Resolution Optical Coherence Tomography Research Articles

Reference-Based OCT Angiogram Super-Resolution With Learnable Texture Generation.

Optical coherence tomography angiography (OCTA) can visualize retinal microvasculature and is important to qualitatively and quantitatively identify potential biomarkers for different retinal diseases. However, the resolution of optical coherence tomography (OCT) angiograms inevitably decreases when increasing the field-of-view (FOV) given a fixed acquisition time. To address this issue, we propose a novel reference-based super-resolution (RefSR) framework to preserve the resolution of the OCT angiograms while increasing the scanning area. Specifically, textures from the normal RefSR pipeline are used to train a learnable texture generator (LTG), which is designed to generate textures according to the input. The key difference between the proposed method and traditional RefSR models is that the textures used during inference are generated by the LTG instead of being searched from a single reference (Ref) image. Since the LTG is optimized throughout the whole training process, the available texture space is significantly enlarged and no longer limited to a single Ref image, but extends to all textures contained in the training samples. Moreover, our proposed LTGNet does not require an Ref image at the inference phase, thereby becoming invulnerable to the selection of the Ref image. Both experimental and visual results show that LTGNet has competitive performance and robustness over state-of-the-art methods, indicating good reliability and promise in real-life deployment. The source code is available at https://github.com/RYY0722/LTGNet.

Artificial intelligence for geographic atrophy: pearls and pitfalls.

This review aims to address the recent advances of artificial intelligence (AI) in the context of clinical management of geographic atrophy (GA), a vision-impairing late-stage manifestation of age-related macular degeneration (AMD). Recent literature shows substantial advancements in the development of AI systems to segment GA lesions on multimodal retinal images, including color fundus photography (CFP), fundus autofluorescence (FAF) and optical coherence tomography (OCT), providing innovative solutions to screening and early diagnosis. Especially, the high resolution and 3D-nature of OCT has provided an optimal source of data for the training and validation of novel algorithms. The use of AI to measure progression in the context of newly approved GA therapies, has shown that AI methods may soon be indispensable for patient management. To date, while many AI models have been reported on, their implementation in the real-world has only just started. The aim is to make the benefits of AI-based personalized treatment accessible and far-reaching. The most recent advances (pearls) and challenges (pitfalls) associated with AI methods and their clinical implementation in the context of GA will be discussed.

O-PRESS: Boosting OCT axial resolution with Prior guidance, Recurrence, and Equivariant Self-Supervision

Optical coherence tomography (OCT) is a noninvasive technology that enables real-time imaging of tissue microanatomies. The axial resolution of OCT is intrinsically constrained by the spectral bandwidth of the employed light source while maintaining a fixed center wavelength for a specific application. Physically extending this bandwidth faces strong limitations and requires a substantial cost. We present a novel computational approach, called as O-PRESS, for boosting the axial resolution of OCT with Prior guidance, a Recurrent mechanism, and Equivariant Self-Supervision. Diverging from conventional deconvolution methods that rely on physical models or data-driven techniques, our method seamlessly integrates OCT modeling and deep learning, enabling us to achieve real-time axial-resolution enhancement exclusively from measurements without a need for paired images. Our approach solves two primary tasks of resolution enhancement and noise reduction with one treatment. Both tasks are executed in a self-supervised manner, with equivariance imaging and free space priors guiding their respective processes. Experimental evaluations, encompassing both quantitative metrics and visual assessments, consistently verify the efficacy and superiority of our approach, which exhibits performance on par with fully supervised methods. Importantly, the robustness of our model is affirmed, showcasing its dual capability to enhance axial resolution while concurrently improving the signal-to-noise ratio.

Microbiological and Imaging-Based Evaluations of Photodynamic Therapy Combined with Er:YAG Laser Therapy in the In Vitro Decontamination of Titanium and Zirconia Surfaces.

The oral cavity's soft and hard tissues create a conducive environment for microbial proliferation and biofilm development, facilitating the colonization of prosthodontic and implant materials such as titanium (Ti) and zirconia (Zr). This study aimed to compare the efficacy of conventional decontamination methodologies (i.e., chemical and mechanical, using 0.12% digluconate chlorhexidine (CHX) solution-treatment and airflow) to adjunctive laser-based interventions on Ti and Zr substrates inoculated with Staphylococcus (S.) aureus ATCC 25923. Additionally, this investigation sought to elucidate the impact of these treatments on temperature variations and surface integrity, analyzing the laser irradiation effects on these prevalent dental materials. Experimental configurations were delineated for both Ti and Zr samples across four groups: (1) a conventional treatment group (CV); (2) a photodynamic therapy group (PDT); (3) an Er:YAG laser treatment group (Er); (4) a combined PDT and Er:YAG treatment group (PDTEr). Also, a negative control group (C) that received no treatment was considered. The decontamination of the inoculated disc samples was evaluated by quantifying the microbial colonies in colony-forming units per milliliter (CFU/mL). Temperature variations on the surface of the samples were determined during laser treatments. Surface modifications were investigated using scanning electron microscopy (SEM) and optical coherence tomography (OCT). For statistical analysis, Fisher 95% confidence intervals, Hsu's MCB method, and the Kruskal-Wallis test were applied. With regard to the 105 CFU/mL of the negative control group, results indicated average values equal for each study group to (1) 2.66 CFU/mL for Ti and 2 CFU/mL for Zr for the CV group; (2) 0.33 CFU/mL for Ti and 1 CFU/mL for Zr for the PDT group; (3) 1.25 CFU/mL for Ti and 0 CFU/mL for Zr for the Er group; (4), and 0 CFU/mL for both Ti and Zr for the PDTEr group. Therefore, the combined PDT and Er:YAG treatment (PDTEr) and the singular PDT modality outperformed conventional decontamination methods in eradicating S. aureus biofilms from both Ti and Zr surfaces. Notably, the PDTEr regime achieved a comprehensive elimination of microbial colonies on treated substrates. Surface examination employing OCT demonstrated discernible alterations in the surface morphology of samples subjected to Er:YAG and combined PDT and Er:YAG treatments. Temperature checks during treatments showed no major changes, suggesting the applied laser methods are safe. In conclusion, PDTEr and PDT eliminated bacteria more effectively, but Zr surfaces were more resilient, making them better for microbe-controlling applications. Also, the study demonstrated that the (less costly but lower resolution) OCT method can replace SEM for such investigations.

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.