patients might improve individual CAVIH prevention.

ADC-Net: An Open-Source Deep Learning Network for Automated Dispersion Compensation in Optical Coherence Tomography.

Chromatic dispersion is a common problem to degrade the system resolution in optical coherence tomography (OCT). This study is to develop a deep learning network for automated dispersion compensation (ADC-Net) in OCT. The ADC-Net is based on a modified UNet architecture which employs an encoder-decoder pipeline. The input section encompasses partially compensated OCT B-scans with individual retinal layers optimized. Corresponding output is a fully compensated OCT B-scan with all retinal layers optimized. Two numeric parameters, i.e., peak signal to noise ratio (PSNR) and structural similarity index metric computed at multiple scales (MS-SSIM), were used for objective assessment of the ADC-Net performance and optimal values of 29.95 ± 2.52 dB and 0.97 ± 0.014 were obtained respectively. Comparative analysis of training models, including single, three, five, seven and nine input channels were implemented. The mode with five-input channels was observed to be optimal for ADC-Net training to achieve robust dispersion compensation in OCT.

Repeatability and Comparison of Corneal Tomography in Mild to Severe Keratoconus Between the Anterior Segment OCT MS-39 and Pentacam HR.

To detect keratoconus progression, accuracy of tomographic measurements is crucial. The impoved axial resolution of optical coherence tomography (OCT) compared to Scheimpflug photography serves as the motivation to investigate and compare the repeatability of the anterior segment OCT MS-39 (CSO) to Pentacam HR (Oculus Optikgeräte GmbH) in patients with keratoconus. One hundred twenty-three eyes of 123 patients with keratoconus were enrolled and subdivided in four groups by maximum keratometry (Kmax): Kmax < 48.00 diopters (D), Kmax of 48.00 to 53.01 D, Kmax of 53.00 to 58.00 D, and Kmax > 58.00 D. Three consecutive measurements per eye were acquired with the MS-39 and compared to the Pentacam HR. Kmax, thinnest pachymetry, anterior asphericity, and posterior elevation data were compared. Within-subject standard deviation (Sw), coefficient of variation (CoV), test-retest repeatability (TRT), and the intra-class correlation (ICC) were calculated and evaluated. Bland-Altman plots were also analyzed. The Pentacam HR measures significantly higher Kmax values than the MS-39, with a more pronounced difference for severe cases of keratoconus (0.57 D for all cases; 1.88 D for cases with Kmax > 58.00 D). Thinnest pachymetry was approximately 5 µm thinner when measured by the Pentacam HR than the MS-39, independently of keratoconus stage. A further progressed keratoconus stage was significantly associated with increased measurement errors and resulted in worse repeatability (Kmax < 48.00 D: Sw = 0.18 D, TRT = 0.50 D, CoV = 0.39%, ICC = 0.989; Kmax > 58.00 D: Sw = 0.53 D, TRT = 1.48 D, CoV = 0.90%, ICC = 0.984). The behavior was similar for other tomographic parameters. The Pentacam HR and the MS-39 have an overall good agreement for keratoconus; however, the Pentacam HR measures steeper and thinner than the MS-39. The association between the magnitude of topographic and tomographic parameters and their measurement errors suggests that the diagnosis of keratoconus disease progression should be based on the stage and the test-retest repeatability rather than on a fixed value (eg, 1.00 D). [J Refract Surg. 2022;38(4):250-255.].

Comparative Study of Conventional and Ultrahigh-resolution Optical Coherence Tomography Imaging in Esophageal Neoplasia

Early diagnosis of esophageal cancer can be enhanced by the application of optical coherence tomography (OCT) to gastrointestinal endoscopy. One of the most salient examples is the use of OCT to augment the detection of dysplasia during Barrett's esophagus (BE) surveillance, the established precursor to esophageal adenocarcinoma (EAC). 1 Reid BJ Li X Galipeau PC et al. Barrett’s oesophagus and oesophageal adenocarcinoma: time for a new synthesis. Nat Rev Cancer. 2010; 10: 87-101https://doi.org/10.1038/nrc2773 Crossref PubMed Scopus (303) Google Scholar , 2 Pohl H Welch HG The role of overdiagnosis and reclassification in the marked increase of esophageal adenocarcinoma incidence. J Natl Cancer Inst. 2005; 97: 142-146https://doi.org/10.1093/jnci/dji024 Crossref PubMed Scopus (1069) Google Scholar A previously commercially available balloon-based imaging catheter system, also known as volumetric laser endomicroscopy (VLE), was designed to provide circumferential esophageal imaging at the time of endoscopy. The VLE system uses a 1300 nm wavelength-swept laser and provides images with an axial resolution of 7 µm up to a depth of 3 mm. VLE is capable of resolving microarchitectural features associated with early neoplasia in BE including irregular glandular morphology and increased surface signal intensity. 3 Leggett CL Gorospe EC Chan DK et al. Comparative diagnostic performance of volumetric laser endomicroscopy and confocal laser endomicroscopy in the detection of dysplasia associated with Barrett’s esophagus. Gastrointest Endosc. 2016; 83: 880-888.e2https://doi.org/10.1016/j.gie.2015.08.050 Abstract Full Text Full Text PDF PubMed Scopus (86) Google Scholar Scoring systems that incorporate these features are associated with a sensitivity of 76-83% and specificity of 71-79% in the diagnosis of BE neoplasia. 3 Leggett CL Gorospe EC Chan DK et al. Comparative diagnostic performance of volumetric laser endomicroscopy and confocal laser endomicroscopy in the detection of dysplasia associated with Barrett’s esophagus. Gastrointest Endosc. 2016; 83: 880-888.e2https://doi.org/10.1016/j.gie.2015.08.050 Abstract Full Text Full Text PDF PubMed Scopus (86) Google Scholar , 4 Swager AF Tearney GJ Leggett CL et al. Identification of volumetric laser endomicroscopy features predictive for early neoplasia in Barrett’s esophagus using high-quality histological correlation. Gastrointest Endosc. 2017; 85: 918-926.e7https://doi.org/10.1016/j.gie.2016.09.012 Abstract Full Text Full Text PDF PubMed Scopus (52) Google Scholar Similarly, esophageal OCT has been used in the diagnosis and staging of squamous cell carcinoma (ESCC) where layer effacement predicts the depth of invasion. 5 Trindade AJ Benias PC Inamdar S et al. Use of volumetric laser endomicroscopy for determining candidates for endoscopic therapy in superficial esophageal squamous cell carcinoma. United European Gastroenterol J. 2018; 6: 838-845https://doi.org/10.1177/2050640618761701 Crossref PubMed Scopus (5) Google Scholar In the last decade, ultra-high resolution (UHR) OCT systems that operate at 800 nm and achieve an axial resolution closer to 2.5 µm have been developed. Our group previously described a super-achromatic OCT capsule designed for UHR esophageal imaging. 6 Li K Liang W Mavadia-Shukla J et al. Super-achromatic optical coherence tomography capsule for ultrahigh-resolution imaging of esophagus. J Biophotonics. 2019; 12e201800205https://doi.org/10.1002/jbio.201800205 Crossref PubMed Scopus (16) Google Scholar In the present study, we compare the imaging capability of UHR OCT to VLE in distinguishing microarchitectural features associated with esophageal neoplasia by imaging ex vivo esophageal resection specimens obtained from patients undergoing clinical endoscopy.

Extraction of phase-based optoretinograms (ORG) from serial B-scans acquired over tens of seconds by mouse retinal raster scanning OCT system.

Several specialized retinal optical coherence tomography (OCT) acquisition and processing methods have been recently developed to allow in vivo probing of light-evoked photoreceptors function, focusing on measurements in individual photoreceptors (rods and cones). Recent OCT investigations in humans and experimental animals have shown that the outer segments in dark-adapted rods and cones elongate in response to the visible optical stimuli that bleach fractions of their visual photopigment. We have previously successfully contributed to these developments by implementing OCT intensity-based "optoretinograms" (ORG), the paradigm of using near-infrared OCT (NIR OCT) to measure bleaching-induced back-scattering and/or elongation changes of photoreceptors in the eye in vivo. In parallel, several groups have successfully implemented phase-based ORGs, mainly in human studies, exploiting changes in the phases of back-scattered light. This allowed more sensitive observations of tiny alterations of photoreceptors structures. Applications of the phase-based ORG have been implemented primarily in high speed and cellular resolution AO-OCT systems that can visualize photoreceptor mosaic, allowing phase measurements of path length changes in outer segments of individual photoreceptors. The phase-based ORG in standard resolution OCT systems is much more demanding to implement and has not been explored extensively. This manuscript describes our efforts to implement a phase analysis framework to retinal images acquired with a standard resolution and raster scanning OCT system, which offers much lower phase stability than line-field or full-field OCT detection schemes due to the relatively slower acquisition speed. Our initial results showcase the successful extraction of phase-based ORG signal from the B-scans acquired at ∼100 Hz rate and its favorable comparison with intensity-based ORG signal extracted from the same data sets. We implemented the calculation of phase-based ORG signals using Knox-Thompson paths and modified signal recovery by adding decorrelation weights. The phase-sensitive ORG signal analysis developed here for mouse retinal raster scanning OCT systems could be in principle extended to clinical retinal raster scanning OCT systems, potentially opening doors for clinically friendly ORG probing.