K. U. Leuven

Normal tension glaucoma: A dynamic optical coherence tomography angiography study

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Purpose: Vascular dysregulation seems to play a role in the pathogenesis of glaucoma, in particular normal tension glaucoma (NTG). The development of optical coherence tomography angiography (OCTA) enabled the measurement of the retinal microvasculature non-invasively and with high repeatability. Nonetheless, only a few studies transformed OCTA into a dynamic examination employing a sympathomimetic stimulus. The goal of this study was to use this dynamic OCTA exam (1) to differentiate healthy individuals from glaucoma patients and (2) to distinguish glaucoma subcategories, NTG and high-tension primary open angle glaucoma (POAG). Methods: Retinal vessel density (VD) in NTG patients (n = 16), POAG patients (n = 12), and healthy controls (n = 14) was compared before and during a hand grip test with a hydraulic dynamometer. Results: At baseline, mean peripapillary VD was lower in POAG and NTG (42.6 and 48.5%) compared to healthy controls (58.1%; p < 0.001) and higher in NTG com...

Optical Coherence Tomography-Based Atlas of the Human Cochlear Hook Region

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Advancements in intracochlear diagnostics, as well as prosthetic and regenerative inner ear therapies, rely on a good understanding of cochlear microanatomy. The human cochlea is very small and deeply embedded within the densest skull bone, making nondestructive visualization of its internal microstructures extremely challenging. Current imaging techniques used in clinical practice, such as MRI and CT, fall short in their resolution to visualize important intracochlear landmarks, and histological analysis of the cochlea cannot be performed on living patients without compromising their hearing. Recently, optical coherence tomography (OCT) has been shown to be a promising tool for nondestructive micrometer resolution imaging of the mammalian inner ear. Various studies performed on human cadaveric tissue and living animals demonstrated the ability of OCT to visualize important cochlear microstructures (scalae, organ of Corti, spiral ligament, and osseous spiral lamina) at micrometer ...

Optical coherence tomography as a prognostic tool for disability progression in MS: a systematic review

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Since multiple sclerosis (MS) is characterized by an unpredictable disease course, accurate prognosis and personalized treatment constitute an important challenge in clinical practice. We performed a qualitative systematic review to assess the predictive value of retinal layer measurement by spectral-domain optical coherence tomography (SD-OCT) in MS patients. Longitudinal MS cohort studies that determined the risk of clinical deterioration based on peripapillary retinal nerve fiber layer (pRNFL) and/or macular ganglion cell-inner plexiform layer (mGCIPL) atrophy were included. Our search strategy and selection process yielded eight articles in total. Of those, five studies only focused on patients with a relapsing-remitting disease pattern (RRMS). After correction for confounders such as disease duration, we found that (1) cross-sectional measurement of pRNFL thickness ≤ 88 µm; (2) cross-sectional measurement of mGCIPL thickness < 77 µm; (3) longitudinal measureme...

An optically-guided cochlear implant sheath for real-time monitoring of electrode insertion into the human cochlea

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In cochlear implant surgery, insertion of perimodiolar electrode arrays into the scala tympani can be complicated by trauma or even accidental translocation of the electrode array within the cochlea. In patients with partial hearing loss, cochlear trauma can not only negatively affect implant performance, but also reduce residual hearing function. These events have been related to suboptimal positioning of the cochlear implant electrode array with respect to critical cochlear walls of the scala tympani (modiolar wall, osseous spiral lamina and basilar membrane). Currently, the position of the electrode array in relation to these walls cannot be assessed during the insertion and the surgeon depends on tactile feedback, which is unreliable and often comes too late. This study presents an image-guided cochlear implant device with an integrated, fiber-optic imaging probe that provides real-time feedback using optical coherence tomography during insertion into the human cochlea. This nov...

Pointwise Visual Field Estimation From Optical Coherence Tomography in Glaucoma Using Deep Learning

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Purpose : Standard automated perimetry is the gold standard to monitor visual field (VF) loss in glaucoma management, but it is prone to intrasubject variability. We trained and validated a customized deep learning (DL) regression model with Xception backbone that estimates pointwise and overall VF sensitivity from unsegmented optical coherence tomography (OCT) scans. Methods : DL regression models have been trained with four imaging modalities (circumpapillary OCT at 3.5 mm, 4.1 mm, and 4.7 mm diameter) and scanning laser ophthalmoscopy en face images to estimate mean deviation (MD) and 52 threshold values. This retrospective study used data from patients who underwent a complete glaucoma examination, including a reliable Humphrey Field Analyzer (HFA) 24-2 SITA Standard (SS) VF exam and a SPECTRALIS OCT. Results : For MD estimation, weighted prediction averaging of all four individuals yielded a mean absolute error (MAE) of 2.89 dB (2.50–3.30) on 186 test images, reducing the...

Automatic Segmentation of the Optic Nerve Head Region in Optical Coherence Tomography

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The optic nerve head (ONH) represents the intraocular section of the optic nerve, which is prone to damage by intraocular pressure (IOP). The advent of optical coherence tomography (OCT) has enabled the evaluation of novel ONH parameters, namely the depth and curvature of the lamina cribrosa (LC). Together with the Bruch's membrane minimum-rim-width (BMO-MRW), these seem to be promising ONH parameters for diagnosis and monitoring of retinal diseases such as glaucoma. Nonetheless, these OCT derived biomarkers are mostly extracted through manual segmentation, which is time-consuming and prone to bias, thus limiting their usability in clinical practice. The automatic segmentation of ONH in OCT scans could further improve the current clinical management of glaucoma and other diseases. This review summarizes the current state-of-the-art in automatic segmentation of the ONH in OCT. PubMed and Scopus were used to perform a systematic review. Additional works from other databases (IEEE, Goo...

Optical Coherence Tomography of Coronary Plaque Progression and Destabilization: JACC Focus Seminar Part 3/3

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The development of optical coherence tomography (OCT) has revolutionized our understanding of coronary artery disease. In vivo OCT research has paralleled with advances in computational fluid dynamics, providing additional insights in the various hemodynamic factors influencing plaque growth and stability. Recent OCT studies introduced a new concept of plaque healing in relation to clinical presentation. In addition to known mechanisms of acute coronary syndromes such as plaque rupture and plaque erosion, a new classification of calcified plaque was recently reported. This review will focus on important new insights that OCT has provided in recent years into coronary plaque development, progression, and destabilization, with a focus on the role of local hemodynamics and endothelial shear stress, the layered plaque (signature of previous subclinical plaque destabilization and healing), and the calcified culprit plaque. ( Read Full Article )

Hyperspectral Imaging, OCT Team to Detect Early Biomarkers of Alzheimer’s Disease

A team of scientists and engineers from Katholieke Universiteit (KU) Leuven, Universitair Ziekenhuis (UZ) Leuven, and the research organization VITO, collaborating with the international research and development group imec, used imec’s hyperspectral snapshot camera, SNAPSCAN, to collect information from 16 spectral bands (460 to 620 nm, 10-nm bandwidth) in a single capture. The potential for retinal imaging to serve as a tool for the early diagnosis of Alzheimer’s disease is the focus of the team’s research, which is specifically exploring retinal imaging techniques to quantify the accumulation of amyloid-beta protein in the brain. Using SNAPSCAN, the team combined hyperspectral retinal imaging and OCT to create an instrument with the capabilities of both techniques. Researchers mounted the hyperspectral camera on top of a standard fundus camera. In addition to information from 16 spectral bands, the system was able to detect the wavelength signature of each...

OCTA Multilayer and Multisector Peripapillary Microvascular Modeling for Diagnosing and Staging of Glaucoma

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Purpose: To develop and assess an automatic procedure for classifying and staging glaucomatous vascular damage based on optical coherence tomography angiography (OCTA) imaging. Methods: OCTA scans (Zeiss Cirrus 5000 HD-OCT) from a random eye of 39 healthy subjects and 82 glaucoma patients were used to develop a new classification algorithm based on multilayer and multisector information. The averaged circumpapillary retinal nerve fiber layer (RNFL) thickness was also collected. Three models, support vector machine (SVM), random forest (RF), and gradient boosting (xGB), were developed and optimized for classifying between healthy and glaucoma patients, primary open-angle glaucoma (POAG) and normal-tension glaucoma (NTG), and glaucoma severity groups. Results: All the models, the SVM (area under the receiver operating characteristic [AUROC] 0.89 ± 0.06), the RF (AUROC 0.86 ± 0.06), and the xGB (AUROC 0.85 ± 0.07), with 26, 22, and 29 vascular features obtained aft...

Combination of snapshot hyperspectral retinal imaging and optical coherence tomography to identify Alzheimer’s disease patients

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The eye offers potential for the diagnosis of Alzheimer’s disease (AD) with retinal imaging techniques being explored to quantify amyloid accumulation and aspects of neurodegeneration. To assess these changes, this proof-of-concept study combined hyperspectral imaging and optical coherence tomography to build a classification model to differentiate between AD patients and controls. ( Read Full Article )

Circadian variations in pathogenesis of ST-segment elevation myocardial infarction: an optical coherence tomography study

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Previous studies have reported a circadian variation in the onset of ST-segment elevation myocardial infarction (STEMI). However, underlying mechanisms for the circadian variation have not been fully elucidated. We investigated the relationship between onset of STEMI and the underlying pathology using optical coherence tomography (OCT). Patients with a diagnosis of STEMI were selected from a multicenter OCT registry. Patients were divided into 4 groups based on the estimated time of onset (00:00–05:59, 06:00–11:59, 12:00–17:59, or 18:00–23:59). Underlying pathologies of MI (plaque rupture, plaque erosion, and calcified plaque) were compared among the 4 groups. Among 648 patients, plaque rupture was diagnosed in 386 patients (59.6%), plaque erosion in 197 patients (30.4%), and calcified plaque in 65 patients (10.0%). A marked circadian variation was detected in the incidence of plaque rupture with a peak at 09:00, whereas it was not evident in plaque erosion o...

KU Leuven leads €6 million research project on heart disease and dementia

The starting point is an observation that people with conditions such as high blood pressure and obesity, or who are simply getting old, have a higher risk of certain kinds of dementia and heart disease. In particular, they seem to have a greater chance of developing vascular dementia, which is associated with reduced blood flow to the brain, and diastolic heart failure, which happens when the heart muscle cannot relax properly. ( Read Full Article )

PHD POSITION – OPTICAL COHERENCE TOMOGRAPHY ON AGRO-FOOD PRODUCTS

(ref. BAP-2019-576) The MeBioS group performs groundbreaking research on innovative sensor technologies and the associated data analysis methods to understand and control the quality of products and ongoing processes. The research on sensors mainly focusses on optical sensor systems (spectroscopy, hyperspectral imaging, thermography, smart cameras,…). While the data research involves the optimal design of experiments, chemometrics, process monitoring and control, as well as artificial intelligence and deep learning. OCT/OCM is a challenging new technique for non-destructive 3D imaging of biological tissues, without the need for sample preparation! Project Monitoring living tissues and organisms for an extended period of time, while not harming them or affecting their environment, is often required when studying agro-food products. Moreover, a good visualization of food microstructure is essential when evaluating physical quality features, which have a large impact on consumer...

Optical coherence tomography—A review of the opportunities and challenges for postharvest quality evaluation

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Optical Coherence Tomography (OCT) is an established non-destructive and contactless photonic technique which has now been shown to be suitable for monitoring the near-surface internal structure of tissues in stored fruit and vegetables. Such real-time cross-sectional imaging allows for better visualisation and understanding of the temporal changes in internal structure. However, despite these advantages, problems persist around the trade-off between imaging resolution and penetration depth, image analysis and data processing, and the applicability of in situ studies outside of the laboratory setting. This review summarises previous postharvest OCT research and assesses resulting mechanistic outcomes, and future potential. ( Read Full Article )

Neoatherosclerosis in Patients With Coronary Stent Thrombosis: Findings From Optical Coherence Tomography Imaging (A Report of the PRESTIGE Consortium)

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Objectives The purpose of this study was to assess neoatherosclerosis in a registry of prospectively enrolled patients presenting with stent thrombosis using optical coherence tomography . Background In-stent neoatherosclerosis was recently identified as a novel disease manifestation of atherosclerosis after coronary stent implantation. Methods Angiography and intravascular optical coherence tomography were used to investigate etiologic factors of neoatherosclerosis in patients presenting with stent thrombosis >1 year after implantation (very late stent thrombosis [VLST]). Clinical data were collected according to a standardized protocol. Optical coherence tomographic acquisitions were analyzed in a core laboratory. Cox regression analysis was performed to identify factors associated with the formation of neoatherosclerosis and plaque rupture as a function of time. Results Optical coherence tomography was performed in 134 patients presenting with VLST. A total of 58 lesions in 58...

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